Preparation of Poly[N-Isopropylacrylamide-Co-(Maleic acid)] hydrogel mambrane by electrospinning

A copolymer of N-isopropylacrylamide (NIP A) and maleic acid (MA) acting as sites for the crosslinking was synthesized via free radical polymerization. Copolymer films of the synthesized copolymer by casting technique were fabricated, and then crosslinked with diethylene glycol DEG acting as crosslinker by a heat-induced esterification crosslinking reaction at 145°C. The solubility in water of the films was tested. The crosslinked copolymer film synthesit.ed from molar feed ratio of 35%mollmol (MA comonomerlNIPA monomer) in copolymerization process and W%wtlv (synthesized copolymer in ethanol) with 5%wtlwt (crosslinking agent DEG/copolymer), followed by a heat-induced crosslinking reaction was water-insoluble material. The yield of the synthesized copolymer was 55%. The copolymer was characterized by infrared and nuclear magnetic resonance spectroscopy and acid-base titration. Consequently, a new poly[N-isopropylaclylamide-co-(maleic acid)], poly(NIPA-co-MA) hydrogel membrane was fabricated by electrospinning the polymer solution. The effects of electrospinning parameters (e.g. applied voltage and distance between the needle and the collection screen) on the morphology and diameter of poly(NIPA-co-MA) hydrogel fibrous membranes were investigated by scanning electron microscopy. The range of the applied voltage studied was from 15 to 30 kV and the distance between the needle and the collection screen studied was from 10 to 25 cm. The optimal condition for fabrication of hydrogel membrane was the applied voltage ~t 25 kV and distance between the needle and the collection screen at 25 cm using a diameter of needle at 0.80 mm and the flow rate of I mL hour-I. The average diameter of electrospun fibers was I 17±33 nm. The hydrogel membrane which has esterification crosslinked was characterized by Infrared spectroscopy. The hydrogel membrane showed temperature sensitive property. Its minimum and maximum water absorption ratio was 4±0 g g-I at 50°C and 17±4 g g-I at 34 °C, respectively_ The electrospun membrane dissolved in water at the temperature below the lower critical solution temperature (LCST, 34°C), while the cast film did not本研究通过自由基聚合法，合成了可作为交联位点的N-异丙基丙烯酰胺（N-isopropylacrylamide, NIPA）与马来酸（maleic acid, MA）共聚物。采用流延法制备所得共聚物薄膜，随后以二甘醇（diethylene glycol, DEG）作为交联剂，在145℃下通过热诱导酯化交联反应完成交联，并对该薄膜的水溶性进行了测试。 在共聚过程中采用35%mol/mol（马来酸共聚单体/N-异丙基丙烯酰胺单体）的摩尔投料比、质量体积分数为W%的该共聚物乙醇溶液，交联剂二甘醇与共聚物的质量比为5%wt/wt，经热诱导交联反应后得到的交联共聚物薄膜为水不溶性材料。所合成共聚物的产率为55%。采用红外光谱、核磁共振波谱以及酸碱滴定法对该共聚物进行了结构表征。 随后通过将聚合物溶液静电纺丝，制备得到新型聚(N-异丙基丙烯酰胺-co-马来酸) [poly(NIPA-co-MA)]水凝胶膜。采用扫描电子显微镜，研究了静电纺丝参数（如施加电压、针头与接收屏间距）对聚(NIPA-co-MA)水凝胶纤维膜形貌与纤维直径的影响。实验所考察的施加电压范围为15~30 kV，针头与接收屏间距范围为10~25 cm。制备水凝胶膜的最优工艺条件为：施加电压约25 kV、针头与接收屏间距25 cm、针头内径0.80 mm、进料流速1 mL·h⁻¹。静电纺丝所得纤维的平均直径为117±33 nm。 对经酯化交联的水凝胶膜采用红外光谱进行了表征，结果表明该水凝胶膜表现出温度响应特性。其吸水率最低值为4±0 g·g⁻¹（50℃时），最高值为17±4 g·g⁻¹（34℃时）。当环境温度低于最低临界溶解温度（lower critical solution temperature, LCST，34℃）时，静电纺丝膜可溶于水，而流延制备的薄膜则不溶于水。