Nguyen T H, Shih C, Himmelstein K J, Higuchi T
J Pharm Sci. 1984 Nov;73(11):1563-8. doi: 10.1002/jps.2600731119.
The hydrolysis of poly(ortho-ester)s and a monomeric model compound, 3,9-dibenzyloxy-3,9-diethyl-2,4,8,10-tetraoxaspiro[5,5]un decane, was carried out in dioxane-d8-dioxane and followed by 1H-NMR and HPLC, respectively. Experimental results suggested that the polymer degradation proceeds to a large extent via random scission. The hydrolysis was catalyzed by the acid; the catalytic rate constant increased predictably with decreasing aqueous pKa of the acid. The reaction is first order with respect to the catalyst concentration and the number of ortho-ester linkages present, and it is independent of water in the concentration range studied. Strain at the ortho-ester bond may be a factor influencing the hydrolysis rate.
聚原酸酯和一种单体模型化合物3,9 - 二苄氧基 - 3,9 - 二乙基 - 2,4,8,10 - 四氧杂螺[5,5]十一烷在氘代二氧六环中进行水解反应，分别采用¹H - NMR和HPLC进行跟踪监测。实验结果表明，聚合物降解在很大程度上是通过无规断链进行的。水解反应由酸催化；催化速率常数随着酸的水相pKa值降低而呈可预测性增加。该反应对催化剂浓度和存在的原酸酯键数量呈一级反应，并且在所研究的浓度范围内与水无关。原酸酯键处的应变可能是影响水解速率的一个因素。
