Statistical Bottlebrushes: Synthetically Accessible Substitutes for Miktoarm Star Polymers

Abstract

Bottlebrush copolymers having a random or statistical sequence of A and B side chains attached to a long polymeric backbone structurally mimic the core connectivity of AmBn miktoarm stars within small segments along the backbone. One might expect, therefore, that the phase behavior of statistical bottlebrushes also shares similarities with miktoarm stars, such as order–order phase boundaries being deflected to large volume fractions of discrete minority A-block domains compared to linear analogues. In this work, under the guidance of self-consistent field theory simulations, poly(lactide)-stat-poly(dodecyl acrylate) (PLA-stat-PDDA) bottlebrushes with long PLA and short PDDA side chains were designed to maximize such conformational asymmetry effects and accentuate order–order phase boundary deflection. Mesophases with discrete PLA domains were observed to be stable at volume fractions exceeding 0.5. Frank–Kasper phases also emerged as anticipated by theory for conformationally asymmetric materials, with ordering improved by adding small amounts of solvent. These results suggest that statistical bottlebrushes may serve as a more synthetically accessible substitute for asymmetric miktoarm star polymers when non-conventional phase behavior is of primary importance.