Rapid sulfur–oxazoline polymerization for biobased dynamic polyamide networks

Abstract

Inverse vulcanization has been continuously studied for over 10 years and extended to a wide range of organic crosslinkers. However, most reported systems require high temperature and hours to complete the reaction. Here, the reaction between 2-methyl-2-oxazoline or 2-ethyl-2-oxazoline and sulfur is found to complete within 6 min at 140 °C in the absence of any catalyst, and generate sulfur-chain modified polyamides. The sulfur–oxazoline reaction proceeds well in a broad range of charging ratios (sulfur >10 wt%). With a bulkier substituent, 2-phenyl-2-oxazoline was almost inert to sulfur at 160 °C and took 2 hours at 180 °C to reach complete conversion. Sulfur-modified polyamide networks from the crosslinking of sulfur with biobased oxazoline-ene difunctional monomers exhibited tunable mechanical properties and photothermal properties for photo-triggered shape programming.