Competition and Coupling Between Crystallization and Microphase Separation in a Triblock Copolymer

ABSTRACT Block copolymers (BCPs) can self‐assemble into various nanostructures. The introduction of polymers with special properties, such as liquid crystalline (LC) and semicrystalline ones, will affect the self‐assembled structures of BCPs. In this work, BCPs containing a coil block polydimethylsiloxane (PDMS), an LC block poly[4′‐(methoxy)‐2‐vinylbiphenyl‐4‐methyl ether] (PMVBP) that is a mesogen‐jacketed LC polymer (MJLCP), and a semicrystalline poly(L‐lactic acid) (PLLA) were synthesized. The diblock copolymer PLLA‐ b ‐PMVBP does not form ordered nanostructures because the solubility parameters of the two blocks are quite close. The triblock copolymer PDMS‐ b ‐PLLA‐ b ‐PMVBP forms the lamellar (LAM) structure at ambient temperature and the hexagonally packed cylindrical (HEX) structure at high temperatures. The results of temperature‐dependent small‐angle x‐ray scattering show that the crystallization of PLLA significantly affects the self‐assembled structures of the BCPs. Crystallization of PLLA may compete or couple with the microphase separation of the BCP. In addition, a rare type of phase transformation, lower disorder‐order transition (LDOT), is observed in the sample D 56 L 19 V 4 .