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Abstract
Side-chain liquid crystal polyethyleneimines (PEI; P-n) with different spacer lengths (n) were synthesized, and their thermal and liquid crystalline properties were examined. The P-n polymers showed liquid-crystalline phases upon heating and cooling. P-n with a short methylene spacer (n=2-5) formed a smectic A (SmA2 ) phase with a bilayered structure. However, P-n with a longer methylene spacer than a pentamethylene chain (n=6-12) exhibited a smectic A (SmA1 ) phase with a monolayered structure. P-2, P-3 and P-4 showed only the SmA2 phase. P-n with n=5-9 revealed a nematic phase and the smectic A phase. P-8 and P-9 displayed smectic C and F phases, as well as the SmA1 and nematic phases. P-10, P-11 and P-12 exhibited SmA1 and smectic F phases. These results indicate that the microstructures of the liquid crystalline phases depend on the balance between the spacer length and the length of the mesogenic group containing the terminal unit. This is useful information for the design of side-chain liquid crystal polymers.