Synthesis, characterization, and deuterium labeling of polyamides studied by nuclear magnetic resonance spectroscopy
The synthesis, characterization, and deuterium labeling of polyamides of polyamides have been investigated. In Chapter II, selective deuterium labeling of various polyamides was demonstrated via a facile method which does not require organic solvent or catalyst. Quantitative solution-state NMR analysis showed deuterium incorporation at the carbon alpha to the carbonyl ranged from 20-75%. Incorporation in [varepsilon]-caprolactam increased with repeated treatments. Isotopic shift effects for the deuterated materials were additive for all sites within experimental error. In Chapter III, the effect of stoichiometric imbalances on the polymerization of poly(dodecamethylene terephthalamide)was investigated. Molecular weight was varied by polymerizing the monomer salt with excess diaminododecane, terephthalic acid, or benzoic acid. End groups were identified and number average molecular weights were calculated by NMR analysis. Intrinsic viscosity measurements correlated well with NMR measurements and were used to calculate the Mark-Houwink constants of K=55.8*10 -5 dL/g and α = 0.81. Eutectic melting behavior of PA-10,T-6,T and PA-12,T-6,T copolymers are described in Chapter IV. Nuclear magnetic resonance spectra showed that comonomer sequences were distributed statistically to give random copolymers. Melt pressed film behavior, NMR, DSC, and WAXD analysis agree that PA-6,T monomer units do not co-crystallize with PA-10,T or PA-12,T monomer units, and do not form isomorphic structures in the copolymers studied. Instead, a eutectic melting point at 30 wt-% PA-6,T is observed for both copolymers. Compared to PA-10,T comonomer, PA-12,T comonomer has a greater effect on disrupting the crystallization of PA-6,T homo-segments above the eutectic point. Chapter V describes the synthesis of a new family of compounds which form hydrogen-bonded supramolecular assemblies. As-synthesized materials did not assemble into supramolecular polymers until after they had been melted and cooled. Thermal treatment and solvent precipitation produced differently organized structures and extents of crystallinity. Crystallization diminished polymer-like behavior. Chiral centers played an important role in ordered domain behavior. Compounds containing urea linkages, or copolymers of compounds containing amide linkages formed glassy materials. Macroscopic assembly was demonstrated by fiber formation.