Oxa-Michael polyaddition of vinylsulfonylethanol for aliphatic polyethersulfones

Abstract

Polyethersulfones are an interesting class of polymers for industrial applications due to their unusual properties such as a high refractive index, flame-retardant properties, and high temperature and chemical resistance. The common aromatic polymers however require high temperatures for processing, while alternative aliphatic polyethersulfones remain overall scarce in the literature with only oligomeric materials being reported so far. Nevertheless, these materials have similar promising properties to those observed for their aromatic equivalents. Here, we describe the reactivity of a novel AB-type monomer vinylsulfonylethanol, which enables a successful and straightforward synthesis of aliphatic polyethersulfones. Various organic and inorganic catalysts were tested, and the kinetics of the resulting polymerizations were examined. Rapid conversions were observed resulting in polymers with molar masses in the range of 2000 to 4000 g mol⁻¹ within a few minutes. A closer characterization of the resulting polymers revealed that all organic catalysts initiate the polymerization process by a nucleophilic addition to the vinyl group, even if strong but sterically hindered bases are used. Inorganic bases in turn seem to deprotonate the hydroxy groups to initiate the polymerization, as the vinyl end groups are preserved. The resulting polymers are characterized by excellent heat resistance with degradation temperatures >300 °C in air, which is significantly higher than previous observations for other aliphatic polyolefinsulfones. Further analysis reveals a semi-crystalline nature of the polymer if processed from solvents although recrystallization appears to be kinetically hindered. With the possibility to prepare the starting material vinylsulfonylethanol by a straightforward method and on a large scale, such polymers become easily accessible using the described preparation routes, while the beneficial thermal properties of the polymer may open up interesting opportunities for their application.