Synthesis of thermosensitive hydrogels from acryloyloxyethyl trialkyl phosphonium chloride–N‐isopropylacrylamide–N,N′‐methylenebisacrylamide terpolymers and their temperature dependence of water absorption

Thermosensitive polymer hydrogels were prepared by the copolymerization of three kinds of acryloyloxyethyl trialkyl phosphonium chlorides (AETRs) with alkyl chains of different lengths, with N‐isopropyl acrylamide (NIPAAm) and N,N′‐methylenebisacrylamide (MBAAm). The water content of the AETR–NIPAAm–MBAAm terpolymers obtained at molar ratios of the crosslinking agent greater than 2 decreased with increasing temperature and decreased sharply around 35 °C. However, the water contents of the AETR–NIPAAm–MBAAm (X/100/1) terpolymers obtained at a molar ratio of 1 of the crosslinking agent increased once with increasing temperature and then decreased from 3 to around 40 °C. The water contents of the AETR–NIPAAm–MBAAm (3/100/1 or 2) terpolymers decreased with the increasing length of alkyl chains in phosphonium groups in the terpolymers. The water contents of the AETR–NIPAAm–MBAAm terpolymers increased by the addition of a small amount of urea and then decreased with increasing urea concentration. However, the water contents decreased abruptly with the addition of NaCl. The AETR–NIPAAm–MBAAm terpolymers exhibited high adsorption for sodium dodecylbenzene sulfonate but no adsorption for sodium benzene sulfonate.