分散聚合法合成聚（N-异丙基丙烯酰胺）温敏性微凝胶

以PVP为稳定剂,在水或醇/水介质中通过分散聚合法合成出聚（N-异丙基丙烯酰胺）（PNIPAM）温敏性微凝胶。研究结果表明,可通过改变稳定剂用量和分散介质极性来控制PNIPAM微凝胶的大小,这两种因素对PNIPAM微凝胶的溶胀比有明显的影响,而对其相转变行为影响不大;交联剂用量对PNIPAM微凝胶的粒径、溶胀比和相转变行为都有比较明显的影响。PNIPAM微凝胶可能主要通过接枝共聚物聚结机理成核,通过初级粒子之间的聚并完成粒子增长过程。     

聚（N-异丙基丙烯酰胺）/聚丙烯酸半互穿网络微凝胶的合成及表征

利用IPN技术合成了一种具有温度和pH双重敏感性的聚（N-异丙基丙烯酰胺）/聚丙烯酸半互穿网络微凝胶（PNIPAM/PAAc semi-IPN）。这种微凝胶在酸性条件下发生典型的体积相转变;而在弱碱性条件下,当温度低于聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶的体积相转变温度（VPTT）时,微凝胶的粒径随着温度的上升而增大,当温度达到VPTT后,粒径突然急剧减小,并随着温度的逐渐上升而减小,最终趋向平衡。     

PNIPAM微凝胶/PVDF温敏膜的制备及其性能研究

将自由基聚合法合成的聚N-异丙基丙烯酰胺(PNIPAM)微凝胶和聚偏氟乙烯(PVDF)共混,制备出了具有温度响应性的复合膜。采用FTIR、SEM对PNIPAM微凝胶/PVDF温敏膜的组成及结构进行分析,可以发现PNIPAM微凝胶被成功包裹在PVDF膜孔中,并使膜的孔径增大。PNIPAM微凝胶对温度具有较好的响应性,可以通过改变温度调节微凝胶的溶胀和收缩,进而调控复合膜的水通量。     

基于PNIPAM微凝胶的复合水凝胶制备及其性能研究

利用乳液聚合法制备分散性良好的聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶,再以微凝胶为交联点制备PNIPAM水凝胶。分析微凝胶粒径、双键质量摩尔浓度对PNIPAM水凝胶溶胀度的影响,结果表明,水凝胶在25～50℃的溶胀度最大能达到4 054. 35%。分别采用原位包裹和后包裹法制备了载药水凝胶,体外释放结果表明,水凝胶的结构和载药方式对释药行为有影响,其中含原位包裹微凝胶的载药水凝胶缓释效果最好。     

近红外光响应氧化石墨烯/微凝胶复合智能水凝胶

设计合成了一种包含氧化石墨烯（GO）片层、聚（N-异丙基丙烯酰胺）（PNIPAM）微凝胶球体和PNIPAM链段的复合结构水凝胶。通过控制聚合时间得到负载双键且粒径不同的PNIPAM微凝胶,将其作为交联点与N-异丙基丙烯酰胺（NIPAM）聚合,GO作为纳米填料掺入水凝胶体系,GO片层上的含氧基团与NIPAM上的胺基产生氢键物理交联。此方法制备的复合水凝胶同时具有温度敏感和近红外光敏感特性,通过改变GO浓度、微凝胶的合成时间、NIPAM浓度等条件,水凝胶的光敏感性和温度敏感性得到提升。相比于传统PNIPAM水凝胶,此种复合水凝胶能够对光响应,实现非接触式控制形变,且响应速率快、响应程度高,可应用于光控开关等领域。     

近红外光响应氧化石墨烯/微凝胶复合智能水凝胶

设计合成了一种包含氧化石墨烯(GO)片层、聚(N-异丙基丙烯酰胺)(PNIPAM)微凝胶球体和PNIPAM链段的复合结构水凝胶。通过控制聚合时间得到负载双键且粒径不同的PNIPAM微凝胶,将其作为交联点与N-异丙基丙烯酰胺(NIPAM)聚合,GO作为纳米填料掺入水凝胶体系,GO片层上的含氧基团与NIPAM上的胺基产生氢键物理交联。此方法制备的复合水凝胶同时具有温度敏感和近红外光敏感特性,通过改变GO浓度、微凝胶的合成时间、NIPAM浓度等条件,水凝胶的光敏感性和温度敏感性得到提升。相比于传统PNIPAM水凝胶,此种复合水凝胶能够对光响应,实现非接触式控制形变,且响应速率快、响应程度高,可应用于光控开关等领域。     

固载型杂化微球模拟催化氧化脱硫性能

以N-异丙基丙烯酰胺(PNIPAM)高聚物微凝胶为载体,利用外源沉积法制备表面担载有过氧磷钨杂多酸季胺盐(PW-HPW)的杂化微球(PW-HPW/PNIPAM).该杂化微球具有明显的核-壳结构,内部为PNIPAM水凝胶,表面均匀覆盖具有催化活性的过氧磷钨酸季胺盐.以过氧化氢为氧化剂,主要以二苯并噻吩(DBT)为模拟硫化物,研究了该杂化微球在催化氧化脱硫方面的催化性能.结果表明,杂化微球具有较高的催化活性,最佳条件下,40℃下反应8h,DBT转化率达到了90.32%.与过氧磷钨杂多酸季胺盐相比,担载后的杂化微球便于从体系中分离,经简单处理后可再次循环使用达3次以上.     

多重响应壳聚糖微凝胶的制备及溶胀性

采用无皂乳液聚合法制备聚(N-异丙基丙烯酰胺)/壳聚糖微凝胶(PNIPAM/CS),透射电镜和动态光散射研究了微凝胶外貌形态及刺激响应性。结果显示,微凝胶颗粒呈球形,具有核、壳结构形态。加入壳聚糖对PNIPAM的体积相转变温度(VPTT)有影响,微凝胶VPTT随壳聚糖用量的增加向高温迁移,此结果与示差量热法(DSC)测定一致。不同pH条件下微凝胶粒径变化表明,颗粒直径随pH增大逐渐减小,至碱性又增大,显示明显的pH敏感性;相应颗粒Zeta电位逐渐减小,接近中性达到等电点,至碱性反转为负值,这一变化能对微凝胶pH敏感性进行合理解释。     

PNIPAM/锂藻土纳米复合凝胶微球的制备及其弹性力学性能

利用微流控技术,以锂藻土作为交联剂,成功制备得到温度响应型聚（N-异丙基丙烯酰胺）（PNIPAM）与锂藻土的纳米复合凝胶微球,并利用一种简单的微步进单轴压缩装置,分别在25℃和37℃下对具有不同锂藻土含量的PNIPAM/锂藻土纳米复合凝胶微球的弹性力学性能进行系统研究。该微步进单轴压缩装置主要包括三个部分：一个程控进样器用以实现对凝胶微球的微步进压缩,一套配有高分辨率数码相机的侧视光学系统用以记录凝胶微球受压时发生的形变,一台精密电子天平作为力传感器用来记录凝胶微球在特定形变下所受的外力。研究结果表明,纳米复合凝胶微球在25℃和37℃下的形变量H与所受压力F的实验数据与Hertz弹性接触理论方程呈现良好的拟合关系,证明了PNIPAM/锂藻土纳米复合凝胶微球在25℃和37℃下均具有弹性形变行为。同时,随着锂藻土含量的增加,PNIPAM/锂藻土纳米复合凝胶微球的温敏性降低,但其杨氏模量增大。具有相同锂藻土含量的纳米复合凝胶微球,由于温度升高凝胶体积收缩、凝胶结构变得致密,因此在37℃下的杨氏模量大于其在25℃下的杨氏模量。研究结果可为PNIPAM/锂藻土纳米复合凝胶微球的设计与实际应用提供指导。     

聚(N-异丙基丙烯酰胺)微凝胶的流变性能研究

首先采用无皂乳液聚合法成功制备出粒径均匀的聚N-异丙基丙烯酰胺(PNIPAM)微凝胶,利用动态光散射法(DLS)测得微凝胶的粒径随温度的升高而下降,结果表明:PNIPAM微凝胶具有明显的温度敏感性。利用旋转流变仪对微凝胶分散液的稳态和动态粘弹性进行了研究,结果表明:当温度低于体积相转变温度(VTPP)时,微凝胶呈现出剪切变稀的特性;应力、应变保持不变,随着温度的升高及温度不变,随着频率的增加微凝胶都由液态变成了粘弹性固体,这可能是由于出现了三维逾渗网络结构造成的。     

Fluorescence analysis for thermo-sensitive hydrogel microspheres

Poly(N-isopropylacrylamide) (PNIPAM) hydrogel microspheres were prepared by precipitation polymerization above the polymer's lower critical solution temperature (LCST) in water. The hydrodynamic size of PNIPAM microspheres exhibited a thermo-sensitive change around the LCST. In order to obtain information about the interface of the hydrogels, contact angle measurement, protein adsorption, and fluorescence analysis were performed. Contact angle measurement and protein adsorption showed a gradual change around the LCST similar to the change of the hydrodynamic size. However, fluorescence study exhibited a sharp change at the LCST. In addition, a quenching experiment was employed to elucidate the location of the fluorescent probes. In the PNIPAM latex, the probes were located where they were less quenchable as compared to the PNIPAM solution. It seems probable that the probes can penetrate into the crosslinked PNIPAM hydrogel and might reflect the inner environment of the hydrogel. The effect of salt on thermo-sensitive behaviour was also detected by fluorescence analysis. On the other hand, the hydrogel microsphere prepared from poly(acryloyl pyrrolidine) (PAPr) showed a gradual change in fluorescence with temperature.     

Flow characteristics of thermo‐responsive microspheres in microchannel during the phase transition

To probe into the flow and aggregation behaviors of thermo‐responsive microspheres in microchannel during the phase transition, the flow characteristics of monodisperse poly(n‐isopropylacrylamide) (PNIPAM) microspheres in microchannel with local heating are investigated systematically. When the fluid temperature in the microchannel increases across the lower critical solution temperature (LCST), the PNIPAM microspheres finish the phase transition within 10 s and are easily get aggregated during the phase transition. The diameter ratio of microsphere to microchannel, number of microspheres, initial distance between microspheres, and flow direction of fluid in microchannel, are key parameters affecting the flow and aggregation behaviors of the microspheres in microchannel during the phase transition. If a proper combination of these parameters is designed, the microspheres can aggregate together during the phase transition and stop automatically at a desired position in the microchannel by local heating, which is what the targeting drug delivery system expected. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Preparation and Characterization of Temperature‐Sensitive Poly(Styrene‐Butadiene‐Styrene)/Poly(N‐Isopropylacrylamide) Hydrogel Elastomer with Interpenetrating Polymeric Networks

A poly(styrene‐butadiene‐styrene)/poly(N‐isopropylacrylamide) (SBS/PNIPAM) hydrogel elastomer with interpenetrating polymeric network structure is prepared by using solution free radical polymerization in benzene/tetrahydrofuran solvent mixture. The characterizations of hydrogel elastomers are investigated by Fourier transform infrared spectroscopy, scanning electron microscope, rheology, equilibrium swelling studies, and oscillatory swelling study. Results show that these hydrogel elastomers exhibit a temperature‐sensitivity inherited from PNIPAM component at the temperature around 30 °C. Besides, change with tetrahydrofuran to different proportion in solvent mixtures, constituent, and properties as gel content, swelling capacity, mechanical strength and volume phase transition degree are affected deeply.     

Flow and aggregation characteristics of thermo-responsive poly(N-isopropylacrylamide) spheres during the phase transition

To date, a great many researches were focused on improving stimuli-responsive and controlled-release properties of thermo-responsive hydrogel carriers, whereas for the research on flow characteristics during the phase transition, prior reports have not been found. In this paper, poly(N-isopropylacrylamide) (PNIPAM) spheres with thermo-responsive phase transition characteristics were prepared by cross-linked polymerization. In a transparent Pyrex glass pipe with hydrophilic inner wall, flow and aggregation characteristics of PNIPAM spheres during the phase transition from low temperature which was lower than the lower critical solution temperature (LCST) to high temperature (T>LCST) was studied for the first time. Many interesting phenomena about the flow and aggregation behaviors of PNIPAM spheres were found. The velocity of PNIPAM spheres in horizontal pipe decreased from 1.07 cm/s before the phase transition to 0.65 cm/s or even became zero after the phase transition, which is what targeting drug delivery systems desired. When the initial distance was about 5.5 mm at the entrance of testing pipe section, the PNIPAM spheres could aggregate together after the phase transition and subsequently roll forward; but when the initial distance was as large as 8.5 mm, the distance became close at first during the phase transition and then far after the phase transition. Similar results were also found as mentioned above in vertical pipe. When 10 spheres aggregated together, they stopped at a certain position just after the phase transition in horizontal pipe. If the flowrate was more than 40 ml/min, the aggregation configurations such as triangle, tetrahedron, hexahedron and octahedron which formed after the phase transition at flowrate of 20 ml/min disappeared. The results provided valuable information for future applications of thermo-responsive PNIPAM spheres.     

交联三维网络结构PINPAm的制备及其性能研究

聚N-异丙基丙烯酰胺(PINPAm)水凝胶是一种亲水但不溶于水,具有交联三维网络结构的高分子聚合物,具有一定条件下的溶胀/退溶胀行为,同时具有输送和渗透性、能量转换、吸附分离、生物相容性等功能。本文研究了用不同量的引发剂过硫酸铵(APS)对水凝胶形成的影响;反应温度分别为低温(低于5℃、20℃、30℃、40℃对水凝胶形成的影响。所制备的PNIPAm水凝胶分别测定了相转变温度(LCST)和凝胶溶胀率(SR)。结果表明引发剂量用量增多时水凝胶形成反应时间变短;反应温度升高水凝胶外观出现由无色透明凝胶→乳白半透明凝胶→乳白色凝胶→乳白色且无固定形态凝胶的变化。低温生成的水凝胶相转变温度(LCST)在33~34℃之间,水凝胶体积发生不连续收缩现象;交联剂N,N-亚甲基双丙烯酞胺(BIS)使用量越多溶胀率越小。     

Novel Thermoreversible Injectable Hydrogel Formulations Based on Sodium Alginate and Poly(N-Isopropylacrylamide)

Novel injectable thermoreversible hydrogel compositions with semi-interpenetrating network structure were prepared through the addition of sodium alginate (SA) to poly(N-isopropylacrylamide) (PNIPAM) aqueous solutions. The addition of the hydrophilic alginate strongly improved the stability against syneresis of the 15 wt% PNIPAM hydrogels formed at 37°C from less than 15 min in the absence of alginate to more than 7 days in the presence of 4 wt% SA. Besides the SA concentration, the hydrogel stability depended on the molecular weight and polydispersity of PNIPAM, being lower when a high molecular weight fraction was present. The phase transition temperature (T_ph) of the PNIPAM aqueous solutions decreased with alginate concentration, while the dynamic viscosity and elastic modulus of the hydrogels increased. By decreasing the PNIPAM molecular weight and polydispersity, the dynamic viscosity and elastic modulus of the PNIPAM–alginate hydrogels formed above T_ph diminished, while their viscoelastic behavior changed from predominantly elastic to predominantly viscous.     

温敏性水凝胶对蛋白质和酶浓缩分离性能

报道了温敏性水凝胶———交联聚Ｎ异丙基丙烯酰胺（ＰＮＩＰＡＭ）的合成方法,研究了它对蛋白质和酶的浓缩分离性能。结果表明,ＰＮＩＰＡＭ凝胶对蛋白质和酶的分离效率在相转变温度附近发生突跃,显示出很好的浓缩分离能力。当ＰＮＩＰＡＭ凝胶中交联剂（Ｂｉｓ）质量百分数大于４％时,能实现高的分离效率。     

Dual pH‐ and temperature‐responsive hydrogels with extraordinary swelling/deswelling behavior and enhanced mechanical performances

pH‐ and temperature‐responsive semi‐interpenetrating nanocomposite hydrogels (NC hydrogels) were prepared with surface‐functionalized graphene oxide (GO) as the crosslinker, N‐isopropylacrylamide (NIPAM) as the monomer, and chitosan (CS) as an additive. The effects of 3‐(trimethoxysilyl)propylmethacrylate‐modified GO sheets and CS content on various physical properties were investigated. Results show that PNIPAM/CS/GO hydrogels undergo a large volumetric change in response to temperature. Swelling ratios of PNIPAM/CS/GO hydrogels are much larger than those of the conventional organically crosslinked PNIPAM hydrogels. The deswelling test indicates that the deswelling rate was greatly enhanced by incorporating CS into the hydrogel network and using the surface‐functionalized GO as the crosslinker. The pH‐sensitivity of PNIPAM/CS/GO hydrogels is evident below their volume phase transition temperature. Moreover, the PNIPAM/CS/GO hydrogels have a much better mechanical property compared with traditional hydrogels even in a high water content of 90%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41530.