A solid-state C-13-NMR study of the mesophases of PEIM-9 (poly(4,4 '-phthaloimidobenzoylnonamethylene- oxycarbonyl))

On cooling from the melt, poly(4,4'-phthaloimidobenzoylnonamethyleneoxycarb onyl) (PEIM-9) forms a monotropic, smectic liquid crystal phase (T-i = 369. 2 K). The main driving force for this mesophase formation is the attainment of nanophase separation of the mobile nonamethylene spacer from the geomet rically rigid but irregular, phthaloimidobenzoyl group, coupled with partia l conformational ordering of the CH2 groups (about 20% of the CH2 groups at tain trans-conformations). It is shown by nuclear magnetic resonance that P EIM-9 consists at room temperature of two motionally distinguishable compon ents. One is the liquid crystal that remains mobile to its glass transition temperature (T-g approximate to 323 K), the other a more rigid crystal wit h a large degree of conformational disorder. In this crystal phase (T-m app roximate to 415 K) the conformationally disordered nonamethylene spacer has a similar amount of disorder than in the liquid crystal phase and the phth aloimidobenzoyl group is also not fully ordered. Even after long-term annea ling, all molecules remain conformationally disordered but T-m increases to about approximate to 437 K.