Novel liquid crystalline block copolymers by ATRP and ROMP

Two new liquid crystalline block copolymers have been synthesized: a side-on liquid crystalline/isotropic (LC/Iso) triblock copolymer ABA (B = LC) by ATRP and a side-on LC/Iso diblock copolymer AB' (B' = LC) by first synthesizing the LC block (B') using ROMP and then the Iso block using ATRP. Absolute values of molar masses of the homopolymers and of the block copolymers were determined using SEC with an on-line light-scattering instrument: M-n = 1.43 x 10(4), M-w/M-n = 1.04 for homopolymer B, M-n = 3.47 x 10(4), M-w/M-n = 1.32 for triblock copolymer ABA, M-n = 2.29 x 10(4), M-w/M-n = 1.06 for homopolymer B', and M-n = 3.61 x 10(4), M-w/M-n = 1.28 for diblock copolymer AB'. The di and triblock copolymers self-assemble into lamellar mesophases in which the LC blocks undergo transitions similar to those of the homopolymers. Lamellar structures were studied as a function of temperature by polarized optical microscopy, DSC and X-ray diffraction. Those new liquid crystalline block copolymers could be used as model systems for "artificial muscles".