Synthesis and characterisation of novel functional polyolefin containing sulfonic acid groups

The strong polar group, sulfonic acid, has successfully been introduced into ethylene/allylbenzene copolymers without degradation or crosslinking via chlorosulfonation reaction with chlorosulfonic acid as a chlorosulfonating agent in 1,1,2,2-tetrachloroethane followed by hydrolysis. The degree of sulfonation (DS) can be easily controlled by changing the ratio of chlorosulfonic acid to the pendant phenyls of the copolymer. The microstructure of sulfonated copolymers were unambiguously revealed by 1H NMR and 1H–1H COSY spectral analyses, which indicates that all the sulfonation reactions exclusively took place at the para-position of the aromatic rings. The thermal behaviors were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC data exhibit a systematic trend of melting temperature increasing with DS. TGA data of sulfonated copolymers show an increase in degradation temperature from 444 to 460 °C compared to the received copolymer. Sulfonated copolymers also show an additional minor loss of mass at approximately 261 °C, which is not observed in the received copolymer. The wetting properties of the sulfonated copolymers were also evaluated by contact angle measurement, and a notable increase in surface hydrophilicity was identified.