| Research Abstract |
Side-chain liquid crystalline (LC) conjugated polymer with stable radical group is expected to afford a parallel spin alignment with aids of spontaneous orientation and externally forced macroscopic alignment of LC side chains. The present study is aimed to achieve a macroscopic spin alignment through LC orientation, For this aim, di-substituted polyacetylene with LC group and stable radical group in side chains is useful, where the intrachain parallel spin alignment can be easily constructed on the basis of topological stereoregularity satisfying Ovchinnikov rule.
Di-substituted polyacetylene was synthesized by introducing both liquid crystalline LC group and stable radical group into side chains. Di-tert-butylphenol derivative, where the hydroxy moiety of the phenyl group was protected by trimethylsilyl group, was adopted as a stable radical precursor. Acetylene monomer substituted with the LC group and the radical precursor was polymerized using metathesis catalyst of TaCI_5-(n-Bu)_4Sn. The polymer synthesized was soluble in organic solvents and showed an enantiotropic smectic phase. ESR spin intensity of the polymer was evaluated after the radical precursor was deprotected and oxidized, Anisotropy in spin intensity, owing to spontaneous alignment of LC side chains, was confirmed.
Next, the mono-substituted polyacetylene copolymer was synthesized, where either the LC group or the radical group was substituted into the unit cell of main chain. The copolymer, in which the ratio of radical group-substituted polyene segment is less than 10 %, showed a smectic phase in 150 - 160ﾟC.The ESR intensity increased in the LC temperature. This is ascribed to the spin alignment of phenoxy radical electrons within LC domains.
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