On the morphological behavior of ABC miktoarm stars containing poly(cis 1,4‐isoprene), poly(styrene), and poly(2‐vinylpyridine)

Abstract

ABSTRACTFundamental understanding of microphase separation in ABC miktoarm copolymers is vital to access a plethora of nonconventional morphologies. Miktoarm stars based on poly(cis 1,4‐isoprene) (I), poly(styrene) (S), and poly(2‐vinylpyridine) (V) are model systems, which allow systematic studies of the effects of composition, chemical microstructure, and temperature on the thermodynamics of microphase separation. Eleven ISV‐x (I:S:V = 1:1:x, v:v:v) miktoarm copolymers were synthesized by anionic polymerization affording well‐defined copolymers with a variable V arm. Equilibrium bulk morphologies of all samples, as evidenced by small‐angle X‐ray scattering, transmission electron microscopy (TEM), and self‐consistent field theory, showed a systematic transition from lamellae (x ≈ 0–0.2) to [8.8.4] tiling (x ≈ 0.6–0.9) to cylinders in undulating lamellae (x ≈ 2–4) and, finally, to hexagonally packed core–shell cylinders (x ≈ 5–8). Chemical microstructure of the I arm [poly(cis 1,4‐isoprene)] versus poly(3,4‐isoprene) is shown to play important role in affecting morphological behavior. To reconcile differences between ISV‐x star morphologies reported in the literature and those reported herein, even for the same composition, effects of the microstructure of I arm on the Flory–Huggins parameter between I and V arms were taken into account in a qualitative manner. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1491–1504