Phase behavior and molecular structure of liquid-crystalline polyesters with flexible lateral substituents

The characterization of segmented liquid-crystalline polyesters (LCP's) with short flexible lateral substituents is reported. The general formula of polymers is [-p-C6H4OOC-p-C6H3(R)COO-p-C6H4O(CH2)(n)O-](x) with n=2 and R=-O(CH2)(m-1)CH3(m=1-4). They have nematic liquid-crystalline behavior. At room temperature, polymers show a crystalline phase, whose structure has been solved for the term with n = 3. Cell parameters are a = 13.20(1) Angstrom, b = 6.48(1) Angstrom, c = 20.11(2) Angstrom, alpha = 138.3(1)degrees, beta = 110.9(1)degrees, and gamma = 80.8(1)degrees (space group P (1) over bar, two chains per cell, rho(c) = 1.367 g cm(-3)). The molecular packing is characterized by the organization of chains in double stacks with the lateral flexible substituents confined in between.