Proposed hydrolytic degradation release

For the hydrolytic degradation of polyphosphazenes several mechanisms have been proposed (Allcock et al, 1977-1994 Goedemoed et al., 1988). Ffowever, analysis of the degradation products revealed that the main hydrolysis pathway involves release of the amino acid ester side group, followed by hydrolysis of the ester with formation of the amino acid and the alcohol (Crommen et al, 1992) (Fiigpre 12). 

Scheme 1 Proposed mechanism for porous silicon degradation in aqueous solutions, adapted from Allongue et al. (1993). (a) A Si-H-terminated surface immersed in H2O. (b) The Si-H bond undergoes hydrolytic attack and is converted to Si-OH and produces a hydrogen molecule, (c) The Si-OH at the surface polarizes and weakens the Si-Si backbonds, which are then attacked by H2O, producing HSi(OH)3. (d) In solution, the HSi(OH)3 molecule is quickly converted to Si(OH)4 releasing a second hydrogen molecule...

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