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2018 Volume Issue 4
2018, (4): 429-444
doi: 10.11777/j.issn1000-3304.2018.18034
Abstract:
Chemical modification of proteins is of great significance in protein engineering, biomaterials, and chemical biology. Genetically encoded peptide-protein reactive pair, or "molecular superglue", refers to a peptide tag and its protein partner that can spontaneously reconstitute to form an isopeptide or ester bond between the side chains of specific residues of the two components. It is entirely based on natural amino acids and thus genetically encodable, providing a new way to do chemistry with proteins. This feature article summarizes the development of this unique set of chemical tools and elaborates on the principles and mechanisms of the isopeptide formation as well as the application of these tools in diverse fields. To date, a toolbox of peptide-protein reactive pairs has been developed and gradually gained its popularity in various fields such as protein topology engineering, protein-based biomaterials and protein nano-assemblies. Typical pairs include the isopeptide-bond-forming SpyTag/SpyCatcher, SnoopTag/SnoopCatcher, SdyTag/SdyCatcher etc. and the ester-bond-forming Cpe0147-A/Cpe0147-B. It allows the programming of post-translational modification of nascent proteins in vivo, which, in combination with protein folding, leads to versatile nonlinear protein topologies with unique properties, including circular proteins, star proteins, and protein catenanes. The protein catenation is found to enhance both the stability and the activity of the enzyme like dihydrofolate reductase. Their reactivity in vitro is also excellent. The covalent nature of SpyTag/SpyCatcher interaction has facilitated the processing of proteins into various materials forms including all-protein-based, chemically cross-linked hydrogels, functional layer-by-layer thin films, hybrid colloidal assemblies, and "living" materials. In this sense, they can serve as the "iron grip" to bring two parts together to form the conjugate, which may be helpful for diverse purposes such as the sortase activity enhancer. It also allows the preparation of protein nano-assemblies with ultra-high affinity, which are useful for applications like protein nanoreactors, synthetic vaccines, and protein therapeutics. The peptide-protein reactive pair technique thus opens new horizon in protein chemistry and paves the road to the synthesis and application of precision macromolecules with huge potential in real applications.
Chemical modification of proteins is of great significance in protein engineering, biomaterials, and chemical biology. Genetically encoded peptide-protein reactive pair, or "molecular superglue", refers to a peptide tag and its protein partner that can spontaneously reconstitute to form an isopeptide or ester bond between the side chains of specific residues of the two components. It is entirely based on natural amino acids and thus genetically encodable, providing a new way to do chemistry with proteins. This feature article summarizes the development of this unique set of chemical tools and elaborates on the principles and mechanisms of the isopeptide formation as well as the application of these tools in diverse fields. To date, a toolbox of peptide-protein reactive pairs has been developed and gradually gained its popularity in various fields such as protein topology engineering, protein-based biomaterials and protein nano-assemblies. Typical pairs include the isopeptide-bond-forming SpyTag/SpyCatcher, SnoopTag/SnoopCatcher, SdyTag/SdyCatcher etc. and the ester-bond-forming Cpe0147-A/Cpe0147-B. It allows the programming of post-translational modification of nascent proteins in vivo, which, in combination with protein folding, leads to versatile nonlinear protein topologies with unique properties, including circular proteins, star proteins, and protein catenanes. The protein catenation is found to enhance both the stability and the activity of the enzyme like dihydrofolate reductase. Their reactivity in vitro is also excellent. The covalent nature of SpyTag/SpyCatcher interaction has facilitated the processing of proteins into various materials forms including all-protein-based, chemically cross-linked hydrogels, functional layer-by-layer thin films, hybrid colloidal assemblies, and "living" materials. In this sense, they can serve as the "iron grip" to bring two parts together to form the conjugate, which may be helpful for diverse purposes such as the sortase activity enhancer. It also allows the preparation of protein nano-assemblies with ultra-high affinity, which are useful for applications like protein nanoreactors, synthetic vaccines, and protein therapeutics. The peptide-protein reactive pair technique thus opens new horizon in protein chemistry and paves the road to the synthesis and application of precision macromolecules with huge potential in real applications.
2018, (4): 445-455
doi: 10.11777/j.issn1000-3304.2017.17285
Abstract:
Functionalization and intelligentialization are the trends of the fiber development. The single component fiber is hard for performace optimization. The multi-component fiber could combine the characteristic of different components, and realize the properties integration and optimization. Different polymers aggregate together based on non-covalent bonds to form homogenous phase, which is defined as polymer complex. Polymer complex can be classified into several categories according to their characteristic rmolecular interaction, including polyelectrolyte complex, stereocomplex, hydrogen-bonded complex, inclusion complex, polymer-metal complex and charge-transfer complex. Polymer complex fibers are defined as those prepared through polymer complexation process or by directly spinning polymer complex. In polymer complex fibers, different polymers have miscibility on the molecular level, which provides a platform to design the functionality and to futher explore intelligentialization. Polymer complex fibers could be retrospected to stereocomplex fibers in early 1990s, but the mainly investigated ones were polyelectrolyte complex fibers (polyion complex fibers). Recently, hydrogen-bonded polymer complex fibers have been reported. Wan et al. made a review on polyelectrolyte complex fibers. But up to now, there is no unified concept for polymer complex fiber. This review collects research works on fibers of different types of compexes, and puts forward to the concept of polymer complex fibers. Different approaches that adopted to fabricate polymer complex fibers, like interfacial drawing, coaxial spinning, and electrospinning, are discussed. The review summarizes the properties of polymer complex fibers, such as conductivity, fluorescence, and elasticity, and focuses on their apllications in separation, controlled release, tissue engineering, anti-bacterials and catalysis. Using newly synthetized polymers or modified polymers to fabricate polymer complex fibers with multi-functionality and developing new methods and technologies to improve the efficiency of fiber fabrication are our effort directions of polymer complex fiber research.
Functionalization and intelligentialization are the trends of the fiber development. The single component fiber is hard for performace optimization. The multi-component fiber could combine the characteristic of different components, and realize the properties integration and optimization. Different polymers aggregate together based on non-covalent bonds to form homogenous phase, which is defined as polymer complex. Polymer complex can be classified into several categories according to their characteristic rmolecular interaction, including polyelectrolyte complex, stereocomplex, hydrogen-bonded complex, inclusion complex, polymer-metal complex and charge-transfer complex. Polymer complex fibers are defined as those prepared through polymer complexation process or by directly spinning polymer complex. In polymer complex fibers, different polymers have miscibility on the molecular level, which provides a platform to design the functionality and to futher explore intelligentialization. Polymer complex fibers could be retrospected to stereocomplex fibers in early 1990s, but the mainly investigated ones were polyelectrolyte complex fibers (polyion complex fibers). Recently, hydrogen-bonded polymer complex fibers have been reported. Wan et al. made a review on polyelectrolyte complex fibers. But up to now, there is no unified concept for polymer complex fiber. This review collects research works on fibers of different types of compexes, and puts forward to the concept of polymer complex fibers. Different approaches that adopted to fabricate polymer complex fibers, like interfacial drawing, coaxial spinning, and electrospinning, are discussed. The review summarizes the properties of polymer complex fibers, such as conductivity, fluorescence, and elasticity, and focuses on their apllications in separation, controlled release, tissue engineering, anti-bacterials and catalysis. Using newly synthetized polymers or modified polymers to fabricate polymer complex fibers with multi-functionality and developing new methods and technologies to improve the efficiency of fiber fabrication are our effort directions of polymer complex fiber research.
2018, (4): 456-463
doi: 10.11777/j.issn1000-3304.2017.17124
Abstract:
In the polymer solar cells research field, dithieno[3, 2-b:2', 3'-d]pyrrole (DTP) is a good donor unit due to its good planarity when it is used as build donor-acceptor (D-A) polymer. In this work, three DTP based polymers (named P1, P2, P3) are synthesized by polymerizing DTP with DPP, DTBO and TQ co-monomer acceptor unit, respectively. These three polymers exhibit good solubility in common solvent such as dichlorobenzene. GPC results show that the polymers show moderate number-average molecular weights (Mn, 9×103 to 2.2×104) and narrow PDI (1-2). UV-Vis absorption spectra in solution and thin film show that the polymers have a relatively narrow band gap (P1:1.23 eV; P2:1.51 eV; P3:1.50 eV), which enhances the polymer absorption of sunlight, with P1 showing the widest absorption (extending UV-Vis absorption to nearly 1000 nm). The thermal property of these polymers is measured by thermogravimetric analysis (TGA), giving their Td located at 313-410℃. The highest occupied molecular orbital (HOMO) energy levels of the polymers are between -5.2 eV and -5.4 eV, as tested by CV method. Photovoltaic devices are fabricated with P1-P3 as donor and PC71BM as acceptor in active layer. The solar cells J-V test results reveal that P1 has the highest PCE of 3.33% with JSC of 15.82 mA/cm2, VOC of 0.38 V when the mass ratio of P1 to PC71BM is kept at 1:3. The relative high PCE of P1 based PSCs devices is due to the wide light absorption, leading to high JSC of PSCs devices, which also can be confirmed by external quatum efficiency (EQE) test. For the polymers P2 and P3, with the mass ratio of polymer/PC71BM at 1:2, PCE of 1.20% for P2 and 1.37% of P3 are achieved respectively, and the relatively low PCE is caused by low short circuit current density (JSC) (P2:9.70 mA/cm2, P3:9.21 mA/cm2) and the low open-circuit voltage (VOC, only around 0.3 V). Transmission electron microscopy is also used to explore the polymer solar cells active layer morphology, which correlates closely with the donor and the acceptor aggregations and the phase separation.
In the polymer solar cells research field, dithieno[3, 2-b:2', 3'-d]pyrrole (DTP) is a good donor unit due to its good planarity when it is used as build donor-acceptor (D-A) polymer. In this work, three DTP based polymers (named P1, P2, P3) are synthesized by polymerizing DTP with DPP, DTBO and TQ co-monomer acceptor unit, respectively. These three polymers exhibit good solubility in common solvent such as dichlorobenzene. GPC results show that the polymers show moderate number-average molecular weights (Mn, 9×103 to 2.2×104) and narrow PDI (1-2). UV-Vis absorption spectra in solution and thin film show that the polymers have a relatively narrow band gap (P1:1.23 eV; P2:1.51 eV; P3:1.50 eV), which enhances the polymer absorption of sunlight, with P1 showing the widest absorption (extending UV-Vis absorption to nearly 1000 nm). The thermal property of these polymers is measured by thermogravimetric analysis (TGA), giving their Td located at 313-410℃. The highest occupied molecular orbital (HOMO) energy levels of the polymers are between -5.2 eV and -5.4 eV, as tested by CV method. Photovoltaic devices are fabricated with P1-P3 as donor and PC71BM as acceptor in active layer. The solar cells J-V test results reveal that P1 has the highest PCE of 3.33% with JSC of 15.82 mA/cm2, VOC of 0.38 V when the mass ratio of P1 to PC71BM is kept at 1:3. The relative high PCE of P1 based PSCs devices is due to the wide light absorption, leading to high JSC of PSCs devices, which also can be confirmed by external quatum efficiency (EQE) test. For the polymers P2 and P3, with the mass ratio of polymer/PC71BM at 1:2, PCE of 1.20% for P2 and 1.37% of P3 are achieved respectively, and the relatively low PCE is caused by low short circuit current density (JSC) (P2:9.70 mA/cm2, P3:9.21 mA/cm2) and the low open-circuit voltage (VOC, only around 0.3 V). Transmission electron microscopy is also used to explore the polymer solar cells active layer morphology, which correlates closely with the donor and the acceptor aggregations and the phase separation.
2018, (4): 464-474
doi: 10.11777/j.issn1000-3304.2017.17130
Abstract:
The living cationic ring opening polymerization of tetrahydrofuran (THF) was carried out using polyisobulylene with functional terminal group (PIB-AllylBr) as a macroinitiator in the presence of AgClO4 to synthesize PIB-b-PTHF living polymer chains. And then, the novel PBLG-g-(PTHF-b-PIB) block graft copolymer/silver (Ag) nanocomposites were in situ prepared via grafting the living polymer chains onto poly(γ-benzyl-L-glutamate) (PBLG) backbone. Several PBLG-g-(PTHF-b-PIB)/Ag nanocomposites with different grafting densities and average branch lengths have been achieved. The effect of grafting density on the surface morphology and self-assembly behavior of PBLG-g-(PTHF-b-PIB)/Ag nanocomposites was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The effects of grafting density and average branch length on the drug loading and release behavior were studied using ibuprofen (IBU) as a mimetic drug. The content, distribution, crystal form and morphology of nano-silver in nanocomposites were investigated by thermogravimetric analysis (TGA), UV-Vis spectroscopy (XPS), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The content of nano-silver in the above nanocomposites was ranged from 0.25% to 3.9%, which coincided with the theoretical content of nano-silver. The crystal form of nano-silver was face-centered cubic structure as observed by XRD test. The size of the nano-silver particles was ranged from 5 nm to 10 nm, estimated by HRTEM, and the obvious diffraction fringes were observed. The water contact angle of the above nanocomposite films increased from 96° to 118° with an increase in grafting density from 15% to 45%, and with that in nano-silver content from 0.45% to 1.48%. PBLG-g-(PTHF-b-PIB)/Ag/IBU microspheres were found to be well drug-loaded with ibuprofen as mimetic drug, attributed to the α-helical secondary structure in PBLG backbone in the middle, the amide bond in PBLG backbone and the ether bond in PTHF segments. Both drug loading and cumulative release rate increased with increasing grafting density or length of PTHF segment. The release rate at 37℃ was around 3 times of that at 25℃ for the same copolymer. No cytotoxicity of the nanocomposite was found by MTT assay since the cell viability was 97.7% after one week with the content of nano-silver of 1.48%. Antimicrobial experiments were performed on PBLG-g-(PTHF-b-PIB)/Ag nanocomposites by antibacterial ring method and the results showed that these nanocomposites demonstrated excellent antibacterial activity.
The living cationic ring opening polymerization of tetrahydrofuran (THF) was carried out using polyisobulylene with functional terminal group (PIB-AllylBr) as a macroinitiator in the presence of AgClO4 to synthesize PIB-b-PTHF living polymer chains. And then, the novel PBLG-g-(PTHF-b-PIB) block graft copolymer/silver (Ag) nanocomposites were in situ prepared via grafting the living polymer chains onto poly(γ-benzyl-L-glutamate) (PBLG) backbone. Several PBLG-g-(PTHF-b-PIB)/Ag nanocomposites with different grafting densities and average branch lengths have been achieved. The effect of grafting density on the surface morphology and self-assembly behavior of PBLG-g-(PTHF-b-PIB)/Ag nanocomposites was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The effects of grafting density and average branch length on the drug loading and release behavior were studied using ibuprofen (IBU) as a mimetic drug. The content, distribution, crystal form and morphology of nano-silver in nanocomposites were investigated by thermogravimetric analysis (TGA), UV-Vis spectroscopy (XPS), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The content of nano-silver in the above nanocomposites was ranged from 0.25% to 3.9%, which coincided with the theoretical content of nano-silver. The crystal form of nano-silver was face-centered cubic structure as observed by XRD test. The size of the nano-silver particles was ranged from 5 nm to 10 nm, estimated by HRTEM, and the obvious diffraction fringes were observed. The water contact angle of the above nanocomposite films increased from 96° to 118° with an increase in grafting density from 15% to 45%, and with that in nano-silver content from 0.45% to 1.48%. PBLG-g-(PTHF-b-PIB)/Ag/IBU microspheres were found to be well drug-loaded with ibuprofen as mimetic drug, attributed to the α-helical secondary structure in PBLG backbone in the middle, the amide bond in PBLG backbone and the ether bond in PTHF segments. Both drug loading and cumulative release rate increased with increasing grafting density or length of PTHF segment. The release rate at 37℃ was around 3 times of that at 25℃ for the same copolymer. No cytotoxicity of the nanocomposite was found by MTT assay since the cell viability was 97.7% after one week with the content of nano-silver of 1.48%. Antimicrobial experiments were performed on PBLG-g-(PTHF-b-PIB)/Ag nanocomposites by antibacterial ring method and the results showed that these nanocomposites demonstrated excellent antibacterial activity.
2018, (4): 475-481
doi: 10.11777/j.issn1000-3304.2017.17231
Abstract:
An amphiphilic iniferter, 2-(N, N-dicarboxymethyl dithiocarbamate) dodecyl isobutyrate (DIBDC), was synthesized and characterized by 1H-NMR spectroscopy. Dodecyl 2-bromo-2-methylpropionate was prepared from lauryl alcohol and 2-bromo-2-methylpropionyl bromide in the presence of triethylamine in ice water bath. Sodium N, N-dicarboxymethyl dithiocarbamate was synthesized from iminodiacetic acid, carbon disulfide and sodium hydroxide at room temperature. DIBDC was synthesized by the reaction between dodecyl 2-bromo-2-methylpropionate and sodium N, N-dicarboxymethyl dithiocarbamate at 60℃. Since DIBDC is not only a surfactant, but also used as an initiator, miniemulsion polymerization of styrene was performed in the presence of DIBDC using Cu(OAc)2 as the catalyst. The miniemulsion systemconsisted of distilled water, surfactant, hexadecane and styrene. Stable miniemulsion was obtained after stirring and ultrasonic treatment. After adding copper acetate and heating up to 80℃, the polymerization began.To characterize the hollow spheres, dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used. The results indicated that hollow polystyrene nanospheres with diameters of 100 nm to 200 nm were successfully prepared by the living radical miniemulsion polymerization. The PDI of diameter was below 0.1, showing good monodispersity of the nanospheres. It is well known that dithiocarbamates act as pseudohalogens, therefore, DIBDC can be used to perform a living radical polymerization, which is similar to atom transfer radical polymerization under catalysis of Cu(OAc)2. Due to the amphiphilicity of DIBDC and the reversible equilibrium between the active and the dormant species, thepolymerization was realized in aconfinedspace of the oil-water interface. As a result, hollow nanospheres were formed. And moreover, the formation of solid polymer nanoparticles was avoided. However, when azobisisobutyronitrile (AIBN) was used as the initiator instead of Cu(OAc)2 as a catalyst, solid polystyrene nanospheres were obtained. The reason is that the polymerization is no longer carried out in the confined space, which is similar to suspension polymerization because AIBN is dissolved in the micelles.
An amphiphilic iniferter, 2-(N, N-dicarboxymethyl dithiocarbamate) dodecyl isobutyrate (DIBDC), was synthesized and characterized by 1H-NMR spectroscopy. Dodecyl 2-bromo-2-methylpropionate was prepared from lauryl alcohol and 2-bromo-2-methylpropionyl bromide in the presence of triethylamine in ice water bath. Sodium N, N-dicarboxymethyl dithiocarbamate was synthesized from iminodiacetic acid, carbon disulfide and sodium hydroxide at room temperature. DIBDC was synthesized by the reaction between dodecyl 2-bromo-2-methylpropionate and sodium N, N-dicarboxymethyl dithiocarbamate at 60℃. Since DIBDC is not only a surfactant, but also used as an initiator, miniemulsion polymerization of styrene was performed in the presence of DIBDC using Cu(OAc)2 as the catalyst. The miniemulsion systemconsisted of distilled water, surfactant, hexadecane and styrene. Stable miniemulsion was obtained after stirring and ultrasonic treatment. After adding copper acetate and heating up to 80℃, the polymerization began.To characterize the hollow spheres, dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used. The results indicated that hollow polystyrene nanospheres with diameters of 100 nm to 200 nm were successfully prepared by the living radical miniemulsion polymerization. The PDI of diameter was below 0.1, showing good monodispersity of the nanospheres. It is well known that dithiocarbamates act as pseudohalogens, therefore, DIBDC can be used to perform a living radical polymerization, which is similar to atom transfer radical polymerization under catalysis of Cu(OAc)2. Due to the amphiphilicity of DIBDC and the reversible equilibrium between the active and the dormant species, thepolymerization was realized in aconfinedspace of the oil-water interface. As a result, hollow nanospheres were formed. And moreover, the formation of solid polymer nanoparticles was avoided. However, when azobisisobutyronitrile (AIBN) was used as the initiator instead of Cu(OAc)2 as a catalyst, solid polystyrene nanospheres were obtained. The reason is that the polymerization is no longer carried out in the confined space, which is similar to suspension polymerization because AIBN is dissolved in the micelles.
2018, (4): 482-489
doi: 10.11777/j.issn1000-3304.2017.17132
Abstract:
Stimuli-responsiveness in biological body and high drug loading efficiency are two of the prerequisites to conduct controlled drug release of supramolecular hyperbranched polymers (SHPs). Herein, the redox-responsive long chain SHP was constructed by click reaction of AB2 type macromonomer (MM), which contains thiol and alkynyl groups as well as β-cyclodextrin (β-CD)/Fcrrocene (Fc). A linear cationic polymer with thiol group at one end and β-cyclodextrin at the other end was first synthesized by the combination of reversible addition-fragmentation chain transfer polymerization (RAFT), ring-opening reaction and end group modification. And then, the AB2-type macromonomer was prepared by the inclusion complexation between β-CD and Fc in aqueous solution. The final SHP was achieved by click reaction of thiol group with alkynyl group under UV irradiation. The polymer structure and supramolecular interaction of MM and SHP were confirmed by 1H nuclear magnetic resonance and 2D NOSEY spectra. The self-assembly of SHP in aqueous solution was further investigated through transmission electron microscopy (TEM) and dynamic light scattering (DLS). Both TEM and DLS results indicated that SHP self-assembled into branched aggregates without external stimuli, and then dissociated and secondly self-assembled into irregular spherical self-assemblies due to the dissociation of β-CD and Fc complexes induced by reducing agent H2O2. The SHP self-assemblies possess a high doxorubicin (DOX) loading capacity compared with linear supramolecular polymer self-assemblies. Furthermore, by utilizing the above H2O2-tuned self-assembly morphology transition feature, a smart drug delivery behavior was observed through the cumulative release curves of DOX-loaded SHP self-assemblies. The controlled drug release behavior of SHP self-assemblies embedded DOX under pH=7.4 and 5.0 was deeply studied. The results indicated that H2O2 broke the host-guest interaction between β-CD and Fc, leading to a fast release of DOX. Meantime, the dissociation of SHP self-assemblies further self-assembled into small solid micelles. Therefore, the release behavior of DOX-loaded SHP self-assemblies presented the redox-responsive characteristics.
Stimuli-responsiveness in biological body and high drug loading efficiency are two of the prerequisites to conduct controlled drug release of supramolecular hyperbranched polymers (SHPs). Herein, the redox-responsive long chain SHP was constructed by click reaction of AB2 type macromonomer (MM), which contains thiol and alkynyl groups as well as β-cyclodextrin (β-CD)/Fcrrocene (Fc). A linear cationic polymer with thiol group at one end and β-cyclodextrin at the other end was first synthesized by the combination of reversible addition-fragmentation chain transfer polymerization (RAFT), ring-opening reaction and end group modification. And then, the AB2-type macromonomer was prepared by the inclusion complexation between β-CD and Fc in aqueous solution. The final SHP was achieved by click reaction of thiol group with alkynyl group under UV irradiation. The polymer structure and supramolecular interaction of MM and SHP were confirmed by 1H nuclear magnetic resonance and 2D NOSEY spectra. The self-assembly of SHP in aqueous solution was further investigated through transmission electron microscopy (TEM) and dynamic light scattering (DLS). Both TEM and DLS results indicated that SHP self-assembled into branched aggregates without external stimuli, and then dissociated and secondly self-assembled into irregular spherical self-assemblies due to the dissociation of β-CD and Fc complexes induced by reducing agent H2O2. The SHP self-assemblies possess a high doxorubicin (DOX) loading capacity compared with linear supramolecular polymer self-assemblies. Furthermore, by utilizing the above H2O2-tuned self-assembly morphology transition feature, a smart drug delivery behavior was observed through the cumulative release curves of DOX-loaded SHP self-assemblies. The controlled drug release behavior of SHP self-assemblies embedded DOX under pH=7.4 and 5.0 was deeply studied. The results indicated that H2O2 broke the host-guest interaction between β-CD and Fc, leading to a fast release of DOX. Meantime, the dissociation of SHP self-assemblies further self-assembled into small solid micelles. Therefore, the release behavior of DOX-loaded SHP self-assemblies presented the redox-responsive characteristics.
2018, (4): 490-498
doi: 10.11777/j.issn1000-3304.2017.17138
Abstract:
A series of sulfonated galactose-based glycopolymers with different chemical structures were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization. Galactose modified hydroxyethyl methacrylate and sodium p-styrene sulfonate were used as monomers to construct homo-, block-, and random-glycopolymers. The chemical structures and molecular weights of the synthesized polymers were characterized through 1H-NMR spectroscopy and GPC-MALLS analyses. Results showed that each glycopolymer possessed an average molecular weight of 1.5 x 104 with narrow molecular weight distribution (PDI~1.1). The turbidimetry assay indicated that the interactions between the glycopolymers and peanut agglutinin (PNA), which were used as model lectin, were influenced by the structure of the glycopolymers. The introduction of the sulfonic group significantly improved the PNA-binding ability of the glycopolymers through the synergistic effect of specific recognition and electrostatic interactions. Importantly, this effect was adjustable by varying the amount and distribution of the sulfonic groups. Both block-and random-glycopolymers exhibited significantly enhanced PNA-binding behavior with increasing amount of sulfonic groups. Moreover, the binding ability peaked when the molar ratio of the sulfonic groups was 66.7%. By contrast, the random-type glycopolymer, namely, P(Gal21-r-SS41), exhibited the strongest PNA-binding ability, which increased by 2.7-fold compared with that of the homo-type glycopolymer PGal. The ELISA assay further revealed that the polymerization and random distribution of the sulfonic groups in the glycopolymer substantially enhanced the recognition between PNA and the galactose moiety. The inhibition rate of galactose (30 mmol/L) against the PNA binding of PGal, P(Gal21-b-SS43), and P(Gal21-r-SS41) were 80%, 57.3%, and 34.2%, respectively. However, the contents of the galactose moiety in these samples were 3.8, 2.1 and 2.0 mmol/L, respectively. Overall, the order of PNA-binding ability was:P(Gal-r-SS) > P(Gal-b-SS) > PGal > PSS. In addition, the viability of B16 cancer cells and COS7 normal cells was higher than 80% when the concentration of the glycopolymers was 256 mg/L, indicating a good biocompatibility of these polymers. Based on the analysis of glycopolymer-lectin interactions, P(Gal21-r-SS41) effectively inhibited the migration of B16 tumor cells and thus can be applied in clinical therapy for tumor metastasis.
A series of sulfonated galactose-based glycopolymers with different chemical structures were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization. Galactose modified hydroxyethyl methacrylate and sodium p-styrene sulfonate were used as monomers to construct homo-, block-, and random-glycopolymers. The chemical structures and molecular weights of the synthesized polymers were characterized through 1H-NMR spectroscopy and GPC-MALLS analyses. Results showed that each glycopolymer possessed an average molecular weight of 1.5 x 104 with narrow molecular weight distribution (PDI~1.1). The turbidimetry assay indicated that the interactions between the glycopolymers and peanut agglutinin (PNA), which were used as model lectin, were influenced by the structure of the glycopolymers. The introduction of the sulfonic group significantly improved the PNA-binding ability of the glycopolymers through the synergistic effect of specific recognition and electrostatic interactions. Importantly, this effect was adjustable by varying the amount and distribution of the sulfonic groups. Both block-and random-glycopolymers exhibited significantly enhanced PNA-binding behavior with increasing amount of sulfonic groups. Moreover, the binding ability peaked when the molar ratio of the sulfonic groups was 66.7%. By contrast, the random-type glycopolymer, namely, P(Gal21-r-SS41), exhibited the strongest PNA-binding ability, which increased by 2.7-fold compared with that of the homo-type glycopolymer PGal. The ELISA assay further revealed that the polymerization and random distribution of the sulfonic groups in the glycopolymer substantially enhanced the recognition between PNA and the galactose moiety. The inhibition rate of galactose (30 mmol/L) against the PNA binding of PGal, P(Gal21-b-SS43), and P(Gal21-r-SS41) were 80%, 57.3%, and 34.2%, respectively. However, the contents of the galactose moiety in these samples were 3.8, 2.1 and 2.0 mmol/L, respectively. Overall, the order of PNA-binding ability was:P(Gal-r-SS) > P(Gal-b-SS) > PGal > PSS. In addition, the viability of B16 cancer cells and COS7 normal cells was higher than 80% when the concentration of the glycopolymers was 256 mg/L, indicating a good biocompatibility of these polymers. Based on the analysis of glycopolymer-lectin interactions, P(Gal21-r-SS41) effectively inhibited the migration of B16 tumor cells and thus can be applied in clinical therapy for tumor metastasis.
2018, (4): 499-506
doi: 10.11777/j.issn1000-3304.2017.17114
Abstract:
The thermal degradation behavior of bisphenol A polycarbonate (BPA-PC) during high temperature shear mixing was investigated. The effects of different antioxidant systems on improving the thermal stability of PC were compared by using a combination of spectrodensitometer, universal tensile testing machine and Ubbelohde viscometer, while the structural transformation of PC during the degradation process was studied by Fourier transform infrared spectrometer (FTIR) and nuclear magnetic resonance spectroscopy (1H-NMR) analysis. The results show that the addition of phosphite antioxidant and complex antioxidant can greatly improve the thermal stability and delay the extent of reduction of molecular weight as well as mechanical properties during the degradation process. Phosphite antioxidant can effectively enhance the color stability of PC by inhibiting the scission of carbonate linkage. Hindered phenolic antioxidant has opposite effects on the thermal stabilization of carbonate bonds and isopropylidene bonds in PC molecular chains. The phenolic hydroxyl groups of hindered phenolic antioxidant result in chain scission that is against the thermal stability of carbonate bond. Furthermore, hindered phenolic antioxidant contributes to the thermal stabilization of isopropylidene bond, which is superior to phosphite antioxidant. Multiple hindered phenolic antioxidant appears more outstanding thermostability to isopropylidene bonds, and the combination with phosphite can decrease the degradation of carbonate bond, which results in an excellent antioxidant effect. In addition, the effects of different degradation products on discoloration were discussed. It is found that chromophore is not derived from chains terminated with acetophenone. However, the yellow index of PC is proportional to the relative amount of chains terminated with phenolic hydroxyl, and the degree of color deterioration is also correlated with the infrared peak intensity of aliphatic ketone and aromatic ketone. Therefore, ketones could be the main degradation products that cause PC yellowing, while the carbonyl conjugated structure in the molecular chain is the main chromophore.
The thermal degradation behavior of bisphenol A polycarbonate (BPA-PC) during high temperature shear mixing was investigated. The effects of different antioxidant systems on improving the thermal stability of PC were compared by using a combination of spectrodensitometer, universal tensile testing machine and Ubbelohde viscometer, while the structural transformation of PC during the degradation process was studied by Fourier transform infrared spectrometer (FTIR) and nuclear magnetic resonance spectroscopy (1H-NMR) analysis. The results show that the addition of phosphite antioxidant and complex antioxidant can greatly improve the thermal stability and delay the extent of reduction of molecular weight as well as mechanical properties during the degradation process. Phosphite antioxidant can effectively enhance the color stability of PC by inhibiting the scission of carbonate linkage. Hindered phenolic antioxidant has opposite effects on the thermal stabilization of carbonate bonds and isopropylidene bonds in PC molecular chains. The phenolic hydroxyl groups of hindered phenolic antioxidant result in chain scission that is against the thermal stability of carbonate bond. Furthermore, hindered phenolic antioxidant contributes to the thermal stabilization of isopropylidene bond, which is superior to phosphite antioxidant. Multiple hindered phenolic antioxidant appears more outstanding thermostability to isopropylidene bonds, and the combination with phosphite can decrease the degradation of carbonate bond, which results in an excellent antioxidant effect. In addition, the effects of different degradation products on discoloration were discussed. It is found that chromophore is not derived from chains terminated with acetophenone. However, the yellow index of PC is proportional to the relative amount of chains terminated with phenolic hydroxyl, and the degree of color deterioration is also correlated with the infrared peak intensity of aliphatic ketone and aromatic ketone. Therefore, ketones could be the main degradation products that cause PC yellowing, while the carbonyl conjugated structure in the molecular chain is the main chromophore.
2018, (4): 507-514
doi: 10.11777/j.issn1000-3304.2017.17121
Abstract:
4, 4'-Diaminobiphenyl-2, 2'-disulfonic acid lead (BDSA(Pb)) is synthesized by ion exchange method, and copolymerized with 4, 4'-diaminodiphenyl ether (ODA) and 1, 2, 4, 5-benzenetetracarboxylic anhydride (PMDA) in N-methyl-2-pyrrolidone (NMP). Through thermal imidization and layer-by-layer casting process, a series of membranes of three-layer sandwich-structured lead-ion-containing polyimide composite material PI(Pb) are prepared, aiming to solve the problems of inhomogeneous distribution of lead, phase segregation and poor mechanical properties. These problems are commonly observed in traditional composite materials prepared by physical blending, which has been widely used for fabrication of X-ray and γ-ray shielding organic-inorganic composite materials by physically doping lead or its salts into a large volume of light-weight, easily-processed polymer matrixe. In this novel sandwich structure, the top and bottom layers are two pure polyimide layers obtained by polymerization of 4, 4'-diaminodiphenyl ether with 1, 2, 4, 5-benzenetetracarboxylic anhydride; the middle layer is the lead-ion-containing polyimide. The chemical and physical properties of this novel PI(Pb) composite material are throughly investigated, using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, thermal gravimetric analysis, tensile testing experiments and γ-ray radiation etc. First, the thermal stability and mechanical properties of the PI(Pb) composite materials are examined and analyzed. Secondly, 60Co γ-ray radiation experiment is carried out on pure PI and PI(Pb) materials to analyze and compare their radiation resistance performances. Finally, the low-medium energy γ-ray radiation shielding properties of the materials are investigated using multi-channel gamma spectroscopy. Compared with pure polyimide material, this PI(Pb) composite material has much better γ-ray shielding capability under exposure of low-medium energy γ-rays (such as 241Am, 59.5 keV; and 238Pu, 79.9, 176.7 keV), enhanced radiation shielding rate, much higher linear attenuation and much lower half-value thickness, higher superior radiation resistance, excellent thermal stability and good mechanical performance.
4, 4'-Diaminobiphenyl-2, 2'-disulfonic acid lead (BDSA(Pb)) is synthesized by ion exchange method, and copolymerized with 4, 4'-diaminodiphenyl ether (ODA) and 1, 2, 4, 5-benzenetetracarboxylic anhydride (PMDA) in N-methyl-2-pyrrolidone (NMP). Through thermal imidization and layer-by-layer casting process, a series of membranes of three-layer sandwich-structured lead-ion-containing polyimide composite material PI(Pb) are prepared, aiming to solve the problems of inhomogeneous distribution of lead, phase segregation and poor mechanical properties. These problems are commonly observed in traditional composite materials prepared by physical blending, which has been widely used for fabrication of X-ray and γ-ray shielding organic-inorganic composite materials by physically doping lead or its salts into a large volume of light-weight, easily-processed polymer matrixe. In this novel sandwich structure, the top and bottom layers are two pure polyimide layers obtained by polymerization of 4, 4'-diaminodiphenyl ether with 1, 2, 4, 5-benzenetetracarboxylic anhydride; the middle layer is the lead-ion-containing polyimide. The chemical and physical properties of this novel PI(Pb) composite material are throughly investigated, using nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elemental analysis, X-ray diffraction, thermal gravimetric analysis, tensile testing experiments and γ-ray radiation etc. First, the thermal stability and mechanical properties of the PI(Pb) composite materials are examined and analyzed. Secondly, 60Co γ-ray radiation experiment is carried out on pure PI and PI(Pb) materials to analyze and compare their radiation resistance performances. Finally, the low-medium energy γ-ray radiation shielding properties of the materials are investigated using multi-channel gamma spectroscopy. Compared with pure polyimide material, this PI(Pb) composite material has much better γ-ray shielding capability under exposure of low-medium energy γ-rays (such as 241Am, 59.5 keV; and 238Pu, 79.9, 176.7 keV), enhanced radiation shielding rate, much higher linear attenuation and much lower half-value thickness, higher superior radiation resistance, excellent thermal stability and good mechanical performance.
2018, (4): 515-523
doi: 10.11777/j.issn1000-3304.2017.17137
Abstract:
Dissipative particle dynamics (DPD) was employed to investigate the self-assembly of tri-block copolymer PS-PAA-PEO into channel membrane by non-solvent induced phase separation method. The micro-phase separation process was simulated by solvent exchange method, which mimics the practical membrane preparation process. The polymer concentration has a significant effect on the micro-phase separation process:a too high polymer concentration would limit the micro-phase separation, while a too low concentration would result in lamellar structure. For the PS-PAA-PEO system, it was found that the channel membrane could be obtained in the concentration range of 30%-45%. The morphology evolution clearly showed the micro-phase separation process. The polymer chains of PS formed the matrix part of the channel membrane and the chains of PAA acted as the "open/close" switch, while the chains of PEO were distributed in the innermost. Because PAA possesses weak acidic groups that can gain or lose protons in response to pH, the sizes of the channel pores at different pH are calculated. At pH lower than the pKa of PAA, the carboxyl groups of PAA are protonated, therefore the membrane pore is in the "open" state because of the reduced electrostatic repulsion between PAA on the inner pore surface. In contrast, at neutral pH, the carboxyl groups of PAA are dissociated and negatively charged; the membrane pore is in the "closed" state because the repulsion between negative groups makes PAA chains extensively swelled. With pH values changing from 1 to 6.25, the membrane pore size decreased from 19.3 nm to 2.9 nm. After the porous membrane was solidified, small-sized nanoparticles could pass through the middle of the channel. The filtration of different sized nanoparticles was studied to justify the accuracy of the pore sizes under different dissociation degrees. The permeation results confirmed that the channel membrane, which was in the "close" state due to the swollen conformation of PAA, had the size-based filtration function.
Dissipative particle dynamics (DPD) was employed to investigate the self-assembly of tri-block copolymer PS-PAA-PEO into channel membrane by non-solvent induced phase separation method. The micro-phase separation process was simulated by solvent exchange method, which mimics the practical membrane preparation process. The polymer concentration has a significant effect on the micro-phase separation process:a too high polymer concentration would limit the micro-phase separation, while a too low concentration would result in lamellar structure. For the PS-PAA-PEO system, it was found that the channel membrane could be obtained in the concentration range of 30%-45%. The morphology evolution clearly showed the micro-phase separation process. The polymer chains of PS formed the matrix part of the channel membrane and the chains of PAA acted as the "open/close" switch, while the chains of PEO were distributed in the innermost. Because PAA possesses weak acidic groups that can gain or lose protons in response to pH, the sizes of the channel pores at different pH are calculated. At pH lower than the pKa of PAA, the carboxyl groups of PAA are protonated, therefore the membrane pore is in the "open" state because of the reduced electrostatic repulsion between PAA on the inner pore surface. In contrast, at neutral pH, the carboxyl groups of PAA are dissociated and negatively charged; the membrane pore is in the "closed" state because the repulsion between negative groups makes PAA chains extensively swelled. With pH values changing from 1 to 6.25, the membrane pore size decreased from 19.3 nm to 2.9 nm. After the porous membrane was solidified, small-sized nanoparticles could pass through the middle of the channel. The filtration of different sized nanoparticles was studied to justify the accuracy of the pore sizes under different dissociation degrees. The permeation results confirmed that the channel membrane, which was in the "close" state due to the swollen conformation of PAA, had the size-based filtration function.
2018, (4): 524-531
doi: 10.11777/j.issn1000-3304.2017.17140
Abstract:
To fabricate oil/water separating material with good selective absorption capacity, natural materials including cotton and calcium carbonate (CaCO3)were selected. Cotton fibers/CaCO3 composites were prepared by a biomimetic mineralization approach, through which CaCO3 particles were uniformly coated on the surface of cotton fibers by an alternative soaking process (ASP). Polyacrylic acid (PAA) was first introduced onto the surface of the cotton before CaCO3 mineralization to avoid the agglomeration of the formed inorganic particles. The prepared cotton fibers/CaCO3 composites were further modified by sodium stearate, which is a cost-efficient hydrophobic agent commonly used to modify CaCO3. By this way, the water contact angle of the composites increased to 145°, as compared with the water contact angle (0°) of the pristine cotton, illustrating that the surface wettability of the cotton fibers was changed successfully from hydrophilic to hydrophobic. FTIR results demonstrated that the hydrogen bonds existed between CaCO3 and cotton fibers, which provided the binding force for the composites. A series of samples with different concentrations of CaCO3 were prepared, and the relationship between the wetting behavior and the concentration of modified CaCO3 were investigatged and discussed in detail. In addition, the selective absorbing capability against oil/water mixture was measured for the composite. The resultant hydrophobic cotton fibers showed good selective absorption to different oils, including vegetable oil, crude oil, paraffin oil, simethicone and chloroform, from the oil/water mixtures. The absorption capacity achieved was as high as (17.4 ±1.16), (23.6 ±1.9), (20.5 ±1.5), (22.7 ±1.2) and (27.3 ±1.0) g/g for different oils. In particular, the adsorption rates of simethicone and chloroform were maintained higher than 80% even after 30 cycles of readsorptions, indicating the good reusability of the composite fibers. All these results demonstrated that the novel hydrophobic cotton fiber/calcium carbonate composites had potential applications in the treatment of oil-water pollutants.
To fabricate oil/water separating material with good selective absorption capacity, natural materials including cotton and calcium carbonate (CaCO3)were selected. Cotton fibers/CaCO3 composites were prepared by a biomimetic mineralization approach, through which CaCO3 particles were uniformly coated on the surface of cotton fibers by an alternative soaking process (ASP). Polyacrylic acid (PAA) was first introduced onto the surface of the cotton before CaCO3 mineralization to avoid the agglomeration of the formed inorganic particles. The prepared cotton fibers/CaCO3 composites were further modified by sodium stearate, which is a cost-efficient hydrophobic agent commonly used to modify CaCO3. By this way, the water contact angle of the composites increased to 145°, as compared with the water contact angle (0°) of the pristine cotton, illustrating that the surface wettability of the cotton fibers was changed successfully from hydrophilic to hydrophobic. FTIR results demonstrated that the hydrogen bonds existed between CaCO3 and cotton fibers, which provided the binding force for the composites. A series of samples with different concentrations of CaCO3 were prepared, and the relationship between the wetting behavior and the concentration of modified CaCO3 were investigatged and discussed in detail. In addition, the selective absorbing capability against oil/water mixture was measured for the composite. The resultant hydrophobic cotton fibers showed good selective absorption to different oils, including vegetable oil, crude oil, paraffin oil, simethicone and chloroform, from the oil/water mixtures. The absorption capacity achieved was as high as (17.4 ±1.16), (23.6 ±1.9), (20.5 ±1.5), (22.7 ±1.2) and (27.3 ±1.0) g/g for different oils. In particular, the adsorption rates of simethicone and chloroform were maintained higher than 80% even after 30 cycles of readsorptions, indicating the good reusability of the composite fibers. All these results demonstrated that the novel hydrophobic cotton fiber/calcium carbonate composites had potential applications in the treatment of oil-water pollutants.
2018, (4): 532-540
doi: 10.11777/j.issn1000-3304.2017.17146
Abstract:
By using the improved 3D printer based on the fused deposition method (FDM), thermoplastic polyurethane (TPU) elastomer soft materials were printed into stereoscopic objects. The conventional 3D printer in a FDM mode was improved for soft materials TPU. That is, the distance between the pulling wheels and heated nozzle was shortened and a polytetrafluoroethylene pipe was added to avoid the bending of the soft linear feedstock during 3D printing process. Influence of 3D printing parameter on the appearance and interlayer bonding strength of the printed products were explored. TPU with appropriate content of hard and soft segments could be used for 3D printing. In terms of printing parameter, the layer space has great influence on the appearance of the printed product. When the layer space is set too large, the bonding area will be smaller and the product prone to deform at the corner. If the layer space is set too small, the printing soft line will squeeze each other and cause the printed product deformation and the hollow structure is hard to put up. A novel model for tensile test was designed to characterize the interlayer bonding strength of the printed products. The models, which are divided into two parts during 3D printing process, are bonded to each other layer by layer. The interlayer bonding strength of the 3D printed products with TPU soft materials can catch 70% of that of the samples prepared by mould pressing, and only 48% for that of stiff printing materials. Both the layer space and platform temperature have significant impact on the interlayer bonding strength of the printed product. High platform temperature and low layer space could strengthen the interlayer bonding. The printing speed and printing temperature have little influence on the interlayer bonding strength. The outer contour error of the geometrical shape printed by TPU soft materials is within 1.65% only. Furthermore, the objects printed using TPU soft materials have great resilience and are also easy to bend.
By using the improved 3D printer based on the fused deposition method (FDM), thermoplastic polyurethane (TPU) elastomer soft materials were printed into stereoscopic objects. The conventional 3D printer in a FDM mode was improved for soft materials TPU. That is, the distance between the pulling wheels and heated nozzle was shortened and a polytetrafluoroethylene pipe was added to avoid the bending of the soft linear feedstock during 3D printing process. Influence of 3D printing parameter on the appearance and interlayer bonding strength of the printed products were explored. TPU with appropriate content of hard and soft segments could be used for 3D printing. In terms of printing parameter, the layer space has great influence on the appearance of the printed product. When the layer space is set too large, the bonding area will be smaller and the product prone to deform at the corner. If the layer space is set too small, the printing soft line will squeeze each other and cause the printed product deformation and the hollow structure is hard to put up. A novel model for tensile test was designed to characterize the interlayer bonding strength of the printed products. The models, which are divided into two parts during 3D printing process, are bonded to each other layer by layer. The interlayer bonding strength of the 3D printed products with TPU soft materials can catch 70% of that of the samples prepared by mould pressing, and only 48% for that of stiff printing materials. Both the layer space and platform temperature have significant impact on the interlayer bonding strength of the printed product. High platform temperature and low layer space could strengthen the interlayer bonding. The printing speed and printing temperature have little influence on the interlayer bonding strength. The outer contour error of the geometrical shape printed by TPU soft materials is within 1.65% only. Furthermore, the objects printed using TPU soft materials have great resilience and are also easy to bend.
2018, (4): 541-552
doi: 10.11777/j.issn1000-3304.2017.17150
Abstract:
A new Gemini basic morpholine ionic liquid (IL, [Nbmd]OH) was synthesized with morphline, bromodecane and 1, 4-dibromobutane via a two-step procedure. The structure of the new IL was characterized by 1H-NMR and FTIR. A series of anion exchange membranes (PVA-FP/[Nbmd]OH) were prepared by casting method with pyridine functionalized poly(vinyl alcohol) as the polymer matrix. The PVA-FP/[Nbmd]OH composite membranes were characterized in details by AC-impedance spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and tensile strength test. The results indicated that PVA-FP/[Nbmd]OH composite membranes have uniform morphology, and the introduction of pyridine groups enhance the thermal stability and alkali resistance of PVA matrix, due to the formation of the hyper conjugation structure between σ bond (C-H bond in methyl group) and π-bond conjugated region (pyridine group), therefore enlarging the conjugated region, decreasing the positive charge density of the cations. Meanwhile, [Nbmd]OH ionic liquid not only provided more cationic active sites but also reduced the crystalline of the composite membranes, resulting in an increase of OH- conductivity and an improvement of the mechanical properties. When the weight ratio of[Nbmd]OH to PVA was 2.5, the thermal decomposition temperature of the composite membrane was 75℃ higher than that of the pristine PVA membrane; the maximum OH- conductivity was found at about 4.42×10-2 S·cm-1 at 70℃; no obvious decrease in OH- conductivity was observed for the composite membrane after immersing in 6 mol/L KOH solution at 80℃. On the contrary, the OH- conductivity was improved to 1.6 times of the initial OH- conductivity after 400 h immersion time, showing an excellent alkali resistance stability. In addition, the methanol permeability of the composite membrane determined using 3 mol/L methanol solution at 30℃ was only about 2.5%-5% of the commercial Nafion®-117 membrane under the same test conditions, indicating a promising potential use in alkaline direct methanol fuel cells.
A new Gemini basic morpholine ionic liquid (IL, [Nbmd]OH) was synthesized with morphline, bromodecane and 1, 4-dibromobutane via a two-step procedure. The structure of the new IL was characterized by 1H-NMR and FTIR. A series of anion exchange membranes (PVA-FP/[Nbmd]OH) were prepared by casting method with pyridine functionalized poly(vinyl alcohol) as the polymer matrix. The PVA-FP/[Nbmd]OH composite membranes were characterized in details by AC-impedance spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and tensile strength test. The results indicated that PVA-FP/[Nbmd]OH composite membranes have uniform morphology, and the introduction of pyridine groups enhance the thermal stability and alkali resistance of PVA matrix, due to the formation of the hyper conjugation structure between σ bond (C-H bond in methyl group) and π-bond conjugated region (pyridine group), therefore enlarging the conjugated region, decreasing the positive charge density of the cations. Meanwhile, [Nbmd]OH ionic liquid not only provided more cationic active sites but also reduced the crystalline of the composite membranes, resulting in an increase of OH- conductivity and an improvement of the mechanical properties. When the weight ratio of[Nbmd]OH to PVA was 2.5, the thermal decomposition temperature of the composite membrane was 75℃ higher than that of the pristine PVA membrane; the maximum OH- conductivity was found at about 4.42×10-2 S·cm-1 at 70℃; no obvious decrease in OH- conductivity was observed for the composite membrane after immersing in 6 mol/L KOH solution at 80℃. On the contrary, the OH- conductivity was improved to 1.6 times of the initial OH- conductivity after 400 h immersion time, showing an excellent alkali resistance stability. In addition, the methanol permeability of the composite membrane determined using 3 mol/L methanol solution at 30℃ was only about 2.5%-5% of the commercial Nafion®-117 membrane under the same test conditions, indicating a promising potential use in alkaline direct methanol fuel cells.
