G. Galli et al., SYNTHESIS AND THERMAL-BEHAVIOR OF LIQUID-CRYSTALLINE BLOCK-COPOLYMERSCONTAINING BOTH MAIN-CHAIN AND SIDE-CHAIN MESOMORPHIC BLOCKS, Macromolecular chemistry and physics, 195(6), 1994, pp. 2247-2260
A novel type of block copolymers comprising both side-chain and main-c
hain liquid-crystalline (LC) blocks in the same macromolecular structu
re was synthesized and studied. The former block was either one of two
LC polymethacrylates containing an azobenzene mesogen with different
substituents (block A), and the latter was a semiflexible LC polyester
block (block B). Thermal, dynamic-mechanical, and X-ray diffraction d
ata indicated that the two structurally different blocks were at least
partly phase-separated within the glassy and LC states. The thermodyn
amic phase transition parameters of block A were not affected by copol
ymer composition. However, significant deviations of the thermodynamic
parameters of block B were observed relative to those of the correspo
nding homopolymers. In particular, the normalized transition enthalpie
s of block B were much lower, suggesting the occurrence of a more or l
ess diffuse interphase. An increase in the nematic-isotropic temperatu
re was found at variance with previous results on most of the LC block
copolymers, in which only one block was an LC component.