LAUSR

Lyotropic liquid crystallinity was investigated for a concentrated solution of linear and 3-arm star poly(quinoxaline-2,3-diyl), of which the main chain has a rigid helical nature in tetrahydrofuran. Four samples for both linear and star chains were prepared with the weight-average molar mass Mw ranging from 50 to 250 kg mol–1. Two phase boundary concentrations, cI between the isotropic and biphasic regions and cA between the biphasic and anisotropic regions, were determined as a function of Mw. The resultant cI and cA for the linear chain increased gradually with lowering Mw. This behavior was successfully explained by the latest theory for lyotropic liquid crystallinity based on the scaled particle theory (SPT) for the wormlike spherocylinder. The phase diagram for star chains, on the other hand, has similar cI and cA at the high Mw region but increased abruptly with decreasing Mw. It can be explained by a modified SPT theory in which we assumed that two or three arm chains align parallel in the nematic...