Abstract
Hydroxy-terminated poly(pentamethylene p,p′-bibenzoate) oligomers with different molecular weights were prepared. The poly(pentamethylene p,p′-bibenzoate) oligomers showed rather high crystallinity, and some of them exhibited a monotropic smectic phase. Block copolyesters with hard segments of poly(pentamethylene p,p′-bibenzoate) and soft segments of poly(tetramethylene adipate) were prepared by coupling the poly(pentamethylene p,p′-bibenzoate) oligomer and a poly(tetramethylene adipate)glycol with methylene-4,4′-diphenylene diisocyanate in solution. The block copolyesters were characterized by IR, 1 H NMR, differential scanning calorimetry, a polarized microscope, and X-ray diffraction. The thermal transitions of the block copolyesters were dependent on the composition and the molecular weight of the poly-(pentamethylene p,p′-bibenzoate) oligomer used. The hard segments in the block copolyesters showed no liquid crystallinity and exhibited rather low crystallinity or were even amorphous. The molecular weight of the poly(pentamethylene p,p′-bibenzoate) oligomer used influences the glass-transition temperature and crystalline properties of the soft segments in the block copolyesters significantly. The effect on the glass-transition temperature of the soft segments is described as the difference in miscibility between the hard and soft segments.