温度及pH敏感水凝胶的制备与溶胀性能研究

用顺丁烯二酸酐(MAH)对β-环糊精(β-CD)进行化学改性,合成出了一种新型功能性单体MAH-β-CD。以N,N'-亚甲基双丙烯酰胺(BIS)为交联剂,过硫酸铵(APS)为引发剂,通过氧化还原自由基引发单体MAH-β-CD、N-异丙基丙烯酰胺(NIPA)及阴离子单体丙烯酸钠(SA)共聚,合成出一种新型水凝胶。用核磁共振、红外光谱对水凝胶进行了表征。溶胀研究结果表明,该水凝胶具有较好的pH及温度敏感性。     

聚（N-异丙基丙烯酰胺）／海藻酸钠／粘土复合水凝胶的制备及溶胀动力学研究

以无机粘土为交联剂制备了聚（N-异丙基丙烯酰胺）／海藻酸钠／粘土（PINPA／SA／Clay）复合水凝胶,通过红外光谱、X射线衍射对凝胶的结构进行了表征,结果表明：粘土的结晶结构已被破坏,粘土规整的片层被剥离并在凝胶中无序分布,起到交联剂的作用;随粘土含量的增加,凝胶网络交联密度增加,溶胀速度下降。在不同温度下对不同粘土含量的凝胶进行了溶胀动力学测试,表明在低于其相转变温度时,凝胶的扩散类型为non－Fickian扩散。     

温度与pH敏感P(NIPAM-co-MAA)水凝胶的制备及性能研究

室温条件下,以安息香双甲醚作为光引发剂、N,N-亚甲基双丙烯酰胺为交联剂,在乙醇溶液中,采用紫外光照聚合的方法,合成了透明均质的聚(N-异丙基丙烯酰胺-co-甲基丙烯酸)共聚物水凝胶。用红外光谱和扫描电镜分析了水凝胶的结构,通过测定水凝胶的溶胀率和退涨率考察了单体、引发剂及交联剂用量对其性能的影响。通过p H敏感性测定,发现该共聚凝胶为阴离子型p H敏感水凝胶。在弱碱性溶液中有最高的溶胀率。     

P(AAm-co-MAA)/PANI复合水凝胶的制备及pH敏感性增强的研究

以甲基丙烯酸-丙烯酰胺共聚网络P(AAm-co-MAA)为基体,以聚苯胺(PANI)为互穿组分,制备一种P(AAm-co-MAA)/PANI复合水凝胶。实验表明,P(AAm-co-MAA)表现出pH敏感性。将PANI引入到P(AAm-co-MAA)网络中,使复合水凝胶获得更为优越的pH敏感性以及良好的膨胀可逆性,使复合水凝胶更加适用于药物的负载释放等。     

温度与pH敏感性大孔聚P（NIPAM-co-MAA）水凝胶的制备及性能研究

以乙醇水溶液作为反应介质,成功制备了温度与p H快速响应性聚（N-异丙基丙烯酰胺-co-甲基丙烯酸）[P（NIPAM-co-MAA）]水凝胶,研究了乙醇水溶液的浓度对凝胶性能的影响。通过红外光谱（FT-IR）﹑扫描电镜（SEM）﹑测溶胀比对凝胶性能进行了表征。结果表明,凝胶具有相同的化学组成与结构,但具有不同的微观形态;当乙醇浓度为30%-80%时,凝胶的溶胀率和退涨率随着反应介质中乙醇浓度的增加而增加。所制备的凝胶表现出较强的温度与p H敏感性以及较快的去溶胀速率。     

聚N异丙基丙烯酰胺/黏土纳米复合自修复水凝胶的制备及性能

以N异丙基丙烯酰胺(PNIPA)为单体,纳米黏土硅酸镁锂(LXG)为交联剂,通过原位聚合反应制备了一种具有自修复功能的高分子/纳米黏土复合水凝胶。探讨了单体和黏土配比、单体与分散剂配比等参数对水凝胶成胶性能的影响。重点对该复合水凝胶自修复机理及性能进行评价。结果表明,当单体与黏土比例为1.5~2：1,单体与分散剂比例为1：10时水凝胶成胶性能良好;水凝胶的溶胀性能随黏土含量的增加而下降,最大溶胀率为12.8 g/g;合成的水凝胶在室温下无需任何修复剂,24 h即可实现损伤断面的良好修复,自修复效率最高为43.1 %。     

快速响应的温敏性PNIPAAm／粘土复合水凝胶的合成及性能研究

以碳酸钠为制孔剂合成了快速响应的温敏性PNIPAAm／粘土复合水凝胶(NNC水凝胶),DSC分析表明,其体积相转变温度在33℃左右,与传统的PNIPAAm水凝胶没有很大的偏差。动力学研究表明,该水凝胶在温敏膨胀或收缩时,具有快速的响应速率,在5 min内的失水率达90％以上,这与扫描电镜观察到水凝胶具有大而连贯的孔洞结构相一致。     

pH-温度双重敏感性水凝胶的制备及溶胀性能研究

制备具有pH及温度双重敏感性水凝胶。通过自由基聚合反应制备出NIPAM-co-PMAA水凝胶材料。考察不同单体甲基丙烯酸(MAA)和N-异丙基丙烯酰胺(NIPA)配比对pH和温度的响应能力,探究其溶胀性能。结果表明,不同配比的水凝胶具有双重敏感性。NIPA含量不同时,对于LSCT温度有影响,MAA含量不同时,在酸性条件下溶胀率较大。结论,NIPAM-co-PMAA水凝胶有望成为药物载体。     

聚乙烯醇/水杨酸/纳米二氧化钛复合水凝胶膜的制备及性能

用纳米二氧化钛(nano-TiO_2)对聚乙烯醇/水杨酸(PVA/SA)水凝胶膜进行改性,考查了不同nano-TiO_2用量的PVA/SA/nano-TiO_2复合水凝胶膜的结构与性能。结果表明:复合膜的透明度随nano-TiO_2用量的增加而降低,而其抗菌性、抗紫外线性及透气性均随nano-TiO_2用量的增加而提高;复合膜的力学性能随nano-TiO_2用量的增加呈先上升后下降的趋势,而其溶胀性却恰好与之相反;当nano-TiO_2用量为5.0%时,复合水凝胶膜的透气系数为0.737 9 m~2/(s·kPa),拉伸强度为8.44 MPa,最大紫外线透过率仅为71.12%,透光率达69.08%,对大肠杆菌与霉菌均具有较好的抑制作用,15℃时溶胀度达19.41%。     

温度及pH敏感生物水凝胶的研究

运用互穿网络技术,合成了具有温敏性的聚(N 异丙基丙烯酰胺)(PNIPAm)和生物大分子明胶(gelatin)的互穿网络聚合物(PNIPAm/Gelatinsemi IPN和PNIPAm/GelatinIPN)水凝胶,该水凝胶的最低临界溶液温度(LCST)与PNIPAm水凝胶的LCST基本相同,均为33℃左右,但在LCST以下的平衡溶胀率减小、相变区域略微变宽。在此基础上,通过N 异丙基丙烯酰胺(NIPAm)与丙烯酸(AAc)交联共聚,改变了水凝胶的LCST,在pH=4 0的缓冲溶液中,各水凝胶的溶胀行为基本一致,与AAc含量无关,LCST都为28℃左右;在pH>4 0的缓冲溶液中,LCST随AAc组分含量的增加而增加,但温敏性减小。同时,AAc的加入,使水凝胶具有pH敏感性,敏感点为pH=4 5左右。还考察了该水凝胶降解的特点:戊二醛(GA)交联后的明胶网络,保留了明胶的生物降解性,但互穿网络水凝胶在实验条件下几乎未被胃蛋白酶和胰蛋白酶降解,在pH=9 6的碱性条件下,水凝胶可发生化学降解。     

甲基丙烯酸2-羟乙酯的合成研究

以四甲基氢氧化铵为催化剂 ,由甲基丙烯酸甲酯和乙二醇合成了甲基丙烯酸 2 -羟乙酯。通过正交实验获得了最佳反应条件为 :反应温度 75℃ ,反应时间 4h,酯醇摩尔比 1∶ 2 .0 ,催化剂的用量为 2 .0 ml,产品收率为 91.4%。     

Synthesis and dielectric properties of poly(methyl methacrylate)–clay nanocomposite materials

Poly(methyl methacrylate) (PMMA)–clay nanocomposite (PCN) materials were synthesized through in situ intercalative polymerization. A cationic surfactant, [2(dimethylamino)ethyl]triphenylphosphonium bromide, was used as an intercalating agent with pristine Na⁺‐montmorillonite (MMT). The synthesized PCN materials were subsequently investigated by a series of characterization techniques, including wide‐angle powder X‐ray diffraction, Fourier transform IR spectroscopy, transmission electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. Compared to pure PMMA, the PCN materials exhibit higher thermal degradation temperatures and glass‐transition temperatures. The dielectric properties of PCN blending with a commercial PMMA material in film form with clay loading from 0.5 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 35–100°C. Significantly depressed dielectric constants and losses were observed for these PCN‐blending materials. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2175–2181, 2005     

Poly(2-hydroxyethyl methacrylate) (PHEMA)/poly(styrene-co-acrylamide) (PSAm) blends: miscibility and hydrogel properties

The blend miscibility of poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(styrene-co-acrylamide) (PSAm) was studied by DSC. A ‘miscible window’ was found in the range 47–57 mol% of acrylamide in blending PSAm with PHEMA (1:1 w/w) and was analysed by the mean-field theory. The water content and permeability coefficients of proteins were measured. The results show that the water content of the blends depends on the composition of PSAm and the blends, and the behaviour of blends swollen in water in Fickian type. However, the permeability of the solutes not only related to water content, but was also affected by phase behaviour. Controlled release of somatotropin from a cylindrical device coated with PHEMA/PSAm was achieved.     

Poly (2-hydroxyethyl methacrylate)-based hydrogels for slow release of pralidoxime chloride

Pralidoxime chloride (PAM-Cl)-loaded poly (2-hydroxyethyl methacrylate) (PHEMA)-based hydrogels were prepared by bulk copolymerization of 2-hydroxyethyl methacrylate (HEMA) with different mol fractions (0.02–0.10) of trimethylsilyl methacrylate. Characterization of the gels was done by dynamic swelling measurements. It was found that copolymerization does not alter the swelling mechanism of PHEMA and it essentially remains Fickian in nature. In vitro drug-release studies show the increase in release time from 6 to 12 h on incorporation of a 0.1 mol fraction of trimethylsilyl methacrylate on the PHEMA backbone. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 267–270, 1997     

Entrapping of acid phosphatase in poly(2-hydroxyethyl methacrylate) matrices: Preparation and kinetic properties

The present work was undertaken to determine the influence of immobilization of acid phosphatase by entrapment in poly(2-hydroxyethyl methacrylate) (poly-HEMA) gels on the rate and duration of p-nitrophenyl phosphate hydrolysis. This enzyme was selected as model system for the sake of comparison with other immobilization techniques studied previously making use of natural polymers. Under certain conditions, catalyst inactivation induced by chemical agents employed during polymerization was very low. Activity recovery in the enzymatically filled hydrogels depends on acid phosphatase loading and attains a maximum at 2 mg per gram of support. The use of low molecular weight linear polymers as matrix fillers is advisable. The best results were achieved with poly(ethylene oxide) PEG 1500, but PEG 6000 and poly(N-vinylpyrrolidone) PVP 10 000 are also effective. Bovine serum albumin (BSA) is useless. The highest value of activity recovery obtained was 24% that of free enzyme. Roughly 30% of enzyme is retained in active form in the hydrogel and works with an efficiency ranging from 97% to 90% depending on average particle size. The kinetic parameters K_m and E_a suggest the presence of a combined diffusive and enzymatic reaction-controlling mechanism. Only a minor shift of optimum pH was observed. Both operational and storage stability are largely improved upon entrapping in hydrogels.     

Physico-chemical characterization of hybrid polymers obtained by 2-hydroxyethyl(methacrylate) and alkoxides of zirconium

Hybrid monolithic materials were prepared through polymerisation of 2-hydroxyethyl methacrylate (HEMA) mixed with zirconium alkoxides (Zr(OBuⁿ)₄, Zr(OPrⁿ)₄ and Zr(OEt)₄), modified by acetylacetonate groups. The molar ratio HEMA/Zr varied between 1 and 4. Thermo-Gravimetry coupled with Mass Spectroscopy (TG-MS) analyses, ¹³C MAS NMR and Dynamical Mechanical Thermal Analysys (DMTA) indicated the polymeric chains were interconnected by the inorganic component.The presence of zirconium alkoxides modified substantially the poly-HEMA properties. Glass transition temperature of hybrid materials derived from butoxy and propoxy was found in the range 50-80 °C, depending on the composition. The typical swelling of p-HEMA in the water, was suppressed by the presence of zirconium compounds. After immersion in distilled water, hybrid polymers showed an initial slight weight increase, followed by a small mass loss, which increases proportionally to the length of alkoxyl group (ethoxide(propoxide(butoxide) and reaches a constant value after about 40 days. The hybrids remained always rigid and transparent. Flexural modulus and strength of about 400-900 and 4-8 MPa were measured.     

共轴微反应器制备单分散聚N-异丙基丙烯酰胺/蒙脱石纳米复合微凝胶

以蒙脱石(Clay)为交联剂,采用含有N,N,N′N′-四甲基乙二胺(TEMED)的豆油溶液为连续相,含有单体N-异丙基丙烯酰胺(NIPAm)、引发剂过硫酸钾(KPS)和分散有蒙脱石的水溶液为分散相,在共轴毛细管微反应器中制备了单分散聚N-异丙基丙烯酰胺/蒙脱石(PNIPAm/Clay)复合微凝胶。红外光谱分析表明:单体的C C双键的红外特征峰917、965 cm-1和992 cm-1在聚合后的微凝胶红外谱图中消失,而Clay的Si—O键特征峰1 000 cm-1则出现在微凝胶的红外谱图中。研究了不同内径的管头、分散相的流速和表面活性剂的浓度对微凝胶大小的影响。结果表明通过更换微反应器内管管头可以将微凝胶的直径从300μm变为450μm左右;通过调节连续相的流速可以制备粒径分散系数<5%、粒径在315～435μm的微凝胶;连续相中加入表面活性剂聚甘油聚蓖麻醇酯(PGPR)也可以有效降低微凝胶粒径。     

Synthetic hydrogels 3. Solvent effects on poly(2-hydroxyethyl methacrylate) networks

Poly(2-hydroxyethyl methacrylate) networks were synthesized in aqueous solutions of propylene glycol, ethylene glycol, ethylene glycol monomethyl ether, or ethylene glycol dimethyl ether and the influences of solvent on phase separation during the polymerization process studied. Results from conversion-phase diagrams, turbidity measurements, swelling studies, and viscosity measurements show that the phase separation process is dependent upon the solubility parameter of the organic solvent, the instantaneous monomer concentration at each stage of the gel formation process, and the crosslinker content of the reaction mixture.     

Superporous poly(2-hydroxyethyl methacrylate) based scaffolds: Preparation and characterization

Superporous poly(2-hydroxyethyl methacrylate) (PHEMA) scaffolds with pore size from 10¹ to 10² μm range were prepared by radical polymerization of 2-hydroxyethyl methacrylate (HEMA) with 2 wt.% ethylene dimethacrylate (EDMA) with the aim to obtain a support for cell cultivation. Superpores were formed by salt-leaching technique using NaCl or (NH₄)₂SO₄ as a porogen. Addition of liquid porogen (cyclohexanol/dodecan-1-ol (CyOH/DOH) = 9/1 w/w) to the polymerization mixture did not substantially affect the formation of meso- and macropores. The prepared slabs were characterized by several methods including water and cyclohexane regain by centrifugation, water regain by suction, scanning electron microscopy (SEM), mercury porosimetry and dynamic desorption of nitrogen. High-vacuum scanning electron microscopy (HVSEM) confirmed permeability of hydrogel slabs to 8-μm microspheres, whereas low-vacuum scanning electron microscopy (LVSEM) at cryo-conditions showed the undeformed structure of the frozen slabs. Interconnection of pores in the PHEMA slabs was proved. Water regain estimated by centrifugation method did not include volume of large superpores (imprints of porogen crystals), in contrast to water regain by suction method. The porosities of the slabs ranging from 81 to 91% were proportional to the volume of porogen in the feed.