Thermoreversible Order−Order Transition of a Triblock Copolymer Containing a Mesogen‐Jacketed Liquid Crystalline Polymer with a Re‐Entrant Phase Behavior

Abstract

Poly{2,5‐bis[(4‐butoxyphenyl)‐oxycarbonyl]styrene} (PBPCS) with a re‐entrant phase behavior is used to synthesize a new kind of ABC triblock copolymers (triBCPs), poly(dimethylsiloxane)‐b‐polystyrene‐b‐PBPCS (PDMS‐b‐PS‐b‐PBPCS, DSB). Two well‐defined triBCPs D120S100B50 and D120S100B120 with different molecular weights (MWs) and narrow MW distributions are synthesized by sequential atom transfer radical polymerization. The volume fractions of PDMS, PS, and PBPCS in D120S100B50 are 0.24, 0.26, and 0.50, respectively, while the values in D120S100B120 are 0.14, 0.16, and 0.70, respectively. At low temperatures, PBPCS is amorphous. Both samples form a core–shell hexagonally packed cylindrical (CSH) morphology. At high temperatures, PBPCS in the triBCPs can form a liquid crystalline (LC) phase, the transformation of which can induce an order−order transition (OOT) of D120S100B120. The nanostructure changes from a CSH structure to a three‐phase‐four‐layer lamellar structure, and the transition is thermoreversible. The sequence of the OOT is opposite to that of a coil−coil−coil triBCP. The unusual LC behavior of PBPCS plays an important role on the thermoreversible morphological transition of the triBCP. image