Synthesis and properties of amphotropic hydrogen bonded liquid crystalline (LC) poly(ester amide)s (PEA): effect of aromatic moieties on LC behavior

Abstract

Twelve hydrogen bonded aromatic-aliphatic poly(ester amide)s differing in the structures of their aromatic moieties (isophthalic, terephthalic, 2.6-naphthyl and 4,4/-biphenyl moieties of the dicarboxylic acid and phenylene, and xylylene moieties of the amido diol part) were prepared by the polycondensation of amido diols with acid chlorides of isophthalic acid, terephthalic acid. 2.6-naphthalic dicarboxylic acid and 4,4'-biphenyl dicarboxylic acid, respectively. The amido diols were prepared by the aminolysis of gamma-butyrolactone with hexamethylene diamine, para phenylene diamine and para xylylenene diamine, respectively. The PEAs were characterised for elemental analysis, FTIR, C-13 NMR, TGA. DSC. POM. isothermal viscosity measurements and WAXD. Here we are presenting the effect of aromatic moieties on the thermotropic and lyotropic (amphotropic) properties of PEAs. These PEAs are essentially constituted of six types of structural entities. i.e. isophthalic, terephthalic. 2,6-naphthalic and 4,4'-biphenyl moieties containing dicarboxylic acid and the aliphatic, aromatic (phenylene and xylylene moieties) of the di-amide linkage of the amido diol part. The structure of the polymers even in the mesophase is dominated by hydrogen bond interaction between the adjacent chains and also inter plane mesogenic interaction between the rigid aromatic group. It was observed morphologically that the formation of different forms of nematic/smectic/columnar/ spherullitic phases in PEAs are due to the delicate balance of self assembling through hetero intermolecular hydrogen bonded amide-amide and amide-ester net works and also inter-plane mesogenic interactions.