| The morphology, crystal structure, phase transitions and blend compatibility of a series of semiflexible thermotropic liquid crystal terpolyesters (LCPs) were studied to understand their crystallization behavior and establish relationships between their microstructure and physical properties. Main characterization methods were electron microscopy and diffraction, and differential scanning calorimetry.;The LCPs were composed of equimolar amounts of p-oxybenzoate, p-dioxyphenyl, and aliphatic segments, containing variable number, n, of methylenes. Most work was done with P7, n = 7, which has been reported to exhibit chain folding in thin films, with 100 A thick lamellae and unit cell dimensions of a = 8.3 A and b = 5.1 A. An analogue terpolyester, P7-X, with a chlorine pendant group was also investigated; although exhibiting mostly glassy behavior, crystallized samples had unit cell dimensions of a = 7.6 A and b = 5.0 A.;Effects of crystallization conditions such as cooling rate, state from which crystallized, and annealing, in the melt and in solution, were analyzed using bulk samples, and quiescent and sheared films. The morphology was observed to be more sensitive to small changes in cooling rate as well as to the type of solvent, while crystal structure and phase transitions depended mostly on the state from which the sample was crystallized.;Attempts to produce polymer single crystals, by a method called Confined Thin Film Melt Polymerization, resulted in the formation of oligomers with an average number of six repeat units. These samples produced macrocrystals with lateral dimensions of up to 0.65 mm, and diffraction measurements and thermal behavior similar to those of their corresponding bulk versions. Deviations from the typical p-oxybenzoate homopolymer crystal structures were observed for n = 3.;Compatibility of P7 and P7-X in binary blends with polyethylene (PE), polyethylene terephthalate (PET), and nylon 6 (Ny6), was examined to evaluate the effect of the aliphatic segment in promoting good adhesion at the interphase. Partial compatibility was observed for PE blends, while miscibility was obtained in PET and Ny6 blends mixed at high temperatures due to the occurrence of transreactions. |
