Poly(imide-amide)s and poly(imide-esters)s based on silarylene units containing (l)-alanine moiety: synthesis and characterization

Abstract

Optically active poly(imide-amide)s (PIAs) and poly(imide-ester)s (PIEs) containing two silicon atoms in the main chain and l-alanine as chiral residue, were synthesized. The former were prepared by direct polycondensation between two dicarboxilic acids and bis(4-aminophenyl)dipenylsilane according to the triphenyl phosphate method. PIEs were synthesized with bis(4-hydroxyphenyl)dimethyl o ethylmethylsilane, according to the tosyl chloride method. Monomers and polymers were characterized by IR and 1H, 13C, and 29Si NMR spectroscopy and elemental analysis, and the results were in agreement with the proposed structures. PIAs and PIEs showed low values of ηinh, indicative of low molecular weight species, probably of oligomeric nature. Polymers were soluble in polar aprotic solvents and also in common solvents such as CH2Cl2, CHCl3, and acetone, due to the effect of both, the polarity of the Si–C bond and the presence of an aliphatic residue provided by the l-alanine amino acid. The glass transition temperatures (Tg) of the PIAs were higher than those obtained for PIEs, due to the higher flexibility of the ester group. The thermal decomposition temperatures (TDT) were lower than 400 °C and dependent of the polymer structure.