PVA-PAMPS-PAA三元互穿网络型水凝胶的合成及其性能研究

以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)以及聚乙烯醇(PVA)为原料,制备了PVA-PAMPS-PAA三元互穿网络型(T-IPN)水凝胶.红外分析表明,PVA与PAA以及PAMPS之间形成了较强的氢键,使得PVA分子上的C—O伸缩震动吸收峰移向了低波数处.X射线衍射以及电镜分析表明,当PVA用量较低时,PVA能均匀的穿插于凝胶网络中,形成完善的互穿网络结构,当PVA用量过高时,部分的PVA结晶而使得凝胶出现相分离.研究了该三元互穿网络型水凝胶的溶胀性能,结果表明,该水凝胶的平衡溶胀比在200至340之间,并且随着AA以及AMPS用量的增加,凝胶的溶胀速率以及平衡溶胀比均升高.该三元互穿网络型水凝胶在酸性溶液中和在碱性溶液中表现出截然不同的消溶胀性能;并且随着溶液pH的升高,凝胶在pH=9.0附近出现体积突变,表现出pH敏感性.通过研究T-IPN水凝胶的抗压缩性能发现,利用线型高分子、柔性高分子网络以及刚性高分子网络制备的三元互穿网络型水凝胶能在高溶胀比下保持较高的强度.溶胀比为180的T-IPN水凝胶,其最大抗压缩强度可达12.1 MPa.进一步研究发现,凝胶的组成以及溶胀比均对凝胶的抗压缩强度和压缩应变均存在较大的影响.     

pH敏感的聚(L-谷氨酸)-交联聚丙烯酸水凝胶的合成与性能研究

通过在聚L-谷氨酸侧链部分接枝甲基丙烯酸2-羟乙酯得到含有双键的聚(L-谷氨酸),将其与丙烯酸共聚得到由聚(L-谷氨酸)侧链接枝并交联聚丙烯酸的pH敏感水凝胶.研究水凝胶在不同pH的缓冲溶液中的溶胀性、溶胀动力学,并通过SEM观察水凝胶的微观结构.结果表明,水凝胶在低pH环境下的溶胀率明显低于高pH环境中的溶胀率,不同...     

Fabrication and characterization of poly(vinyl alcohol)/chitosan hydrogel thin films via UV irradiation

A series of poly(vinyl alcohol)/chitosan (PVA/CTS) hydrogel thin films were prepared via ultraviolet (UV) irradiation, with acrylic acid (AA) monomer added as a crosslinker without the addition of any other photo-initiator. The swelling behaviors, intermolecular chemical bonds, molecular structures, thermal behaviors, degrees of crystallinity, morphologies of the surfaces and internal structure, and their relationship to the AA content were characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Poly(acrylic acid) (PAA) and its chemical crosslinks formed in hydrogel films via free-radical reactions were confirmed using FTIR and DSC analyses. The XRD patterns indicated that the degree of crystallinity of the hydrogel films decreased as the PAA content was increased. SEM micrographs showed that a uniform interconnected pore structure was formed through the entire hydrogel structure, and a gradient in the crosslinking density through the film thickness was observed to result from extended irradiation times. The swelling behaviors revealed that the formation of PAA and its crosslinking in the hydrogel thin films improved the pH stability and controlled the degree of swelling while retaining a high swelling rate. The successful formation of chemical crosslinking without any specific photo-initiator improves the natural characteristics of CTS and PVA and imparts the resulting PVA/CTS hydrogel thin films with properties that make them very promising in biomedical applications.     

Synthesis,characterization, and swelling behaviors of chitosan‐g‐poly(acrylic acid)/poly(vinyl alcohol) semi‐IPN superabsorbent hydrogels

A series of granulated semi‐interpenetrating polymer network (semi‐IPN) superabsorbent hydrogels composed of chitosan‐g‐poly(acrylic acid) (CTS‐g‐PAA) and poly(vinyl alcohol) (PVA) were prepared by solution polymerization using ammonium persulfate (APS) as an initiator and N,N′‐methylenebisacrylamide (MBA) as a crosslinker. The effects of reaction conditions such as the concentration of MBA, the weight ratio of AA to CTS, and the content of PVA on water absorbency were investigated. Infrared (IR) spectra and differential scanning calorimetry (DSC) analyses confirmed that AA had been grafted onto CTS backbone, and PVA semi‐interpenetrating into CTS‐g‐PAA networks. SEM analyses indicated that CTS‐g‐PAA/PVA has improved porous surface and PVA was uniformly dispersed in CTS‐g‐PAA network. The semi‐IPN hydrogel containing 10 wt% PVA shows the highest water absorbency of 353 and 53 g g^?1 in distilled water and 0.9 wt% NaCl solution, respectively. Swelling behaviors revealed that the introduction of PVA could improve the swelling rate and enhance the pH stability of the superabsorbent hydrogel. Copyright © 2009 John Wiley & Sons, Ltd.     

HPAN/SPI水凝胶纤维的PH刺激响应性能

探索了聚丙烯腈(PAN)和大豆分离蛋白(SPI)在NaOH水溶液中进行PAN碱解,然后挤到凝固浴中凝固、交联,制备水解聚丙烯腈(HPAN)／SPI水凝胶纤维的方法。通过测定凝胶纤维的平衡溶胀伸长率和溶胀伸长率,观察到HPAN／SPI水凝胶纤维的滞后和可逆的伸长／收缩行为,同时在不同组成的凝胶纤维中,随着PAN含量的逐渐增大,水凝胶纤维的响应速率呈现由小到大然后减小的变化规律,当mPAN／mspt=6／4时有最好的响应性能。     

温度及pH敏感性N-乙烯基吡咯烷酮与丙烯酸β-羟基丙酯共聚物/聚(丙烯酸)互穿网络水凝胶的合成及其性能研究

由N 乙烯基吡咯烷酮与丙烯酸 β 羟基丙酯共聚物 /聚 (丙烯酸 )所得的互穿网络水凝胶P(NVP co β HPA) /PAA具有温度及pH双重敏感特性 .在酸性条件下 ,由于P(NVP)与PAA间络合作用 ,随温度升高迅速退胀 ;在碱性条件下 ,凝胶的溶胀率远大于酸性条件下的溶胀率 ,且随温度的升高而逐渐增大     

PVA/PAA水凝胶纤维的电刺激响应性能

以过硫酸胺为引发剂,在PVA水溶液中原位聚合丙烯酸单体,得到的PVA／PAA混合水溶液在凝固浴硫酸胺饱和水溶液中纺丝制备了物理缠结和氢固定网络形式的PVA／PAA水凝胶纤维。该纤维于NaCl溶液中在直流电场作用下具有电流－刺激敏感性,表现为溶胀、收缩、弯曲行为。纤维的弯曲速度和最大弯曲度随电场强度和凝胶网络中PAA含量的增加而增大,随电解质溶液离子强度的变化出现临界最大值。纤维向负极弯曲的过程中,在电场下自由离子和反庆子迁移引起的渗透压主导作用,弯曲过程主要是溶胀弯曲;向正极弯曲过程中,由于电化学反应和电场作用下产生的PH梯度导致凝胶网络构像变化主导作用,弯曲主要是收缩弯曲;弯曲由负极向正极转化过程中,两种机理对弯曲的影响相对平衡。     

Application of sensitive hydrogels in chemical and pH sensors

In the present work, pH-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blends as well as hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm), which are sensitive to organic solvent concentration in aqueous solutions, were used in silicon micromachined sensors. A sensitivity of approximately 15 mV/pH was obtained for a pH sensor with a 50 μm thick PVA/PAA hydrogel layer in a pH range above the acid exponent of acrylic acid (pK_a=4.7). The output voltage versus pH-value characteristics and the long-term signal stability of hydrogel-based sensors were investigated and the measurement conditions necessary for high signal reproducibility were determined. The influence of the preparation conditions of the hydrogel films on the sensitivity and response time of the chemical and pH sensors is discussed.     

Ultrafine hydrogel fibers with dual temperature‐ and pH‐responsive swelling behaviors

Ultrafine hydrogel fibers that were responsive to both temperature and pH signals were prepared through the electrospinning of poly(N‐isopropylacrylamide) (PNIPAAm) and poly(acrylic acid) mixtures in dimethylformamide. Both the diameters (700 nm to 1.2 μm) and packing of the fibers could be controlled through changes in the polymer compositions and PNIPAAm molecular weights. These fibers were rendered water‐insoluble by the addition of either Na₂HPO₄ or poly(vinyl alcohol) (PVA) to the solution, followed by the heat curing of the fibers. The fibers crosslinked with Na₂HPO₄ swelled to 30–120 times in water; this was significantly higher than the swelling of those crosslinked with PVA. The PVA‐crosslinked hydrogel fibers, however, exhibited faster swelling kinetics; that is, they reached equilibrium swelling in less than 5 min at 25 °C. They were also more stable after 1 week of water exposure; that is, they lost less mass and retained their fibrous form better. All the hydrogel fibers showed a drastic increase in the swelling between pH 4 and 5. The PVA‐crosslinked hydrogel fibers exhibited distinct temperature‐responsive phase‐transition behavior of PNIPAAm, whereas the Na₂HPO₄‐crosslinked hydrogel fibers showed altered two‐stage phase transitions that reflected side‐chain modification of PNIPAAm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6331–6339, 2004     

Complexation between poly(acrylic acid) and poly(vinylpyrrolidone): Influence of the molecular weight of poly(acrylic acid) and small molecule salt on the complexation

Poly(acrylic acid) (PAA) with different molecular weight and poly(vinylpyrrolidone) (PVP) were prepared by free radical polymerization using 2,2′-azoisobutyronitrile (AIBN) as initiator in anhydrous methanol for PAA, and in distilled water for PVP. Then, the complexation between PAA and PVP in aqueous solution was studied by UV transmittance measurement and fluorescence probe technique. The result shows that (1) at low pH, the formation of complexation between PAA and PVP bases on the intermacromolecular hydrogen bond and the composition of the formed complex is around 3:2 (the unit molar ratio of PAA to PVP) at pH 2.60 over the range of pH investigated. (2) The cooperative interaction through the formation of hydrogen bond among active sites plays an important role in complex formation, and depends on the pH of solution, the required minimum chain length of poly(acrylic acid). (3) The hydrogen bond is not affected by small molecular salt, which only affects those carboxylic groups without forming hydrogen bond on the PAA chain.     

PVA改性PAMPS-PAM超高力学性能双网络水凝胶的制备

采用紫外光引发聚合制备了聚乙烯醇(PVA)改性的聚(2-丙烯酰胺基-2-甲基丙磺酸)-聚丙烯酰胺(PAMPS-PAM)双网络(DN)水凝胶.测定并比较了PVA改性前后PAMPS-PAM双网络水凝胶的溶胀动力学;通过扫描电子显微镜(SEM)观察了单网络水凝胶的结构;测定PVA改性前后PAMPS-PAM双网络水凝胶的压缩及拉伸性能.结果表明,经PVA改性后的PAMPS-PAM双网络水凝胶有较高的溶胀比;0.82%PVA用量的PAMPS-PAM双网络水凝胶在90%压缩形变率下仍保持完整、最大拉伸应力达到0.5 MPa,大幅提高PAMPS-PAM双网络水凝胶的力学性能.     

聚乙烯醇/丙烯酸共聚物水凝胶的制备及溶胀性

制备了具有pH敏感性的聚乙烯醇(PVA)/丙烯酸(AA)共聚物水凝胶,研究了PVA与AA之间配比、交联剂、引发剂用量对凝胶转化率的影响,对水凝胶的溶胀行为和pH敏感性也进行了详细研究.实验表明PVA与AA的质量比为(1∶9)~(3∶7)之间时,引发剂和交联剂分别为PVA和AA总量的0.2%和0.3%时,凝胶转化率高.随着水溶液pH值从3增加到9,凝胶的溶胀比也相应的增加,表现出明显的pH敏感性.     

Poly(acrylic acid) with disulfide bond for the elaboration of pH-responsive brush surfaces

We report on a new route for the facile preparation of pH-responsive tethered brushes on metallic surfaces, starting from poly(acrylic acid) (PAA) containing a disulfide (S-S) bond (PAA-S-S-PAA). First, atom transfer radical polymerization (ATRP) of 1-ethoxyethyl acrylate (EEA) with a disulfide-containing initiator was performed to obtain the poly(EEA) precursor polymer (PEEA-S-S-PEEA). Deprotection of PEEA by a heating step resulted in the desired PAA chains without any further purification. The brushes, obtained by the ‘grafting to’ of PAA-S-S-PAA onto gold, were then characterized by atomic force microscopy in water at various pH values. The results evidence a large collapsing/swelling capacity.     

聚乙烯醇/羧甲基壳聚糖共混水凝胶的辐射合成及性能

采用电子加速器辐照法制备了聚乙烯醇(PVA)/羧甲基壳聚糖(CMCH)共混水凝胶;研究了PVA与CMCH的配比、辐照剂量、温度以及pH值对PVA/CMCH共混水凝胶性能的影响.实验发现,PVA与CMCH在辐照剂量为40 kGy、配比为w(PVA)/w(CMCH)=5/1的条件下可得到强度较好的PVA/CMCH共混水凝胶,该水凝胶具有一定的温度和pH敏感性:在5~20℃时具有较高的溶胀率,温度在20℃以上溶胀率较低;水凝胶在pH<4.0和pH>6.0时溶胀率均较大,而当pH为4.0~6.0时溶胀率较小.     

Synthesis and Properties of IPN Hydrogels Based on Konjac Glucomannan and Poly（acrylic acid）

As a random copolymer of β-(1,4) linked D-mannose and D-glucose, konjac gluco- mannan (KGM) is a naturally occurring water-soluble polysaccharide, and has been paid attention in the field of drug controlled release carriers potentially used in colon1,2. …     

High-performance membranes for pervaporation II. Crosslinked poly(vinyl alcohol)–poly(acrylic acid) blends

Dense membranes made by crosslinking of poly(vinyl alcohol) (PVA) with poly(acrylic acid) (PAA) were prepared and tested in pervaporation and differential permeation of water–alcohol mixtures. Instead of a decrease of permeation flux as generally observed with most crosslinking agents, an increase in the permeability was observed with PAA crosslinked membranes at low PAA contents. The permeation flux increases with PAA contents in the polymer with no selectivity reduction for membranes containing less than 15 wt. % PAA. The membranes show good performances to water–2-propanol and water–ethanol mixtures, i.e. high fluxes and high selectivities to pure water. The membranes were stable and highly permeable to water. The enhancement of the permeability of PVA can be explained by a reduced crystallinity and an improved diffusivity due to the presence of PAA.     

Photo-grafting Poly(acrylic acid) onto Poly(lactic acid) Chains in Solution

Poly(lactic acid)(PLA)is one of the most important bio-plastics,and chemical modification of the already-polymerized poly(lactic acid)chains may enable optimization of its material properties and expand its application areas.In this study,we demonstrated that poly(lactic acid)can be readily dissolved in acrylic acid at room temperature,and acrylic acid can be graft-polymerized onto poly(lactic acid)chains in solution with the help of photoinitiator benzophenone under 254 nm ultraviolet(UV)irradiation.Similar photo-grafting polymerization of acrylic acid(PAA)has only been studied before in the surface modification of polymer films.The graft ratio could be controlled by various reaction parameters,including irradiation time,benzophenone content,and monomer/polymer ratios.This photo-grafting reaction resulted in high graft ratio(graft ratio PAA/PLA up to 180%)without formation of homopolymers of acrylic acid.When the PAA/PLA graft ratio was higher than 100%,the resulting PLA-g-PAA polymer was found dispersible in water.The pros and cons of the photo-grafting reaction were also discussed.     

基于互穿网络结构的pH/温度双重刺激响应性微凝胶的研究

室温下采用氧化-还原引发体系,以低交联密度的聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶为种子,通过种子乳液聚合法合成由PNIPAM和聚丙烯酸(PAA)形成的具有互穿聚合物网络结构的微凝胶.傅立叶变换红外光谱分析结果表明微凝胶由PNIPAM和PAA两种聚合物组成,透射电镜表征结果证实微凝胶中PNIPAM和PAA两种聚合物形成了互穿网络结构.用动态激光光散射测试不同温度或pH值水介质中微凝胶的粒径,结果发现微凝胶具有良好的pH/温度双重刺激响应性.在水介质pH值大于5.5的情况下,PAA组分对微凝胶的体积相转变温度没有影响;而在水介质pH值为4.0的情况下,由于PAA与PNIPAM之间的氢键作用,微凝胶的体积相转变温度稍微降低.微凝胶中PAA组分含量越高,其pH刺激响应性越显著.     

瓜胶/聚丙烯酸互穿聚合物网络水凝胶对模型药物的负载与控制释放

考察了以牛乳清蛋白(BSA)为模型药物,通过相平衡分配法制备载药瓜胶(GG)/聚丙烯酸(PAA)互穿聚合物网络(IPN)水凝胶的工艺条件.借助紫外可见光谱仪研究了载药水凝胶在结肠酶存在下的控制释放行为.结果表明:载药容量(CM)随瓜胶、丙烯酸用量的增加而下降,半IPN水凝胶的Cm较全IPN的略大;结肠酶能明显提高半IPN与全IPN中的BSA释放速率,且提高幅度随GG含量的增加而加快,GG/PAA IPN水凝胶具有结肠定位降解的特性,有望成为靶向结肠给药的理想载体材料.     

Effect of copolymer architecture on the response of pH sensitive fibers based on acrylonitrile and acrylic acid

Copolymers of acrylonitrile and acrylic acid with high acrylic acid feed ratio of 43 mol% were synthesized using free radical polymerization. The architecture of copolymers was modified by regulating the dosing of more reactive comonomer-acrylic acid. ¹³C NMR analysis confirmed that two copolymers - one (A) containing enriched blocks of individual monomer-residues (architecture close to a block copolymer) and the second (B) having nearly random distribution of the comonomers, could be successfully synthesized. The resultant acrylic acid content was determined to be nearly 50 mol% for both the copolymers. These copolymers were converted to fine fibers by solution spinning in DMF-water system, drawn in coagulation bath, and annealed at 120 °C for 2 h. The fibers were evaluated for pH response behavior, mechanical stability, and retracting stresses. The fiber A was found to have significantly higher swelling percentage (3300-3700%), faster response, and higher stability to repeated cycling compared to fiber B. Also, Fiber A showed lower thermal shrinkage, better mechanical properties during swelling and higher retracting forces during deswelling. These results indicate that the copolymer with enriched block architecture could possibly form segregated domain structure with acrylic acid domains facilitating enhanced pH response while acrylonitrile domains providing physical crosslinks for stronger mechanical strength. The study suggests that above approach may be more useful than chemically cross-linked gel rods in producing artificial muscles with faster response and good mechanical properties.