Formation of nanophases in epoxy thermosets containing ABC and ACB triblock copolymers: A comparative investigation

- Two block terpolymers were prepared with close compositions and molecular weights.
- Both of the triblock copolymers had quite different sequential structures.
- By using the triblock copolymers, nanostructured epoxy thermosets were obtained.
- The nanostructures depend on the sequential structures of the triblock copolymers.

Poly(ε-caprolactone)-block-polystyrene-block-poly(2,2,2-trifluoroethylacrylate (PCL-b-PS-b-PTFEA) and poly(ε-caprolactone)-block-poly(2,2,2-trifluoroethyl acrylate)-block-polystyrene (PCL-b-PTFEA-b-PS) triblock copolymers were synthesized via the combination of ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) polymerizations. Both of the triblock copolymers had the similar composition and molecular weights but different sequential structures. These two triblock copolymers were utilized to modulate the nanostructures of epoxy thermosets. It was found that the microdomains in the thermosets were formed through the mechanism of reaction-induced demixing of PS blocks in the presence of the self-assembled PTFEA microdomains. In the thermosets containing PCL-b-PS-b-PTFEA, the spherical and cylindrical microdomains with the core-shell structure were formed. In those containing PCL-b-PTFEA-b-PS, the spherical microdomains were formed but the size of the microdomains displayed a bimodal distribution. The difference in morphology is accounted for by the influence of sequential structures of the copolymers on the reaction-induced demixing behavior of the triblock copolymers in the epoxy thermosets.