最新刊期
卷 53 ， 期 8 ， 2022
- 摘要：Since the birth of synthetic polymers, researchers have usually constructed polymerization catalysts by the "trial and error" method based on their structural understanding of monomer and target polymer, which involves screening an active basic monomer unit followed by further optimization of the catalyst structure. Despite its remarkable success, this approach suffers from a lack of law resulting in a time-consuming and labor-intensive process. Recently, Wang and coworkers at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, proposed a strategy for constructing polymeric catalyst. This novle design strategy is based on regulating the side chain structures of polymers by copolymerizing the monomeric aluminum complex and cocatalyst into a polymer chain, which enables the connection of active units to the side chains. The resulting polymeric aluminum porphyrin catalysts are then utilized for the copolymerization of CO2/epoxides, hence successfully addressing the issues of low efficiency and selectivity of the monomeric catalyst. Distinct from the singlet intramolecular interactions in conventional catalysts, the polymeric catalysts strategy can realize multiple intramolecular synergistic effects, thereby enhancing the error tolerance of catalyst design. Benefiting from the adaptability of monomers and controllability of polymer structures, the polymeric catalyst is expected to be a rich ore worthy of further exploring in the field of polymer synthetic chemistry, serving as a building block to the treasury of knowledge of polymer science.关键词：Polymeric catalyst;Intramolecular synergistic effect;Aluminum porphyrin;Carbon dioxide;CO2 copolymer
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发布时间：2024-10-08
Research Highlight
- 摘要：Microneedle (MNs) is a new technology for transdermal drug delivery, which can penetrate the stratum corneum to form micropore channels and promote the penetration and absorption of drugs. Based on the structure and function properties of MNs, the structure and function design of polymer MNs are systematically described in this review. And the materials and methods for the fabrication of polymer MNs and their drug administration are discussed as well. The recent progresses of MNs in anti-tumor, vaccine delivery, blood glucose regulation, tissue fluid extraction and detection are reviewed. The challenge of MNs technology is summarized and the future development trend of MNs is also prospected.关键词：Polymer microneedles;Anti-tumor;Vaccine delivery;Blood glucose regulation;Transdermal drug delivery
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发布时间：2024-10-08 - 摘要：Currently, most epoxy thermosets especially diglycidyl ether of bisphenol A (DGEBA)-type epoxy monomers are sourced from petroleum resources. Due to the restrictions on greenhouse gas emissions, the development of bio-based epoxy thermosets to replace petroleum-based epoxy thermosets has received more and more attention. However, like petroleum-based counterparts, bio-based epoxy thermosets are highly flammable. Therefore, the development of intrinsically flame-retardant bio-based epoxy thermosets is extremely important. The future development direction of intrinsically flame-retardant bio-based epoxy thermosets must be green and sustainable. At present, intrinsically flame-retardant bio-based epoxy thermosets still have some defects such as poor thermal stability, and there is a long way to go. Considering the development trend in this field, increasing the functionality of bio-based epoxy monomers or curing agents, improving biomass content and biodegradability are several key factors for the future development of flame-retardant bio-based epoxy thermosets with high-performance. This review mainly discusses the recent progress and prospects of the preparation of intrinsically flame-retardant bio-based epoxy thermosets from bio-based resources. The mechanical properties, thermal stability and flame retardancy of partly bio-based intrinsically flame-retardant epoxy thermosets from either bio-based epoxy monomers or bio-based curing agents are emphatically introduced. In addition, the fully bio-based flame-retardant epoxy thermosets are also introduced. Finally, the opportunities and challenges of the future development of the intrinsically flame-retardant bio-based epoxy thermosets have been briefly prospected.关键词：Bio-based epoxy;Intrinsically flame-retardant;Flame-retardant performances;Mechanical properties
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发布时间：2024-10-08
Review
- 摘要：Natural products have good biocompatibility and environmental friendliness. Herein, the photoluminescence (PL) of dextran aqueous solutions at different temperatures as well as that of their solid powders with different molecular weights is systematically investigated. It is found that dextran demonstrates the characteristics of concentration-enhanced emission and aggregation-induced emission (AIE). In addition, strong blue and green phosphorescence are observed after ceasing the 312 and 365 nm UV light at 77 K in concentrated solutions, respectively, featuring excitation-dependent characteristics. With the increment of the molecular weights (20 kDa, 70 kDa, 150 kDa, 500 kDa), the quantum efficiency of dextran powders is progressively increased (1.6%, 2.4%, 3.2%, 3.6%). Furthermore, the dextran solid powders with high molecular weights (150 kDa, 500 kDa) even exhibit distinct persistent room temperature phosphorescence (p-RTP). Dextran tablets readily offer much more conspicuous afterglow with comparison to those of their powder counterparts. These phenomena can be well rationalized by the clustering-triggered emission (CTE) mechanism. Namely, in dilute solutions, polymer chains are well stretched and difficult to be excited owing to their short absorption. However, with the increasing concentration of dextran or the formation of aggregates, the clustering of oxygen atoms results in diverse emissive clusters with extended delocalization, which can get excited to emit with rigidified conformations induced by synergistic effect of O···O contacts, hydrogen bonds, chain entanglements, etc. The presence of varying emissive species with diverse electronic conjugation results in the excitation-dependent emission. Moreover, triplets are stabilized on account of the impeded molecular motions and decreased oxygen and moisture quenching, thus favoring p-RTP emissions. The study of dextran is conducive to gaining deeper insights into CTE mechanism and to develop environment-friendly luminescent materials.关键词：Dextran;Photoluminescence;Phosphorescence;Clustering-triggered emission
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发布时间：2024-10-08 - 摘要：In order to simultaneously achieve photothermal properties, photodynamic effects and second near-infrared (NIR-II 1000-1700 nm) fluorescence emission of conjugated polymers, herein a novel ternary conjugated polymer (BDP) was designed and synthesized by copolymerization of an electron-withdrawing monomer diketopyrrolopyrrole and two electron-donating monomers (benzodithiophene derivatives and 1,10-phenanthroline). Then water-soluble nanoparticles (BDP NPs) were further prepared by self-assembling with amphiphilic Pluronic F127 through nanoprecipitation method. The nanoparticles with a diameter of around 90 nm exhibited excellent stability in aqueous solution. The absorption and emission peaks of BDP NPs were determined to be 735 nm and 1039 nm, respectively. The mass extinction coefficient of the nanoparticles was as high as 4.67 mL/(mg·cm) the fluorescence quantum yield of BDP NPs was measured to be 0.62% by using IR-26 as a reference, and the photothermal conversion efficiency was 18.2%. Under 730 nm laser irradiation, the temperature of BDP NPs (150 μg/mL) can reach 64 ℃, which was high enough for photothermal therapy. Besides, the BDP NPs also produce reactive oxygen species with the same laser, which can be used for photodynamic therapy. Cell experiments confirmed that there was no obvious dark toxicity to both NIH3T3 cells and HeLa cells. While under NIR laser irradiation, strong phototoxicity toward cancer cells was observed, indicating the high therapeutic efficacy with the combination therapy. After intravenous injection of BDP NPs, the blood vessels in living mice can be observed which confirmed the high resolution of NIR-II imaging. Importantly, the BDP NPs can accumulate at the tumor sites at 12 h post-injection, indicating the possibility of NIR-II imaging guided combination therapy in vivo. Overall the obtained BDP NPs with high biocompatibility strong absorption in the first near-infrared (NIR-I, 650-900 nm) range, intense emission in NIR-II region, and the ability to produce reactive oxygen species and hyperthermia were, excellent candidate for tumor diagnosis and phototherapy. In addition, this work also provides a promising method for the rational design of conjugated polymer-based high performance phototheranostic nanoplatforms.关键词：Conjugated polymer;Photothermal therapy;Photodynamic therapy;Combination therapy;NIR-II fluorescence imaging
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发布时间：2024-10-08 - 摘要：Polylactide (PLA) and poly(lactic-co-glycolic acid) (PLGA) are degradable polyesters with excellent properties. It is practically important to develop green and environment friendly catalysts that can realize the bulk melt ring opening polymerization (ROP) of lactide and its copolymerization with glycolide. In this work,we report the bulk polymerization of lactide catalyzed by Lewis pairs composed of ZnCl2,MgCl2 or FeCl3 and three different oganobases. We then systematically studied the effects of Lewis pair structures,mixing ratios and polymerization time on the ROP of lactide. The three types of Lewis pairs all showed great thermal stability and high catalytic activities at 180 ℃. In particular, the combination of FeCl3/DBU can effectively catalyze the ROP of lactide and its copolymerization with glycolide at 180 ℃ to obtain high monomer conversion and high molecular weight at the same time. The resulting PLA homopolymer can reach molecular weight as high as 64.2 kg/mol via bulk polymerization,which are comparable to other metal catalytic systems. The molecular structures of PLLA and PLGA copolymer were verified by 1H-NMR spectroscopy and MALDI-TOF MS. The microstructures of the PLGA copolymers were carefully analyzed by 13C-NMR,and the results showed that the monomer sequence lengths can be easily modulated by varying the feeding ratio of two monomers. The resulting PLGA copolymer were all amorphous solids, and the glass transition temperature decreased with the increase of GA contents.关键词：Polylactide;Lactide;Ring opening polymerization;Lewis acid-base pair;Degradable polymer
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发布时间：2024-10-08 - 摘要：Photonic crystals (PCs) are a kind of optical material composed of periodic arranged refractive medias. Different with traditional chemical pigments, PCs' structural colors are produced by the physical interaction between refraction media and light, which makes PCs bleach resistant. Thus PCs show a great potential application in the field of rewritable paper, but the lack of light induced-color change ability limited its application. We design a Near-infrared (NIR) response photonic crystals hydrogel based on poly(N-isopropyl acrylamide-co-2-hydroxyethyl methacrylate) and gold nanorods. The incorporated gold nanorods endow hydrogel with NUR induced color change. The swelling of the polymer chain expands the spacing distance between polystyrene microspheres in the photonic crystal, resulting in the red-shift of structural color change and providing the possibility for NIR response. After NIR irradiation, the temperature of photonic hydrogel would increase due to the LSPR effect of Au NRs. Then, the NIPAm segment shrinks and reduces the spacing between polystyrene microspheres, resulting in the blue shift of structural color. The NIPAm chains would swell once NIR removed, leading to photonic hydrogel's structural color restore. The response time and displaying performance could be regulated by changing the content of hydroxyethyl methacrylate. A significant color change (34 nm) appeared in the 30% content of hydroxyethyl methacrylate, resulting the hydrogel could cover a range from red to blue by changing the diameter of the polystyrene templates. The photonic hydrogel could fabricate NIR responsive devices via polyethene terephthalate encapsulate. The color of the irradiated area would change under the NIR light irradiation. Moreover, the device shows excellent reversibility in the loop test. This strategy would pave a new route for smart displays, NIR detectors, and rewritable paper applications.关键词：Gold nanorods;Hybrid photonic hydrogel;Rewritable paper;Near-infrared responsiveness
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发布时间：2024-10-08 - 摘要：Conductive hydrogels, as a kind of functional polymeric soft material, have been demonstrated a wide application prospect in the field of flexible electronics devices in recent years. Therefore, it is of great value to develop a synthesis method for conductive hydrogels with high strength in both fundamental and applied research. In this work, we present a facile method for preparing high-strength hydrogels, in which one-dimensional silver nanowires (AgNWs) are effectively composited with sulfur-containing organic polymers via Ag-S coordination, significantly improving the strength of hydrogel, and also imposing high conductivity. The details for this hydrogel are as follows: First, linear polythioether (P1) with side vinyl groups is obtained by ring-opening polymerization of 1-allyloxy-2,3-sulfopropane, and subsequently a sufficient amount of carboxyl groups are introduced through thiol-ene click reaction to endow its solubility in water. The modified linear polythioether (P2) interacts with AgNWs to afford composited cross-linking agent (AgNWs@P2) through Ag-S coordination. The cross-linking agent and acrylamide (Am) monomer were polymerized in water using potassium persulfate (KPS) as the free radical initiator to prepare silver nanowire/polyacrylamide composite hydrogels (AgNWs/PAms, AC gels). The images of high-resolution field emission scanning electron microscope confirm the effective composition of AgNWs and P2 in nanoscale. The introduction of rigid AgNWs provides hydrogel with excellent mechanical strength and the largest elongation and maximum fracture stress strength can reach ~4500% and ~2.2 MPa, respectively. In addition, this hydrogel has high conductivity of 0.44 S/m. During the stretching process, the change of electrical resistance is linearly related to the deformation of the hydrogel, and especially this process has good cyclic stability. The stable resistance response capability of AC gel provides a promising application in the field of flexible electronics devices.关键词：Hydrogels;Ag-S coordination;Nanocomposite;Conductivity
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发布时间：2024-10-08 - 摘要：Graphite sheet (GS) is very promising for commercial use in SCs, due to its low cost and high conductivity. Nevertheless, the 2D flat surface of GS would limit the charge transport between GS and electroactive materials, because of the dissatisfactory interface being formed. Here, a facile mechanically exfoliated method is proposed to treat GS to obtain mechanically exfoliated GS (MEGS) as current collector, which shows a unique layered microstructures. And meanwhile, the electropolymerization parameter-dependent supercapacitive performance of the poly(3,4-ethylenedioxythiophene) (PEDOT) films as the electroactive material is investigated in detail. Electrochemical measurements verify that the electrochemical properties of PEDOT electrodes are substantially enhanced by using optimized electropolymerization parameters. More importantly, the electrochemical properties of PEDOT electrodes are further observably boosted through using MEGS current collector compared to GS, attributed to the 3D interface established between the PEDOT films and MEGS. The resulting MEGS/PEDOT electrodes yield areal capacitance of 96.2 mF·cm-2 at 0.5 mA·cm-2, superior rate performance, and remarkable cycling stability (90.6% of capacitance retention for 10000 cycles). Such characteristics of MEGS/PEDOT electrodes offer great promise in high performance supercapacitor applications.关键词：Charge storage;Electrochemical capacitors;Flexible devices;Electrochemical properties
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发布时间：2024-10-08 - 摘要：The phase separation of poly(methyl methacrylate)/poly(vinyl acetate)/silica (PMMA/PVAc/SiO2) blends was investigated by optical microscope, rheology, morphological observation and Fourier transform infrared spectroscopy. Strong inter-molecular interaction between PMMA and PVAc was found by the shift of the carbonyl peak position compared to the FTIR of pure polymer and the reduction of chain entanglements inferred from the rheological curves. The addition of nano-silica led to the adsorption of chains of both polymers on the particle surfaces, which changed the inter-molecular interaction between pure PMMA and PVAc. The complex inter-molecular interaction and polymer-particle interaction resulted in the failure of time-temperature superposition over the entire temperature range. So the normalized Cole-Cole plot was proposed to analyze the phase separation process of the blend. Due to the inter-molecular interaction, the normalized Cole-Cole plot of the PMMA/PVAc blend deviates from the polymer, and secondary deviation occurs at the end of the curve during the heating process, which is the contribution of the phase interface. The nanoparticles have different influences on the phase separation behavior of the blend, depending on the blend composition. In the near-critical blends, nano-silica promoted the phase separation and was finally located at the interface of the two phases. In the off-critical blends, nano-silica had little effect on phase separation and was finally located in the island domains. The effect of nanoparticles on phase separation of different blends is related to the mechanism of phase separation: the near-critical blends form discontinuous shapes through the decomposition of the spiral nodal line. The phase separation speed is faster than the Brownian motion speed of nanoparticles, which results in the initial distribution of nano-silica in the two phases, and the subsequent movement towards the interface of two phases. The off-critical blends form island shapes through nucleation growth mechanism. Due to the slow phase separation rate, the nano-slica play the role of nuclei during the phase separation. In other words, the phase separation mechanism, Broenian motion of nanoparticles and dynamic adsorption and desorption of polymer chains on the surface of nanoparticles jointly determine the distribution of nanoparticles. Such selective location of nanoparticles determined by the phase separation mechanism supplied a new approach for the control of aggregation of nanoparticles in polymers.关键词：Nanoparticle;Phase separation;Rheology;Selective location
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发布时间：2024-10-08 - 摘要：Polyhexahydrotriazine (PHTs) films were prepared by polycondensation between the two aromatic diamine monomers and paraformaldehyde and then the thermal curing process. Those two aromatic diamine monomers were 4,4'-diaminodibenzocrown ether (DACr) and 2,2-bis(P-aminophenoxy) ether (BAPE), which contained both flexible ether and rigid benzene ring structures. Through structural characterization and a variety of performance tests, including thermal performance analysis, tensile testing, contact angle, chemical resistance performance testing, and degradation performance testing, the effect of structural units of DACr and BAPE on the crosslinking structures formation and properties of polymer were investigated. The results show that the rigidity of the structural unit was related to the completeness of the cross-linked structure of the hexahydrotriazine (HT) ring and jointly determined the performance of the PHT film material. The PHT containing the flexible acyclic BAPE structural unit tended to form perfect HT rings, and behaved the high thermal stability (5% thermogravimetric loss temperature is 296.8 ℃), hydrophilicity and relatively low degree of acid hydrolysis. The PHT film containing the more rigid DACr structural unit had the higher mechanical strength (tensile strength 53.6 MPa), hydrophobicity, resistance to organic reagents and the degree of acid hydrolysis, it was complete degaration in glacial acetic acid solution and recyling the raw monomer of DACr with high yield of more than 83%. Due to the influence of both the structural integrity of HT and the rigidity of the structural unit, the two PHT materials showed the similar glass transition temperatures (Tgs were 117.8 and 117.9 ℃, respectively). This study provides theoretical basis and experience for the structural design and performance regulation of PHT materials. Meantime, the obtained PHT materials meet the degradation requirements and have the potential application value.关键词：Polyhexahydrotriazine;Flexible and Rigid;Properties;Degradation
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发布时间：2024-10-08 - 摘要：To study the effects of second-melt penetration on the external fields (shear field and thermal field) as well as the morphological evolution along the flow direction, polyvinylidene difluoride (PVDF) and poly(methyl methacrylate) (PMMA) were applied in the multi-melt multi-injection molding (M3IM) in which PVDF and PMMA were used for the first and second shots, respectively. The whole process of M3IM was also simulated by Fluent software using Cross-WLF model to quantitively investigate the distributions of melt temperature and shear rate and to better understand the formation mechanism of various morphologies in M3IM products. The results from polarized light microscopy (PLM) with hot-stage showed that two different layers were formed in PVDF part. Specifically, one is the primary flow layer and the other is the secondary flow layer. The former one was dominated by the first shot of PVDF, while the latter one was significantly affected by the second shot of PMMA. Moreover, a penetration area was clearly observed in the region close to the end of the primary flow layer. Characterizations with differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed that the content of PVDF β phase dramatically increased in the penetration area. This is mainly caused by the secondary shearing effect of PMMA melt in M3IM which is in good agreement with numerical simulation. Moreover, an interesting structure, "bright ribbon", with a higher melting temperature (~190 ℃) was found in the domains after penetration area. This might be due to the shear heating of the secondary flow, which results in the annealing of PVDF crystals. Finally, this work provides a detailed investigation of the secondary flow behavior of polymer melt in M3IM and helps us better understand the corresponding effects on the structural evolution along the flow direction.关键词：Multi-melt Multiple-injection Molding;Polyvinylidene difluoride;β Phases;Morphology
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发布时间：2024-10-08
Research Article
- 摘要：In recent years, organic optoelectronic devices, including organic light emitting diodes (OLEDs) and organic solar cells (OSCs), have attracted great attention and developed rapidly. The matching of the electronic energy levels (HOMO and LUMO energy levels) of the organic semiconductors with the work-functions of the electrodes is of great importance for the optoelectronic properties of the devices. In addition, the matching of the HOMO and LUMO energy levels of the donor and acceptor materials is also crucial for the photovoltaic performance of the OSCs. Therefore, it is very important to accurately measure the HOMO and LUMO energy levels of the organic semiconductors. In this paper, we will introduce the commonly used measurement methods of the electronic energy levels of the organic semiconductors, including ultraviolet photoelectron spectroscopy (UPS) and electrochemical methods. And we will explain the measurement mechanism, sample preparation, attention items of the measurements, and give the calculation equations of the electronic energy levels. We also give several examples to measure the energy levels of the organic semiconductors including conjugated polymers and conjugated organic small molecule semiconductors, and liste the HOMO and LUMO energy levels of some typical organic semiconductor materials reported in literatures, for the reference of the readers.关键词：Organic semiconductor;Measurement of electronic energy levels;Ultraviolet photoelectron spectroscopy (UPS);Cyclic voltammetry;HOMO and LUMO energy levels
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发布时间：2024-10-08
Review (Special Topic: Techniques of Polymer Characterization)
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