Guo J H, Robertson R E, Amidon G L
College of Pharmacy, University of Michigan, Ann Arbor 48109-1065.
Pharm Res. 1991 Dec;8(12):1500-4. doi: 10.1023/a:1015890232106.
The effects of physical aging on the water permeation of cellulose acetate and ethylcellulose, the mechanical properties of ethylcellulose, and the dissolution property of hydroxypropyl methylcellulose phthalate were investigated. The water permeabilities of cellulose acetate and ethylcellulose and the dissolution rate of hydroxypropyl methylcellulose phthalate were found to decrease with physical aging time after being quenched from above the glass transition temperatures to sub-Tg temperatures. The gradual approach toward thermodynamic equilibrium during physical aging decreases the free volume of the polymers. This decrease in free volume is accompanied by a decrease in the transport mobility, with concomitant changes in those properties of the polymer that depend on it. The effects of long-term aging on the dissolution rate and water permeabilities of these polymers can be estimated from a linear double-logarithmic relationship between the mobility properties and physical aging time. The existence of the linear double-logarithmic relationship can be derived from the Williams-Landel-Ferry equation, the Doolittle equation, Struik's model, and Fujita's relationship between diffusion and free volume.
研究了物理老化对醋酸纤维素和乙基纤维素水渗透性、乙基纤维素力学性能以及邻苯二甲酸羟丙基甲基纤维素溶解性能的影响。发现醋酸纤维素和乙基纤维素的水渗透性以及邻苯二甲酸羟丙基甲基纤维素的溶解速率在从玻璃化转变温度以上骤冷至低于玻璃化转变温度后，会随着物理老化时间的增加而降低。物理老化过程中逐渐趋向热力学平衡会减少聚合物的自由体积。自由体积的这种减少伴随着传输迁移率的降低，同时聚合物中那些依赖于自由体积的性能也会发生相应变化。这些聚合物的溶解速率和水渗透性的长期老化效应可以通过迁移率性能与物理老化时间之间的线性双对数关系来估算。线性双对数关系的存在可以从威廉姆斯-兰德尔-费里方程、杜利特尔方程、斯特鲁伊克模型以及藤田扩散与自由体积之间的关系推导得出。
