Synthesis and transformation reactions of engineering polymers

Abstract

Polyarylethers have been synthesized earlier via nucleophilic aromatic substitution, using aqueous caustic and polar solvent such as DMSO. This route even though rapid, suffers from serious limitations.

We have modified this procedure considerably to synthesize a wide variety of high molecular weight polyarylethers. Our methodology utilized a higher boiling solvent namely N-methylpyrrolidone, a weak base such as K₂CO₃ and an azeotroping solvent such as toluene. Such a process allows one to synthesize the polymer in situ. We have also shown the feasibility of utilizing the procedure to synthesize functionally terminated controlled molecular weight oligomers.

High molecular weight tetramethyl substituted bis A arylene ether ketones, sulfones, and nitrile functional polyarylethers have been synthesized successfully. The ketone containing tetramethyl bisphenol A polymers has been found to be a photocrosslinkable resin and hence a potential candidate as a negative photo-resist for electronic materials. Investigation of the thermal behavior of these polymers have indicated considerable interchain forces to be operating with the nitrile functional polymers.

The nitrile functional polymers have been modified via hydrolysis to produce more hydrophilic and thermally stable amide functional polymers. Attempts at crosslinking the pendant nitrile groups via cyclization using Lewis acid were not as successful as expected. However, the use of the pendant nitrile group as a site for anionic grafting has been demonstrated.

A wide variety of crystalline poly aryl ether ketones have been synthesized by using a modified synthetic strategy in which an amorphous polymer is first synthesized to high molecular weight in NMP and then chemically modified to produce crystalline polymers.

All amorphous ketone functional polymers have been modified to produce, more hydrophilic, less thermally stable but potentially crosslinkable, alcohol functional polymers.

All the homo and copolymers synthesized have been characterized at the molecular level by solution ¹³C NMR and FT-IR spectroscopy. Proton NMR was also used for compositional analysis. All polymers were also characterized thermally by DSC; other thermal characterization techniques such as TG and TMA have also been used. Molecular weight characterization included intrinsic viscosity measurement on all polymers and selective utilization of GPC.

For crystalline insoluble polymers, solid state ¹³C NMR was used extensively for molecular level characterization. Wide angle x-ray measurement and DSC have been obtained in order to prove the existence and the level of crystallinity in these samples.

Limited characterization by SEM and EDAX was also conducted, primarily to gain information concerning the surface structure.