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2019 Volume 50 Issue 3
2019, 50(3):
Abstract:
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2019, 50(3): 199-208
doi: 10.11777/j.issn1000-3304.2019.18191
Abstract:
With the rapid development of modern organic chemistry and polymer chemistry, a variety of highly efficient and controllable synthetic methods have been discovered and applied extensively, such as click chemistry, atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, and ring-opening metathesis polymerization. Their comprehensive application has realized the controlled preparation of unimolecular polymer nanomaterials with well-designed topological structures, including cyclodextrane polyrotaxanes, dendrimers, multiarm star-shaped polymers, wormlike polymer brushes, etc. Functioning as probes and drug carriers for disease diagnoses and treatments, respectively, these specifically fabricated materials are featured with such advantages as high designability, controllability, and stability of chemical structures, favorable reproducibility of pharmacokinetic and pharmacological profiles, great abundancy in reactive groups for multiple functionalization, and desirable ability to covalent-combine drugs for responsive targeted drug release. The highly controllable chemical structures of these unimolecular polymer nanomaterials make them the most suitable objects for studying the relationship between chemical and morphological structures and biological performance. Herein, the recent progress of our group is introduced, with specific focuses on the preparation of unimolecular polymer nanomaterials through controllable synthetic strategies, the precise control of their chemical structures and sizes, and the effect of their chemical structures and sizes on their in vitro and in vivo biological performance. The objectives of our research include cyclodextrane polyrotaxanes, dendrimers, multiarm star-shaped polymers, and wormlike polymer brushes, and their sizes range from several nanometers to dozens of nanometers. Based on our experiments, some important conclusions have been drawn as follows. Within the dimensional range between ten nanometers and dozens of nanometers, the size reduction of such nanomaterials favors higher cellular uptake, shorter blood circulation, as well as higher tumor accumulation and penetration. Besides, the nanomaterials with zwitterionic poly(carboxybetaine) (PCB) surface exhibit higher cellular uptake, longer blood circulation, and higher tumor accumulation and penetration than those with the poly(ethylene glycol) (PEG) surface do thanks to the surface-tethered phenylboronic acid groups. These results can be much conducive to the design of polymer nanocarriers for tumor diagnosis and therapy.
With the rapid development of modern organic chemistry and polymer chemistry, a variety of highly efficient and controllable synthetic methods have been discovered and applied extensively, such as click chemistry, atom transfer radical polymerization, reversible addition-fragmentation chain transfer polymerization, and ring-opening metathesis polymerization. Their comprehensive application has realized the controlled preparation of unimolecular polymer nanomaterials with well-designed topological structures, including cyclodextrane polyrotaxanes, dendrimers, multiarm star-shaped polymers, wormlike polymer brushes, etc. Functioning as probes and drug carriers for disease diagnoses and treatments, respectively, these specifically fabricated materials are featured with such advantages as high designability, controllability, and stability of chemical structures, favorable reproducibility of pharmacokinetic and pharmacological profiles, great abundancy in reactive groups for multiple functionalization, and desirable ability to covalent-combine drugs for responsive targeted drug release. The highly controllable chemical structures of these unimolecular polymer nanomaterials make them the most suitable objects for studying the relationship between chemical and morphological structures and biological performance. Herein, the recent progress of our group is introduced, with specific focuses on the preparation of unimolecular polymer nanomaterials through controllable synthetic strategies, the precise control of their chemical structures and sizes, and the effect of their chemical structures and sizes on their in vitro and in vivo biological performance. The objectives of our research include cyclodextrane polyrotaxanes, dendrimers, multiarm star-shaped polymers, and wormlike polymer brushes, and their sizes range from several nanometers to dozens of nanometers. Based on our experiments, some important conclusions have been drawn as follows. Within the dimensional range between ten nanometers and dozens of nanometers, the size reduction of such nanomaterials favors higher cellular uptake, shorter blood circulation, as well as higher tumor accumulation and penetration. Besides, the nanomaterials with zwitterionic poly(carboxybetaine) (PCB) surface exhibit higher cellular uptake, longer blood circulation, and higher tumor accumulation and penetration than those with the poly(ethylene glycol) (PEG) surface do thanks to the surface-tethered phenylboronic acid groups. These results can be much conducive to the design of polymer nanocarriers for tumor diagnosis and therapy.
2019, 50(3): 209-218
doi: 10.11777/j.issn1000-3304.2019.18212
Abstract:
Bulk-heterojunction (BHJ) structures that comprise donor and acceptor blended physically in photoactive layers are proved very promising for applications in organic solar cells, of which a power conversion efficiency (PCE) of 15% has already been achieved in single-junction devices. However, their nanophase separation is susceptible to heat and light and hence lower the stability of solar cells during long-term service. To this end, single-component organic solar cells (SCOSCs) are developed as potential alternatives with better photovoltaic stability. Double-cable conjugated polymers, which consist of electron-rich conjugated backbone and electron-deficient conjugated side chains, can be applied into SCOSCs by forming BHJ structures in a single conjugated polymer. Relevant research on double-cable conjugated polymers and SCOSCs has rarely been reported in the past years and their PCEs lagged far behind those of the BHJ solar cells. Herein, we first provide a general review on the research progress of SCOSCs and then center the discussion on some recent findings in our group about double-cable conjugated polymers, including the development of new synthetic methods, the design ideas for novel double-cable polymers composed of varied conjugated backbones with conjugated side chains and linkers, the tuning approaches toward nanophase separation in double-cable polymers, and the ultimate applications in SCOSCs. Given the existing studies, we believe that SCOSCs based on double-cable polymers will receive more attention and advance further with higher PCEs in the near future.
Bulk-heterojunction (BHJ) structures that comprise donor and acceptor blended physically in photoactive layers are proved very promising for applications in organic solar cells, of which a power conversion efficiency (PCE) of 15% has already been achieved in single-junction devices. However, their nanophase separation is susceptible to heat and light and hence lower the stability of solar cells during long-term service. To this end, single-component organic solar cells (SCOSCs) are developed as potential alternatives with better photovoltaic stability. Double-cable conjugated polymers, which consist of electron-rich conjugated backbone and electron-deficient conjugated side chains, can be applied into SCOSCs by forming BHJ structures in a single conjugated polymer. Relevant research on double-cable conjugated polymers and SCOSCs has rarely been reported in the past years and their PCEs lagged far behind those of the BHJ solar cells. Herein, we first provide a general review on the research progress of SCOSCs and then center the discussion on some recent findings in our group about double-cable conjugated polymers, including the development of new synthetic methods, the design ideas for novel double-cable polymers composed of varied conjugated backbones with conjugated side chains and linkers, the tuning approaches toward nanophase separation in double-cable polymers, and the ultimate applications in SCOSCs. Given the existing studies, we believe that SCOSCs based on double-cable polymers will receive more attention and advance further with higher PCEs in the near future.
2019, 50(3): 219-232
doi: 10.11777/j.issn1000-3304.2019.18222
Abstract:
A carbon sheet with single-atom thickness, graphene is unique for its nature in two-dimensional polymers (2DP). Recently, three-dimensional (3D) graphene architecture assembled from flexible 2D graphene via non-covalent interaction has attracted great attention, for the collective interaction between graphene sheets enables various functional advances while having the intrinsic properties of individual sheet well preserved. Typical macrostructures of 3D graphene involve hierarchical porosity, large specific surface area, superior mechanical strength, and excellent electrical conductivity, which endow this emerging material with great potential in catalytic, environmental, biomedical, and to the upmost importance, energy-related applications. Ever-growing concerns caused by fossil fuels about sustainability and environmental issues have urged extensive research on high-performance materials for electrochemical energy storage and conversion. Taking advantage of the controlled synthesis of novel electrochemically active nanomaterials and their efficient integration with 3D graphene framework, our group is innovatively developed several versatile strategies and successfully fabricated a series of 3D graphene composites. Carrying elaborate microstructures and synergistic effect, as-obtained materials demonstrate outstanding electrochemical performance when employed in flexible electrodes and devices such as supercapacitors, lithium/sodium-ion batteries, lithium-sulfur batteries, and electrocatalysts. Our studies have been decently recognized as effective solutions to address the impending energy problems. Meanwhile, the natural 2DP attribute of graphene has aroused great enthusiasm for rational organic synthesis of new 2DPs at the atomic or molecular level. The controllable synthesis of 2DPs with tailored molecular structure and excellent processability can promote immensely the progress of polymer synthetic chemistry. Further, it exhibits vast strength in the development of novel polymeric materials that hold desirable properties and functions rare in conventional one-dimensional polymers. Since it is challenging but meaningful in the energy arene to design and synthesize 2DPs that integrate simultaneously 2D conjugated plane, in-plane uniform micropores, and electrochemical active groups. This feature article summarizes the synthesis of 3D graphene-based composites and 2DPs progressed in our group, followed by their applications in energy storage and conversion. The contribution ends with brief discussions and outlook about the future challenges and opportunities of graphene materials and relevant research field.
A carbon sheet with single-atom thickness, graphene is unique for its nature in two-dimensional polymers (2DP). Recently, three-dimensional (3D) graphene architecture assembled from flexible 2D graphene via non-covalent interaction has attracted great attention, for the collective interaction between graphene sheets enables various functional advances while having the intrinsic properties of individual sheet well preserved. Typical macrostructures of 3D graphene involve hierarchical porosity, large specific surface area, superior mechanical strength, and excellent electrical conductivity, which endow this emerging material with great potential in catalytic, environmental, biomedical, and to the upmost importance, energy-related applications. Ever-growing concerns caused by fossil fuels about sustainability and environmental issues have urged extensive research on high-performance materials for electrochemical energy storage and conversion. Taking advantage of the controlled synthesis of novel electrochemically active nanomaterials and their efficient integration with 3D graphene framework, our group is innovatively developed several versatile strategies and successfully fabricated a series of 3D graphene composites. Carrying elaborate microstructures and synergistic effect, as-obtained materials demonstrate outstanding electrochemical performance when employed in flexible electrodes and devices such as supercapacitors, lithium/sodium-ion batteries, lithium-sulfur batteries, and electrocatalysts. Our studies have been decently recognized as effective solutions to address the impending energy problems. Meanwhile, the natural 2DP attribute of graphene has aroused great enthusiasm for rational organic synthesis of new 2DPs at the atomic or molecular level. The controllable synthesis of 2DPs with tailored molecular structure and excellent processability can promote immensely the progress of polymer synthetic chemistry. Further, it exhibits vast strength in the development of novel polymeric materials that hold desirable properties and functions rare in conventional one-dimensional polymers. Since it is challenging but meaningful in the energy arene to design and synthesize 2DPs that integrate simultaneously 2D conjugated plane, in-plane uniform micropores, and electrochemical active groups. This feature article summarizes the synthesis of 3D graphene-based composites and 2DPs progressed in our group, followed by their applications in energy storage and conversion. The contribution ends with brief discussions and outlook about the future challenges and opportunities of graphene materials and relevant research field.
2019, 50(3): 233-246
doi: 10.11777/j.issn1000-3304.2019.18269
Abstract:
The field of the " frustrated Lewis pair” (FLP) chemistry has been receiving sustained intense interests ever since the seminal work reported by Stephan and Erker. On the one hand, the application of FLPs has now been well established in the small molecule chemistry, such as the activation of small molecules, catalytic hydrogenation reactions, and new reactivity/reaction developments. On the other hand, Lewis pair polymerization (LPP) has emerged as the hotspot and frontier of polymer synthesis and generated some exciting results in polymer synthesis, especially in the polymerization of various polar vinyl monomers. Although the polymerization promoted by LPs, either FLPs or classical Lewis adducts (CLAs), exhibited high activity for polymerization of polar vinyl monomers, the application of such polymerization is hampered by both the low initiation efficiencies and chain-termination side reactions, evidenced by the much higher obtained number-average molecular weight (Mn) than the calculated Mn and broader molecular weight distribution (MWD, or large Đ values) of the resulting polymers, thus giving rise to low initiation efficiencies (I*) and rendering the inability to produce well-defined block copolymers. Therefore, it remains as a challenge to achieve the living polymerization of polar vinyl monomers by a non-interacting, true FLP, or LP-promoted living polymerization of less bulky methacrylates, particularly methyl methacrylate (MMA), a very important fundamental monomer in the polymer industry. Herein, we summarized the recent developments achieved in the polar vinyl monomer polymerization by LPP since the first successful polymerization catalyzed by LP in 2010, including the scopes of monomers, investigation of reaction mechanism, and different polymerization catalyst systems based on classic Lewis acid-base adduct (CLA) or FLP. These results indicated that the synergistic effects of the LA and LB sites of LPs were essential to achieve an effective and controllable polymerization system. By choosing appropriate combination of Lewis acid and Lewis base, not only the living polymerization of polar vinyl monomer could be achieved, but also the synthesis of ultrahigh molecular weight polymer with Mn > 106 g mol−1 and narrow MWD was obtained through this FLP polymerization strategy. Last but not least, with the aim to push forward the studies on LPP, more attention should be paid by chemists from but not limited to the field of frustrated Lewis pairs chemistry for the developing and enriching polymer synthesis by LPP.
The field of the " frustrated Lewis pair” (FLP) chemistry has been receiving sustained intense interests ever since the seminal work reported by Stephan and Erker. On the one hand, the application of FLPs has now been well established in the small molecule chemistry, such as the activation of small molecules, catalytic hydrogenation reactions, and new reactivity/reaction developments. On the other hand, Lewis pair polymerization (LPP) has emerged as the hotspot and frontier of polymer synthesis and generated some exciting results in polymer synthesis, especially in the polymerization of various polar vinyl monomers. Although the polymerization promoted by LPs, either FLPs or classical Lewis adducts (CLAs), exhibited high activity for polymerization of polar vinyl monomers, the application of such polymerization is hampered by both the low initiation efficiencies and chain-termination side reactions, evidenced by the much higher obtained number-average molecular weight (Mn) than the calculated Mn and broader molecular weight distribution (MWD, or large Đ values) of the resulting polymers, thus giving rise to low initiation efficiencies (I*) and rendering the inability to produce well-defined block copolymers. Therefore, it remains as a challenge to achieve the living polymerization of polar vinyl monomers by a non-interacting, true FLP, or LP-promoted living polymerization of less bulky methacrylates, particularly methyl methacrylate (MMA), a very important fundamental monomer in the polymer industry. Herein, we summarized the recent developments achieved in the polar vinyl monomer polymerization by LPP since the first successful polymerization catalyzed by LP in 2010, including the scopes of monomers, investigation of reaction mechanism, and different polymerization catalyst systems based on classic Lewis acid-base adduct (CLA) or FLP. These results indicated that the synergistic effects of the LA and LB sites of LPs were essential to achieve an effective and controllable polymerization system. By choosing appropriate combination of Lewis acid and Lewis base, not only the living polymerization of polar vinyl monomer could be achieved, but also the synthesis of ultrahigh molecular weight polymer with Mn > 106 g mol−1 and narrow MWD was obtained through this FLP polymerization strategy. Last but not least, with the aim to push forward the studies on LPP, more attention should be paid by chemists from but not limited to the field of frustrated Lewis pairs chemistry for the developing and enriching polymer synthesis by LPP.
2019, 50(3): 247-260
doi: 10.11777/j.issn1000-3304.2019.18237
Abstract:
Mechanically adaptive polymers (MAPs) can regulate their mechanical properties in response to external stimuli or environmental changes, such as pressure, temperature, humidity, etc. In recent years, mechanically adaptive electronic polymers (MAEPs), which integrate delicate electronic functions together with mechanical adaptive properties, are expected to play important roles in such fields as wearable electronics, biomedical devices, and energy storage systems. This new type of polymer materials have attracted growing attention from both academia and industry. In this review article, a brief introduction is firstly given to mechanically adaptive electronic polymers, and several representative works in the related research field are described in the following, with specific focuses on the design principles, synthetic/preparation routes, and potential applications of these emerging polymeric materials. The key principle of MAEPs design sits in the combination of molecular chemistry and supramolecular chemistry, for it functions essentially in tuning the polymer structure and properties on a molecular level. When dynamic bonds (e.g. hydrogen bond, metal-ligand interaction, π-π stacking) are incorporated into the polymer system with electronic active units, products obtained will possess simultaneously the required electronic functions and adaptive mechanics properties. Generally, MAEPs fall into two major categories according to their working mechanisms, namely, self-healing electronic polymers and energy dissipating polymers. Elaborate material designs have realized a variety of successful demonstrations for both mechanically adaptive electrical conductors and mechanically adaptive ionic conductors. The booming of mechanically adaptive electronic polymers is expected to bring new breakthroughs in the area of wearable electronics, energy storage devices, and artificial muscles, etc. Challenges and outlook in this burgeoning area are discussed in the end. Enormous challenges still remain despite the significant advances have made already. For instance, the polymer performance requires further improvement for practical applications. Meanwhile, new polymer structures, novel synthetic methods, and innovative design strategies are also desired for the development of MAEPs.
Mechanically adaptive polymers (MAPs) can regulate their mechanical properties in response to external stimuli or environmental changes, such as pressure, temperature, humidity, etc. In recent years, mechanically adaptive electronic polymers (MAEPs), which integrate delicate electronic functions together with mechanical adaptive properties, are expected to play important roles in such fields as wearable electronics, biomedical devices, and energy storage systems. This new type of polymer materials have attracted growing attention from both academia and industry. In this review article, a brief introduction is firstly given to mechanically adaptive electronic polymers, and several representative works in the related research field are described in the following, with specific focuses on the design principles, synthetic/preparation routes, and potential applications of these emerging polymeric materials. The key principle of MAEPs design sits in the combination of molecular chemistry and supramolecular chemistry, for it functions essentially in tuning the polymer structure and properties on a molecular level. When dynamic bonds (e.g. hydrogen bond, metal-ligand interaction, π-π stacking) are incorporated into the polymer system with electronic active units, products obtained will possess simultaneously the required electronic functions and adaptive mechanics properties. Generally, MAEPs fall into two major categories according to their working mechanisms, namely, self-healing electronic polymers and energy dissipating polymers. Elaborate material designs have realized a variety of successful demonstrations for both mechanically adaptive electrical conductors and mechanically adaptive ionic conductors. The booming of mechanically adaptive electronic polymers is expected to bring new breakthroughs in the area of wearable electronics, energy storage devices, and artificial muscles, etc. Challenges and outlook in this burgeoning area are discussed in the end. Enormous challenges still remain despite the significant advances have made already. For instance, the polymer performance requires further improvement for practical applications. Meanwhile, new polymer structures, novel synthetic methods, and innovative design strategies are also desired for the development of MAEPs.
2019, 50(3): 261-270
doi: 10.11777/j.issn1000-3304.2019.18201
Abstract:
The development of high-performance polymers using bio-renewable feedstocks will promote a sustainable society. However, it remains a challenge to fabricate polyimides rich in bio-based component while high in heat resistance. In this work, three types of bio-based dianhydrides were synthesized using bio-renewable creosol as the raw material, which were then applied for preparing three series of polyimides via polycondensation with petroleum- or bio-based diamines. The molecular weights of these bio-based polyimides were in the range of 14 – 233 kg mol−1. The inherent viscosity of these polymers spanned a range 0.4 – 2.06 dL g−1. Most of the polyimides were soluble in common organic solvents, and flexible films could be readily cast from their solutions. The bio-based contents of these polymers ranged from 31.8% to 56.4%. The temperatures at 5% weight loss (T5%) and the glass transition temperatures (Tg) of bio-based polyetherimides (PI-I and PI-II series) were 406 – 453 °C and 213 – 235 °C, respectively, while PI-III series containing dioxin segments exhibited a T5% at 490 – 508 °C and Tg at 378 – 424 °C due to the existence of fused aromatic rings. The tensile strength, modulus, and elongation at break of these polyimides were 70 – 115 MPa, 1.80 – 2.8 GPa, and 3.5% – 20.4%, respectively. The above mentioned results indicated comparable thermal and mechanical properties between the bio-based polyimies in this study and those made from petroleum-based monomers, such as Ultem® and Kapton®. Due to an excellent combination of high bio-based contents and outstanding thermal and mechanical properties, these polyimides showed great potential in various applications as films and engineering plastics, replacing petroleum-based polyimides.
The development of high-performance polymers using bio-renewable feedstocks will promote a sustainable society. However, it remains a challenge to fabricate polyimides rich in bio-based component while high in heat resistance. In this work, three types of bio-based dianhydrides were synthesized using bio-renewable creosol as the raw material, which were then applied for preparing three series of polyimides via polycondensation with petroleum- or bio-based diamines. The molecular weights of these bio-based polyimides were in the range of 14 – 233 kg mol−1. The inherent viscosity of these polymers spanned a range 0.4 – 2.06 dL g−1. Most of the polyimides were soluble in common organic solvents, and flexible films could be readily cast from their solutions. The bio-based contents of these polymers ranged from 31.8% to 56.4%. The temperatures at 5% weight loss (T5%) and the glass transition temperatures (Tg) of bio-based polyetherimides (PI-I and PI-II series) were 406 – 453 °C and 213 – 235 °C, respectively, while PI-III series containing dioxin segments exhibited a T5% at 490 – 508 °C and Tg at 378 – 424 °C due to the existence of fused aromatic rings. The tensile strength, modulus, and elongation at break of these polyimides were 70 – 115 MPa, 1.80 – 2.8 GPa, and 3.5% – 20.4%, respectively. The above mentioned results indicated comparable thermal and mechanical properties between the bio-based polyimies in this study and those made from petroleum-based monomers, such as Ultem® and Kapton®. Due to an excellent combination of high bio-based contents and outstanding thermal and mechanical properties, these polyimides showed great potential in various applications as films and engineering plastics, replacing petroleum-based polyimides.
2019, 50(3): 271-280
doi: 10.11777/j.issn1000-3304.2019.18213
Abstract:
Recently, photonic crystals with short-range ordered structures have aroused extensive interest in scientific research owing to their structural color independent of angle variation. This unique property sets mateirals free from the angle-dependent color variation and plays a critical role in the practical applications involving color observation. However, such fascinating applications may be undesirably compromised by the poor durability of photonic crystals due to their delicate structures. In this study, we developed a series of polyborosiloxane-based photonic elastomers that possessed angle-independent structural color and self-healing capability. Specifically, hydroxyl-terminated poly(dimethylsiloxane) (Hydroxyl-PDMS) was reacted with boric acid (BA) by forming reversible dynamic covalent bonds, dative bonds, and hydrogen bonds, and as-obtained polyborosiloxane (PBS) elastomers were further incorporated with isotropically arranged SiO2 nanoparticles (NPs) and carbon black NPs. Optical properties of the photonic elastomers were characterized by reflection spectroscopy at varied detection angles, and angle independence was found for structural colors. Futhermore, the structural color of these elastomers could be tuned by simply adjusting the size or loading fraction of the SiO2 NPs in elastomers. The mateirals obtained had a Young’s modulus up to ~200 kPa and also exhibited mechanochromic behavior thanks to the good flexibility of polymeric matrix. Moreover, the intriguing combination of flexibility with reversible bonding endowed the photonic elastomers with a rapid self-healing ability towards superficial scratches or cuts at room temperature, which in turn afforded the necessary durabilities both optically and mechanically. In addition, since photonic elastomer films with a large area could be readily fabricated through a simple spray-coating process, the materials developed have shown great prospects for applications in color-coating, displaying, sensing, and printing.
Recently, photonic crystals with short-range ordered structures have aroused extensive interest in scientific research owing to their structural color independent of angle variation. This unique property sets mateirals free from the angle-dependent color variation and plays a critical role in the practical applications involving color observation. However, such fascinating applications may be undesirably compromised by the poor durability of photonic crystals due to their delicate structures. In this study, we developed a series of polyborosiloxane-based photonic elastomers that possessed angle-independent structural color and self-healing capability. Specifically, hydroxyl-terminated poly(dimethylsiloxane) (Hydroxyl-PDMS) was reacted with boric acid (BA) by forming reversible dynamic covalent bonds, dative bonds, and hydrogen bonds, and as-obtained polyborosiloxane (PBS) elastomers were further incorporated with isotropically arranged SiO2 nanoparticles (NPs) and carbon black NPs. Optical properties of the photonic elastomers were characterized by reflection spectroscopy at varied detection angles, and angle independence was found for structural colors. Futhermore, the structural color of these elastomers could be tuned by simply adjusting the size or loading fraction of the SiO2 NPs in elastomers. The mateirals obtained had a Young’s modulus up to ~200 kPa and also exhibited mechanochromic behavior thanks to the good flexibility of polymeric matrix. Moreover, the intriguing combination of flexibility with reversible bonding endowed the photonic elastomers with a rapid self-healing ability towards superficial scratches or cuts at room temperature, which in turn afforded the necessary durabilities both optically and mechanically. In addition, since photonic elastomer films with a large area could be readily fabricated through a simple spray-coating process, the materials developed have shown great prospects for applications in color-coating, displaying, sensing, and printing.
2019, 50(3): 281-290
doi: 10.11777/j.issn1000-3304.2019.18218
Abstract:
Anodic aluminum oxide (AAO) templates with parallel aligned nanochannels provide an ideal scenario for constructing the one-dimensional (1D) nanoconfinement environment. In recent years, while many studies have been conducted on the orientation of crystalline polymers in AAO, a universal model is still absent for explaining the diverse or even contradictory observations in different polymer systems and further understanding the complicated evolution of orientation upon changing the crystallization conditions. In this work, the texture of isotactic polypropylene (iPP) in AAO template was studied by X-ray pole figure analysis, with two major modes of uniaxial orientation, b* or a*║\begin{document}${\vec{{n}}}$\end{document} ![]()
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Anodic aluminum oxide (AAO) templates with parallel aligned nanochannels provide an ideal scenario for constructing the one-dimensional (1D) nanoconfinement environment. In recent years, while many studies have been conducted on the orientation of crystalline polymers in AAO, a universal model is still absent for explaining the diverse or even contradictory observations in different polymer systems and further understanding the complicated evolution of orientation upon changing the crystallization conditions. In this work, the texture of isotactic polypropylene (iPP) in AAO template was studied by X-ray pole figure analysis, with two major modes of uniaxial orientation, b* or a*║
2019, 50(3): 291-299
doi: 10.11777/j.issn1000-3304.2019.18219
Abstract:
Cyclic topology exerts significant effects on the properties and potential applications of polymers; however, the precisely controlled systhesis of cyclic diblock copolymers remains challenging. In this study, we reported a novel and versatile synthetic strategy toward cyclic diblock copolymers by using the linear polymer precursors generated from reversible addition-fragmentation transfer (RAFT) polymerization. Key innovation of the technique proposed lies in the facile and complete conversion of terminal RAFT groups on linear polymers into clickable alkyne groups via a one-pot aminolysis/Michael addition reaction, which laid a foundation for subsequent intrachain Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAc) on the linear α-alkyne-ω-azide preursors. Full decoration of the RAFT termini was confirmed by Ellman study. Specifically, a cyclic double hydrophilic block copolymer (DHBC), poly(N-isopropylacrylamide)-b-poly(oligo(ethylene glycol) monomethyl ether methacrylate) (c-(PNIPAAm-b-POEGMA)), with thermo-responsiveness was synthesized following this approach successfully as confirmed by 1H-NMR, 13C-NMR, FTIR, and SEC-MALLS analyses. Thermo-induced phase transitions and self-assembly behaviors of the resulting cyclic DHBCs were then investigated by the combined analytical techniques of UV-Vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), and further compared with those of the linear analogues. Intriguingly, the cyclic thermo-sensitive DHBCs exhibited a lower critical solution temparature (LCST, 41.5 °C) significantly higher than the linear counterparts (39 °C), for POEGMA moiety with two block juntions in the cyclic copolymers could raise the LCST of PNIPAAm segment. More importantly, the spherical micelles self-assembled from cyclic DHBCs above LCST were smaller in size and narrower in size distribution compared with the ones derived from linear analogues, which resulted most likely from a more restricted cyclic topology. This study therefore developed an efficient alternative synthetic method for cyclic diblock copolymers and meanwhile provided new insights into the structure-property relationships of cyclic DHBCs.
Cyclic topology exerts significant effects on the properties and potential applications of polymers; however, the precisely controlled systhesis of cyclic diblock copolymers remains challenging. In this study, we reported a novel and versatile synthetic strategy toward cyclic diblock copolymers by using the linear polymer precursors generated from reversible addition-fragmentation transfer (RAFT) polymerization. Key innovation of the technique proposed lies in the facile and complete conversion of terminal RAFT groups on linear polymers into clickable alkyne groups via a one-pot aminolysis/Michael addition reaction, which laid a foundation for subsequent intrachain Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAc) on the linear α-alkyne-ω-azide preursors. Full decoration of the RAFT termini was confirmed by Ellman study. Specifically, a cyclic double hydrophilic block copolymer (DHBC), poly(N-isopropylacrylamide)-b-poly(oligo(ethylene glycol) monomethyl ether methacrylate) (c-(PNIPAAm-b-POEGMA)), with thermo-responsiveness was synthesized following this approach successfully as confirmed by 1H-NMR, 13C-NMR, FTIR, and SEC-MALLS analyses. Thermo-induced phase transitions and self-assembly behaviors of the resulting cyclic DHBCs were then investigated by the combined analytical techniques of UV-Vis spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM), and further compared with those of the linear analogues. Intriguingly, the cyclic thermo-sensitive DHBCs exhibited a lower critical solution temparature (LCST, 41.5 °C) significantly higher than the linear counterparts (39 °C), for POEGMA moiety with two block juntions in the cyclic copolymers could raise the LCST of PNIPAAm segment. More importantly, the spherical micelles self-assembled from cyclic DHBCs above LCST were smaller in size and narrower in size distribution compared with the ones derived from linear analogues, which resulted most likely from a more restricted cyclic topology. This study therefore developed an efficient alternative synthetic method for cyclic diblock copolymers and meanwhile provided new insights into the structure-property relationships of cyclic DHBCs.
2019, 50(3): 300-310
doi: 10.11777/j.issn1000-3304.2019.18220
Abstract:
Microbes with the biofilm mode of growth are highly resistant against antibiotics partially due to the ineffective antibiotic penetration to the depth of a biofilm where the bacteria reside and proliferate. To enhance the penetration of antibiotics, we herein demonstrated a delivery nanocapsule that could deliver antibiotics deeply into the deep layer of the biofilm and release the antibiotics inside. The delivery nanocapsule performs a core-shell structure. The core is formed via nanoprecipitation with two different types of antibiotics in the presence of an acid-liable polymer, which allows the effective release of the antibiotics in response to the acidic environment when reaching the deep layer of the biofilm. The shell of the delivery nanocapsule is synthesized by co-polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-(3-Aminopropyl) methacrylamide hydrochloride (APM) to form a cationic and protein adsorption-resistant film encapsulating around the core. Such a core-shell structure could effectively reduce the diffusion resistance of the delivery nanocapsule into the biofilm, resulting in an enhanced penetration capability. Confocal laser scanning macroscopy (CLSM) imaging demonstrated that the nanocapsule could efficiently penetrate into the mature biofilms formed by S. aureus ATCC12600GFP. Moreover, such nanocapsules could load multiple drugs simultaneously, allowing the spontaneously co-delivery of various types of antibiotics into the biofilm. Exemplified with piperacillin and tazobactam, the co-delivery of the two types of antibiotics with the nanocapsule resulted in the synergetic therapeutic effect on the β-lactam resistance bacteria of S. aureus ATCC43300, achieving an efficient eradication of the bacteria embedded in the biofilm. In conclusion, the nanocapsule-based delivery system assisted with antibiotics in penetrating into the deep layer of biofilm and released the antibiotics in response to the acidic environment of the biofilm. Compared to directly applying antibiotics to the biofilm, the delivery of antibiotics with the nanocapsule exhibited more effective penetration and accumulation deeply inside the layer, achieving a more efficient eradication of the residual bacteria in the biofilm.
Microbes with the biofilm mode of growth are highly resistant against antibiotics partially due to the ineffective antibiotic penetration to the depth of a biofilm where the bacteria reside and proliferate. To enhance the penetration of antibiotics, we herein demonstrated a delivery nanocapsule that could deliver antibiotics deeply into the deep layer of the biofilm and release the antibiotics inside. The delivery nanocapsule performs a core-shell structure. The core is formed via nanoprecipitation with two different types of antibiotics in the presence of an acid-liable polymer, which allows the effective release of the antibiotics in response to the acidic environment when reaching the deep layer of the biofilm. The shell of the delivery nanocapsule is synthesized by co-polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-(3-Aminopropyl) methacrylamide hydrochloride (APM) to form a cationic and protein adsorption-resistant film encapsulating around the core. Such a core-shell structure could effectively reduce the diffusion resistance of the delivery nanocapsule into the biofilm, resulting in an enhanced penetration capability. Confocal laser scanning macroscopy (CLSM) imaging demonstrated that the nanocapsule could efficiently penetrate into the mature biofilms formed by S. aureus ATCC12600GFP. Moreover, such nanocapsules could load multiple drugs simultaneously, allowing the spontaneously co-delivery of various types of antibiotics into the biofilm. Exemplified with piperacillin and tazobactam, the co-delivery of the two types of antibiotics with the nanocapsule resulted in the synergetic therapeutic effect on the β-lactam resistance bacteria of S. aureus ATCC43300, achieving an efficient eradication of the bacteria embedded in the biofilm. In conclusion, the nanocapsule-based delivery system assisted with antibiotics in penetrating into the deep layer of biofilm and released the antibiotics in response to the acidic environment of the biofilm. Compared to directly applying antibiotics to the biofilm, the delivery of antibiotics with the nanocapsule exhibited more effective penetration and accumulation deeply inside the layer, achieving a more efficient eradication of the residual bacteria in the biofilm.
2019, 50(3): 311-318
doi: 10.11777/j.issn1000-3304.2019.18229
Abstract:
Thermal transition temperatures (e.g. glass transition temperatures) play an important role in various applications of shape memory polymers that can recover from temporary shapes to original (permanent) shapes upon heating. This study reports a shape memory epoxy with unsaturated double bonds, enabling a secondary photocuring process. Dual-functional epoxy monomer, E44, and monofunctional epoxy monomer, glycidyl methacrylate, are first thermally cured via a polyether amine crosslinker. Properties of the cured epoxy can be finely tuned by controlling the feed compositions. The increase of feed ratio of glycidyl methacrylate will lead to lower glass transition temperature and elastic modulus, whereas larger strain at break. In the secondary photocuring process, the unsaturated bonds provided by glycidyl methacrylate are polymerized after light exposure, forming additional crosslinking points. As a result, the glass transition temperature of the material increases. Herein, digital photo-masking technique is applied for the photocuring process via a commercial projector. The regional exposure time of the material can be conducted, and thus, the local glass transition temperature can be controlled in a range of approximately 40 − 70 °C. Storage modulus at the rubbery state of the material increases from approximately 0.5 MPa to 8 MPa after photo exposure for 240 s, implying that there is a remarkable increase of the crosslinking density via the secondary photocuring. Both the materials before and after the secondary photocuring provide ideal shape memory performance. The shape fixity ratios and shape recovery ratios retain nearly 100% during six shape memory cycles, indicating good thermo-mechanical stability of the material. The material with regional controllable glass transition temperature enables a programmable multi-shape recovery process. Complex original shapes can be fabricated if the secondary photocuring is conducted towards a thermally cured epoxy. In addition, the material can be potentially applied as a novel substrate for stretchable electronics due to its strain isolation functionality.
Thermal transition temperatures (e.g. glass transition temperatures) play an important role in various applications of shape memory polymers that can recover from temporary shapes to original (permanent) shapes upon heating. This study reports a shape memory epoxy with unsaturated double bonds, enabling a secondary photocuring process. Dual-functional epoxy monomer, E44, and monofunctional epoxy monomer, glycidyl methacrylate, are first thermally cured via a polyether amine crosslinker. Properties of the cured epoxy can be finely tuned by controlling the feed compositions. The increase of feed ratio of glycidyl methacrylate will lead to lower glass transition temperature and elastic modulus, whereas larger strain at break. In the secondary photocuring process, the unsaturated bonds provided by glycidyl methacrylate are polymerized after light exposure, forming additional crosslinking points. As a result, the glass transition temperature of the material increases. Herein, digital photo-masking technique is applied for the photocuring process via a commercial projector. The regional exposure time of the material can be conducted, and thus, the local glass transition temperature can be controlled in a range of approximately 40 − 70 °C. Storage modulus at the rubbery state of the material increases from approximately 0.5 MPa to 8 MPa after photo exposure for 240 s, implying that there is a remarkable increase of the crosslinking density via the secondary photocuring. Both the materials before and after the secondary photocuring provide ideal shape memory performance. The shape fixity ratios and shape recovery ratios retain nearly 100% during six shape memory cycles, indicating good thermo-mechanical stability of the material. The material with regional controllable glass transition temperature enables a programmable multi-shape recovery process. Complex original shapes can be fabricated if the secondary photocuring is conducted towards a thermally cured epoxy. In addition, the material can be potentially applied as a novel substrate for stretchable electronics due to its strain isolation functionality.
2019, 50(3): 319-326
doi: 10.11777/j.issn1000-3304.2019.18234
Abstract:
Breaking the out-of-plane symmetry of 2D materials, which results so-called janus 2D materials, will endow them different physical and chemical properties, and thus will further enrich their applications in different fields. In this work, we designed and fabricated a Janus single-layered covalent organic framework using an amphiphilic planar molecule (truxene), which having different chians at both sides, as monomer. This amphiphilic truxene derivative is prepared by functionalization at its three active methylene positions with hydrophilic and hydrophobic chains, respectively. Since methylene carbon is a sp3 carbon, the induced hydrophobic and hydryphilic chains are located perpendicular to the phenyl ring in truxene. After poly-condensation reaction with p-phenylenediamine at water/dichlormethane interface, a colorless membrane is formed. Fourier transform infrared spectroscopy (FTIR) spectra of the product indicated the almost complete consumption of the starting materials and the formation of imine bond. Transmission electron microscopy (TEM) images of the resulting membrane show that, the shape of product is a well-defined plate like nano-structure. Further investigation through atomic force microscopy (AFM) measurement confirmed the products from the interface consists of film with ~1 nm in thickness, corresponding to the thickness of a single-layered covalent organic framework. Due to the templating effect of water and oil interface, the hydrophilic and hydrophobic chains are orientated to water and oil phase during the poly-condensation reaction, respectively. After the formation of single layered COF, these chains are fixed at different surfaces of the resulting COF. As a consequence, the obtained COF possesses a single layered structure with two different surfaces, in another word, is a Janus covalent organic framework. Demonstrated by contact angle experiments, two surfaces of this Janus COF show different affinities to water droplets.
Breaking the out-of-plane symmetry of 2D materials, which results so-called janus 2D materials, will endow them different physical and chemical properties, and thus will further enrich their applications in different fields. In this work, we designed and fabricated a Janus single-layered covalent organic framework using an amphiphilic planar molecule (truxene), which having different chians at both sides, as monomer. This amphiphilic truxene derivative is prepared by functionalization at its three active methylene positions with hydrophilic and hydrophobic chains, respectively. Since methylene carbon is a sp3 carbon, the induced hydrophobic and hydryphilic chains are located perpendicular to the phenyl ring in truxene. After poly-condensation reaction with p-phenylenediamine at water/dichlormethane interface, a colorless membrane is formed. Fourier transform infrared spectroscopy (FTIR) spectra of the product indicated the almost complete consumption of the starting materials and the formation of imine bond. Transmission electron microscopy (TEM) images of the resulting membrane show that, the shape of product is a well-defined plate like nano-structure. Further investigation through atomic force microscopy (AFM) measurement confirmed the products from the interface consists of film with ~1 nm in thickness, corresponding to the thickness of a single-layered covalent organic framework. Due to the templating effect of water and oil interface, the hydrophilic and hydrophobic chains are orientated to water and oil phase during the poly-condensation reaction, respectively. After the formation of single layered COF, these chains are fixed at different surfaces of the resulting COF. As a consequence, the obtained COF possesses a single layered structure with two different surfaces, in another word, is a Janus covalent organic framework. Demonstrated by contact angle experiments, two surfaces of this Janus COF show different affinities to water droplets.
