Random and Block Copolymers of Poly(dodecamethylene terephthalamide)
The following dissertation focuses on the synthesis and characterization of poly(dodecamethylene terephthalamide) (PA-12,T) and novel copolymers. Chapter I details the synthesis of PA-12,T homopolymer by melt condensation polymerization. A series of homopolymers with different molecular weights were obtained by adjusting the stoichiometry of the polymerization using 1,12-diaminododecane, terephthalic acid and benzoic acid. End group 13 C NMR spectroscopy resonances were obtained by correlating peak intensities with intrinsic viscosity values. From the NMR data, total end group concentrations and molecular weights were determined for each sample. The data exhibited a linear trend when plotting log (IV) versus log (M n ), and previously unknown PA-12,T Mark-Houwink solution constants were found. Chapter II examines the synthesis and characterization of PA-12,T, 6,T and 10,T, 6,T copolymers. Melt condensation procedures and solution constants from Chapter I were used to synthesize and confirm that high molecular weight copolymers were obtained. The substituted aromatic carbon resonance of 13 C NMR spectra was found to be sensitive to copolymer sequence, and was used to determine that the copolymers are random. Differential scanning calorimetry data shows that the copolymers exhibit eutectic melting behavior, displaying a decrease in copolymer melting temperature and enthalpy up to the eutectic point of 30 wt-% PA-6,T, and a corresponding increase in both up to 60 wt-% PA-6T. Optically clear materials were obtained at 30 wt-% PA-6,T. Data collection was stopped at 60 wt-% due to phase separation of PA-6,T rich phases. Wide angle x-ray diffraction data displayed three distinct regions: (1) sharp PA-10,T crystal diffractions from 0-20% PA-6,T, (2) broad amorphous scattering between 25-45% PA-6,T, (3) sharp diffraction peaks from 50-60 wt% PA-6,T. All copolymers had relatively high glass transition temperatures from 137-149 °C determined from dynamic mechanical analysis. This study provides a method in which crystallinity and optical clarity of semi-aromatic polyamides can be tuned while maintaining high glass transition temperatures. In Chapter III, a novel, one pot polyamide-polyamide block copolymer synthetic strategy is explained. The synthesis of PA-12,T - PA-6 block copolymers occurs in two sequential steps, in which it was found that CaCl2 is needed to avoid crosslinking of the material. First, reaction variables of the solution, step growth polymerization of 1,12-diaminododecane and biscaprolactam terephthalamide (BCT) in caprolactam were investigated. PA-12,T with an average degree of polymerization of 15 and n-terephthaloyl end groups was obtained using 5 mol-% excess BCT. The second stage of synthesis uses anionic polymerization of the caprolactam using the n-terephthaloyl caprolactam end groups. While CaCl 2 concentration had little effect on this step growth reaction, it was found that the CaCl2 greatly effected the conversion and transamidation of the anionic polymerization. This effect yielded a variety of materials with different molecular weights and blockiness that display unique thermal and solubility properties not obtained with polymer blends. Furthermore, this technique can be applied to wide variety of monomers to create novel polyamide-polyamide block copolymers currently undiscovered.