水凝胶-水凝胶复合材料的制备与表征

将聚乙二醇400(PEG400)溶胀的交联N-乙烯吡咯烷酮(NVP)水凝胶微粒浸渍在含有引发剂过氧化苯甲酰(BPO)的甲基丙烯酸-2-羟基乙酯(HEMA)单体中并加热引发聚合反应,制备水凝胶-水凝胶复合材料,研究了产物的溶胀行为,并采用SEM、DSC对产物进行了表征。结果表明,水凝胶-水凝胶复合材料的饱和含水量随交联NVP水凝胶颗粒的含量及饱和含水量增大而增大,两种水凝胶之间的界面结构可分为包埋、部分互穿网络以及完全部分互穿网络等三种,其原因在于HEMA单体部分进入交联NVP水凝胶微粒并进行原位聚合的程度不同;处于分散相的水凝胶与处于连续相的水凝胶的吸水倍率不同,导致水凝胶-水凝胶复合材料吸水溶胀时不同相结构之间互相制约,处于分散相的水凝胶的大分子链不能充分伸展,非冻结水的熔融峰被自由水的熔融峰掩盖,表现为DSC谱图上非冻结水的熔融峰被自由水的熔融峰掩盖。     

聚乙烯吡咯烷酮/壳聚糖共混水凝胶的制备与水的状态

以戊二醛作为交联剂,制备了聚乙烯吡咯烷酮（PVP）/壳聚糖（CHI）共混水凝胶,共混物的玻璃化转变温度T_g随CHI含量的升高而升高,SEM图谱观察到PVP/CHI凝胶表面呈现随CHI∶PVP比而变化的微相分离.凝胶溶胀率随着PVP含量升高、PVP分子量降低、CHI脱乙酰度增大而升高.DSC分析表明,非冷冻状态下,CHI∶PVP为1∶2时,游离水、可冻结结合水、非冻结结合水含量分别为42.7%、43.3 %、14.0 %;CHI∶PVP为1∶8时,凝胶中含非冻结结合水少,DSC曲线上只有一个明显的失水吸热峰,由游离水与可冻结结合水叠加而成.-123℃冷冻条件下凝胶的DSC升温曲线在0、38、53℃观察到一组明显的焓化峰,这是由于低温时冻结为结晶相的游离水、可冻结结合水,随温度升高吸热又转化为游离水、可冻结结合水所致.     

含硅水凝胶角膜接触镜材料的脱水行为

采用重量法研究了γ–（甲基丙烯酰氧）丙基三甲氧基硅烷（KH570）与甲基丙烯酸–2–羟基乙酯（HEMA）及N–乙烯基吡咯烷酮（NVP）共聚物水凝胶角膜接触镜材料的脱水行为。结果表明,含硅水凝胶接触镜材料的脱水机理可采用两种极限情况下的幂律模型来描述,即脱水动力学级数n=0.5和n=1;当n=1时,水凝胶的失水率（Mt/M0c）与时间t成正比,为蒸发阶段;随后的脱水阶段中n=0.5,水凝胶的Mt/M0c与时间t1/2成正比,为扩散阶段;含硅水凝胶接触镜材料的脱水速率随单体NVP和 KH570含量增大而降低,随脱水温度的升高而提高,随盐离子浓度的增加而降低。     

NVP-HEMA-AM三元共聚物水凝胶对氯霉素的缓释作用

采用本体共聚法制备了丙烯酰胺(AM)与甲基丙烯酸-2羟-基乙酯(HEMA)以及N-乙烯基吡咯烷酮(NVP)共聚物水凝胶,研究了AM-HEMA-NVP共聚物水凝胶对广谱抗菌药物氯霉素的缓释作用。结果表明,随氯霉素溶液浓度增大、NaC l浓度降低、温度升高以及NVP或者AM组分的含量增大,AM-HE-MA-NVP三元共聚物水凝胶对氯霉素的吸收量增大;随AM-HEMA-NVP三元共聚物水凝胶中NVP或者AM组分含量的增大,氯霉素的释放速度明显增大;氯霉素从水凝胶中缓释的动力学可采用Fick扩散动力学描述,其释放过程受水凝胶溶胀过程以及氯霉素扩散过程控制。     

三甲基壳聚糖季铵盐水凝胶的制备及性能

采用反应活性强和交联条件温和的二乙烯基砜为交联剂,制备了N,N,N-三甲基壳聚糖季铵盐水凝胶（TMCG）并研究了TMCG的溶胀行为、水的状态和分布以及力学性能等。结果表明,TMCG在水中溶胀迅速,平衡溶胀度达40倍,并且具有离子响应性;水分子在TMCG中以自由水、可冻结的结合水和非冻结的结合水三种形式存在,其非冻结的结合水含量随交联剂浓度的增加而增大。TMCG具有良好的力学性能,拉伸强度达13.8 MPa,断裂伸长率达135.3%。     

硅水凝胶隐形眼镜材料的合成与性能研究

以甲基丙烯酸羟乙酯（HEMA）、N-乙烯基毗咯烷酮（NVP）和γ-（甲基丙烯酰氧）丙基三甲氧基硅烷（KH-570）为单体,以偶氮二异丁腈（AIBN）为引发剂,通过本体聚合反应合成新型硅水凝胶角膜接触镜.考察了各单体配比、反应温度等对聚合的影响.结果表明,当反应温度为90℃,反应时间为2h,V（HEMA）：V（NVP）：V（KH-570） =8∶ 1∶1时,合成的隐形眼镜透氧量（DK/t）达到64.0×10-9（cm3O2·cm）/（cm2·s·mmHg）,含水量38％,透光率95.5％以上.     

智能水凝胶的制备研究

以N-乙烯基吡咯烷酮(NVP)、丙烯酸(AA)为原料,N,N′-亚甲基双丙烯酰胺为交联剂,过硫酸钾(K2S2O8)为引发剂,采用自由基聚合合成水凝胶。分别研究了原料配比、交联剂用量、引发剂比例、盐浓度、p H对水凝胶吸水能力的影响,确定了最佳用量及条件。结果表明,NVP/丙烯酸共聚物水凝胶的最佳条件为:丙烯酸跟NVP的质量比为1∶1.1~1∶1.2,引发剂的用量为丙烯酸单体质量的4%~5%,交联剂的用量为丙烯酸单体质量的7%~8%。水凝胶的吸水率随着盐浓度的增加而减小,p H为7~9时水凝胶的吸水率最高。     

AM与HEMA共聚制备水凝胶接触镜材料及其溶胀性能

采用丙烯酰胺(AM)与甲基丙烯酸β-羟乙酯(HEMA)进行本体共聚制备水凝胶接触镜材料,研究了水凝胶的溶胀性能及其温度和pH值敏感性。结果表明,引发剂过氧化苯甲酰(BPO)用量为反应单体总质量的0.3%、反应温度80℃,产物溶胀之后为无色透明的玻璃状水凝胶;共聚物水凝胶具有较好的pH值敏感性,水凝胶在酸性溶液中溶胀,在碱性溶液中收缩:含有AM的水凝胶,其pH值敏感性较大:随AM的含量增大,共聚物水凝胶的溶胀速度和饱和含水量增大,随温度升高,水凝胶的饱和含水量下降,共聚物水凝胶中AM的含量对其温度敏感性无显著影响:SEM照片显示,AM与HEMA共聚物存在均匀的纤维状结构,并且共聚物中AM的含量越大,这种纤维状结构越大、越明显。     

水凝胶-水凝胶复合材料的热分析研究

在甲基丙烯酸羟乙酯单体中加入聚乙二醇400溶胀的交联N-乙烯基吡咯烷酮水凝胶,制备了水凝胶-水凝胶复合材料,采用DSC与TG研究了该复合材料中水的特异性。结果表明,分散相水凝胶与连续相水凝胶的吸水倍率不同,导致复合材料吸水溶胀时不同相结构之间互相制约,复合材料中非冻结水的含量较多,DSC谱图上非冻结水的熔融峰被自由水的熔融峰掩盖;水凝胶中不同存在状态的水的形成与水凝胶的溶胀行为密切相关,非冻结水与中间水的形成都需要足够的空间。     

温敏型水凝胶的制备及溶胀特性

采用N-异丙基丙烯酰胺(NIPA)与N-乙烯基-2-吡咯烷酮(NVP)为共聚单体,以N,N-亚甲基双丙烯酰胺(BIS)为交联剂,过硫酸钾(KPS)为引发剂,通过化学交联的方法在水溶液中制备出P(NIPA-co-NVP)共聚物水凝胶。分别探讨了单体配比、交联剂用量等实验条件对水凝胶的温敏特性和溶胀性能的影响。利用傅里叶红外(FT-IR)对共聚物水凝胶的结构进行了表征。通过实验可知:当交联剂BIS和引发剂KPS分别为单体用量的5%和0.8%,制备的水凝胶具有较高的转化率、较好的机械强度和共聚性质。共聚物水凝胶中NVP含量越高,溶胀率越大,升温时溶胀率下降程度越大,自然条件下脱水速率越快;BIS用量越大,溶胀率越小,保水率越高,需要更长时间达到溶胀平衡。     

DSC studies on states of water in crosslinked poly(methyl methacrylate-co-n-vinyl-2-pyrrolidone) hydrogels

Mixtures of methyl methacrylate (MMA) with N-vinyl-2-pyrrolidone (VP) of various composition in the presence of fixed concentration of ethylene glycol dimethacrylate (EDMA) have been copolymerized to 100% conversion by γ-irradiation. The resultant solid xerogels were swollen in water to yield hydrogels of equilibrium water contents ranging from 15 to 76wt%. The state of water in the poly(MMA-co-VP) hydrogels has been studied by differential scanning calorimetry (DSC) and the percentages of free freezing, freezable bound and nonfreezing water were found to vary with the xerogel composition, i.e. the degree of hydration of the hydrogels. At low equilibrium swelling, most of the water exists as a non-freezing type, whereas at higher equilibrium swelling the majority of water exists as free freezing water. The maximum number of non-freezing water molecules per VP unit in the hydrogel is about 7.5.     

Swelling and mechanical properties of crosslinked hydrogels containing N-vinylpyrrolidone

Copolymers of 2-hydroxyethyl methacrylate/N-vinyl-2-pyrrolidone (HEMA/NVP) and methyl methacrylate (MMA)/NVP were prepared in the presence of varying amounts of ethylene glycol dimethacrylate (EGDMA) and methylene diacrylamide (MDA) as crosslinkers by photopolymerisation. The resultant solid polymers were swollen to equilibrium in water at 293 K to produce hydrogels. These hydrogels were characterised by soluble fraction and equilibrium water content. The gels were also characterised by compression—strain measurements, which enabled the calculation of Young's modulus and effective crosslink density. The differences in these properties of HEMA/NVP and MMA/NVP polymer series and the effects of MDA versus EGDMA as a crosslinker were explained in terms of compositional drift of polymerisation, heterogeneous crosslinking and hydrophilicity/hydrophobicity of the components involved. In comparison with EGDMA, MDA was found to be more effective in reducing the soluble fraction of the polymers studied and to produce less rigid networks when swollen.     

Photomodification of polymer surface by utilizing photoinitiated amino-groups formation–effects of comonomers on the dyeing of irradiated polymer surface

Photomodifications of polymer surface are investigated from the viewpoint of dyeing of the irradiated polymer surface. For this purpose, several kinds of acryloyl acetophenone oxime (AAPO) copolymers are prepared. As the other monomer components, methyl methacrylate (MMA), styrene (St), 2,3-epoxypropyl methacrylate (EPMA), 2-hydroxyethyl methacrylate (HEMA), N-vinyl pyrroridone (NVP), and n-butyl methacrylate (BMA) are used. In the photolysis of acyloxyimino (AOI) groups in AAPO copolymers, alkylimino groups can be introduced very effectively, which can be easily transformed to ammonium groups by hydrolysis in an aqueous solution of HCI. The surface of AAPO copolymers becomes dyeable with an acid dye (Congo Red) by the irradiation followed by HCI treatment and the degree of dyeing of the surface depends on not only the contents of ammonium groups but also the physical properties of the other monomer components. Although the hydrophilic or polar monomer such as NVP, HEMA, and MMA are cooperative for dyeing, the hydrophobic monomer such as St decreases the function of ammonium groups for dyeing. Although the undecomposed AAPO components in AAPO–MMA do not affect the degree of dyeing up to 24.5 mol % of AAPO contents in AAPO–MMA copolymers, they show the inhibition effect for dyeing of AAPO(38.8)–MMA at an earlier stage in irradiation. Aromatic moieties in AAPO are thought to inhibit the dyeing.     

Thermal decomposition of copolymers of methyl methacrylate and alkyl methacrylates obtained from a CSTR

Thermal decomposition of the copolymers of methyl methacrylate (MMA) with ethyl methacrylate (EMA) or n-butyl methacrylate (BMA) were investigated. The copolymers were obtained in a continuous stirred tank reactor (CSTR) using toluene and benzoyl peroxide, as solvent and initiator, respectively, at 80C. The volume was 1.2 litters and residence time was 3 hours. The thermal decomposition followed the second order kinetics for both MMA/EMA and MMA/BMA copolymers, which were almost in accordance with the order of copolymerization in a CSTR. The activation energies of thermal decomposition were in the ranges of 32-37 kcal/mol and 27-37 kcal/mole for MMA/EMA and MMA/BMA copolymers, respectively and a good additivity rule was observed against each composition for both copolymers. The thermogravimetric trace curve agreed well with the theoretical calculation.     

甲基丙烯酸丁酯-PEG梳形共聚物的合成与表征

以偶氮双异丁腈(AIBN)为引发剂,四氢呋喃为溶剂,采用甲基丙烯酸正丁酯(BMA)与聚乙二醇单甲醚甲基丙烯酸酯(POEM)共聚制备了支链上含聚乙二醇(PEG)的梳形共聚物。采用1H-NMR、DSC和表面接触角等方法研究了梳形共聚物的结构与性能。结果表明,聚合物中两结构单元的含量与单体投料比中的含量基本一致;投料比对聚合物的结构和性能有较为显著的影响;梳形聚合物的熔点、焓值及静态接触角随着共聚物中BMA含量的升高而升高。     

Hydrogel–hydrogel composites: The interfacial structure and interaction between water and polymer chains

This work examines the interfacial structure and interaction between water and polymer chains in the hydrogel–hydrogel composites with the goal of establishing foundations for further investigation of drug diffusion from one hydrogel to another in the soft contact lens. This is based on the ability of the hydrogel–hydrogel composites to release ophthalmic drugs in a sustained manner. The hydrogel–hydrogel composites were synthesized by immersing the glycerol-swollen particles of crosslinked N-vinyl-2-pyrrolidone (NVP) into the monomer of hydroxyethylmethacrylate (HEMA) containing initiator benzoylperoxide (BPO) that polymerizes to form a matrix in the presence of the first networks. The hydrogel–hydrogel composites were characterized by UV/Vis spectrophotometer, scanning electronic micrography (SEM), and differential scanning calorimetry (DSC). The results showed that the samples of hydrogel–hydrogel composites of the particles of crosslinked NVP and poly-HEMA were transparent and glassy and suitable for soft contact lens. Three types of the interfacial structure, no interpenetrating interface, partly interpenetrating interface, and fully interpenetrating interface, of the hydrogel–hydrogel composites existed, and the type of the interfacial structure was determined by the degree to which the monomer of HEMA penetrated into the first networks before formation of the matrix. Different from poly-HEMA hydrogels, the peaks near 0°C on DSC curves of the hydrogel–hydrogel composites did not split while they were kept acute, and the amount of freezable-bound water was less. This shows that the water incorporated in the hydrogel–hydrogel composites does not strongly interact with polymer matrix, so the hydrogel–hydrogel composites cannot keep their shape during the phase transition of water. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Observations by DSC on bound water structure in some physically crosslinked hydrogels

Linear, compositionally homogeneous copolymers containing 23–62 wt% N-vinyl-2-pyrrolidone (VP) were prepared by a semi-continuous copolymerisation with methyl methacrylate (MMA) in the absence of chemical crosslinker. Films cast from solution in chloroform were swollen in water at various temperatures (T) within the range 283–343 K. The total water content (11–80 wt%) of the resultant hydrogels at swelling equilibrium, as well as its subdivision into freezing and non-freezing water components, were measured and found to be dependent on copolymer composition and T. The network structure of these hydrogels is considered to arise from a combination of normal VP–water interactions with physical crosslinking due to hydrophobic MMA sequences, and the novel, albeit only semi-quantitative, findings are discussed on this basis.