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2020 Volume 51 Issue 4
2020, 51(4):
Abstract:
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2020, 51(4): 319-325
doi: 10.11777/j.issn1000-3304.2020.20031
Abstract:
The adhesion of bacteria and the subsequent formation of biofilms on the surfaces of biomaterials cause a series of adverse consequences, resulting in serious problems in both human healthcare and industrial applications. Therefore, endowing the surfaces with antibacterial capabilities has attracted considerable interests and development of antibacterial surfaces has become an active field of research. The traditional antibacterial strategies are mainly focused on killing bacteria attached on the surfaces, however, neglecting many problems raised from the accumulation of dead bacteria and debris such as degradation of biocidal efficiency and secondary contamination. Aiming to solve these problems, a promising smart antibacterial strategy based on switchable function between bacteria-killing and bacteria-releasing was proposed. Based on this strategy, a series of smart antibacterial surfaces have been developed to kill the attached bacteria and then trigger the on-demand release of dead bacteria from the surface by regulation of bacteria-surface interactions, so as to maintain the effective antibacterial activity for long-term applications. In this feature article, we summarize our achievements and the recent progress in the field of smart antibacterial surfaces. These surfaces have been divided into three categories based on the methods for applying biocidal agents on to the surfaces: (1) the surfaces with permanently immobilized biocidal agents; (2) the surfaces with reversibly incorporated biocidal agents; and (3) the surfaces without common biocidal agents but with physically biocidal activity. In the end, we provide a brief perspective of the future research directions in this promising area.
The adhesion of bacteria and the subsequent formation of biofilms on the surfaces of biomaterials cause a series of adverse consequences, resulting in serious problems in both human healthcare and industrial applications. Therefore, endowing the surfaces with antibacterial capabilities has attracted considerable interests and development of antibacterial surfaces has become an active field of research. The traditional antibacterial strategies are mainly focused on killing bacteria attached on the surfaces, however, neglecting many problems raised from the accumulation of dead bacteria and debris such as degradation of biocidal efficiency and secondary contamination. Aiming to solve these problems, a promising smart antibacterial strategy based on switchable function between bacteria-killing and bacteria-releasing was proposed. Based on this strategy, a series of smart antibacterial surfaces have been developed to kill the attached bacteria and then trigger the on-demand release of dead bacteria from the surface by regulation of bacteria-surface interactions, so as to maintain the effective antibacterial activity for long-term applications. In this feature article, we summarize our achievements and the recent progress in the field of smart antibacterial surfaces. These surfaces have been divided into three categories based on the methods for applying biocidal agents on to the surfaces: (1) the surfaces with permanently immobilized biocidal agents; (2) the surfaces with reversibly incorporated biocidal agents; and (3) the surfaces without common biocidal agents but with physically biocidal activity. In the end, we provide a brief perspective of the future research directions in this promising area.
2020, 51(4): 326-337
doi: 10.11777/j.issn1000-3304.2019.19215
Abstract:
Developing high-performance battery systems requires the collaborative optimization of every battery components, including electrodes, electrolyte, separators and binder systems. The strategies of synthesizing electrode materials and developing novel electrolyte system are widely investigated. Cathode binder, a crucial material to maintain structure stability of cathode, plays an essential role in efficiently enhancing energy density and ensuring safety of lithium ion battery. In recent years, designing advanced binder systems has attracted researchers’ attention. In this account, the research progress on material and structural design of cathode binder and application about cathode binder of lithium ion battery are reviewed comprehensively. The effects that cathode binders play on stabilizing cathode material, promoting reduction of battery internal impedance and regulating electrochemical performances of lithium ion battery are primarily introduced. Meanwhile, the characteristics of the oil-soluble binder represented by poly(vinylidene fluoride) (PVDF), polyimide (PI), functional polymer binder and the water-soluble binder represented by poly(acrylic acid) (PAA) and carboxymethyl cellulose (CMC) are concluded in detail. PVDF has good chemical stability and adhesion, but suffers from large swelling ratio; PI has excellent high temperature resistance and good mechanical properties, but the cost is relatively high; functional polymer binder has good electrical conductivity and can effectively suppress the shuttle effect of Li-S lithium batteries, but the preparation process is complicated; PAA is flexible, but mechanical properties are poor; CMC has good dispersibility and large mechanical strength, but it needs to be matched with styrene-butadiene rubber due to the large brittleness. Furthermore, combining with the existing research reports, methods of designing advanced cathode binder systems are concluded to provide valuable guidance for the performance optimization. The development prospects and application exploration are also discussed.
Developing high-performance battery systems requires the collaborative optimization of every battery components, including electrodes, electrolyte, separators and binder systems. The strategies of synthesizing electrode materials and developing novel electrolyte system are widely investigated. Cathode binder, a crucial material to maintain structure stability of cathode, plays an essential role in efficiently enhancing energy density and ensuring safety of lithium ion battery. In recent years, designing advanced binder systems has attracted researchers’ attention. In this account, the research progress on material and structural design of cathode binder and application about cathode binder of lithium ion battery are reviewed comprehensively. The effects that cathode binders play on stabilizing cathode material, promoting reduction of battery internal impedance and regulating electrochemical performances of lithium ion battery are primarily introduced. Meanwhile, the characteristics of the oil-soluble binder represented by poly(vinylidene fluoride) (PVDF), polyimide (PI), functional polymer binder and the water-soluble binder represented by poly(acrylic acid) (PAA) and carboxymethyl cellulose (CMC) are concluded in detail. PVDF has good chemical stability and adhesion, but suffers from large swelling ratio; PI has excellent high temperature resistance and good mechanical properties, but the cost is relatively high; functional polymer binder has good electrical conductivity and can effectively suppress the shuttle effect of Li-S lithium batteries, but the preparation process is complicated; PAA is flexible, but mechanical properties are poor; CMC has good dispersibility and large mechanical strength, but it needs to be matched with styrene-butadiene rubber due to the large brittleness. Furthermore, combining with the existing research reports, methods of designing advanced cathode binder systems are concluded to provide valuable guidance for the performance optimization. The development prospects and application exploration are also discussed.
2020, 51(4): 338-345
doi: 10.11777/j.issn1000-3304.2019.19206
Abstract:
Poly(3-hexylthiophene) (P3HT) with good electronic transmission capacity is one of promising material for organic photodetector. Compared with organic solar cells, the research of photodetector based on P3HT is deficient, especially in how to improve the light absorption efficiency and electronic transmission ability of active layer. Here, bulk heterojunction photodetectors with a structure of ITO/PEDOT:PSS/P3HT:PC61BM/C60/Al were prepared by using P3HT as a donor and fullerene derivative (PC61BM) as an acceptor. The change of active layer thickness plays an important role in the effective transfer of photogenerated charge to the electrode. Although increasing the thickness of active layer can increase the light absorption efficiency, it may also lead to the recombination of electrons and holes in the process of long distance transmission. In addition, annealing condition is the key to the film forming process. Adjusting the annealing temperature can control the self-assembly of active layer, thus obtaining the ideal nano-size phase separation structure and reducing the recombination probability of photoexcitons. Therefore, the active layer thickness in P3HT devices varied at 120, 160, 180 and 200 nm and the devices were annealed at 100, 120, 130, 140 and 150 °C in order to probe the effect of these variables on photodetector performance. It was found that the device with a 180-nm thick active layer, after being annealed at 150 °C, exhibited the maximal responsivity of 268 mA/V at 550 nm and more than 200 mA/W in the wavelengths of 470 − 610 nm under the bias of −2 V. Furthermore, the same device showed a linear dynamic range of 95 dB after annealing at 120 °C. Our study demonstrates that the thickness of active layer is of great importance to the light absorption efficiency and the device performance, while the annealing treatment can significantly affect the morphology of active layer, as evidenced by AFM study, which reduces the recombination probability of holes and the electrons and thus improves the photodetector performance.
Poly(3-hexylthiophene) (P3HT) with good electronic transmission capacity is one of promising material for organic photodetector. Compared with organic solar cells, the research of photodetector based on P3HT is deficient, especially in how to improve the light absorption efficiency and electronic transmission ability of active layer. Here, bulk heterojunction photodetectors with a structure of ITO/PEDOT:PSS/P3HT:PC61BM/C60/Al were prepared by using P3HT as a donor and fullerene derivative (PC61BM) as an acceptor. The change of active layer thickness plays an important role in the effective transfer of photogenerated charge to the electrode. Although increasing the thickness of active layer can increase the light absorption efficiency, it may also lead to the recombination of electrons and holes in the process of long distance transmission. In addition, annealing condition is the key to the film forming process. Adjusting the annealing temperature can control the self-assembly of active layer, thus obtaining the ideal nano-size phase separation structure and reducing the recombination probability of photoexcitons. Therefore, the active layer thickness in P3HT devices varied at 120, 160, 180 and 200 nm and the devices were annealed at 100, 120, 130, 140 and 150 °C in order to probe the effect of these variables on photodetector performance. It was found that the device with a 180-nm thick active layer, after being annealed at 150 °C, exhibited the maximal responsivity of 268 mA/V at 550 nm and more than 200 mA/W in the wavelengths of 470 − 610 nm under the bias of −2 V. Furthermore, the same device showed a linear dynamic range of 95 dB after annealing at 120 °C. Our study demonstrates that the thickness of active layer is of great importance to the light absorption efficiency and the device performance, while the annealing treatment can significantly affect the morphology of active layer, as evidenced by AFM study, which reduces the recombination probability of holes and the electrons and thus improves the photodetector performance.
2020, 51(4): 346-354
doi: 10.11777/j.issn1000-3304.2019.19192
Abstract:
To improve the quality of fluorescence imaging and effectiveness of photothermal therapy, We designed a novel conjugated-polymer (BDT-TTQ) with a narrow band gap for NIR-II fluorescence and NIR-II photothermal effect. To realize solubility of BDT-TTQ in water, we enveloped the hydrophobic polymer BDT-TTQ into amphiphilic copolymer (PEG-b-PPG-b-PEG, F-127) shells for NIR-II water-soluble nanoparticles (BDT-TTQ NPs) through the nanoprecipitation method. With strong absorption in the NIR-II region of 1000 − 1200 nm, the BDT-TTQ NPs can realize fluorescence image during 1200 − 1400 nm excited by 1064 nm laser. The prepared BDT-TTQ NPs were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The average hydrodynamic radius of BDT-TTQ NPs was around 62 nm and spherical morphology was observed from TEM. Besides, the BDT-TTQ NPs showed the similar hydrodynamic radius in physiological environment such as phosphate buffer saline (PBS), Dulbecco's Modified Eagle Medium (DMEM) and fetal bovine serum (FBS) and exhibited the excellent biological stability, indicating the potential for further in vivo application. To study the NIR-II fluorescence characters, we firstly detected the maximum imaging depth of BDT-TTQ NPs in vitro and the penetration depth can achieve 6 mm at 1064 nm laser. High-resolution NIR-II fluorescence imaging of living blood vessels in mice was also achieved by BDT-TTO NPs under 1064 nm laser irradiation. In addition, the real-time NIR-II images of brain and abdomen were obtained with an ultrahigh signal-to-background ratio. Photothermal experiments suggested the BDT-TTQ NPs exhibited excellent photothermal conversion and outstanding photothermla stability under 1064 nm excitation, which revealed the potential of BDT-TTQ NPs for photothermal therapy in vivo. MTT assay and confocal laser scanning microscopy (CLSM) were used to analyse photothermal treatment toward human cervical carcinoma (HeLa) cells in vitro and the results indicated the nanoparticles performed an effective photothermal inhibition at the cellular level under laser irradiation. Morever, BDT-TTQ NPs developed in this study can realize NIR-II fluorescence imaging-guided photothermal therapy in vivo at 1064 nm laser.
To improve the quality of fluorescence imaging and effectiveness of photothermal therapy, We designed a novel conjugated-polymer (BDT-TTQ) with a narrow band gap for NIR-II fluorescence and NIR-II photothermal effect. To realize solubility of BDT-TTQ in water, we enveloped the hydrophobic polymer BDT-TTQ into amphiphilic copolymer (PEG-b-PPG-b-PEG, F-127) shells for NIR-II water-soluble nanoparticles (BDT-TTQ NPs) through the nanoprecipitation method. With strong absorption in the NIR-II region of 1000 − 1200 nm, the BDT-TTQ NPs can realize fluorescence image during 1200 − 1400 nm excited by 1064 nm laser. The prepared BDT-TTQ NPs were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The average hydrodynamic radius of BDT-TTQ NPs was around 62 nm and spherical morphology was observed from TEM. Besides, the BDT-TTQ NPs showed the similar hydrodynamic radius in physiological environment such as phosphate buffer saline (PBS), Dulbecco's Modified Eagle Medium (DMEM) and fetal bovine serum (FBS) and exhibited the excellent biological stability, indicating the potential for further in vivo application. To study the NIR-II fluorescence characters, we firstly detected the maximum imaging depth of BDT-TTQ NPs in vitro and the penetration depth can achieve 6 mm at 1064 nm laser. High-resolution NIR-II fluorescence imaging of living blood vessels in mice was also achieved by BDT-TTO NPs under 1064 nm laser irradiation. In addition, the real-time NIR-II images of brain and abdomen were obtained with an ultrahigh signal-to-background ratio. Photothermal experiments suggested the BDT-TTQ NPs exhibited excellent photothermal conversion and outstanding photothermla stability under 1064 nm excitation, which revealed the potential of BDT-TTQ NPs for photothermal therapy in vivo. MTT assay and confocal laser scanning microscopy (CLSM) were used to analyse photothermal treatment toward human cervical carcinoma (HeLa) cells in vitro and the results indicated the nanoparticles performed an effective photothermal inhibition at the cellular level under laser irradiation. Morever, BDT-TTQ NPs developed in this study can realize NIR-II fluorescence imaging-guided photothermal therapy in vivo at 1064 nm laser.
2020, 51(4): 355-365
doi: 10.11777/j.issn1000-3304.2019.19179
Abstract:
Cationic copolymerization of isobutylene (IB) and chloromethylstyrene was investigated with n-hexane (Hex)/dichloromethane (CH2Cl2) (V/V = 6/4) as solvent, TiCl4, AlEt1.5Cl1.5, AlEt2Cl, AlCl3 as co-initiators and water or cumyl alcohol as initiators. The molecular weight, molecular weight distribution (MWD) and structure composition of the resulting copolymers were analyzed by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. The reactivity ratios were determined by Kelen-Tüdős and Yezreielv-Brokhina-Roskin formula, and the copolymerization mechanism was proposed. It was found that co-initiators with strong Lewis acidity, such as AlEtCl2, AlEt1.5Cl1.5 and AlCl3 can catalyze intermolecular alkylations to form gels while no gel formed with the relatively weaker TiCl4. The chloromethylstyrene with para-substituent, i.e., p-(chloromethyl)styrene (p-CMS) was found to have a low reactivity during the copolymerization with IB (rIB = 4.67, rp-CMS = 0.70) while the ortho-isomer exhibited no activity. The chemical structure of resulting copolymers indicated that p-(chloromethyl)styrene cannot initiate the polymerization of IB which may be due to its low initiation rate compared to the highly active cumyl group at p-CMS/IB molar ratio of 4.11. However, the benzyl chloride group in the formed copolymer chain can slowly initiate polymerization of IB and p-(chloromethyl)styrene, forming branched structures. The content of p-(chloromethyl)styrene increased with increasing molecular weight and monomer conversion. Systematic research on the branched structure, rheological properties and other physical properties of the resulting copolymers is in progress.
Cationic copolymerization of isobutylene (IB) and chloromethylstyrene was investigated with n-hexane (Hex)/dichloromethane (CH2Cl2) (V/V = 6/4) as solvent, TiCl4, AlEt1.5Cl1.5, AlEt2Cl, AlCl3 as co-initiators and water or cumyl alcohol as initiators. The molecular weight, molecular weight distribution (MWD) and structure composition of the resulting copolymers were analyzed by gel permeation chromatography (GPC) and 1H-NMR spectroscopy. The reactivity ratios were determined by Kelen-Tüdős and Yezreielv-Brokhina-Roskin formula, and the copolymerization mechanism was proposed. It was found that co-initiators with strong Lewis acidity, such as AlEtCl2, AlEt1.5Cl1.5 and AlCl3 can catalyze intermolecular alkylations to form gels while no gel formed with the relatively weaker TiCl4. The chloromethylstyrene with para-substituent, i.e., p-(chloromethyl)styrene (p-CMS) was found to have a low reactivity during the copolymerization with IB (rIB = 4.67, rp-CMS = 0.70) while the ortho-isomer exhibited no activity. The chemical structure of resulting copolymers indicated that p-(chloromethyl)styrene cannot initiate the polymerization of IB which may be due to its low initiation rate compared to the highly active cumyl group at p-CMS/IB molar ratio of 4.11. However, the benzyl chloride group in the formed copolymer chain can slowly initiate polymerization of IB and p-(chloromethyl)styrene, forming branched structures. The content of p-(chloromethyl)styrene increased with increasing molecular weight and monomer conversion. Systematic research on the branched structure, rheological properties and other physical properties of the resulting copolymers is in progress.
2020, 51(4): 366-376
doi: 10.11777/j.issn1000-3304.2019.19210
Abstract:
A set of functional POSS derivatives and star-shaped POSS-cored polyesters are presented. Three POSS derivatives POSS-8OH, POSS-16OH and POSS-8NH2 are prepared by thiol-ene “click” reaction of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) with 2-mercapto-ethanol, 1-thioglycerol and cysteamine hydrochloride. Their chemical structures are confirmed by 1H-NMR, 13C-NMR, and FTIR analyses. Subsequently, POSS-8OH and POSS-16OH are used to initiate the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EOP), resulting in hydrophobic 8-arm (POSS-8PCL) and 16-arm (POSS-16PCL) star-shaped poly(ε-caprolactone), as well as hydrophilic 8-arm star-shaped poly(ethyl ethylene phosphate) (POSS-8PEEP). Three star-shaped POSS-8PCL with different arm lengths are synthesized by changing the feed ratio of the monomer to initiator. As a demonstration, the chemical structure of POSS-8PCL-2 is confirmed by using FTIR, 1H-NMR and 13C-NMR analyses. TGA test indicates that the initial decomposition temperature and decomposition mode are influenced by the molecular weights of POSS-8PCL. In order to compare the thermal stability of star-shaped PCL with a POSS core or an organic core, tripentaerythritol (TPE) is used to initiate the ROP reaction of ε-CL to give eight-arm PCL (TPE-8PCL) with an organic core. TGA test demonstrates that inorganic POSS core has better support to maintain melt stability of 8-arm star-shaped PCL than organic TPE core. The chemical structure and molecular weight information of POSS-16PCL are characterized by FTIR, 1H-NMR and 13C-NMR analyses, as well as GPC test. TGA analysis shows that the initial decomposition temperature is around 200 °C, the decomposition behavior also displays an apparent two-stage mode, and the residue derived from POSS segment is about 3.6% at 700 °C. Finally, POSS-8OH is used to initiate the ROP reaction of EOP to obtain POSS-8PEEP. The chemical structure and molecular weight information of POSS-8PEEP are confirmed by FTIR, 1H-NMR and GPC analyses. Furthermore, TGA analysis demonstrates that the thermal stability of POSS-8PEEP is weaker than star-shaped PCL and the initial decomposition temperature is decreased to about 100 °C. The decomposition of POSS-8PEEP shows a more apparent multi-stage mode and about 19.8% residue is left at 700 °C. This work reports a facile method for the preparation of functional POSS derivatives and star-shaped POSS-cored polymers.
A set of functional POSS derivatives and star-shaped POSS-cored polyesters are presented. Three POSS derivatives POSS-8OH, POSS-16OH and POSS-8NH2 are prepared by thiol-ene “click” reaction of octavinyl polyhedral oligomeric silsesquioxane (OVPOSS) with 2-mercapto-ethanol, 1-thioglycerol and cysteamine hydrochloride. Their chemical structures are confirmed by 1H-NMR, 13C-NMR, and FTIR analyses. Subsequently, POSS-8OH and POSS-16OH are used to initiate the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) and 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EOP), resulting in hydrophobic 8-arm (POSS-8PCL) and 16-arm (POSS-16PCL) star-shaped poly(ε-caprolactone), as well as hydrophilic 8-arm star-shaped poly(ethyl ethylene phosphate) (POSS-8PEEP). Three star-shaped POSS-8PCL with different arm lengths are synthesized by changing the feed ratio of the monomer to initiator. As a demonstration, the chemical structure of POSS-8PCL-2 is confirmed by using FTIR, 1H-NMR and 13C-NMR analyses. TGA test indicates that the initial decomposition temperature and decomposition mode are influenced by the molecular weights of POSS-8PCL. In order to compare the thermal stability of star-shaped PCL with a POSS core or an organic core, tripentaerythritol (TPE) is used to initiate the ROP reaction of ε-CL to give eight-arm PCL (TPE-8PCL) with an organic core. TGA test demonstrates that inorganic POSS core has better support to maintain melt stability of 8-arm star-shaped PCL than organic TPE core. The chemical structure and molecular weight information of POSS-16PCL are characterized by FTIR, 1H-NMR and 13C-NMR analyses, as well as GPC test. TGA analysis shows that the initial decomposition temperature is around 200 °C, the decomposition behavior also displays an apparent two-stage mode, and the residue derived from POSS segment is about 3.6% at 700 °C. Finally, POSS-8OH is used to initiate the ROP reaction of EOP to obtain POSS-8PEEP. The chemical structure and molecular weight information of POSS-8PEEP are confirmed by FTIR, 1H-NMR and GPC analyses. Furthermore, TGA analysis demonstrates that the thermal stability of POSS-8PEEP is weaker than star-shaped PCL and the initial decomposition temperature is decreased to about 100 °C. The decomposition of POSS-8PEEP shows a more apparent multi-stage mode and about 19.8% residue is left at 700 °C. This work reports a facile method for the preparation of functional POSS derivatives and star-shaped POSS-cored polymers.
2020, 51(4): 377-384
doi: 10.11777/j.issn1000-3304.2019.19187
Abstract:
Dichlorosilane functionalized nonconjugated α,ω-diolefin and propylene copolymers, prepared by heterogeneous Ziegler-Natta catalysts, have been newly found to trigger dehydration condensation reaction among/between polypropylene chains to form long-chain branched (LCB) structures in the presence of water. Hydrogen is often used as a chain transfer agent to regulate the molecular weight of the polymer in olefin polymerization. Therefore, whether or how hydrogen affects the insertion of the di(5-hexenyl)dichlorosilane in the polymerization of propylene is a topic worthy of study. Herein, the copolymerization of di(5-hexenyl)dichlorosilane and propylene has been investigated based on MgCl2/TiCl4 catalyst (9,9-bis(methoxymethyl)fluorine (BMMF), as internal electron donor) in bulk polymerization conditions. The polypropylene microstructure was analysed by changing hydrogen content while the amount of di(5-hexenyl)dichlorosilane was fixed. It was found that hydrogen significantly improved the activity of catalyst and reduced the molecular weight of polymer. The 1H-NMR results show that the pendant double bonds in the polypropylene chain decreased from 0.12 mol% to 0.05 mol%, illustrating that hydrogen inhibited the insertion of di(5-hexenyl)dichlorosilane in the polymerization. The higher the hydrogen content, the lower the insertion of di(5-hexenyl)dichlorosilane in the polypropylene chain, which corresponds to the decreasing density of long-branched chains in the polymer. Analysis of the insoluble portion of the polymer in the xylene showed that there is no gel in the presence of hydrogen. The creep test results exhibit that the value of Mb/Mw increases from 0.70 to 0.95, which quantitatively indicates that the long-chain branching density in the polymer decreases with the increasing hydrogen content. The long-branched chain density in polymer decreases with the increasing hydrogen content, which is also confirmed by the results of small amplitude oscillatory shear rheology test.
Dichlorosilane functionalized nonconjugated α,ω-diolefin and propylene copolymers, prepared by heterogeneous Ziegler-Natta catalysts, have been newly found to trigger dehydration condensation reaction among/between polypropylene chains to form long-chain branched (LCB) structures in the presence of water. Hydrogen is often used as a chain transfer agent to regulate the molecular weight of the polymer in olefin polymerization. Therefore, whether or how hydrogen affects the insertion of the di(5-hexenyl)dichlorosilane in the polymerization of propylene is a topic worthy of study. Herein, the copolymerization of di(5-hexenyl)dichlorosilane and propylene has been investigated based on MgCl2/TiCl4 catalyst (9,9-bis(methoxymethyl)fluorine (BMMF), as internal electron donor) in bulk polymerization conditions. The polypropylene microstructure was analysed by changing hydrogen content while the amount of di(5-hexenyl)dichlorosilane was fixed. It was found that hydrogen significantly improved the activity of catalyst and reduced the molecular weight of polymer. The 1H-NMR results show that the pendant double bonds in the polypropylene chain decreased from 0.12 mol% to 0.05 mol%, illustrating that hydrogen inhibited the insertion of di(5-hexenyl)dichlorosilane in the polymerization. The higher the hydrogen content, the lower the insertion of di(5-hexenyl)dichlorosilane in the polypropylene chain, which corresponds to the decreasing density of long-branched chains in the polymer. Analysis of the insoluble portion of the polymer in the xylene showed that there is no gel in the presence of hydrogen. The creep test results exhibit that the value of Mb/Mw increases from 0.70 to 0.95, which quantitatively indicates that the long-chain branching density in the polymer decreases with the increasing hydrogen content. The long-branched chain density in polymer decreases with the increasing hydrogen content, which is also confirmed by the results of small amplitude oscillatory shear rheology test.
2020, 51(4): 385-392
doi: 10.11777/j.issn1000-3304.2019.19193
Abstract:
Forward osmosis (FO), as a promising membrane separation technology, has attracted much attention, whose performance is strongly dependent on the structure and property of FO membrane. Thin film composite (TFC) FO membrane, consisting of a thin film and a porous substrate, is commonly used for FO process due to its high water permeability. Nevertheless, TFC FO membrane still suffers from a trade-off between water permeability and salt rejection, which limits the further application of FO process. Recently, constructing an interlayer between the thin film and the porous substrate has been reported as an effective way to improve the performance of TFC membranes. Herein, a novel TFC FO membrane was prepared by using a polydopamine/polyethyleneimine (PDA/PEI) co-deposition interlayer on cellulose triacetate (CTA) porous substrate followed by an interfacial polymerization. The surface structures and properties of CTA substrates and TFC membranes were systematically investigated by FTIR/ATR spectroscopy, scanning electron microscopy, atom electron microscopy, solute rejection method, and water contact angle test. Compared with CTA substrate and PDA modified CTA substrate, the surface of CTA substrate deposited by PDA/PEI interlayer becomes smooth and has a narrow surface pore size distribution as well as small surface pore size of (30.0 ± 4.1) nm. Meanwhile, the polyamide film formed on the PDA/PEI co-deposition interlayer presents a uniform leaf-like structure and excellent hydrophilicity. Therefore, TFC FO membrane with PDA/PEI co-deposition interlayer achieves an improved water flux of (7.1 ± 2.3) L/(m2·h), rising by 57.6% compared with nascent TFC FO membrane; a low reverse salt flux of (1.4 ± 0.1) g/(m2·h), and a small specific salt flux of (0.2 ± 0.06) g/L, decreasing by 83.9% and 90.6%, respectively. It means that PDA/PEI co-deposition interlayer facilitates to improve both water permeability and selectivity of TFC FO membrane. This work proposes an effective modification method for improving the performance of TFC FO membrane by using PDA/PEI co-deposition interlayer.
Forward osmosis (FO), as a promising membrane separation technology, has attracted much attention, whose performance is strongly dependent on the structure and property of FO membrane. Thin film composite (TFC) FO membrane, consisting of a thin film and a porous substrate, is commonly used for FO process due to its high water permeability. Nevertheless, TFC FO membrane still suffers from a trade-off between water permeability and salt rejection, which limits the further application of FO process. Recently, constructing an interlayer between the thin film and the porous substrate has been reported as an effective way to improve the performance of TFC membranes. Herein, a novel TFC FO membrane was prepared by using a polydopamine/polyethyleneimine (PDA/PEI) co-deposition interlayer on cellulose triacetate (CTA) porous substrate followed by an interfacial polymerization. The surface structures and properties of CTA substrates and TFC membranes were systematically investigated by FTIR/ATR spectroscopy, scanning electron microscopy, atom electron microscopy, solute rejection method, and water contact angle test. Compared with CTA substrate and PDA modified CTA substrate, the surface of CTA substrate deposited by PDA/PEI interlayer becomes smooth and has a narrow surface pore size distribution as well as small surface pore size of (30.0 ± 4.1) nm. Meanwhile, the polyamide film formed on the PDA/PEI co-deposition interlayer presents a uniform leaf-like structure and excellent hydrophilicity. Therefore, TFC FO membrane with PDA/PEI co-deposition interlayer achieves an improved water flux of (7.1 ± 2.3) L/(m2·h), rising by 57.6% compared with nascent TFC FO membrane; a low reverse salt flux of (1.4 ± 0.1) g/(m2·h), and a small specific salt flux of (0.2 ± 0.06) g/L, decreasing by 83.9% and 90.6%, respectively. It means that PDA/PEI co-deposition interlayer facilitates to improve both water permeability and selectivity of TFC FO membrane. This work proposes an effective modification method for improving the performance of TFC FO membrane by using PDA/PEI co-deposition interlayer.
2020, 51(4): 393-402
doi: 10.11777/j.issn1000-3304.2019.19203
Abstract:
A series of main-chain type sulfonated poly(phenylquinoxaline) (SPPQ) were prepared by post-sulfonation of PPQs, which were synthesized from copolymerization of 4,4′ -bis(4-(2-phenylethylenedione)phenoxybiphenyl and 4,4′ -bis(2-phenylethylenedione)diphenylether with 3,3′ ,4,4′ -tetraaminobiphenyl under different molar ratios. They were confirmed by the model compounds that sulfonic acid groups were precisely introduced to the 2,2′-position of the biphenyl fragment with high electron cloud density on SPPQ backbone. Therefore, sulfonic acid groups can be predicablely introduced to the polymer main-chain under mild conditions by the combination of monomer molecular structure design and post-sulfonation proceeding. Relative viscosity of these SPPQs was higher than 3.8 dL/g, indicating their high molecular weight. SPPQ-based proton exchange membranes (PEMs) were prepared by solution casting method. Their properties such as ion exchange capacity (IEC), water uptake, swell ratio, oxidative stability, mechanical properties and proton conductivity were investigated. The TGA results indicated that SPPQ PEMs had good thermal stability with the desulfonic acid groups temperature at about 320 °C and the decompose temperature at about 550 °C. All SPPQ PEMs showed water uptake less than 39% and in-plane swelling ratio linearly increased with increasing IEC and temperature, with the values ranging from 2.1% – 13%. For example, SPPQ-5 with the IEC value up to 2.21 meq/g showed excellent dimensional stability with only 11% and 13% in-plane direction and thickness direction of the swelling ratios at 80 °C, respectively. Free radical oxidative stability test in Fenton reagent showed that the breaking time of SPPQ PEMs decreased with increasing IEC. For example, the SPPQ-1 (1.29 meq/g) has breaking time of over 150 h at 20 °C, whereas the value decreased to 81 h for SPPQ-5 (2.21 meq/g). Proton conductivity of SPPQ PEMs were increased obviously with the increase of temperature and IEC, and the maximum proton conductivity reached 64 mS/cm. The proton conductivities are much lower than that of Nafion NR212, due to the formation of acid-base groups between sulfonic acid groups and quinoxaline groups and the obviously low water uptake of the PEM.
A series of main-chain type sulfonated poly(phenylquinoxaline) (SPPQ) were prepared by post-sulfonation of PPQs, which were synthesized from copolymerization of 4,4′ -bis(4-(2-phenylethylenedione)phenoxybiphenyl and 4,4′ -bis(2-phenylethylenedione)diphenylether with 3,3′ ,4,4′ -tetraaminobiphenyl under different molar ratios. They were confirmed by the model compounds that sulfonic acid groups were precisely introduced to the 2,2′-position of the biphenyl fragment with high electron cloud density on SPPQ backbone. Therefore, sulfonic acid groups can be predicablely introduced to the polymer main-chain under mild conditions by the combination of monomer molecular structure design and post-sulfonation proceeding. Relative viscosity of these SPPQs was higher than 3.8 dL/g, indicating their high molecular weight. SPPQ-based proton exchange membranes (PEMs) were prepared by solution casting method. Their properties such as ion exchange capacity (IEC), water uptake, swell ratio, oxidative stability, mechanical properties and proton conductivity were investigated. The TGA results indicated that SPPQ PEMs had good thermal stability with the desulfonic acid groups temperature at about 320 °C and the decompose temperature at about 550 °C. All SPPQ PEMs showed water uptake less than 39% and in-plane swelling ratio linearly increased with increasing IEC and temperature, with the values ranging from 2.1% – 13%. For example, SPPQ-5 with the IEC value up to 2.21 meq/g showed excellent dimensional stability with only 11% and 13% in-plane direction and thickness direction of the swelling ratios at 80 °C, respectively. Free radical oxidative stability test in Fenton reagent showed that the breaking time of SPPQ PEMs decreased with increasing IEC. For example, the SPPQ-1 (1.29 meq/g) has breaking time of over 150 h at 20 °C, whereas the value decreased to 81 h for SPPQ-5 (2.21 meq/g). Proton conductivity of SPPQ PEMs were increased obviously with the increase of temperature and IEC, and the maximum proton conductivity reached 64 mS/cm. The proton conductivities are much lower than that of Nafion NR212, due to the formation of acid-base groups between sulfonic acid groups and quinoxaline groups and the obviously low water uptake of the PEM.
Effect of Sodium Dodecyl Sulfate on the Rheological Behavior of Poly(vinyl alcohol) Aqueous Solution
2020, 51(4): 403-410
doi: 10.11777/j.issn1000-3304.2019.19178
Abstract:
Rheological behaviors of poly(vinyl alcohol) (PVA) aqueous solution are influenced remarkably by the intermolecular hydrogen bond interaction in the semi-dilute solution region. Owing to the hydrogen bond network, 10 wt% PVA aqueous solution exhibits a high viscosity which limits the development of its solution processing method to some extent. Sodium dodecyl sulfate (SDS), as a surfactant, can destroy the hydrogen bond interaction, thus playing a certain viscosity-reducing role. Based on measuring the critical aggregation concentration (CAC) and critical micelle concentration of SDS in 10 wt% PVA aqueous solution (CMCP), the steady and dynamic rheological behaviors of PVA-SDS aqueous solution were studied in detail. The concentrations of SDS (csur) can influence the rheological behavior of PVA aqueous solution in different ways at various regions. ① csur < CAC, the apparent viscosity (ηa) of the solution doesn’t change a lot as the csur changes. ② CAC < csur < CMCP, ηa decreases as the csur increases. Particularly, ηa reaches the minimum while csur = CMCP and a wider second platform is displayed in this area. ③ csur > CMCP, SDS form micelles that act as physical cross-linking points, and the dynamic storage modulus (G′) of the composite solution also increases significantly. The changes in the hydrogen bond network of the PVA solution was indirectly characterized by the changes of the hydration number measured by Differential Scanning Calorimeter. After introducing SDS, the number of bound water (n) decreases due to the interaction between SDS and PVA. However, n almost keeps constant when csur > CMCP. The viscous activation energy also shows a similar change. When csur is much larger, the micelles formed by SDS in water are conducive to the formation of physical cross-linking network, which contribute more to the solution elasticity, leading to the increase of G′ (greater than that of dynamic loss modulus). Compared with the dilute solution, SDS has a greater viscosity reduction effect on the PVA semi-dilute solution.
Rheological behaviors of poly(vinyl alcohol) (PVA) aqueous solution are influenced remarkably by the intermolecular hydrogen bond interaction in the semi-dilute solution region. Owing to the hydrogen bond network, 10 wt% PVA aqueous solution exhibits a high viscosity which limits the development of its solution processing method to some extent. Sodium dodecyl sulfate (SDS), as a surfactant, can destroy the hydrogen bond interaction, thus playing a certain viscosity-reducing role. Based on measuring the critical aggregation concentration (CAC) and critical micelle concentration of SDS in 10 wt% PVA aqueous solution (CMCP), the steady and dynamic rheological behaviors of PVA-SDS aqueous solution were studied in detail. The concentrations of SDS (csur) can influence the rheological behavior of PVA aqueous solution in different ways at various regions. ① csur < CAC, the apparent viscosity (ηa) of the solution doesn’t change a lot as the csur changes. ② CAC < csur < CMCP, ηa decreases as the csur increases. Particularly, ηa reaches the minimum while csur = CMCP and a wider second platform is displayed in this area. ③ csur > CMCP, SDS form micelles that act as physical cross-linking points, and the dynamic storage modulus (G′) of the composite solution also increases significantly. The changes in the hydrogen bond network of the PVA solution was indirectly characterized by the changes of the hydration number measured by Differential Scanning Calorimeter. After introducing SDS, the number of bound water (n) decreases due to the interaction between SDS and PVA. However, n almost keeps constant when csur > CMCP. The viscous activation energy also shows a similar change. When csur is much larger, the micelles formed by SDS in water are conducive to the formation of physical cross-linking network, which contribute more to the solution elasticity, leading to the increase of G′ (greater than that of dynamic loss modulus). Compared with the dilute solution, SDS has a greater viscosity reduction effect on the PVA semi-dilute solution.
2020, 51(4): 411-420
doi: 10.11777/j.issn1000-3304.2019.19184
Abstract:
The strong adhesion between the rubber and the skeleton material determines the performance of the tire. Most of the damage such as puncture, fatigue, and delamination of the tire are caused by the failure of the adhesion between the rubber and the skeleton material. The adhesion of the material is directly related to the performance and life of the tire. In order to verify and further explore the mechanism of adhesion of the adhesive resin and cobalt salt to the tire and the copper-plated steel cord, the conventional adhesive resin R80 and two new adhesive resins HT1005 and H620 were selected to analyze the mechanism of adhesion through structural analysis, rubber vulcanization characteristics, T extraction test, a new adhesive layer strength test method and adhesive layer characterization method. The results show that the polar adhesive resin containing hydroxyl groups will be auto-phase-separated due to thermodynamic incompatibility with the polarity difference of non-polar natural rubber when vulcanized. The adhesive resin migrates to the interface layer between the rubber and the copper-plated steel wire, producing a resin-rich layer between the rubber and the copper-plated steel wire. Since the crosslinking temperature of the binder resin is about 140 °C, synchronous crosslinking reaction will occur in natural rubber vulcanization reaction. The network modulus of the binder resin is higher than that of the rubber vulcanization network, which will enhance the adhesion strength between the copper-plated steel wire and the rubber, and form a modulus transition layer between the copper-plated steel wire and the rubber. A modulus transition layer between the rubber and the rubber further enhances the adhesive layer.
The strong adhesion between the rubber and the skeleton material determines the performance of the tire. Most of the damage such as puncture, fatigue, and delamination of the tire are caused by the failure of the adhesion between the rubber and the skeleton material. The adhesion of the material is directly related to the performance and life of the tire. In order to verify and further explore the mechanism of adhesion of the adhesive resin and cobalt salt to the tire and the copper-plated steel cord, the conventional adhesive resin R80 and two new adhesive resins HT1005 and H620 were selected to analyze the mechanism of adhesion through structural analysis, rubber vulcanization characteristics, T extraction test, a new adhesive layer strength test method and adhesive layer characterization method. The results show that the polar adhesive resin containing hydroxyl groups will be auto-phase-separated due to thermodynamic incompatibility with the polarity difference of non-polar natural rubber when vulcanized. The adhesive resin migrates to the interface layer between the rubber and the copper-plated steel wire, producing a resin-rich layer between the rubber and the copper-plated steel wire. Since the crosslinking temperature of the binder resin is about 140 °C, synchronous crosslinking reaction will occur in natural rubber vulcanization reaction. The network modulus of the binder resin is higher than that of the rubber vulcanization network, which will enhance the adhesion strength between the copper-plated steel wire and the rubber, and form a modulus transition layer between the copper-plated steel wire and the rubber. A modulus transition layer between the rubber and the rubber further enhances the adhesive layer.
