亲水链段长度对液晶模板水凝胶形态和温敏性的影响

采用疏水烷基(C16H33)相同而亲水的聚氧乙烯链(CH2CH2O)n=2,10,20长度不同的表面活性剂苄泽(Brij 52/56/58)作为模板制备得到3种孔洞尺寸为5～80μm的聚异丙基丙烯酰胺水凝胶(HNB).研究表明,n值越小,疏水性越大.15 wt%浓度下,不同n值的Brij水溶液均呈现明显的液晶织构.在t=4和7 min时HNB58和HNB56凝胶预聚液的透光率迅速下降至3.3～3.5,而HNB52凝胶预聚液的透光度一直保持在3.5.以n=20的Brij 58作为模板制备的HNB58凝胶孔洞数量多,尺寸为5～10μm.以n=2的Brij52为模板制备的HNB52凝胶孔洞形态呈层状,溶胀度最小,为6.9 g/g.而以n=10的Brij56为模板制备的HNB56凝胶孔洞呈蜂窝状,尺寸最大,为40～80μm,溶胀度最高,为7.9 g/g,37℃下20 min时HNB56失水超过80%.由于模板的作用,n值的变化并没有改变HNB凝胶的体积相转变温度(VPTT≈33℃),但吸热峰面积变宽.

EFFECT OF HYDROPHILIC SEGMENT LENGTH OF LIQUID CRYSTAL TEMPLATES ON THE MORPHOLOGY AND THERMAL RESPONSIBILITY OF HYDROGELS

Three kinds of polyisopropylacrylamide hydrogels(HNB) with 5-80 μm of pore size were prepared by using surfactants Brij 52/56/58 with same hydrophobic alkyl chain C16H33 and different hydrophilic poly(ethylene oxide)(PEO,(CH2CH2O)n=2,10,20) segments as template.The results show that the hydrophobicity increases with decreasing n values.The Brij aqueous solutions with different n values show clear liquid crystal texture at a concentration of 15 wt%.At t=4 and 7 min,the transmittance of HNB58 and HNB56 pre-polymerized liquids decreases to 3.3-3.5.However,the transmittance of HNB52 pre-polymerized liquid keeps at 3.5 throughout the reaction time.The HNB58 hydrogel using Brij 58(n=20) as template shows numerous pores,and the size is 5-10 μm.The HNB52 hydrogel using Brij 52(n=2) as template shows layered pore structure,and the maximum swelling ratio is 6.9 g/g.The HNB56 hydrogel using Brij 56(n=10) as template presents honeycombed state,having largest pore size from 40 to 80 μm.In addition,the maximum swelling ratios of HNB56 is 7.9 g/g,and water loss rate exceeds 80% at 37 ℃ and 20 min.Since the template action of Brij,the volume phase transition temperature(VPTT≈33 ℃) of HNB hydrogels keeps almost the same in spite of the difference of n value,but the endothermic peak area becomes wider with increasing n value.