热敏性印迹水凝胶的合成及对甘草酸分离性能的研究

以甘草酸分子为印迹分子,N-异丙基丙烯酰胺作为温度响应性单体,和甲基丙烯酸共同为甘草酸的吸附性单体,在大量交联剂存在下,N-甲基吡咯烷酮中经自由基模板聚合,制备了一种热敏性印迹凝胶,对水凝胶的热收缩动力学进行了表征;用红外光谱证实了甘草酸分子与单体分子间的相互作用,以旁证其模板作用的存在：同时还与没有模板作用所合成的同种凝胶作了实施对比,发现模板聚合所得的水凝胶可以富集水溶液中的甘草酸,并对它表现出特殊的选择性分离作用,分配系数约为非模板聚合水凝胶的11倍。     

Application of Crosslinked Ionic Poly(Vinyl Alcohol) Nanogel as Adsorbents for Water Treatment

Core-shell smart ionic nanogels based on poly(vinyl alcohol) (PVA) core and poly(N-isopropylacrylamide/acrylic acid) p(NIPAm-AAc) shell particles were successfully synthesized through a one-step surfactant-free emulsion polymerization method (SFEP). Different mole ratios of p(NIPAm-AAc) shells were synthesized. The morphologies of PVA/p(NIPAm-AAc) nanogels were investigated by transmission electron microscope (TEM). The data showed the formation of spherical nanoparticles and well-defined core-shell nanogels. PVA/p(NIPAm-AAc) core-shell nanogels were applied as a novel polymeric adsorbent to remove heavy metal pollutants from aqueous solution. Copper(II) (Cu²⁺) ions were selected as the target pollutant to evaluate these nanoparticles’ adsorption capability. The influence of the uptake conditions such as pH, weight ratio of nanoparticles, time, initial feed concentration, and adsorption temperature on the metal ion binding capacity of nanogels was also tested. Adsorption equilibrium data were calculated according to Langmuir and Freundlich isotherms. It was found that the sorption of Cu²⁺ was better suited to the Freundlich adsorption model than the Langmuir adsorption model. Also, the selectivity of the nanogels toward the different metal ions such lead (Pb²⁺) and cadmium (Cd²⁺) were tested. The maximum of Cu²⁺ ions adsorbed on to PVA/p(NIPAm-AAc) core-shell nanogels adsorbent was 94 mg/g obtained under simple and fast experimental conditions, indicating these nanogels can be used as effective and practical polymeric adsorbents.     

The Effect of Number of Arms on the Aggregation Behavior of Thermoresponsive Poly(N-isopropylacrylamide) Star Polymers

The thermoresponsive nature of aqueous solutions of poly(N-isopropylacrylamide) (PNIPAAM) star polymers containing 2, 3, 4, and 6 arms has been investigated by turbidity, dynamic light scattering, rheology, and rheo-SALS. Simulations of the thermosensitive nature of the single star polymers have also been conducted. Some of the samples form aggregates even at temperatures significantly below the lower critical solution temperature (LCST) of PNIPAAM. Increasing concentration and number of arms promotes associations at low temperatures. When the temperature is raised, there is a competition between size increase due to enhanced aggregation and a size reduction caused by contraction. Monte Carlo simulations show that the single stars contract with increasing temperature, and that this contraction is more pronounced when the number of arms is increased. Some samples exhibit a minimum in the turbidity data after the initial increase at the cloud point. The combined rheology and rheo-SALS data suggest that this is due to a fragmentation of the aggregates followed by re-aggregation at even higher temperatures. Although the 6-arm star polymer aggregates more than the other stars at low temperatures, the more compact structure renders it less prone to aggregation at temperatures above the cloud point.     

一种新型生物可降解温敏互穿聚合物网络水凝胶

采用互穿聚合物网络（IPN）技术合成了以魔芋葡甘聚糖（KGM）和聚（N-异丙基丙烯酰胺）（PNIPA）为组分的IPN凝胶，对所得凝胶结构进行了红外光谱分析．讨论了不同反应条件对产物凝胶溶胀性能和去溶胀性能的影响，观察到IPN凝胶的较低临界溶解温度约为31℃．当外界温度从20℃迅速转变为37℃时，凝胶在5min内快速收缩，大量失水，表现出良好的温度敏感性．体外降解实验结果显示IPN凝胶选择性地被伊糖苷酶以较高速率降解，且凝胶降解率随着KGM含量的增加而增加，即这种新型的IPN凝胶同时具备了KGM的生物可降解性和酶降解特异性，以及PNIPA的温度敏感性．     

Thermosensitive injectable hydrogels from poly(N-isopropylacrylamide)–dextran aqueous solutions: Thermogelation and drug release properties

Novel injectable thermosensitive hydrogel formulations with improved both water retention (WR) and drug release profile were prepared by adding dextran (DXT) to poly(N-isopropylacrylamide) (PNIPAM) aqueous solutions as a remedy against the demixing/syneresis phenomenon. The addition of the hydrophilic polysaccharide improved the WR of the hydrogel at 37°C from about 12% in the absence of DXT to about 40–55% out of the initial amount introduced, depending on both PNIPAM and DXT concentrations. Also, the 5-fluorouracil release experiments showed an appreciably reduced “burst effect” for the DXT-containing hydrogels. The shape of the release profiles revealed the presence of two stages, differing each other from the point of view of the drug release rate.     

Preparation of thin polymer films with controlled drug release

Poly(N-isopropylacrylamide) (PAAm) is a thermal responsive polymer that undergoes a structural change in aqueous solution at its lower critical solution temperature (LCST). PAAm-modified silicon substrates were prepared and the effect of PAAm density on the thermal response of the modified surface was examined in terms of changes in the water contact angle as a basis for applying the structural change of the polymer to controlled drug release. Changes with temperature in the ability to load and release of the modified layer for drug were also examined using 2-acetoxybenzoic acid (aspirin) as a model drug. The amount of PAAm was found to greatly affect the thermal response and the ability to load and release of the modified layer for aspirin.     

基于γ-环糊精和聚N-异丙基丙烯酰胺色谱固定相的制备及应用

以多孔硅胶为载体,通过聚合反应将N-异丙基丙烯酰胺和甲基丙烯酸缩水甘油醚接枝于硅胶表面,并在聚合物链中植入γ-环糊精.用1H核磁共振、元素分析、红外光谱对其结构进行表征,并将此材料用作液相色谱固定相,通过考察在高亲水有机流动相中极性亲水化合物的保留,发现此固定相具有亲水色谱(HILIC)的特征,可以用于核苷类亲水化合物的分离.此外,还可以用于富勒烯碳60(C60)和碳70(C70)的分离,相比于C60,此固定相对C70有更强的保留,表明此固定相表面γ-环糊精对C70具有立体选择性.并且,此固定相具有一定的温敏特性,仅通过改变柱温就可以达到分离的目的.     

具有温度敏感和智能荧光特性的聚合物包覆金纳米粒子的研究

以4-二甲氨基吡啶稳定的金纳米粒子(DMAP-AuNPs)为前驱体,通过与端基含二甲氨基查尔酮的聚N-异丙基丙烯酰胺(PNIPAM-DMAC)进行配体置换,制备了具有温度敏感和智能荧光特性的PNIPAM-DMAC聚合物包覆的金纳米粒子(PNIPAM-AuNPs),并通过紫外可见吸收光谱、透射微镜、核磁共振氢谱、红外光谱和热重分析仪对其形貌和结构进行了分析和表征.PNIPAM-AuNPs能够很好地分散在水、乙醇、丙酮、氯仿和四氢呋喃中,其表面等离子共振(SPR)吸收特征波长分别为537、527.6、527.4、532.2和530.4 nm.PNIPAM-AuNPs的表面聚合物接枝密度为1～2条聚合物链/nm2.温敏性结果表明,PNIPAM-AuNPs具有低临界溶解温度(LCST),其LCST温度比相应的PNIPAM-DMAC聚合物低2.5 K;在PNIPAM-AuNPs发生相转变前后,金纳米粒子的SPR特征峰由537 nm蓝移至525 nm处.荧光性能研究表明,随着溶剂极性的增加,PNIPAM-AuNPs 的荧光特征波长发生红移,荧光强度先增加后减小,具有极性敏感的荧光特性;在25℃时,PNIPAM-AuNPs水溶液几乎无荧光,而当温度升高到45℃后,荧光强度显著提高,表现出温度“开/关”的荧光特性.     

用红外光谱研究具有互穿网络结构的pH/温度双重敏感性微凝胶的相转变行为

采用傅立叶变换红外光谱仪测试了由聚(N-异丙基丙烯酰胺)(PNIPA)和聚丙烯酸(PAA)两种聚合物网络形成的具有互穿聚合物网络结构(IPN)的pH/温度双重敏感性微凝胶D2O分散液,通过差谱技术对不同pH值和温度条件下的红外吸收光谱进行处理,研究微凝胶相转变过程中分子链微环境的变化.结果表明,随着D2O介质的pH值增...     

Preparation of multisensitive poly (N-isopropylacrylamide-co-acrylic acid)/TiO2 composites for degradation of methyl orange

Composites of poly (N-isopropylacrylamide-co-acrylic acid)/titanium dioxide (TiO₂) have been prepared via UV-initiated free radical polymerization. Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), environmental scanning electron microscope (ESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to study the composition, structure, and morphology of the as-prepared composites. TiO₂ is found to be successfully encapsulated in the copolymer in spherical shapes with size of 2.5 μm. The thermo- and pH-responsive properties of the composites are observed using dynamic light scattering (DLS). The photocatalytic property of the composites is studied using UV–vis spectrophotometer on the degradation of methyl orange (MO) solution under various pHs and temperatures. Degradation ratio is higher at low pH and increases with increasing temperature above volume phase transition temperature (VPTT).