Nanostructured thermosets involving epoxy and poly(ionic liquid)-Containing diblock copolymer

Abstract

A novel poly(ionic liquid) (PIL)-containing diblock copolymer was synthesized via a sequential living/controlled polymerization approach. First, the ring-opening polymerization of ε-caprolactone (CL) was carried out to obtain a monohydroxyl-terminated PCL. The terminal hydroxyl group of the PCL chain was then exploited to react with carboxyl group of 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid to obtain a trithiocarbonate-terminated PCL. Thereafter, such trithiocarbonate-terminated PCL was used to mediate the radical polymerization of tri-n-butyl-(4-vinylbenzyl) phosphoniumbis(trifluoromethane)sulfonamide (TBP+-TFSI-) to afford PIL diblock copolymers. Notably, the PIL diblock copolymers are capable of displaying self-assembly behavior in selective solvent (e.g., ethyl acetate). In the suspensions of ethyl acetate, the self-assembly generated the spherical micelles with the aggregates of P(TBP+-TFSI-) as the cores and with PCL blocks as the coronas. Such a self-assembly behavior was further employed to obtain epoxy thermoset with nanostructures. Owing to the introduction of fluorine-containing PIL diblock copolymer, the surface dewettability of the thermosets was significantly improved owing to the enrichment of P(TBP+-TFSI-) at the surface. The introduction of PIL microdomains in epoxy resulted that the dielectric constants of the materials were significantly enhanced. More importantly, the dielectric constants were temperature-dependent and can be further enhanced while the nanostructured thermosets were heated above the glass transition temperature of PIL blocks.