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。     

Effect of Different Crosslinking Strategies on Physical Properties and Biocompatibility of Freestanding Multilayer Films Made of Alginate and Chitosan

Freestanding multilayer films prepared by layer‐by‐layer technique have attracted interest as promising materials for wound dressings. The goal is to fabricate freestanding films using chitosan (CHI) and alginate (ALG) including subsequent crosslinking to improve the mechanical properties of films while maintaining their biocompatibility. Three crosslinking strategies are investigated, namely use of calcium ions for crosslinking ALG, 1‐ethyl‐3‐(‐3‐dimethylaminopropyl) carbodiimide combined with N‐hydroxysuccinimide for crosslinking ALG with CHI, and Genipin for crosslinking chitosan inside the films. Different characteristics, such as surface morphology, wettability, swelling, roughness, and mechanical properties are investigated showing that films became thinner, exhibited rougher surfaces, had lower water uptake, and increased mechanical strength after crosslinking. Changes of wettability are moderate and dependent on the crosslinking method. In vitro cytotoxicity and cell attachment studies with human dermal fibroblasts show that freestanding CHI‐ALG films represent a poorly adhesive substratum for fibroblasts, while studies using incubation of plastic‐adherent fibroblast beneath floating films show no signs of cytotoxicity in a time frame of 7 days. Results from cell experiments combined with film characteristics after crosslinking, indicate that crosslinked freestanding films made of ALG and CHI may be interesting candidates for wound dressings.     

Synthesis and thermal properties of antimony doped tin oxide/waterborne polyurethane nanocomposite films as heat insulating materials

The waterborne polyurethane (WPU) was synthesized from the polycondensation between isophorone diisocyanate (IPDI) and polyoxypropylene glycol (N‐210) and then dispersed into water. Subsequently, the WPU emulsion was modified with antimony doped tin oxide (ATO) nanoparticle by ultrasonic dispersion. The ATO/WPU emulsion was cast onto Teflon molds. After being dried, ATO/WPU films were prepared. TEM indicated that the ATO nanoparticles were homogeneously dispersed in the polymer matrix at the nanometer scale. DSC showed that the ATO/WPU nanocomposites displayed increased glass transition temperatures compared to the control WPU. The mechanical properties of the films were characterized by dynamic‐mechanical analysis (DMA). The higher glass transition temperature and storage modulus indicates the superior mechanical properties of WPU modified by ATO nanoparticles over the conventional unmodified WPU. The thermal behaviors of the films were evaluated by thermogravimetric analysis (TGA). It could be found that the incorporation of ATO into WPU can improve the thermal stability dramatically. The results from UV–visible–near infrared spectra indicated that the ATO/WPU films could decrease the infrared transmission effectively. The heat‐insulation measurements showed that glass coated with ATO/WPU films possessed better heat‐insulating effect than empty glass. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation,Characterization, and Property Analysis of Environmentally Friendly Waterborne Polyurethane-Acrylate

Waterborne polyurethane (WPU) prepolymer was first prepared based on isophorone diisocyanate (IPDI), polyether polyol (NJ-210), dimethylol propionic acid (DMPA), and hydroxyethyl methyl acrylate (HEMA) via an in situ method. A series of waterborne polyurethane-acrylate (WPUA) dispersions were obtained with different proportions of acrylate (butyl acryolate and ethyl acrylate) and initiating agent by in situ dispersion technique. The structures and thermal properties of prepared WPU and WPUA were analyzed and characterized with FT-IR, UV-vis spectroscopy, and DSC. Performance of the emulsion and film was studied by means of apparent viscosity, particle size and polydispersity, surface tension, and mechanical properties. The results indicated that the particle sizes of the WPUA dispersions were larger than those of the pure WPU and the solvent resistance and mechanical properties of WPUA films were improved over those of the WPU film. The film had the greatest hardness and the least water absorption when the BA:EA mass ratio was 50:50. The obtained WPUAs have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings, and wood finishes.     

Mesomorphic properties of liquid crystalline polysiloxanes and elastomers based on a tri-vinyl crosslinker

A series of crosslinked liquid crystalline polymers and the corresponding uncrosslinked liquid crystalline polymers were prepared by graft copolymerization; their liquid crystalline properties were characterized by DSC, POM and X-ray measurements. The results show that the crosslinking obtained in the isotropic state leads to a reduction of the clearing point (T_c) of the crosslinked polymers, as compared with the corresponding uncrosslinked polymers. The crosslinked polymers with low crosslinking density (P₁-P₇) exhibit nematic mesogenic phases, as do the uncrosslinked polymers. In contrast, a high crosslinking density leads to the crosslinked polymers P₈ and P₉ losing their thermotropic liquid crystalline phases; they instead exhibit stress-induced orientation.     

Effect of Molecular Weight of WPU on the Heterogenic PUA Composite Latex Prepared by Soap-Free Emulsion Polymerization

Aqueous acrylic-polyurethane (PUA) composite emulsion was prepared by soap-free seeded emulsion copolymerization. Waterborne polyurethane (WPU) was used as the seeded emulsion and functioned as surfactant. The effect of molecular weight of WPU on the heterogenic was investigated. The molecular weight of WPU was controlled by varying the NCO/OH mole ratio. The GPC results confirmed that the molecular weight of WPU presented double distribution. And the molecular weight of WPU decreased with the increasing NCO/OH mole ratio. Surface tension test indicated that the molecular weight had little influence on the surface activity of WPU. However, after emulsion copolymerization of acrylic monomers, the morphology and properties of the PUA composite were impacted markedly by the molecular weight of WPU. With an increase in the NCO/OH mole ratio, the morphology of PUA composite latex changed from core-shell structures to fish bowl structure, and the mechanical properties of PUA films changed correspondingly.     

Preparation and Characterization of Nanocomposite Films from Chitin Whisker and Waterborne Poly(ester-urethane) With or Without Ultra-Sonification Treatment

Two series of nanocomposite films were prepared from waterborne poly(ester-urethane) and chitin whisker with and without ultrasound treatment coded as CW/WPU and CHW/WPU, respectively. The effects of ultra-sonification method and chitin whisker content on the chemical compositions, crystallization behavior and miscibility were studied by attenuated total reflection Fourier transform infrared (ATR-FTIR), wide-angle X-ray diffraction (WXRD), dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM). Thermal stability and mechanical properties of the films were measured by thermogravimetric analysis (TGA) and tensile test, respectively. The results revealed that both nanocomposite films exhibited a certain degree of miscibility when chitin whisker content was lower than 30 wt%, resulting in higher thermal stability and tensile strength than the pure waterborne poly(ester-urethane) film. Interestingly, the composite films CW/WPU with ultrasound treatment possessed better miscibility, storage modulus, thermal stability and tensile strength than those without ultrasound treatment over the entire composition range studied here. The difference can be attributed to the relatively higher dispersion level of whisker within poly(ester-urethane) matrix resulting in relatively stronger entanglement and interaction between both components. The ultrasound treatment can effectively improve the miscibility and mechanical properties of the casting nanocomposite films with nano-meter size chitin whisker added. This indicated that the structure, miscibility and mechanical properties of the nanocomposite films depended significantly on the preparation method.     

基于CuAAC反应链间自交联有机-无机杂化水性聚氨酯的合成及性能

利用4,4’-二羟甲基-1,4-庚二炔功能单体作为扩链剂合成了一系列炔基接枝量不同的水性聚氨酯（WPU）,然后基于铜催化的叠氮-炔基环加成（CuAAC）反应,采用3-叠氮基丙基三乙氧基硅烷（APTES-N₃）改性炔基功能化WPU,制备了室温链间自交联有机-无机杂化WPU. 采用红外光谱（FTIR）和核磁氢谱（¹H NMR）表征了自交联有机-无机杂化WPU. 探讨了APTES-N₃接枝量对WPU膜性能和WPU乳液形态的影响. 结果表明,随着APTES-N₃含量增加,WPU膜的结晶性逐渐下降;耐水性、耐溶剂性和热稳定性逐渐增强;WPU乳液粒子黏连程度增加. 当APTES-N₃质量分数从0增大到12%时,WPU膜的拉伸强度从14.3 MPa增加到28.6 MPa.     

Polymerization and crosslinking characteristics of a 3-methoxybutyl acrylate

Polymers of 3-methoxybutyl acrylate (3-MBA) were prepared by máss, solution, and emulsion polymerization techniques. The 3-MBA polymers could be converted from soft, rubbery, soluble, thermoplastic films to hard, glossy, flexible, crosslinked films when exposed to air and/or transition metal catalysts at elevated temperatures. The crosslinked polymers are resistant to common organic solvents and to mineral acids. Strong alkalis degraded the crosslinked polymers. The second-order transition temperature of poly-3-MBA is ?56°C. as determined by volume dilatometry. A comparison of the crosslinking properties of poly-3-MBA and other alkyl and alkoxyalkyl polymers is discussed. An autoxidative mechanism is proposed for the crosslinking of 3-MBA polymers.     

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.     

Improved UHMWPE through the control of sterilization dose and atmosphere

In this study, the effects of sterilization dose and atmosphere on UHMWPE wear properties and crosslinking were examined. The relationship between crosslinking and adhesive / abrasive wear mechanisms of acetabular cups was investigated.

The use of a vacuum sterilization atmosphere resulted in improvements in the wear resistance of UHMWPE for the adhesive/abrasive wear mechanisms for the doses examined in this study. The two measures of crosslinking, swelling ratio and gel fraction, values can be used to predict hip simulator wear rates over the sterilization dose range of 0 to 50 kGy for the vacuum atmosphere samples. Of the two measures, the swelling ratio is a more sensitive measure of the extent of crosslinking, particularly for highly crosslinked materials and therefore a more sensitive predictor of adhesive/abrasive wear rates.     

Physical characteristics and properties of waterborne polyurethane materials reinforced with silk fibroin powder

Degummed silk filament was pulverized with a home‐made machine to obtain silk fibroin (SF) powder, and the structure, morphology, and particle size of the SF powder were investigated. The individual spherical particles and aggregates with different morphology of silk fibroin coexisted in water. A waterborne polyurethane (WPU) aqueous dispersion was blended with the SF powder to prepare novel blended materials with improved physical properties. The average particle size and zeta potential of the WPU/SF aqueous dispersions were characterized. The result showed that the WPU/SF dispersion with higher SF content exhibited a less negative zeta potential and a larger average particle size. Furthermore, the effect of SF content on the morphology, miscibility, and mechanical properties of the resulting blended films was studied by scanning electron microscopy, wide‐angle X‐ray diffraction, dynamic mechanical thermal analysis, and tensile testing. The films showed an improved Young's modulus and tensile strength from 0.3 to 33.8 MPa, and 0.6 to 5.2 MPa, respectively, with the increasing of SF up to a content of 26 wt %. The negative charges in the periphery and the small particle size made a good effort on dispersing SF powder into the WPU matrix as small aggregates, and the SF powder led to the efficient strengthening of WPU materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 940–950, 2010     

核壳结构三维有序水凝胶的制备

随着科学技术的发展 ,人们不断地寻求具有新特性、新功能的高分子材料 .聚合物凝胶作为一种智能高分子材料 ,受到极大的关注[1,2 ] .聚合物凝胶具有外场响应特性 ,其体积可随外界环境如溶剂、温度、电场、磁场、ｐＨ值、化学物质或光照等条件的改变而变化 ,因而在药物可控释放、吸附分离及传感器等方面具有潜在应用价值 .对聚合物凝胶进行图案化处理 ,使之成为有序结构 ,大大拓宽了凝胶的应用范围 .Ｈｕ等[3 ,4 ] 首先报道了环境响应水凝胶表面图案的调控技术 ,图案的特征尺寸在微米级 ,此类凝胶作为光栅 ,在光纤、传感器和光通信中具有潜在…     

Crosslinking of hyaluronic acid with glutaraldehyde

Hyaluronic acid (HA) was chemically crosslinked with glutaraldehyde (GA) to produce water-insoluble films having low water contents when brought into contact with water. The crosslinking reaction was performed using uncrosslinked HA films in acetone–water mixtures. This method could produce water-insoluble HA films with water contents as low as 60 wt % when subjected to swelling with phosphate-buffered saline of pH 7.4 at 37°C. This 60 wt % water content was lower than any values for HA ever reported. There was an optimal HCl concentration around 0.01N for the HA crosslinking with GA in acetone—water mixtures. To get information on the crosslinking mechanism, alginic acid, which possesses hydroxyl and carboxyl groups in one molecule, similar to HA, and poly(vinyl alcohol) (PVA) and amylopectin, which possess only hydroxyl groups, were subjected to crosslinking with GA. PVA and amylopectin were also found to become water-insoluble after reaction with GA. On the basis of the infrared spectra of these crosslinked films, it was concluded that intermolecular formation of hemiacetal bonds with GA between the hydroxyl groups belonging to different HA molecules led to crosslinking. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3553–3559, 1997     

Characterization of crosslinked Macrotyloma uniflorum(Horsegram) protein films for packaging and medical applications

Natural polymers such as proteins and polysaccharides are of great demand in packaging and medical applications. Horse gram (Macrotyloma uniflorum) is a good source of protein and possess excellent antioxidant properties. The present study investigates the development and potential applications of transparent and water-resistant horse gram protein-based films crosslinked with citric acid. Films prepared were further characterized for their physical, chemical and biological properties. Films crosslinked at higher concentrations (15%) of citric acid exhibited 50% reduction in water sorption and reduced water vapor permeability. At 15% citric acid concentration, the films showed excellent free radical scavenging of up to 96%. Also, maximum antimicrobial activity against clinical isolates were observed for the 15% citric acid crosslinked films. Increase in thermal stability and decrease in water vapor permeability was obtained at higher levels of crosslinking. The crosslinked films were cytocompatible and showed potential to be used as substrates for cell culture. Citric acid crosslinked horse gram protein films have good physicochemical properties along with biological activities and could be suitable for applications in the packaging and medical fields.     

Properties of crosslinked polylactides (PLLA & PDLA) by radiation and its biodegradability

Crosslinked materials derived from poly(lactide) (PLA) have been produced by radiation modification in the presence of a suitable crosslinker (triallyl isocyanurate) (TAIC). The crosslinking structure introduced in PLA films has not only much improved the heat stability but also their mechanical properties. The properties of crosslinked samples are governed by crosslinking density and these improvement seemed to increase with radiation dose. This implied that the three dimensional networks have been introduced in material by radiation and the crosslinking density depended on the structure and length of PLA chains. Biodegradability of PLA was also determined by an enzymatic degradation test and burying in compost at 55 °C. Differing with PLLA, PDLA was insignificantly degraded by proteinase K. The degradation rate of PLA in compost was postponed with the introduction of crosslinks.     

Studies on the preparation of hydrolyzed starch-g-PAN (HSPAN)/PVA blend films--Effect of the reaction with epichlorohydrin

Absorbent hydrolyzed starch-g-PAN (HSPAN)/polyvinylalcohol (PVA) blend films crosslinked with epichlorohydrin (ECH) were prepared to overcome the phase separation and improve the mechanical properties of blend films. The absorbency of HSPAN/PVA blend films decreased with PVA contents due to the reduction of HSPAN contents which is known to play a major role in absorbing ability of the film. And also the absorbency decreased with the ECH contents due to the crosslinking reaction. As far as the solubility is concerned, it increased with PVA contents which is water soluble. But because of the crosslinking reaction between HSPAN and PVA by ECH, the solubility decreased with ECH contents. In the mechanical properties, the strength as well as the strain at break of the HSPAN/PVA blend films were improved very much if compared with HSPAN film, and those mechanical properties were improved even more by the reaction with ECH. The DSC thermograms of HSPAN films showed two major endothermic peaks at 32 and 128 °C, while those of PVA film showed two major endothermic peaks at 49 and 190 °C. In the non-crosslinked blend films, each four endothermic peak was apparent. But as the ECH content increased, both peaks at 128 and 190 °C disappeared and a new peak appeared at the intermediate temperature. In other words, the compatibility of blend films was increased by the reaction with ECH. Also, from the results of TGA, it was confirmed that the thermal degradation of blend films was decelerated by the crosslinking reaction.     

Properties of Aqueous Polyurethane Dispersion Modified by Epoxide Resin and Their Use as Adhesive

The aqueous polyurethane hybrid dispersion modified by the epoxy resin were synthesized using 1,4-butanediol ( BDO ) and dimethylolpropionic(DMPA) as chain extenders. A kind of automobile interior decoration adhesive was made by the modified hybrid dispersions. Effects of the content and the kinds of epoxide resin on the properties of dispersions and dispersion-cast films such as appearance, pot life, viscosity, particle size, molecular mass, hardness, swelling in water, contact angle, strength of stress, elongation at break, and other mechanical properties were studied. At the same time the effect of the E20 content on the peel strength of the adhesive for several automobile interior decoration substrates such as rubber/wood, poly(vinyl chloride)/wood; leather/wood, sponge/wood was investigated. The experimental results show that when the epoxy resin E20 content was 8%, the modified polyurethane hybrid dispersions possess better properties and the adhesive made by the modified dispersions posses better adhesion for automobile interior decoration substrates. The stress-strain curve of the modified aqueous polyurethane hybrid dispersions films shows the modified aqueous cast films possess better rigidity and toughness.     

聚(4-偶氮磺酸苯乙烯-co-4-乙烯基吡啶)与本征态聚苯胺的氢键自组装及其光电转换性能

合成了一种新的共聚体——聚(4-偶氮磺酸苯乙烯-co-4-乙烯基吡啶), 它含有吡啶环, 能作为氢受体与本征态聚苯胺进行氢键自组装. 在紫外光照下, 组装膜通过偶氮磺酸基的光解, 形成稳定的共价交联结构, 在电解质水溶液中也不被破坏, 可用作光电转换膜, 并能在盐水溶液中直接测定它的光电流. 结果表明含有本征态聚苯胺的自组装膜是一种良好的光电转换材料.     

Self-assembled Films of Poly(4-diazosulfonate Styrene-co-4-vinylpyridine) with Polyaniline and Their Photoelectric Conversion Properties

Poly(4-diazosulfonate styrene-co-4-vinylpyridine) (P(DSS-co-VP)) can self-assemble (SA) with polyaniline via H-bond interaction. The SA film was then photo-crosslinked under UV irradiation to form a covalent crosslinking structure. The photocurrent of the crosslinked SA films was determined directly in aqueous salt solution. The results showed that the polyaniline SA films were materials with good photoelectron conversion properties.