Preparation of a crosslinked sucrose polymer by thiol-ene photopolymerization using dithiothreitol as comonomer

摘要

The thiol-ene photopolymerization technique was used to prepare a crosslinked sucrose polymer. Sucrose was chemically modified to introduce two allyl groups, however, in the synthesis were also produced mono and triallyl derivatives. After purification by column chromatography, a fraction (F2A2S) with 94% diallyl sucrose (A2S), 4% of triallyl sucrose (A3S) and 2% of monoallyl sucrose (A1S) was obtained. This fraction was subsequently photopolymerized with dithiothreitol (DTT) which is a difunctional thiol. The presence of small concentration of A3S in F2A2S helped to crosslink in situ the obtained polythioether. Photopolymerization kinetics were determined using the Real-Time Infrared technique. It was found that photopolymerization can proceed in the absence of photoinitiators but the rate of photopolymerization and conversion increased considerably when different photoinitiators at 1 mol% were used and when the intensity of UV light was increased. The analysis by DMA of probes of the obtained sucrose polythioether revealed that the difunctionality of both comonomers, A2S and DTT, resulted in flexible materials with a T_g of 30 °C and high storage modulus values. The sucrose polythioether was completely degraded in 2 h in strongly acidic medium. Additionally, the ability of water to absorb the prepared material was tested. We found that it was pH dependent with the maximum absorption at pH = 14. The biopolymer displayed high thermal stability up to 230 °C