Synthesis and characterization of soluble, melt-processible aromatic poly(amide-imides)

Abstract

This dissertation describes investigations of several methodologies appropriate for the synthesis of aromatic poly(amide-imides). An evaluation of the relative merits and drawbacks of each method has also been made based on molecular, thermal and solid state characterization of the polymers. The synthesis of both high molecular weight as well as controlled molecular weight systems has been attempted.

A detailed study of the route employing an acid chloride-anhydride has been conducted, which has particularly emphasized the use of quantitative non-aqueous titrimetry and proton NMR. Residual acid was found to limit molecular weight. Hydrolytic side reactions promoted by the acid have been proposed and were subsequently confirmed. Employment of an acid scavenger such as triethyl amine as well as the effect of alternative work-up procedures on the residual acid content in the polymer has also been determined.

The Yamazaki catalytic amidation reaction was found to be the most efficient among the various synthetic routes explored in this dissertation and it was used to generate a wide range of moderate to very high molecular weight polymers. Characterization of the soluble, amorphous polymers included solution viscometry in conjunction with gel permeation chromatography, vapor pressure osmometry and low angle laser light scattering. The various methods showed good correlation to one another and represent the first extensive solution characterization of soluble poly(amide-imides).

The catalytic imidization of σ- ester acids was found to be a novel and rapid route with a lot of promise.

Solid state transitions were investigated using a combination of a variety of techniques including DSC, Wide angle X-ray scattering, dynamic mechanical thermal analysis and dynamic melt rheometry. Many of the para-linkage containing homopolymers showed the tendency to develop crystallinity upon thermal treatment even though the initial "worked-up" polymers were amorphous. This aspect has hitherto not been reported and promises to be extremely valuable in allowing initially amorphous polymers to be easily processed to the desired shapes followed by a thermal treatment to develop crystallinity that would enhance solvent resistance and thermooxidative stability.

Some novel poly(amide-imides) were also synthesized that showed improvements in existing properties such as increased flame-retardancy and elevated glass transition temperatures.