Poly hydrolytic degradation

Poly(L-malate) decomposes spontaneously to L-ma-late by ester hydrolysis [2,4,5]. Hydrolytic degradation of the polymer sodium salt at pH 7.0 and 37°C results in a random cleavage of the polymer, the molecular mass decreasing by 50% after a period of 10 h [2]. The rate of hydrolysis is accelerated in acidic and alkaline solutions. This was first noted by changes in the activity of the polymer to inhibit DNA polymerase a of P. polycephalum [4]. The explanation of this phenomenon was that the degradation was slowest between pH 5-9 (Fig. 2) as would be expected if it were acid/base-catalyzed. In choosing a buffer, one should be aware of specific buffer catalysis. We found that the polymer was more stable in phosphate buffer than in Tris/HCl-buffer. 

Figure 2 Hydrolytic degradation of poly(phosphoester-urethanes) based on TDI.

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). 

Galbis et al. described a variety of carbohydrate-based linear polyesters 61 of the poly(alkylene dicarboxylate) type that were obtained by polycondensation reactions of the alditols 2,3,4-tri-(9-methyl-L-arabinitol (9) and 2,3,4-tri-O-methyl-xylitol (10), and the aldaric acids 2,3,4-tri-(9-methyl-L-arabinaric acid (26) and 2,3,4-tri-(9-methyl-xylaric acid (27), butanediol, and adipic acid were also used as comonomers [28]. Copolyesters of the poly(aIkylene-c )-arylene dicarboxylate) type were obtained using bisphenols as comonomers (Scheme 1). Chemical polycondensation reactions were conducted in bulk or in solution. Enzymatic polycondensation reactions of adipic acid with the above-mentioned alditols were carried out successfully using Lipozyme and Novozyme 435. The hydrolytic degradations of some of these polyesters were also described. 

Grizzi, I., Garreuau, H., Li, S., and Vert, M. (1995). Hydrolytic degradation of devices based on poly(dl-lactic acid) size dependence. Biomaterials, 16, 305-311. 

Poly((3-PL) has been hydrolytically degraded in a buffered salt solution (pH 7.2) at 37 °C [125,175], Oriented fibers and unoriented fibers showed different mechanical properties on degradation. The changes in tensile strength were slower for the oriented material. The molecular weight decreases rapidly during the first 50 days while the crystalline phase increases, probably due to an anneal-ing-like effect caused by the temperature at which the degradation was performed and rapid water absorption [175]. 

Hydrolytic degradation of poly(e-CL)/PLLA block copolyester at pH 7.4 and 37 °C over a 5-week period is controlled by the initial crystallinity of the poly(e-CL) and its overall composition. The rate of degradation increased with increasing PLLA content [203 ]. Microorganisms, such as Fusarium solani and Fusarium moniliforme, that secrete poly(e-CL) depolymerase (cutinase), were more effective with those polymers that had longer poly(e-CL) sequence lengths [218]. The... 

Block copolymers (228), consisting of a hydrophilic poly(ethylene glycol) and a hydrophobic polyphosphazene residue, have been investigated with respect to their micelle formation in aqueous solution Micelle formation in water has also been observed for polymers (229) with ethyl glycinato substituents. Hydrolytic degradation of these polymers has been studied in aqueous thf. ... 

S. Weidner, G. Kuehn, B. Werthmann, H. Schroeder, U. Just, R. Borowski, R. Decker, B. Schwarz, I. Schmuecking, and I. Seifert, A New Approach of Characterizing the Hydrolytic Degradation of Poly (ethylene terephthalate) by MALDI-MS, John Wiley Sons, New York, 1997, pp. 2183-2192. 

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