壳聚糖-聚乳酸接枝共聚物的制备与表征

以L-乳酸和壳聚糖为原料,辛酸亚锡为催化剂,通过原位聚合法制备了含聚乳酸链段的壳聚糖接枝共聚物,讨论了原料投料比、催化剂浓度对接枝率的影响。通过红外光谱对共聚物化学结构进行分析,并通过热重分析研究其热失重行为。与壳聚糖相比,聚乳酸支链的引入有效削弱了壳聚糖分子的氢键作用,共聚物起始分解温度和热稳定性下降。     

Fracture toughness of exponential layer-by-layer polyurethane/poly(acrylic acid) nanocomposite films

This paper characterizes the fracture toughness of layer-by-layer (LBL) manufactured thin films with elastic polyurethane, a tough polymer, and poly(acrylic acid) as a stiffening agent. A single-edge-notch tension (SENT) specimen is used to study mode I crack propagation as a function of applied loading. Experimental results for the full-field time histories of the strain maps in the fracturing film have been analyzed to obtain R-curve parameters for the nanocomposite. In particular, by using the strain maps, details of the traction law are measured. A validated finite strain phenomenological visco-plastic constitutive model is used to characterize the nanocomposite film while a discrete cohesive zone model (DCZM) is implemented to model the fracture behavior. The LBL manufactured nanocomposite is found to display a higher fracture toughness than the unstiffened base polymer.     

Blood compatibility of polyurethane immobilized with acrylic acid and plasma grafting sulfonic acid

Sulfonic and carboxyl groups can effectively improve the blood compatibility of polyurethane. But it is difficult to obtain an optimum ratio of the two groups. In this article, polyurethane (PU) was dissolved with acrylic acid in a tetrahydrofuran solution and then spread on the glass plate to produce a film. At the same time, acrylic acid partly polymerized and immobilized with the PU films. The films (PU-AA) were exposed to sulfur dioxide plasma to graft sulfonic acid group on its surfaces. Through adjusting the quantity of acrylic acid and the plasma reaction condition, the antithrombin of polyurethane can be improved. The surface-modified PUs were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscope (XPS) and a contact angle goniometer. The blood compatibility of the films was examined by using thrombin time (TT), activated partial thromboplastin time (APTT) and prothrombin time (PT). The TT and APTT were significantly prolonged for the surface-modified films of PU-AA by sulfur dioxide plasma and only APTT was elongated for PU-AA. The results suggest that sulfonic acid and acrylic acid have the different effect on the blood compatibility of surface-modified PUs.     

聚(氨酯-酰亚胺)泡沫材料的研究

采用一步发泡法制备了聚(氨酯-酰亚胺)泡沫,用扫描电子显微镜分析了泡沫的泡孔结构,并对泡沫的吸隔声性能、力学和阻燃性能进行了研究。结果表明,研制的泡沫具有比较均匀的泡孔结构,在125~8000Hz范围内的平均隔声量可达25.5dB(泡沫厚度为22mm),拉伸断裂强度可达2006.4kPa,氧指数可达30以上。     

Preparation and application of acrylic acid grafted polytetrafluoroethylene fiber as a weak acid cation exchanger for adsorption of Er(III)

In this work, a weakly acidic ion exchange fiber (PTFE-g-AA) has been prepared by ⁶⁰Co irradiation grafting with acrylic acid (AA) onto the polytetrafluoroethylene (PTFE) fiber. The grafted fiber was characterized by FTIR, SEM and TGA technique. The exchange capacity of the PTFE-g-AA fiber is 3.87 mmol/g. The adsorbent material was employed for Er(III) uptaking by batch and column experiments. Kinetics studies showed that the adsorption process obeyed pseudo-second-order kinetics. The adsorption isotherms followed both the Freundlich model and Langmuir model. The maximum adsorption capacity of the PTFE-g-AA fiber for Er(III) was evaluated to be 142.0 mg/g for the Langmuir model. It was found that 0.75 M HCl–0.25 M NaCl solution provided effectiveness of the desorption of Er(III) from the PTFE-g-AA fiber. Various thermodynamic parameters such as standard enthalpy (ΔH⁰), standard entropy (ΔS⁰) and standard free energy (ΔG⁰) were evaluated. The adsorption of Er(III) on the PTFE-g-AA fiber was found to be endothermic in nature. The Thomas model was successfully applied to experimental data to predict the breakthrough curves and to determine the characteristics parameters of the column useful for process design.     

壳聚糖接枝丙烯酸高吸水性树脂的制备及性能研究

以壳聚糖(CTS)和丙烯酸(AA)为原料进行接枝共聚,制得高吸水性树脂.通过单因素及正交试验考察AA∶CTS比值、引发剂用量及交联剂用量对树脂吸水性能的影响,确定最佳合成条件.利用红外光谱对产品结构进行表征.结果表明,当AA∶CTS为10∶1,引发剂用量为单体质量的3.5％,交联剂用量为单体质量的0.35％,所制得的树脂吸水率最高,其吸蒸馏水率可达964 g/g,吸盐水率可达58g/g.     

Characterization and modification of commercial acrylic fibers grafted with acrylic acid

The graft copolymerization of acrylic acid (AA) onto commercial acrylic fibers (PAN) has been studied using Azobis(isobutyro)nitrile (AIBN) as an initiator. AA grafting initiated by radicals formed from thermal decomposition of AIBN. In this study, the effects of monomer and initiator concentration, time and temperature reaction on the grafting yield have been investigated. The optimum conditions for this grafting reaction were obtained with an AA concentration of 1.67 M, an AIBN concentration of 0.0097 M, a reaction temperature of T=85 °C and with reaction time of 60 minutes. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water absorption and also in this study has been investigated the mechanical property. The thermal analysis data showed that increasing in grafting yield, decreases the thermal stability of fiber. Grafting also affected slightly the fiber morphology. The experimental data of mechanical properties show clearly that by increasing of grafting yield, max extension will decrease. Grafting of poly AA improved water absorption.     

The actuation of a biomimetic poly(vinyl alcohol)poly(acrylic acid) gel

Active polymer gels expand and contract in response to certain environmental stimuli, such as the application of an electric field or a change in the pH level of the surroundings. This ability to achieve large, reversible deformations with no external mechanical loading has generated much interest in the use of these gels as biomimetic actuators and "artificial muscles". In previous work, a thermodynamically consistent finite-elastic constitutive model has been developed to describe the mechanical and actuation behaviours of active polymer gels. The mechanical properties were characterized by a free-energy function, and the model uses an evolving internal variable to describe the actuation state. In this work, an evolution law for the internal variable is determined from free actuation experiments on a poly(vinyl alcohol)poly(acrylic acid) (PVAPAA) gel. The complete finite-elastic/evolution law constitutive model is then used to predict the response of the PVA-PAA gel to isotonic and isometric loading and actuation. The model is shown to give relatively good agreement with experimental results.     

Lens epithelial cell response to atmospheric pressure plasma modified poly(methylmethacrylate) surfaces

Selective control of cellular response to polymeric biomaterials is an important consideration for many ocular implant applications. In particular, there is often a need to have one surface of an ophthalmic implant capable of promoting cell attachment while the other needs to be resistant to this effect. In this study, an atmospheric pressure dielectric barrier discharge (DBD) has been used to modify the surface region of poly(methyl methacrylate) (PMMA), a well established ocular biomaterial, with the aim of promoting a controlled response to human lens epithelial cells (LEC) cultured thereon. The DBD plasma discharge environment has also been employed to chemically graft a layer of poly(ethylene glycol) methyl ether methacrylate (PEGMA) onto the PMMA and the response to LEC likewise determined. Two different molecular weights of PEGMA, namely 1000 and 2000 MW were used in these experiments. The LEC response to DBD treated polystyrene (PS) samples has also been examined as a positive control and to help to further elucidate the nature of the modified surfaces. The LEC adhered and proliferated readily on the DBD treated PMMA and PS surfaces when compared to the pristine polymer samples which showed little or no cell response. The PMMA and PS surfaces that had been DBD grafted with the PEGMA₁₀₀₀ layer were found to have some adhered cells. However, on closer inspection, these cells were clearly on the verge of detaching. In the case of the PEGMA₂₀₀₀ grafted surfaces no cells were observed indicating that the higher molecular weight PEGMA has been able to attain a surface conformation that is capable of resisting cell attachment in vitro.     

聚乳酸接枝马来酸酐/丙烯酸丁酯共聚物的制备与性能

以马来酸酐(MAH)和丙烯酸丁酯(BA)为单体,通过溶液接枝法制备了聚乳酸(PLA)接枝MAH/BA共聚物(m PLA)。使用红外光谱(FT-IR)、广角X射线衍射(WAXD)、差示扫描量热仪(DSC)、热重分析仪(TG)研究了接枝共聚物的结构和性能。结果表明,随着单体质量比BA/MAH的增加,单体在PLA上的接枝率出现先增大后减小的趋势,当m(MAH)/m(BA)=1/1,m(MAH)/m(PLA)=3/100时,制备的m PLA接枝率最高为1.96%;与纯PLA相比,m PLA的结晶度和热稳定性均比有所下降,且样品的接枝率越大其结晶度越低;随着单体中BA含量的增加,m PLA的熔融温度和玻璃化转变温度有减小的趋势。     

Degradation and compatibility behaviors of poly(glycolic acid) grafted chitosan

The films of poly(glycolic acid) grafted chitosan were prepared without using a catalyst to improve the degradable property of chitosan. The films were characterized by Fourier transform-infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The degradation of the poly(glycolic acid) grafted chitosan films were investigated in the lysozyme solution. In vitro degradation tests revealed that the degradation rate of poly(glycolic acid) grafted chitosan films increased dramatically compared with chitosan. The degradation rate of poly(glycolic acid) grafted chitosan films gradually increased with the increasing of the molar ratio of glycolic acid to chitosan. Additionally, the poly(glycolic acid) grafted chitosan films have good biocompatibility, as demonstrated by in vitro cytotoxicity of the extraction fluids. The biocompatible and biodegradable poly(glycolic acid) grafted chitosan would be an effective material with controllable degradation rate to meet the diverse needs in biomedical fields.     

Grafting of poly(ethylene glycol) onto poly(acrylic acid)-coated glass for a protein-resistant surface

The surface of solid glass supports for samples in optical microscopy and for biosensors needs to be protein-resistant. A coating of a poly(ethylene glycol) monomethyl ether (mPEG) on the surface of the glass is one promising method for preventing the nonspecific adsorption of proteins. In this study, we have developed a novel technique for achieving an optimal coverage of a glass surface with mPEG to prevent protein adhesion. A clean glass substrate previously treated with (3-aminopropyl)dimethylethoxysilane (APDMES) was treated sequentially with poly(acrylic acid) and subsequently a primary amine derivative of mPEG in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The resultant glass surface was demonstrated to be highly protein-resistant, and the adsorption of bovine serum albumin decreased to only a few percentage points of that on a glass surface treated with APDMES alone. Furthermore, to extend the present method, we also prepared a glass substrate on which biotinylated poly(ethylene glycol) was cografted with mPEG, and biotinylated myosin subfragment-1 (biotin-S1) was subsequently immobilized on this substrate by biotin/avidin chemistry. Actin filaments were observed to glide on the biotin-S1-coated glass surface in the presence of ATP, and thus, the method is capable of immobilizing the protein specifically without any loss in its biological function.     

Synthesis and in vitro characterization of a poly(acrylic acid)-homocysteine conjugate

It was the aim of this study to improve our knowledge on thiolated polymers by the synthesis and in vitro characterization of a poly(acrylic acid)-homocysteine conjugate. Mediated by a carbodiimide, homocysteine was therefore covalently attached to poly(acrylic acid) via the formation of an amide bond. The isolated conjugate displayed 930 micromol +/- 83 micromol sulfur atoms per gram polymer. Of these thiol groups, 80.1% were oxidized to disulfide bonds during the coupling reaction. In aqueous solutions the conjugate was rapidly oxidized by the formation of disulfide bonds at pH 8, whereas it remained stable at pH 7 and below during the observation period of 4 hours. Due to the immobilization of thiol groups on the polymer, the mucoadhesive and cohesive properties of poly(acrylic acid) were strongly improved. Furthermore, the thiolated polymer exhibited a significantly (p < 0.05) improved permeation enhancing effect in comparison to the unmodified polymer. Because of these features the poly(acrylic acid)-homocysteine conjugate seems to represent a promising novel tool, which might be useful in particular for aqueous formulations based on thiomers.     

粉体辐射接枝丙烯酸的聚偏氟乙烯超滤膜的制备

采用粉体辐射接枝丙烯酸的聚偏氟乙烯(PVDF-g-PAA)为材料,以浸没沉淀相转化法制备PVDF-g-PAA超滤膜,研究了接枝后材料溶解性能的变化、以及溶剂种类、聚合物浓度、添加剂种类及浓度、凝胶浴温度制膜参数对PVDF-g-PAA膜结构及性能的影响.结果表明:辐射接枝丙烯酸后,聚合物的溶度参数增大,同时聚合物的极性也增强.在溶剂影响的考察中,以二甲基甲酰胺(DMF)和N-甲基吡咯烷酮(NMP)为溶剂制备的PVDF-g-PAA膜表面致密,透过通量小,对牛血清蛋白(BSA)截留率高;而以二甲基亚砜(DMSO)为溶剂制备的PVDF-g-PAA膜表面孔径较大,透过通量最大,对BSA截留率迅速下降;聚合物浓度的增加使得PVDF-g-PAA膜结构更加致密,纯水通量降低,截留率增加;随着添加剂PEG400浓度的增加,PVDF-g-PAA膜透过通量增加,膜的皮层多孔性增加,厚度增加,大孔发生的起始点向膜内部迁移;在考察的温度区间内(12～23℃),随着凝胶浴温度的升高,PVDF-g-PAA膜通量变大,截留率降低.     

聚(丙烯酸-co-丙烯酰胺)/高岭土复合高吸水性树脂的制备

采用N,N'-亚甲基双丙烯酰胺作交联剂,过硫酸铵作引发剂,通过水溶液聚合法制得了聚(丙烯酸-co-丙烯酰胺)/高岭土复合高吸水性树脂.研究了高岭土的添加量、丙烯酰胺用量、中和度、引发剂用量以及交联剂用量等对吸水率的影响.得到的最佳反应条件为:中和度为70%,丙烯酰胺、高岭土、引发剂和交联剂量分别为丙烯酸单体质量24%、18%、0.96%和0.09%.制得的高吸水性树脂在室温下30min每克吸蒸馏水和自来水分别约为其自身质量的890倍和290g倍.     

蓖麻油多元醇在聚氨酯硬泡中的应用研究

以可再生的蓖麻油为主要原料,与甘油进行酯交换反应制备蓖麻油多元醇,通过红外光谱和分子量分布,分别考察了蓖麻油/甘油不同配比、不同温度和不同反应时间下的醇解产物性质。结果证明,在一定的催化条件下,200℃下反应3h蓖麻油多元醇羟值最高达434mgKOH/g,同时蓖麻油反应转化率最高。将此蓖麻油多元醇应用于聚氨酯硬泡中,显示出较好的泡沫性能。     

油酸基多元醇的制备及其在硬质聚氨酯泡沫中的应用研究

以油酸为原料,通过环氧化,开环,酯化三步反应,制备羟值410mgKOH/g的油酸基多元醇,将其与石油基聚醚以不同比例混用制备聚氨酯硬泡,并对这些泡沫进行了机械性能和热力学性能分析测试.结果表明,油酸多元醇替代量50%时,压缩强度230kPa,弯曲强度270kPa,热导率0.035W·m-1·K-1.同时,由TG和DMA分析表明,油酸多元醇基硬泡具有较佳的热稳定性;随着油酸多元醇的增加,Tg降低,储能模量先增大后降低.