Surface control of hydrophilicity and degradability with block copolymers composed of lactide and cyclic carbonate bearing methoxyethoxyl groups

Block copolymers of L-lactide (LA) and trimethylene carbonate (TMC) derivatives bearing methoxyethyl groups [poly(TMCM-MOE1OM)-block-PLLA] were employed as spin-coated films on substrates, and their hydrophilic and degradation behaviors were investigated. Changing the solvents for film preparation, film thickness, and copolymer composition ratios varied the contact angles in the range of 84.3° ± 2.8° at 269 nm thickness and 18.2° ± 2.5° at 15 nm thickness. These contact angles showed dynamic changes from hydrophobic to hydrophilic properties, probably due to the methoxyethoxyl groups connecting the flexible TMC moieties in the copolymer. Immersion into water or hexane affected the dynamic contact angles. X-ray photoelectron spectroscopy analyses revealed that a large amount of hydrophilic groups was segregated onto the surface, although both LA and TMC units existed. Such dynamic contact angle changes were delayed by the crystallization of polylactide. The hydrolyzed behaviors of these films were examined by quartz cell microbalance, showing a slow degradation process.     

Recent advances in nanofiltration,reverse osmosis membranes and their applications in biomedical separation field

In the face of human society’s great requirements for health industry, and the much stricter safety and quality standards in the biomedical industry, the demand for advanced membrane separation technologies continues to rapidly grow in the world. Nanofiltration(NF) and reverse osmosis(RO) as the highefficient, low energy consumption, and environmental friendly membrane separation techniques, show great promise in the application of biomedical separation field. The chemical compositions, microstr...     

环氧树脂的改性研究进展

概述了近年来利用互穿网络法、液晶增韧法、纳米粒子增韧等改性环氧树脂的新方法。     

Modification of polylactide upon physical properties by solution-cast blends from polylactide and polylactide-grafted dextran

Polylactide (PLA)-grafted polysaccharides with various lengths and numbers of graft chains were synthesized using a trimethylsilyl protection method. The properties of the cast films prepared from graft-copolymers were investigated through thermal and dynamic mechanical analyses. The graft-copolymer films exhibited a lower glass transition temperature (T_g), melting temperature, and crystallinity, and higher viscosity properties compared to PLA films. Moreover, the usefulness of graft-copolymer as a plasticizer was investigated with 1:4 blend films prepared from the graft-copolymers and PLA. The blend films showed lower T_g and crystallinity, and higher viscosity properties compared to PLA films.     

Influences of three different ethylene copolymers on the toughness and other properties of polylactide

The aim of this study was to investigate influences of three different ethylene copolymers on the toughness and other properties of very brittle biopolymer PLA (polylactide). For this aim, PLA was melt blended by twin-screw extruder with various amounts of ethylene vinyl acetate (EVA), ethylene-methyl-acrylate (EMA) and ethylene-n-butyl acrylate-glycidyl-methacrylate (EBA-GMA). SEM and DSC analyses indicated that these ethylene copolymers were thermodynamically immiscible with phase separation in the form of 1–5?µm sized round domains in the PLA matrix. Rubber toughening mechanisms of EVA, EMA and EBA-GMA were very effective to improve ductility and toughness of PLA significantly. Depending on the type and content of the ethylene copolymers, the highest increases in % elongation at break, Charpy impact toughness and G_IC fracture toughness values of PLA were as much as 160, 320 and 158%, respectively. Although there were no detrimental effects of using EVA, EMA and EBA-GMA on the thermal properties of PLA, they resulted in certain level of reductions in stiffness, strength and hardness values.     

非弹性体增韧高分子材料的研究进展

对近些年来热塑性树脂增韧体系、核壳粒子增韧体系、液晶高聚物增韧体系及无机刚性粒子增韧体系等增韧高分子材料的研究进展进行了综述。指出非弹性体增韧拓展了高分子材料增韧改性研究的新领域；纳米粒子增韧开辟了高分子材料的研究新方向。     

Recent advances in nanocellulose for biomedical applications

Nanocellulose materials have undergone rapid development in recent years as promising biomedical materials because of their excellent physical and biological properties, in particular their biocompatibility, biodegradability, and low cytotoxicity. Recently, a significant amount of research has been directed toward the fabrication of advanced cellulose nanofibers with different morphologies and functional properties. These nanocellulose fibers are widely applied in medical implants, tissue engineering, drug delivery, wound‐healing, cardiovascular applications, and other medical applications. In this review, we reflect on recent advancements in the design and fabrication of advanced nanocellulose‐based biomaterials (cellulose nanocrystals, bacterial nanocellulose, and cellulose nanofibrils) that are promising for biomedical applications and discuss material requirements for each application, along with the challenges that the materials might face. Finally, we give an overview on future directions of nanocellulose‐based materials in the biomedical field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41719.     

面向应用的石墨烯制备研究进展

二维石墨烯具有卓越的光、电、热和力学等性能,在众多传统产业和战略性新兴产业中有巨大的应用前景,被誉为下一代关键基础材料。然而,石墨烯产业化及应用的瓶颈性问题是如何高效率、规模化、低成本和环境友好地制备高质量石墨烯产品。本综述系统地比较了现有石墨烯制备方法的优缺点,结合不同应用领域的特殊要求,阐明了材料化学工程的放大理论和方法是解决石墨烯大规模制备和应用瓶颈性问题的重要保障。     

微混合技术研究进展

在微尺度混合下,传递和反应性能得到明显改善;微混合器易与微反应系统集成,使化学反应更为可控,效率更高。综述了微混合技术的发展和研究现状,探讨了微混合技术的特点和优势及其在反应过程中的应用前景。     

Stimuli-responsive emulsions:Recent advances and potential applications

Responsive emulsions are the emulsions that can be reversibly switched on-demand between "stable"and "unstable" by environmental stimulus or trigger,which allows a simple and effective adjustment approach to achieve emulsification and demulsification.In recent years,stimuli-responsive emulsions acting as smart soft material are received considerable attention with the advantages of simple manip-ulation,good reversibility,low cost,easy treatment,and little effect on the system.In this paper,the recent research progress of emulsions that can respond to external stimuli,including pH,light,magnetic field,CO2/N2 and dual responsive are reviewed.Also,the potential applications based on responsive emulsion are discussed,such as catalytic reactions,heavy oil recovery,polymer particles synthesis and optical sensor,aiming to summarize the latest achievements and put forward the possible development trends of responsive emulsions.     

无机层柱粘土材料的制备和应用研究新进展

概述了近年来无机层柱粘土材料新的制备方法,如微波法和超声波法,及其相应的结构表征手段和结构特点,并就基于无机层柱粘土的表面酸性、柱撑体的催化氧化性以及材料多孔性、吸附性等的新应用进行了评述.     

Enhanced thermal stability of poly(lactide)s in the melt by enantiomeric polymer blending

Poly(l-lactide) (i.e. poly(l-lactic acid) (PLLA)) and poly(d-lactide) (i.e. poly(d-lactic acid) (PDLA)) and their equimolar enantiomeric blend (PLLA/PDLA) films were prepared and the effects of enantiomeric polymer blending on the thermal stability and degradation of the films were investigated isothermally and non-isothermally under nitrogen gas using thermogravimetry (TG). The enantiomeric polymer blending was found to successfully enhance the thermal stability of the PLLA/PDLA film compared with those of the pure PLLA and PDLA films. The activation energies for thermal degradation (ΔE_td) were evaluated at different weight loss values from TG data using the procedure recommended by MacCallum et al. The ΔE_td values of the PLLA/PDLA, PLLA, and PDLA films were in the range of 205-297, 77-132, and 155-242 kJ mol⁻¹ when they were evaluated at weight loss values of 25-90% and the ΔE_td value of the PLLA/PDLA film was higher by 82-110 kJ mol⁻¹ than the averaged ΔE_td value of the PLLA and PDLA films. The mechanism for the enhanced thermal stability of the PLLA/PDLA film is discussed.     

Recent advances in shear-thinning and self-healing hydrogels for biomedical applications

Shear-thinning and self-healing hydrogels are being investigated in various biomedical applications including drug delivery, tissue engineering, and 3D bioprinting. Such hydrogels are formed through dynamic and reversible interactions between polymers or polypeptides that allow these shear-thinning and self-healing properties, including physical associations (e.g., hydrogen bonds, guest–host interactions, biorecognition motifs, hydrophobicity, electrostatics, and metal–ligand coordination) and dynamic covalent chemistry (e.g., Schiff base, oxime chemistry, disulfide bonds, and reversible Diels–Alder). Their shear-thinning properties allow for injectability, as the hydrogel exhibits viscous flow under shear, and their self-healing nature allows for stabilization when shear is removed. Hydrogels can be formulated as uniform polymer and polypeptide assemblies, as hydrogel nanocomposites, or in granular hydrogel form. This review focuses on recent advances in shear-thinning and self-healing hydrogels that are promising for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48668.     

Recent advances in photorefractive and photoactive polymers for holographic applications

The current state‐of‐the‐art of photorefractive and photoactive polymers for holographic applications is summarized and reviewed. Photorefractive polymers and some kinds of photoactive materials based on the azobenzene chromophore have great potential for updatable holographic applications. Updatable three‐dimensional holographic displays of large size have been developed using photorefractive polymers as well as photoactive azobenzene materials. Time responses of photorefractive polymers of the order of seconds and hundreds of milliseconds are currently improved to be of the order of milliseconds to hundreds of microseconds with high diffraction efficiency and high optical gain. © 2016 Society of Chemical Industry     

黄原胶生物合成的研究进展

结合有关黄原胶的研究报道,针对黄原胶黏度大影响溶氧等问题,从黄原胶的发酵工艺、反应器等方面讨论了目前的研究方向和热点。阐述了解决黏度问题的工艺方案,讨论了碳源和氮源对黄原胶产量的影响,指出了分批流加工艺在黄原胶发酵中的重要性。最后从发酵动力学角度讨论了影响黄原胶发酵产量的因素,阐述了有关黄原胶发酵的动力学模型及其对黄原胶发酵的指导意义。     

Molecular design,synthesis strategies and recent advances of hydrogels for wound dressing applications

With the changes in the modern disease spectrum, pressure ulcers, diabetic feet, and vascular-derived diseases caused refractory wounds is increasing rapidly. The development of wound dressings has partly improved the effect of wound management. However, traditional wound dressings can only cover the wound and block bacteria, but are generally powerless to recurrent wound infection and tissue healing. There is an urgent need to develop a new type of wound dressing with comprehensive performance to achieve multiple effects such as protecting the wound site from the external environment, absorbing wound exudate, anti-inflammatory, antibacterial, and accelerating wound healing process. Hydrogel wound dressings have the aforementioned characteristics, and can keep the wound in a moist environment because of the high water content, which is an ideal choice for wound treatment. This review introduces the wound healing process and the development and performance advantages of hydrogel wound dressings. The choice of different preparation materials gives the particularities of different hydrogel wound dressings. It also systematically explains the main physical and chemical crosslinking methods for hydrogel synthesis. Besides, in-depth discussion of four typical hydrogel wound dressings including double network hydrogels, nanocomposite hydrogels, drug-loaded hydrogels and smart hydrogels fully demonstrates the feasibility of developing hydrogels as wound dressing products and their future development trends.     

甲醇制汽油工艺及催化剂制备的研究进展

甲醇制汽油既能缓解国内油品短缺又能解决甲醇产能过剩。本文综述了甲醇制汽油工艺技术,包括固定床和流化床技术,简要说明了这些工艺的技术特点。同时介绍了甲醇制汽油催化剂的研究现状,着重说明了碱处理和金属改性处理对ZSM-5结构和催化性能的影响,指出了高比表面积催化剂的研制和高稳定性催化剂的开发是甲醇制汽油催化剂的研究方向,并对甲醇制汽油催化剂失活的原因及催化机理进行了初步的探讨。     

Stereocomplex crystallization and spherulite growth behavior of poly(l-lactide)-b-poly(d-lactide) stereodiblock copolymers

The non-isothermally and isothermally crystallized stereodiblock copolymers of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) with equimolar l-lactyl and d-lactyl units and different number-average molecular weights (M_n) of 3.9 × 10³, 9.3 × 10³, and 1.1 × 10⁴ g mol⁻¹, which are abbreviated as PLLA-b-PDLA copolymers, contained only stereocomplex crystallites as crystalline species, causing higher melting temperatures of the PLLA-b-PDLA copolymers compared to those of PLLA homopolymers. In the case of non-isothermal crystallization, the cold crystallization temperatures of the PLLA-b-PDLA copolymers during heating and cooling were respectively lower and higher than those of PLLA homopolymers, indicating accelerated crystallization of PLLA-b-PDLA copolymers. In the case of isothermal crystallization, in the crystallizable temperature range, the crystallinity (X_c) values of the PLLA-b-PDLA copolymers were lower than those of the PLLA homopolymers, and were susceptible to the effect of crystallization temperature in contrast to that of homopolymers. The radial growth rate of the spherulites (G) of the PLLA-b-PDLA copolymers was the highest at the middle M_n of 9.3 × 10³ g mol⁻¹. This trend is different from that of the PLLA homopolymers where the G values increased monotonically with a decrease in M_n, but seems to be caused by the upper critical M_n values of PLLA and PDLA chains as in the case of PLLA/PDLA blends (in other papers), above which homo-crystallites are formed in addition to stereocomplex crystallites. The disturbed crystallization of PLLA-b-PDLA copolymers compared to that of the PLLA/PDLA blend is attributable to the segmental connection between the PLLA and PDLA chains, which interrupted the free movement of those chains of the PLLA-b-PDLA copolymers during crystallization. The crystallite growth mechanism of the PLLA-b-PDLA copolymers was different from that of the PLLA/PDLA blend.     

直接熔融聚合法制备生物降解材料PCEL

研究了直接熔融聚合法合成生物降解材料聚己内酯／聚乙二醇／聚乳酸三元共聚物（PCEL）的聚合工艺,分别讨论了原料投料比、催化剂种类及用量、聚合温度及时间等因素对共聚产物PCEL特性黏数的影响,确立了最佳的反应条件。在本实验条件下,最适宜的直接熔融共聚合工艺为：投料比为n（PEG）／n（ε—CL）／n（D,L-LA）=10／63／27;催化剂为氯化亚锡,用量为反应物质量的0．5％;在压力70Pa、120℃下预聚合除水3h后,再经180℃熔融共聚16h。所合成的聚己内酯／聚乙二醇／聚乳酸（PCEL）共聚物的特性黏数[η]最高可达0．4457dL／g。