Spancake C W, Kildsig D O, Mitra A K
Department of Industrial and Physical Pharmacy, School of Pharmacy and Pharmacal Sciences, Purdue University, West Lafayette, Indiana 47907.
Pharm Res. 1991 Mar;8(3):345-9. doi: 10.1023/a:1015893515442.
The rheologic properties of aqueous solutions and gels of Tetronic 1508 were investigated as a function of polymer concentration and temperature utilizing rotational viscometry. Below the sol-gel transition temperature the polymer solutions were low in viscosity and exhibited Newtonian rheologic behavior even at concentrations of 20 and 25% (w/w). Upon sol-gel transition, the more concentrated polymer solutions underwent a dramatic four- to five-orders of magnitude increase in viscosity, resulting in the formation of a rigid gel structure. Above the sol-gel transition temperature, the gels displayed pseudoplastic and plastic rheologic properties and the viscosity of the gels remained at a relatively constant value over a wide temperature range. Eventually, the thermal energy of the system exceeded the bonding forces within the gel structure, resulting in a gel-sol transition which was marked by a dramatic decrease in the viscosity of the system. Above the gel-sol transition temperature, the system reverted to a Newtonian fluid with viscosities very similar to those found for the Tetronic 1508 solutions at temperatures below the sol-gel transition temperature. The thermodynamic implications of the gel-sol transition are discussed.
利用旋转粘度测定法，研究了Tetronic 1508水溶液和凝胶的流变性质与聚合物浓度和温度的关系。在溶胶-凝胶转变温度以下，聚合物溶液粘度较低，即使在浓度为20%和25%（w/w）时也表现出牛顿流变行为。在溶胶-凝胶转变时，浓度较高的聚合物溶液粘度急剧增加四到五个数量级，形成刚性凝胶结构。在溶胶-凝胶转变温度以上，凝胶表现出假塑性和塑性流变性质，并且在很宽的温度范围内凝胶粘度保持在相对恒定的值。最终，系统的热能超过了凝胶结构内的结合力，导致凝胶-溶胶转变，其特征是系统粘度急剧下降。在凝胶-溶胶转变温度以上，系统恢复为牛顿流体，其粘度与在溶胶-凝胶转变温度以下温度下Tetronic 1508溶液的粘度非常相似。讨论了凝胶-溶胶转变的热力学意义。
