Hydrolytic degradation groups

We have studied the extractant behavior of a series of compounds containing the carbamoylmethylphosphoryl (CMP) moiety in which the basicity of the phosphoryl group and the steric bulk of the substituent group are varied (10,LL). These studies have led to the development of extractants which have combinations of substituent groups that impart to the resultant molecule improved ability to extract Am(III) from nitric acid and to withstand hydrolytic degradation. At the same time good selectivity of actinides over most fission products and favorable solubility properties on actinide loading are maintained (11). 

We have already seen how water solubility and hydrolytic degradability can be built into the carrier macromolecule by the use of specific side groups. Here we will review an additional way in which drug molecules have been Linked to polyphosphazenes—by coordination. 

To conclude, the LCCC method was superior to the gradient LC method because the separation took place mainly according to the end groups. The selectivity of LCCC is lower than the gradient technique however, the 2D plots give a clear picture of the molecular heterogeneity of the samples. The method appearsto be suitable for in-depth studies of the hydrolytic degradation of polycarbonates. 

Fig. 32. Relation between the residual unsaturation ( ) IR-spectroscopy, (O) hydrolytic degradation resp. the titratable acid groups of microgels (a) and their EUP-content [132]. EUP(MA+HD),Mn 1640, c/t 67/33, EUP/S varied, W/M 20.

Allen, N. S., Edge, M., Mohammadian, M. and Jones, K., UV and thermal hydrolytic degradation of poly (ethylene terephthalate) importance of hydroperoxides and benzophenone end groups, Polym. Degrad. Stabil., 41, 191-196 (1993). 

The thermal depolymerization of polyoxymethylene starts from the unstable hydroxy end groups, but the oxidative and acid-catalyzed hydrolytic degradation takes place within the main chain. Flence, if polyoxymethylene is heated in air or in the presence of strong acids samples with blocked end groups will also degrade. 

The polyurethanes based on the 0-benzyl protected 6, 11, and 12 yielded partially debenzylated products with Tg values ranging between 20 and 30°C. Fully benzylated polyurethanes showed high resistance to hydrolytic degradation, whereas polyurethanes with free hydroxyl side groups degraded significantly in saline buffer at pH 10 and 37°C [113, 114]. 

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