N-异丙基丙烯酰胺类环境敏感性水凝胶的聚合及应用研究进展

N-异丙基丙烯酰胺(NIPA)类水凝胶是典型的温敏性凝胶,重点介绍了NIPA的均聚反应及其与天然高分子的复合,并对其在药物释放、物质分离及生物医用材料体系中的研究进展进行了总结。     

pH值／温度双重敏感淀粉水凝胶的合成与表征

首先合成具有功能性基团的淀粉马来酸酯（starch—MAH）,然后将starch—MAH与N-异丙基丙烯酰胺（NI-PA）共聚,合成出一种新型的淀粉水凝胶（starch—MAH／NIPA）。采用红外光谱仪（FT—IR）、扫描电镜（SEM）、差示扫描量热仪（DSC）、溶胀度测定以及体外药物释放试验,对水凝胶的结构和性能进行了表征。实验结果表明,该水凝胶具有良好的pH值、温度敏感性以及药物释放性能。     

含聚氨酯型温度和pH双敏性水凝胶的合成及性能研究

合成了两种阴离子型的端烯基聚氨酯（UAA）预聚物，制备了pH值敏感的水凝胶，比较了它们的pH值响应性，将UAA预聚物与N-异内基丙烯酰胺（NIPA）共聚，得到具有温度和pH值双重敏感性的水凝胶，研究发现聚氨酯侧链的引入对NIPA的相转变温度（LCST）几乎无影响，聚合温度和组成比对所合成的水凝胶性能有较大的影响。     

温敏型复合水凝胶对水中U(Ⅵ)的吸附性能研究

采用自由基聚合法,先用丙烯酸(AA)改性壳聚糖(CS),再以N-异丙基丙烯酰胺(NIPA)和改性后的壳聚糖(AA-co-CS)为主链单体制备了AA-co-CS/NIPA温度敏感型水凝胶。研究了pH、温度、时间等对AA-co-CS/NIPA吸附U(Ⅵ)的影响。结果表明,在温度30℃,pH为6,初始U(Ⅵ)浓度10 mg/L时,AA-co-CS/NIPA改性水凝胶对U(Ⅵ)去除率达到95.59%,较CS/NIPA复合水凝胶的去除率提高8%,其吸附过程遵循准二级和Langmuir等温线模型。AA-co-CS/NIPA具有由温度刺激引起的良好的溶胀性能,经过5次吸附(20℃)-解吸(40℃)后,对U(Ⅵ)的去除率仍保持在78.39%。SEM结果表明,丙烯酸对壳聚糖的改性,增大了水凝胶的接触面积、增加了结合位点。FTIR和XPS结果表明,AA-co-CS/NIPA对铀的吸附主要是羧基、羟基和氨基与铀酰离子进行共价键结合。     

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。     

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。     

温度敏感高分子水凝胶的合成及性能研究

从分子设计的角度出发,选用具有优良温敏性的N-异丙基丙烯酰胺(NIPA)为基本原料,制备了温度敏感水凝胶,系统研究了水凝胶的基本物理性能(密度、平均分子量、交联密度、平衡态水含量、固定电荷密度等),测试了水凝胶在不同离子强度下的溶胀、退溶胀性能,并对其响应机理进行了探讨,同时对水凝胶的机械性能进行了测试.结果表明:温度敏感水凝胶的溶胀受离子强度和温度的影响很大,离子强度越高,溶胀率越低;其机械强度随温度变化显著.     

NIPA系温敏凝胶的制备及应用研究进展

N-异丙基丙烯酰胺(NIPA)同时具有亲水性的酰胺基和疏水性的异丙基,使其系列聚合物具有优良的温敏智能特性和记忆效应,已在药物缓释、物料分离、酶的固定、生物医学材料等领域得到广泛应用.综述了NIPA系温敏凝胶的制备方法及应用方面的研究进展,并提出了未来的发展方向.     

温度/pH敏感型壳聚糖水凝胶的制备及其性能

以天然可降解高分子壳聚糖为载体,选择温度敏感单体N-异丙基丙烯酰胺以及pH敏感单体2-丙烯酰胺基-2-甲基丙磺酸,以偶氮二异丁腈为引发剂,N,N-亚甲基双丙烯酰胺为交联剂,通过自由基接枝共聚反应制备壳聚糖水凝胶。通过红外(IR)、扫描电镜(SEM)对其结构及形貌进行了表征,并探讨了影响水凝胶溶胀率的因素。结果表明,当单体配比NIPAM∶AMPS为6∶4、引发剂用量为单体总质量4%、交联剂用量为单体总质量的4%、反应温度为45℃形成的水凝胶在水中溶胀率可达95%左右。该水凝胶具有一定的温度和pH敏感性,预计在药物控释、组织工程、抗凝血材料等领域拥有广阔的应用前景。     

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。     

Preparation of poly(N-isopropylacrylamide) hydrogel beads by circulation polymerization

Thermosensitive poly(N-isopropylacrylamide) hydrogel (NIPA hydrogel) beads have attracted much attention due to their applications in reaction and separation processes. This study focuses on the preparation of millimeter-sized, monodispersed NIPA hydrogel beads, for which a novel circulation polymerization technique is proposed. The method involves the drop-wise addition of a pre-gel aqueous solution into swirling silicone oil through a nozzle, and the subsequent conventional free-radical polymerization of the suspended pre-gel droplets, which drifts with the swirling oil. NIPA hydrogel beads that are 3.0 mm in diameter were successfully prepared with a very narrow distribution under fundamental conditions with no coalescence of the pre-gel droplets. The circulation polymerization technique improves the residence time and can be applied to a polymerization system that requires a long gelation time. The size of the resultant hydrogel beads corresponds to the size of the pre-gel droplets that are delivered from the tip of the nozzle, and can be controlled by adjusting the size of the nozzle.     

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%。     

Preparation and characterization of a novel responsive hydrogel with a β‐cyclodextrin‐based macromonomer

Based on a combination of poly(N‐isopropylacrylamide), which could respond to an external temperature, and β‐cyclodextrin (β‐CD), which could form a molecular inclusion complex, a novel hydrogel, having both thermal and pH sensitivities and containing β‐CD and N‐isopropylacrylamide (NIPA) segments, was synthesized. For the incorporation of β‐CD into the polymer network, a macromonomer was prepared first by the reaction of a β‐CD‐based polymer with maleic anhydride in dimethylformamide and then by copolymerization with NIPA in an aqueous solution. Elemental analysis, IR spectroscopy, differential scanning calorimetry, and swelling measurements were employed for the characterization of the hydrogel chain structure and its physical properties. With methyl orange as a model compound in inclusion tests, it was found that the hydrogel not only possessed a remarkable supramolecular inclusion ability (with respect to that of the small molecule cyclodextrin) but also could sensitively respond to various external stimuli, including the temperature, pH, and ionic strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 361–367, 2003     

Equilibrium swelling behavior and elastic properties of polymer–clay nanocomposite hydrogels

Nanocomposite hydrogels were prepared by free‐radical polymerization of the monomers acrylamide (AAm), N,N‐dimethylacrylamide (DMA), and N‐isopropylacrylamide (NIPA) in aqueous clay dispersions at 21°C. Laponite XLS was used as clay nanoparticles in the hydrogel preparation. The hydrogels based on DMA or NIPA monomers exhibit much larger moduli of elasticity compared with the hydrogels based on AAm monomer. Calculations using the theory of rubber elasticity reveal that, in DMA‐clay or NIPA‐clay nanocomposites, both the effective crosslink density of the hydrogels and the functionality of the clay particles rapidly increase with increasing amount of Laponite up to 10% (w/v). The results suggest that DMA‐clay and NIPA‐clay attractive interactions are stronger than AAm‐clay interactions due to the formation of multiple layers on the nanoparticles through hydrophobic associations. It was also shown that, although the nanocomposite hydrogels do not dissolve in good solvents such as water, they dissolve in dilute aqueous solutions of acetone or poly(ethylene oxide) of molecular weight 10,000 g/mol, demonstrating the physical nature of the crosslink points. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A structural study of polyelectrolyte gels in a unidirectionally swollen state

We investigated the structures of polyelectrolyte gels, poly(N-isopropylacrylamide-co-2-acrylamido-2-methylpropane sulfonic acid) (NIPA/AMPS) hydrogels in a unidirectionally swollen state by using small-angle X-ray scattering (SAXS). The SAXS results show that the structure of the NIPA/AMPS gels strongly depends upon the composition of NIPA/AMPS. Increase in composition of AMPS causes suppression of concentration fluctuations in the long wavelength. As a consequence, a NIPA/AMPS hydrogel with a low composition of AMPS macroscopically phase-separated at high temperatures, while microphase separation occurred for a NIPA/AMPS gel with a higher composition of AMPS. The instability in the microphase separation initially occurred in the direction perpendicular to the swelling for the latter gel. In the disordered state near the microphase separation region, an elliptic scattering pattern was observed, and the scattering intensity around the peak position in the direction perpendicular to the unidirectionally swelling was larger than that in the direction parallel to it. The behavior became more remarkable, as the interaction parameter χ became larger. These behaviors are consistent with the prediction from the Rabin-Panukov theory. The scattering vector at the scattering maximum in the perpendicular direction q_m,⊥ significantly shifted to smaller q, where q represents the magnitude of the scattering vector, when the microphase separation occurred. It is shown that the periodicity of the microphase-separated structure ranged from 300 to 400 Å.     

智能水凝胶在生物载药领域的研究进展

智能水凝胶是一类具有三维网络结构、膨胀性好、吸水性强、易保水、超仿生等特点的新型功能高分子材料。由于其合成过程中加入了具有特殊结构、基团的单体或者大分子原料,如聚丙烯酰胺(PNIPA)类大分子、酸/碱基团(如羧基和氨基)、丙烯酸、聚氨类、偶氮苯(As)、聚电解质(高分子链上有可以离子化的基团)等,因此智能水凝胶是能够根据环境的温度、酸度、电场、磁场等变化做出有规律的结构和体积调整,或者导致凝胶组成发生变化的新型智能生物化学水凝胶材料,具有较高的智能性和响应性。本文根据水凝胶对外界环境的刺激不同表现出不同的响应情况,将凝胶分为:温度敏感性水凝胶、pH敏感性水凝胶、光敏感性水凝胶、压力敏感性水凝胶、电场敏感性水凝胶等。近年来,随着人们对医用水凝胶和药物缓释研究的深入,具有环境敏感性和较好生物相容性的智能水凝胶成为临床上药物控释材料的首选。     

A Novel NIR Laser Switched Nanocomposite Hydrogel as Remote Stimuli Smart Valve

Thermosensitive nanocomposite (NC) hydrogels are considered as a significant kind of intelligent material to be utilized as sensor, biomaterial, drug carrier, etc. Recently, preparation of remotely controlled NC hydrogel with high‐performance attracts more and more concern. To produce facile remote‐stimuli thermosensitive NC hydrogel, a novel near‐infrared (NIR) laser switched CuS/clay/poly(OEGMA‐co‐MEO₂MA) hydrogel is demonstrated, which can be precisely remote‐stimulated by NIR irradiation based on the excellent NIR photothermal conversion property of CuS nanoparticle. The temperature change of hydrogel is related to the NIR intensity, CuS content, and crosslinking density. Moreover, the influences on dimensional variation of hydrogel on macroscale are systematically studied, and the hydrogel as smart liquid valve is further utilized which can be remotely controlled by NIR switch on/off successfully. Cyclic test illustrates that this novel CuS/clay/poly(OEGMA‐co‐MEO₂MA) hydrogel exhibits stable cyclic volume transition property which has promising applications in the areas of sensors, valves, and intelligent switches.