Abstract
A series of polyimides has been synthesized by polycondensation reaction of 3.3′.4,4-biphenyl tetracarboxylic acid dianhydride (BPDA) and corresponding diamines with various alkyl side chains via polyamic acid formation. The inherent viscosities of the polyamic acids measured in N-methyl-2-pyrrolidone (NMP) were in the range of 0.45 to 1.19 dL/g, which was decreased with the increase of alkyl chain length. The glass transition temperatures of the polyimides were in the range of 247.6∼291.4°C. The effect of curing temperature on the pretilt angle of liquid crystals (BL-002. Merck Ltd.) with polyimides having alkyl side chains was investigated, which revealed that the increase of degree of imidization resulted in higher pretilt angles. On the other hand, the pretilt angles were decreased by the curing reaction above the temperature of 300°C due to decomposition reaction of alkyl side chains. It was also found that the pretilt angles were varied with the length of alkyl side chains.
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