Synthesis of polyorganosiloxanes with imidazolyl groups in the side chain

An imidazolyl ring was introduced into the side chain of poly(3-chlorocarbonylpropylmethyl-siloxane) (4) by esterification with 4(5)-hydroxymethylimidazole (1), the imino group being protected during esterification by the 2-nitrobenzyl group which can be easily cleaved by UV light irradiation without attacking the main chain. The photolytic cleavage of the 2-nitrobenzyl group was completed with a yield of ≈ 100% after 2 h without any remarkable side reaction. The polyorganosiloxanes (6), with a high content of imidazolyl groups in the side chain, are slightly soluble in hot DMSO and DMF. From this fact, in addition to the result of the measurement of Tg, it is suggested that very strong intermolecular hydrogen bonds are operating.