Side-chain liquid-crystalline poly(ketone)s: effect of spacer length, mesogen type and mesogen density on mesomorphic behavior

Abstract

Novel side‐chain liquid‐crystalline copolymers (SCLCPs) were synthesized via the Pd(II) catalyzed alternating copolymerization of mesogenic 1‐alkenes and carbon monoxide. For methoxybiphenyl mesogens, these copolymers exhibited highly ordered smectic E mesophases and high glass transition temperatures. The transition temperatures of these polymers were tuned by altering the spacer length or by dilution of mesogen‐containing alkenes with 1‐hexene. Polymers with cyanobiphenyl or methoxyazobenzene mesogens exhibited nematic mesophases. These polymers were the first ever nitrogen containing copolymers of this type. Increase of the spacer length or the 1‐hexene content of methoxybiphenyl‐containing copolymers resulted in a decrease of the surface polarity of spincoated films. The decomposition temperature of these SCLCPs started far above the isotropization temperature of the polymers.

Polyketones as alternating copolymers of carbon monoxide

“…The isotropiosation temperature of copolymers decreases with an increase in the length of the spacer, { while that for terpolymers decreases with an increase in the content of hex-1-ene. 136 The aliphatic a-alkenes containing mesogenic substituents enter into copolymerisation with carbon monoxide in the presence of Pd(II) complexes. Depending on the type of the ligand (L), products with different stereo-and regioregularities are formed in the palladium complex (Scheme 2).…”

A series of novel side chain liquid crystalline polysiloxanes containing cyano‐ and cholesterol‐terminated substituents: Where will the structure‐dependence of terminal behavior of the side chain reappear?

“…Further analysis and probe showed that d (100) ≈ L m + 2 L s , where L s (1.07 nm) is the calculated length of the spacers from the O atom in the ether groups to the Si atom in the backbones, and L m (1.28 nm) is the calculated length of the achiral mesogenic cores from the O atom in the ether groups to the last N atom of the achiral side chains, respectively. Additionally, previous reports have revealed that the dipole interaction of the strong polarity cyano substituent could induce the side chains to organize in antiparallel pairs to force the cyano away from each other and to minimize the system energy, which played a decisive role on the self‐organization of the molecule . Combining the comprehensive analysis and judgment of above results, as shown in Scheme , we speculated that for this series of polysiloxanes‐containing cyano‐terminated side chains, a monolayer SmA phase with side chains partially interdigitated was self‐assembled, in which the layer period was dominated by the achiral side chains with cyano unit.…”

“…By replacing the CH 3 side chain groups with polar CF 3 groups, Lee et al found the similar results. Sudhölter et al and Chen et al reported that a drastic change in mesogen phase structures was occurred when cyano group was used instead of methoxy group as the terminal group. Zhou et al synthesized a series of mesogen‐jacketed liquid crystalline polymers (MJLCPs) with asymmetric substitutions and found that carboxylic acid terminated asymmetric polymers formed a double layer smectic A phase, while the corresponding alkyl terminated polymers showed no liquid crystallinity or exhibited columnar phase.…”