Copolycondensations of bisphenols with aggregates of isophthalic acid and terephthalic acid activated by tosyl chloride/dimethylformamide/pyridine indifferent manners

A mixture of isophthalic acid (IPA) and terephthalic acid (TPA) was activat ed by a tosyl chloride/dimethylformamide/pyridine (Py) condensing agent in two steps via the treatment of a mixture of the initially activated IPA/TPA with additional TPA followed by the activation of TPA with the agent. The resulting mixture showed a solubility in Py different from that obtained by the activation of them all at once; the difference might be due to differe nt structures of the aggregates of the activated IPA and TPA at the same co mposition of the diacids. The structures of the aggregates were evaluated o n the basis of melting points and the IR spectra of a mixture of dimethyl e sters of IPA and TPA produced by the quenching of the reaction mixtures wit h methanol. The mixture obtained by two-step activation showed lower meltin g points and spectral changes due to enhanced associations of the esters wi th respect to the mixture prepared by the activation of them all at once. T he aggregates were also examined in terms of the distributions of IPA and T PA in thermotropic copolyesters prepared from methylhydroquinone and chloro hydroquinone by their transition temperatures and C-13 NMR. (C) 2001 John W iley & Sons, Inc.