三偏磷酸钠交联壳聚糖膜的制备及其性能研究

将充分溶胀的壳聚糖膜置于一定浓度的三偏磷酸钠溶液中进行交联反应制备出交联壳聚糖膜。用傅立叶变换红外光谱(FT-IR)、X-射线衍射(XRD)和扫描电镜(SEM)表征了其结构,并测试了其吸水率、力学性能和酶降解性能。研究结果表明,交联作用明显提高了膜的抗张强度和抗水性,并有效地降低了溶菌酶对其降解速率。该交联膜有望用作可控降解生物医用材料。     

交联壳聚糖膜的制备及其性能的研究

用环氧氯丙烷成功地制备出交联壳聚糖膜。用FTIR,XRD和SEM方法表征其结构,并测试了其力学性能。结果表明,壳聚糖在低温下只有氨基参与交联反应,反应温度高于40℃时,羟基才发生反应;环氧氯丙烷的交联作用显着提高了壳聚糖膜的抗张强度,并有效地降低了溶菌酶对其降解速率;该交联膜有望用作可控降解的生物医用材料。     

硫酸交联壳聚糖膜质子传导行为的研究

制备了硫酸交联壳聚糖膜, 通过研究其质子传导性能、力学性能、化学成分及结构变化, 分析了硫酸与壳聚糖分子间的交联方式, 并对质子传导机理进行了解析. 结果表明, 硫酸交联可显著改善壳聚糖膜的质子传导能力与力学性能, 这种改善作用在交联6 h后趋于稳定, 交联6 h后的壳聚糖湿膜在室温下时质子传导率为0.0472 S• cm^－1, 比未交联的壳聚糖膜提高5倍左右. 硫酸交联壳聚糖膜中的质子传导率与温度的关系符合Arrhenius定律, 质子传导激活能为18 kJ/mol, 其传导机制应属于Grotthus机制. 硫酸对提高壳聚糖膜的质子传导能力主要有两方面的作用: (1) H₂SO₄可使壳聚糖分子中NH₂质子化形成NH₃^＋. (2) 处于两个氨基之间的SO₄^2－在质子传递过程中起离子桥梁作用, 参与以水分子为载体的质子传导过程, 从而减小质子传导的阻力, 提高了质子传导率.     

交联结构对肝素/壳聚糖层层组装多层膜内皮细胞相容性的影响

采用1-乙基-(3-二甲基氨基丙基)碳酰二亚胺交联技术对具有抗凝血抗菌作用的肝素/壳聚糖多层膜进行交联, 研究了交联结构对多层膜稳定性和血管内皮细胞亲和性的影响. QCM-D结果显示, 交联可有效地提高多层膜的稳定性, 在模拟人体血液流速(3.0 cm/s)下保持良好的稳定. 体外内皮细胞的研究结果显示, 多层膜的交联可有效地调节肝素/壳聚糖多层膜表面粘弹性, 并显著增加内皮细胞的粘附与生长. 交联的肝素/壳聚糖多层膜有望成为理想的心血管功能界面涂层材料.     

光交联壳聚糖膜的制备及其性能研究

成功制备了光交联壳聚糖膜,并用傅立叶红外光谱(FTIR)和扫描电子显微镜(SEM)方法对其结构进行了表征,并测试了其力学性能。结果表明:光交联作用明显提高了膜的抗张强度和抗水性,并有效地降低了溶菌酶对其降解速率。该光交联膜有望用作可控降解生物医用材料。     

壳聚糖与聚乙二醇交联水凝胶研究

研究对壳聚糖(CS)进行化学修饰得到了不同丙烯酰基取代度(1.03%,3.55%和5.21%)的丙烯酰化羟丙基壳聚糖(AHCS);通过自由基引发反应,AHCS与聚乙二醇二丙烯酸酯(PEGDA)交联得到壳聚糖(CS)与聚乙二醇(PEG)为主体的交联水凝胶。通过SEM观察其为通透性良好的多孔性支架材料。水凝胶的溶胶含量和溶胀度随丙烯酰基取代度的增加而降低,水凝胶中壳聚糖的降解速率也随丙烯酰基取代度的升高而降低。对于同一取代度的交联水凝胶,其在酸性和碱性条件下的溶胀度大于中性环境。细胞试验表明,壳聚糖与聚乙二醇交联水凝胶具有良好的生物相容性。     

二醛纤维素交联壳聚糖膜的制备及其染料吸附性能

首先通过浓硫酸水解微晶纤维素(MCC)制备纳米纤维素(NCC)悬浮液,然后通过高碘酸钠选择性氧化NCC悬浮液制备二醛纤维素(DAC)水溶液,最后将DAC水溶液与壳聚糖(CTS)醋酸溶液混合,通过溶液浇注、溶剂蒸发法制得DAC交联CTS膜(DAC-CTS交联膜)。采用红外光谱(FT-IR)、交联度测试、耐酸稳定性测试表征了DAC-CTS交联膜的结构及性能,并研究了其作为吸附剂对阴离子染料活性艳蓝KN-R的吸附能力。结果表明:与纯CTS膜相比,DAC-CTS交联膜的耐酸稳定性与拉伸强度均明显提高;当m(DAC)∶m(CTS)=3%时,该交联膜达到最大饱和吸附量1 118.8mg/g;此外,DAC-CTS交联膜对活性艳蓝KN-R的吸附符合Langmuir吸附等温模型和准2级动力学模型。     

壳聚糖交联膜结构及性能的研究

壳聚糖是一种天然生物高分子聚合物，是甲壳素脱乙酰化产物，具有很好的成膜特性．用一种金属离子把壳聚糖分子中的螫合基团络合保护后，用戊二醛交联，并在酸性条件下将该金属离子洗脱，得到了螯合基团依然保留的壳聚糖交联膜．对壳聚糖交联膜的结构及性能进行了研究．结果表明：金属离子有效地保护了壳聚糖分子上的络合基因，该膜的性能较好，对阴离子的选择透过性比较好，并将其应用于元素的分离．     

分子印迹壳聚糖膜分离手性苯丙氨酸

以L-苯丙氨酸(L-Phe)为印迹分子,采用相转化法制备了分子印迹壳聚糖膜。分别采用碱液处理和硫酸交联两种方法对膜进行处理,降低了壳聚糖膜的溶胀度,印迹膜内识别位点的结构得以保持。采用FT-IR和SEM对膜的化学组成和结构形态进行了表征。通过渗透实验考察了分子印迹壳聚糖膜和非印迹空白壳聚糖膜对D,L-苯丙氨酸(D,L-Phe)混合物的手性拆分性能,并与空白膜进行了比较。印迹膜的分离因子达到1.43。     

甲壳素和壳聚糖在离子液体中的溶解、材料化以及衍生化

甲壳素和壳聚糖是可再生的大分子生物质资源.由于分子内和分子间的强烈氢键作用,甲壳素和壳聚糖不能溶解在水或常规有机溶剂中,这极大地限制了其在诸多领域中的应用.离子液体作为一种新型绿色溶剂,对甲壳素和壳聚糖具有优良的溶解作用.本文综述了离子液体对甲壳素和壳聚糖的溶解性能和溶解机理,概述了均相溶液体系中纤维、膜、凝胶等材料的制备以及酰化、接枝共聚、交联、降解、希夫碱化等多种衍生化反应,总结了离子液体在甲壳素和壳聚糖化学研究中面临的挑战并对其进行了展望.     

Synthesis, characterization and hydrolytic degradation of linear and crosslinked poly[(glycino ethyl ester)(allyl amino)phosphazene]

Polyorganophosphazenes substituted by glycino ethyl ester and allylamine with different ratios were synthesized and their structures were characterized by ¹H NMR, ³¹P NMR and FTIR. Via the crosslink reaction, a novel biodegradable crosslinked polyorganophosphazene material was obtained. DSC and FTIR spectra indicated the occurrence of crosslink. Hydrolysis studies were also performed to compare the crosslinked polymers with linear ones. The co-substituted polyorganophosphazenes with more allylamine at pendant groups exhibited a lower degradation rate than poly[bis(glycino ethyl ester)phosphazene] and crosslinked polyphosphazenes had an even lower degradation rate. SEM photographs characterized the surface of polyphosphazenes films after hydrolytic degradation, confirming that uncrosslinked ones had outstanding hydrolytic evidences at the surface while the crosslinked ones only had sporadic small erosion holes, remaining much smoother.     

Radiation-induced crosslinking of polyvinyltrimethylsilane in the presence of ethylene glycol dimethacrylate and allyl methacrylate

Radiation-induced crosslinking of homogeneous glassy polyvinyltrimethylsilane was carried out either by the γ-irradiation of the polymeric films containing 3–20 wt% of ethylene glycol dimethacrylate or by the radiation-induced grafting of allyl methacrylate from vapour phase onto films made of pure polymer. The dependence of grafting value on the absorbed γ-irradiation dose and film thickness was investigated. The modified films were analyzed for the sol/gel content and the dependence of gel fraction yield of crosslinked polymer on absorbed dose, concentration of the crosslinking agents and film thickness.The radiation-chemical yields of crosslinking and degradation as well as gelation doses were calculated. The permeability of oxygen and nitrogen through the crosslinked films was determined.     

Synthesis and characterization of photocrosslinked poly(ε‐caprolactone)s showing shape‐memory properties

Poly(ε‐caprolactone) (PCL) with a pendent coumarin group was prepared by solution polycondensation from 7‐(3,5‐dicarboxyphenyl) carbonylmethoxycoumarin dichloride and α, ω‐dihydroxy terminated poly(ε‐caprolactone) with molecular weights of 1250, 3000, and 10,000 g/mol. These photosensitive polymers underwent a rapid reversible photocrosslinking upon exposure to irradiation with alternating wavelengths (>280/254 nm) without a photoinitiator. The thermal and mechanical properties of the photocrosslinked films were examined by means of differential scanning calorimetry and stress–strain measurements. The crosslinked films exhibited elastic properties above the melting temperature of the PCL segment along with significant decrease in the ultimate tensile strength and Young's modulus. Shape‐memory properties such as strain fixity ratio (R_f) and strain recovery ratio (R_r) were determined by means of a cyclic thermomechanical tensile experiments under varying maximum strains (ε_m = 100, 300, and 500%). The crosslinked ICM/PCL‐3000 and ‐10,000 films exhibited the excellent shape‐memory properties in which both R_f and R_r values were 88–100% for tensile strain of 100–500%; after the deformation, the films recovered their permanent shapes instantaneously. In vitro degradation was performed in a phosphate buffer saline (pH 7.2) at 37 °C with or without the presence of Pseudomonas cepacia lipase. The presence of the pendent coumarin group and the crosslinking of the polymers pronouncedly decreased the degradation rate. The crosslinked biodegradable PCL showing a good shape‐memory property is promising as a new material for biomedical applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2422–2433, 2009     

Crosslinking and characterization of commercially available poly(VDF-co-HFP) copolymers with 2,4,4-trimethyl-1,6-hexanediamine

Fluorinated copolymers are well known for their large range of applications. These applications can be improved by grafting or crosslinking of several agents. The mechanism of crosslinking of hexamethylene diamine and 2,4,4-trimethyl-1,6-hexanediamine is well known and occurs in four different steps. To elaborate a film of commercially available poly(VDF-co-HFP) copolymer crosslinked by 2,4,4-trimethyl-1,6-hexanediamine, a step of press cure under air is necessary. Temperature, time and pressure were optimised by regarding the solubility of the press cured films, the mechanical properties, the swelling rate in methyl ethyl ketone, and the degradation of the films. The best temperature, time and pressure for press cure were 150 °C, from 15 to 30 min, and 20 bars, respectively. Other properties of crosslinked poly(VDF-co-HFP) copolymers containing 10 mol.% and 20 mol.% of HFP were characterized. First, all films were insoluble in concentrated HCl. Secondly, swelling rates of different amounts of diamine crosslinked copolymers were measured in ethylene carbonate/dimethyl carbonate and in methyl ethyl ketone; it was proved that the higher the molar percentage of diamine, the higher the crosslinking density, so the lower the swelling rate. Concerning thermal properties, glass transition temperature mainly increased when the amount of diamine increased. Thermal stability measurements showed a higher decomposition temperature when the percentage of diamine was very low (5 mol.%). Finally, mechanical properties were measured by dynamic mechanical analysis; the storage tensile modulus (E′) of a diamine crosslinked Kynar^® copolymer versus temperature exhibited a high drop because Kynar^® was a highly amorphous copolymer. Moreover, the higher the amount of diamine, the higher the rubbery modulus.     

Photo-stability of photo-cured organic coatings: Part III—Photo-degradation of organic coatings photo-cured with alkoxyacetophenone and hydroxy alkylacetophenone photo-initiators

Photo-degradation studies of polystyrene (as model) and coating resins were made with three different photo-fragmenting initiators: 2,2-dimethoxy-2-phenylacetophenone, 1-[4-(2-propyl)-phenyl]-2-hydroxy-2-methyl-propanone-1 and 1-benzoyl-1-hydroxy-cyclohexane. Addition of the initiators to a benzene solution of polystyrene gave a rapid decrease in molecular weight when the solutions were uv irradiated. The degradation rate was increased by the presence of oxygen. Irradiation of polystyrene films, containing the same initiators, showed similar effects. In addition, the polymer became partially crosslinked. Addition of a free radical scavenger decreased the degradation rate. Both photo-oxidation rate and yellowing rate were affected by the concentration and the reactivity of the radicals. Photo-oxidation during photo-curing of a coating occurs in a thin surface layer. This is due to a combination of free radicals formed by the uv irradiation and the oxygen present. Oxidation during the photo-curing of a urethane resin corresponds to more than 50% of the total surface oxidation measured with ESCA.     

杯芳烃交联聚硅氧烷热稳定性能研究

聚有机硅氧烷是一类主链由硅-氧键连接而成,侧链为有机基团的聚合物,兼具有机聚合物和无机聚合物的特性,性能优异,尤以卓越的耐高温性能而著称,在大气中于-50~250℃可以长期使用[1].为了进一步提高聚有机硅氧烷的热稳定性,主要有以下几种方法,(1)添加各种耐热性添加剂,或可与聚     

Sintering of Sol-Gel Films

The sintering of films differs from that of bulk gels in several ways. The initial state of a film is generally denser and less crosslinked than a bulk gel made from the same sol, and these factors enhance the densification rate of the film. The substrate constrains the shrinkage of the film, leading to high stresses that retard densification and can influence phase changes. The substrate is a site for heterogeneous nucleation, and crystallization makes densification more difficult, so the competition between sintering and crystallization is particularly important for films. Fast heating favors densification over crystallization, so rapid thermal annealing usually produces denser films. The high surface to volume ratio of a thin film makes it susceptible to degradation by reaction with the substrate and the atmosphere, so choosing compatible materials and avoiding over-firing is essential.     

Comparative Studies on Degradation of Methyl Orange by Nanostructured Zinc and Zinc Oxide Films

Nanostructured zinc and zinc oxide films were prepared by magnetron sputtering processes and succeeded air annealing treatments. Comparison of reductive degradation rate of methyl orange (MO) by zinc films and photocatalytic degradation rate of MO by zinc oxide films was carried out. Both reductive degradation and photocatalytic degradation process of MO by zinc and zinc oxide films can be described by first order kinetic model. It was found that although MO liquid was most quickly decolorized by metallic zinc films, the mineraliza-tion of MO was not thorough. Observation of extra ultraviolet absorption peaks indicated the formation of aromatic intermediates. On the other hand, although the photocatalytic degradation rate of MO liquid by ZnO films was only as about 1/4 large as the reductive degradation rate by zinc films, no signs of aromatic intermediates were found. Moreover, it was found that partially oxidized zinc oxide film showed higher photocatalytic efficiency than the totally oxidized ZnO films. Synergy effect between zinc and zinc oxide phase in the partially oxidized films was considered to be responsible for the higher photocatalytic efficiency.