| dc.description.abstract | Silicon-29 and 'H NMR spectroscopy were used to investigate the hydrolysis
of methyl silicones in a variety of aqueous environments. Dilute acid, dilute base and
one or more of the dissolved constituents of blood plasma were found to catalyse the
degradation of polydimethylsiloxane (PDMS)-and its hydrojty- and methoxyterminated
derivatives-along with the interior and shell of a silicone mammary
prosthesis. Dimethylsilanediol (DMSD) was the principal hydrolysis product,
although in many instances (most notably after long decomposition periods) the dimer
(tetramethyldisiloxanediol) and/or certain cyclodimethylsiloxane species were also
detected. Only for hexamethyldisiloxane was silicic acid detected as an additional
hydrolysis product after long-term interaction with blood plasma. Alcohols and
certain aliphatic polyols, when added to solution, typically caused alkoxylation of
DMSD and the dimer.
The presence of electron withdrawing hydroxy and methoxy end groups greatly
increased the rate of degradation of PDMS. Both the shell and interior of the
mammary prosthesis also hydrolysed faster than pure PDMS, which would suggest
that there is considerably less than 100 % trimethylsilyl capping of their constituent
polymer chains. | |
