Role of the segment distribution in the microphase separation of acrylic diblock and triblock terpolymers

This paper investigates the influence of the “C” segment distribution on phase behavior in a series of ABC terpolymers comprised of poly(hydroxyethyl acrylate) (H, “A” block), poly(octyl acrylate) (O, “B” block), and poly(methyl acrylate) (M, “C” block). We show, using five distinct chain architectures including two triblock terpolymer sequences and three disparate diblock terpolymer sequences, that the manipulation of the “C” segment distribution through statistical copolymerization is a simple tool that polymer chemists may use to tune the stable morphology at constant chemical composition. Using Reversible Addition-Fragmentation chain Transfer (RAFT) techniques, five polymer architectures, HOM (poly(hydroxyethylacrylate-b-octylacrylate-b-methylacrylate)), HO/M (poly(hydroxyethylacrylate-b-octylacrylate-stat-methylacrylate)), H/MO/M, HMO, and H/MO, were synthesized at four chemical compositions with increasing M content and fixed H:O ratio. The self-assembly of the 20 polymers was probed with synchrotron small-angle x-ray scattering (SAXS) and dynamic shear rheology. Up to an M volume fraction of fM = 0.31, architecture H/MO/M was microphase-separated, indicating that M can be distributed into both H and O domains without overly compatibilizing the system. Three distinct morphologies were observed for the architecture HO/M over a narrow composition range, centered around f O M ∗  = 0.50. The results reported here are useful to those seeking to partially decouple the formulation of a block copolymer from its morphology.