Re: How does polydimethyl siloxane react with boric acid?

Most of the information on the interaction between poly(dimethylsiloxane) and boric acid is in the patent literatures, as these reactions are used in a range of synthetic elastomers - in electrical insulators, laminated glass, and 'bouncing putties'.

The boric acid forms cross-links between the polymer chains with the loss of water, in much the same way as it does with poly(vinyl alcohol) to make the 'slime' seen at practically every event where chemistry is on display. These bonds form initially with any free hydroxy groups on the polymer, such as are present at the ends.

Boric acid may also help remove methyl groups from poly(dimethylsiloxane) through conversion to peroxides and hence to alcohols, giving additional binding sites.

(Si-CH₃ to Si-O-O-CH₃ to Si-O-H + O=CH₂)

References:
Chemical Abstracts Service, abstracts to papers in the Russian Literature: Lobkov, V. D.; Klebanskii, A. L.; Kogan, E. V. Vysokomolekul. Soedin. 1965, 7, 1535-1538.
Gruber, V. N.; Klebanskii, A. L.; Kremniiorg. Mater. 1971, 162-163.
Mitrofanov, L. A.; Sidorovich, E. A.; Karlin, A. V.; Marei, A. I.; Lebedeva, L. U. Vysokomol. Soedin., Ser. A1969, 11, 782-788.
Lobkov, V. D.; Karlin, A. V.; Mitrofanov, L. A., Lebedeva, L. U. Latv. PSR Zinat. Akad. Vestis, Kim. Ser. 1968, 125-126.>/P>