Trifluoromethylated N,S-Acetal as a Chemical Platform for Covalent Adaptable Networks: Fast Thiol Exchange and Strong Hydrostability for a Highly Transparent Material

Abstract

This work presents the synthesis and characterization of a highly transparent and colorless covalent adaptable network (CAN) exhibiting short relaxation times (30 s at 150 °C) and limited creep at 100 °C. Based on N,S-acetal functions, strongly stabilized by a trifluoromethyl group, this network, however, retains the ability to undergo fast thiol exchanges. The present article describes a detailed monitoring of the cross-linking via ATR-FTIR and ¹⁹F HRMAS NMR (high-resolution magic angle spinning NMR), the complete structural characterization of the material via ¹³C HRMAS NMR, and the comprehensive study of the rheological properties of this novel N,S-acetal network. This CAN shows hydrolytic stability and higher activation energies (>90 kJ mol^–1) than its nonfluorinated counterparts. Its reprocessing occurs under relatively mild conditions without the need for a catalyst, and depolymerization can be achieved either with an amine (benzylamine), under acidic conditions (1 M HCl) at room temperature, or with a thiol (1-dodecanethiol) at 100 °C.