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。     

N-异丙基丙烯酰胺/甲基丙烯酸/氧化石墨烯复合水凝胶研究

以N-异丙基丙烯酰胺(NIPAM)和甲基丙烯酸(MAA)为单体,N,N-亚甲基双丙烯酰胺(BIS)为交联剂,过硫酸铵(APS)为引发剂,在氧化石墨烯(GO)水溶液中进行自由基原位聚合,制备了聚N-异丙基丙烯酰胺/聚甲基丙烯酸/氧化石墨烯(PNIPAM/PMAA/GO)复合水凝胶,研究了GO的含量变化对复合水凝胶性能的影响。结果表明,GO的加入能明显提高水凝胶的力学性能,复合水凝胶的平衡溶胀比随着GO含量的增加而降低,并且也具有优异的pH敏感性。     

BC/PNIPAM温敏水凝胶的制备及其性能研究

通过自由基聚合使N-异丙基丙烯酰胺(NIPAM)在细菌纤维素(BC)膜的纳米纤维网络内部聚合,获得一种新颖的具有温度响应特性的双网络BC/PNIPAM复合水凝胶膜材料。该复合水凝胶在20℃(TLCST)两种不同温度下具有不同的透明状态。透光率实验进一步证实,与细菌纤维素稳定的透光率相比,BC/PNIPAM的透光率随着温度变化有较大差异。SEM观察证实复合水凝胶内部的孔隙在低温20℃及高温60℃下具有明显差异。以BC为对照组,通过对不同单体浓度合成的复合膜的小鼠成纤维细胞培养,证明该复合膜对细胞没有毒性,膜上细胞的生长情况与BC的类似。该结果表明BC/PNIPAM复合材料作为具温敏特性的水凝胶材料在生物医学领域具有较大的应用潜力。     

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。     

温度及pH敏感共聚/粘土纳米复合水凝胶的合成与性能研究

以无机粘土为交联剂制备了具有温度、pH双重敏感性的聚（N-异丙基丙烯酰胺-co-甲基丙烯酸-β-羟乙酯）/粘土纳米复合水凝胶（P（NIPA-co-HEMA）/clay）,并用红外和X衍射对其结构和形态进行了表征。在弱碱性（pH=7.4）和25℃条件下,分别研究了温度和不同pH缓冲溶液对该凝胶溶胀度的影响,测定了纳米复合水凝胶的力学性能。结果表明：水凝胶的粘土已被剥离成单片层,且均匀分散在凝胶网络中,起交联作用;P（NIPA-co-HEMA）/clay具有良好的温度、pH双重敏感特性;凝胶的断裂伸长率〉1000%。     

化学改性聚N-异丙基丙烯酰胺交联水凝胶的研究进展

综述了国内外关于温敏性聚N-异丙基丙烯酰胺(PNIPAM)交联水凝胶化学改性的研究现状。重点总结了无规共聚、接枝改性、嵌段改性等化学改性方法对PNIPAM交联水凝胶的结构、溶胀性能、温度响应性的影响,并对化学改性的方法和PNIPAM交联水凝胶的应用提出了展望。     

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。     

葡萄糖响应GO/微凝胶复合水凝胶的制备及性能

为了实现胰岛素对糖尿病患者血糖浓度智能调控,提出以3-丙烯酰胺基苯硼酸(AAPBA)、N,N'-二甲基丙烯酰胺(DMAA)、丙烯酰胺(AAm)为单体,70℃下经乳液聚合制备Poly(AAPBA-DMAA-co-AAm)微凝胶。以微凝胶为交联点,氧化石墨烯(GO)为改进剂,制备了GO/微凝胶复合水凝胶。采用傅里叶红外光谱仪(FT-IR),X射线衍谢仪(XRD)和扫描电镜(SEM)对水凝胶的组成、表面形貌进行表征,粒径分析表明微凝胶的粒径分布均匀、分散性良好。通过称重法对水凝胶的葡萄糖响应性进行测试,结果表明在p H为7.3条件下,水凝胶的响应速率随着葡萄糖浓度的增加而增大。当葡萄糖浓度为40 mmol×L~(-1),GO/微凝胶复合水凝胶对葡萄糖最大响应溶胀度为18%,响应时间为30 min,载药水凝胶的体外释放结果表明,10 h胰岛素累计释放率可达到52.59%,GO/微凝胶复合水凝胶对胰岛素具有缓释控释作用。     

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。     

基于苯硼酸微凝胶复合水凝胶的制备及性能

以3-氨基苯硼酸(AAPBA)为葡萄糖敏感基元,N,N′-二甲基丙烯酰胺(DMAA)、丙烯酰胺(AAm)为单体,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,十二烷基硫酸钠(SDS)为表面活性剂,过硫酸钾(KPS)为引发剂,70℃下乳液聚合制备微凝胶。以微凝胶为反应基质作为交联点,添加相应单体,制备复合水凝胶P(AAPBA-DMAA-co-AAm)/P(AAPBA-DMAA-co-AAm)。通过FTIR、SEM和TGA分别对复合水凝胶的化学结构、表面结构和热稳定性能进行表征。通过称量法测试复合水凝胶对葡萄糖的响应性,得出添加微凝胶提高了水凝胶的响应速率,平衡时间在50 min左右。多次的重复实验说明微凝胶的添加提高了水凝胶的机械强度,复合水凝胶的重现性良好。复合水凝胶对葡萄糖响应性能优异,为凝胶用于药物释放体系奠定了基础。     

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.     

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。     

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.     

Graphene Oxide Hybrid Supramolecular Hydrogels with Self‐Healable,Bioadhesive and Stimuli‐Responsive Properties and Drug Delivery Application

Self‐healable hydrogels are promising soft materials with great potential in biomedical applications due to their autonomous self‐repairing capability. Although many attempts are made to develop new hydrogels with good self‐healing performance, to integrate this characteristic along with other responsive multifunctions into one hydrogel still remains difficult. Here, a self‐healable hybrid supramolecular hydrogel (HSH) with tunable bioadhesive and stimuli‐responsive properties is reported. The strategy is imparting graphene oxide (GO) nanosheets and quadruple hydrogen bonding ureido‐pyrimidinone (UPy) moieties into a thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) polymer matrix. The obtained GO–HSH hydrogel shows rapid self‐healing behavior and good adhesion to various surfaces from synthetic materials to biological tissue. In addition, doxorubicin hydrochloride (DOX) release profiles reveal the dual thermo‐ and pH‐responsiveness of the GO–HSH hydrogel. The DOX‐loaded hydrogel can further directly adhere to titanium substrate, and the released DOX from this thin hydrogel coating remains biologically active and has high capability to kill tumor cells.     

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.     

Preparation and Controlled Drug Release Characteristics of Thermoresponsive PEG/Poly (NIPAM-co-AMPS) Hydrogels

Thermosensitive hydrogels were prepared by free radical polymerization of N-isopropylacrylamide (NIPAM) and 2-acrylamido-2-methylpropanesulphonic acid (AMPS) in presence of polyethylene glycol (PEG) as macroinitiator. The incorporation of functional monomer in the hydrogel was confirmed by infrared spectroscopy. The equilibrium swelling ratio (ESR), deswelling rate, volume transition temperature, and surface morphology of synthesized hydrogels are found to be dependent on concentration of AMPS monomer in the feed composition. The equilibrium swelling ratio (ESR) and water retention properties increase with increasing AMPS concentration in hydrogels and decrease with increasing salt concentration in external medium. The hydrogel with high dose of AMPS has high loading efficiency of theophylline drug, whereas the in-vitro release of the drug is delayed for a prolonged period in swollen gels above LCST of PNIPAM.     

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.     

自交联法合成相转变温度范围窄的聚(N-异丙基丙烯酰胺)水凝胶微球

在不使用交联剂的情况下,采用无皂乳液聚合法合成自交联聚(N-异丙基丙烯酰胺)(PNIPAM)水凝胶微球。固体13C NMR分析结果表明,PNIPAM水凝胶微球中存在因链转移反应形成的自交联点。自交联PNIPAM水凝胶微球的相转变温度范围很窄,接近非连续体积相转变行为。合成过程中反应温度、反应时间、引发剂用量对微球粒径和溶胀比有比较明显的影响,这些因素对微球的相转变温度及其范围的影响均很小。     

Enhanced mechanical properties and self-healing behavior of PNIPAM nanocomposite hydrogel by using POSS as a physical crosslinker

In this study, water-soluble octa(3-chloroammoniumpropyl) silsesquioxane (OCAPS) was found to aggregate into nanoparticles with a positive charge in solution, which can attract persulfate anion radical to initiate N-isopropylacrylamide monomers. Due to the electrostatic and hydrogen bond interaction between OCAPS and poly(N-isopropylacrylamide) (PNIPAM) chain, OCAPS can act as an effective physical crosslinker to result in a nanocomposite hydrogel (OCAPS-PNIPAM) with very small loading N, N′-methylene-bisacrylamide (50–100 ppm). The incorporation of OCAPS increases the crosslinking degree of the PNIPAM hydrogel and decreases the swelling ratio in deionized water. The mechanical properties of OCAPS-PNIPAM hydrogel were enhanced greatly by the presence of OCAPS and can be adjusted by the feed ratio. The compression and elasticity moduli vary from 3.52 to 7.59 kPa and 7.67 to 33.91 kPa, respectively. The tensile strength ranges from 6.82 to 243.41 kPa with fracture energy between 503.5 and 4781.7 J·m⁻². Rheological measurements suggest that OCAPS-PNIPAM hydrogels have stable networks and the loss factor decreases as increasing OCAPS content. OCAPS-PNIPAM hydrogels also can self-heal under certain conditions with low crosslinker loading. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48486.     

Fabrication of Photothermally Responsive Nanocomposite Hydrogel through 3D Printing

The responsive hydrogels have received great attention in many fields. However, the molding method and response mode of such hydrogels are criticized when it comes to real applications. In this work, a novel class of poly(N‐isopropyl acrylamide)/graphene oxide (PNIPAm/GO) nanocomposite hydrogel through self‐assembly three‐dimensional (3D) printing via ultraviolet light polymerization. The precursor is ordinarily constituted by NIPAm monomer, crosslinker, and water mixed with a photoinitiator, besides the introduction of nanoclay adjusts the shear thinning properties to an optimal level, which is important for the 3D printing precision. Then, the graphite oxide as infrared light absorber endows the hydrogel fast photothermal excited responsivity instead of conventional temperature response. The shrinkage and swelling of the composite hydrogel can be controlled by turning the near‐infrared light on or off. Meanwhile, the reversible behavior of as‐prepared hydrogel is easily regulated by altering the content of GO and illumination time of near‐infrared light. Additionally, a round tube is obtained based on the as‐prepared hydrogel, which can be driven to get a pencil, indicating their potential applications in actuator and other functional program.