A solid-state13C-NMR study of the mesophases of PEIM-9 (poly(4,4′-phthaloimidobenzoylnonamethylene-oxycarbonyl))

Abstract

On cooling from the melt, poly(4,4′‐phthaloimidobenzoylnonamethyleneoxycarbonyl) (PEIM‐9) forms a monotropic, smectic liquid crystal phase (Ti = 369.2 K). The main driving force for this mesophase formation is the attainment of nanophase separation of the mobile nonamethylene spacer from the geometrically rigid, but irregular, phthaloimidobenzoyl group, coupled with partial conformational ordering of the CH2 groups (about 20% of the CH2 groups attain trans‐conformations). It is shown by nuclear magnetic resonance that PEIM‐9 consists at room temperature of two motionally distinguishable components. One is the liquid crystal that remains mobile to its glass transition temperature (Tg ≈ 323 K), the other a more rigid crystal with a large degree of conformational disorder. In this crystal phase (Tm ≈ 415 K) the conformationally disordered nonamethylene spacer has a similar amount of disorder than in the liquid crystal phase and the phthaloimidobenzoyl group is also not fully ordered. Even after long‐term annealing, all molecules remain conformationally disordered, but Tm increases to about ≈ 437 K.

Effect of the Precise Branching of Polyethylene at Each 21st CH2 Group on Its Phase Transitions, Crystal Structure, and Morphology

“…Calorimetric as well as X-ray data are available for PEIM-22, 58,59 while supporting solid-state NMR information is available PEIM-9 and PEIM-12. 60,61 These precisely segmented PEIMs have a smectic-like layer structure with a coherently scattering stack of 3-4 repeating units, 59 with the methylene sequences being nanophase-separated in a hexagonal condis structure with specific bonds ordered into a trans conformation. 60,61 In these and similar segmented macromolecules the two chemically different segments are at the basis of the nanophase separation, driven by the immiscibility of the two sequences.…”

“…60,61 These precisely segmented PEIMs have a smectic-like layer structure with a coherently scattering stack of 3-4 repeating units, 59 with the methylene sequences being nanophase-separated in a hexagonal condis structure with specific bonds ordered into a trans conformation. 60,61 In these and similar segmented macromolecules the two chemically different segments are at the basis of the nanophase separation, driven by the immiscibility of the two sequences. The crystallinity of the CH 2 sequences provide the largest portion of the heat of crystallization and stabilize the overall crystal stacks, which in turn assume the lamellar superstructure.…”