Hydrogen Bonding in Aromatic Polyamides

Abstract

Rigid, rodlike polyamides, polyesters and polyesteramldes characteristically exhibit a high degree of intermolecular association resulting in crystalline and liquid crystalline materials with high thermal transitions and moderate to poor solubility. Certain structural modifications can diminish intermolecular attractive forces which leads to nearly complete elimination of highly-correlated structures. Many of these materials exhibit unique spectral, thermal, optical and morphological properties, and several are very soluble in common solvents but do not form lyotropic solutions. The specific structural modification primarily responsible for this unusual combination of properties are the 2,2’-disubstituted-4,4’-biphenylene diacid, diol or diamine comonomers. This substitution pattern forces non-coplanarity between the phenyl rings while maintaining the rodlike conformation of the backbone. This paper describes an investigation of the effect of orientation on hydrogen bonding in polyamides containing a non-coplanar biphenyl diamine in the backbone. The results help substantiate the notion that weak intermolecular associations are primarily responsible for many of the properties exhibited by these polymers.