Synthesis and characterization of hyperbranched aromatic polyesters used for polymeric graded-index materials

A series of hyperbranched aromatic polyesters, with different numbers of terminal naphthyl groups per molecule, were synthesized from 5-hydroxyisophthalic acid as an AB(2) type monomer and ethylenediaminetetraacetic acid as an 'initiator core' molecule via an 'one-step' approach, to be modified with beta-naphthol. These polyesters had polydispersities in the range 1.78-2.13, indicated by gel permeation chromatography, and degrees of branching between 0.45 and 0.60 by H-1 NMR using model compounds. Characterization indicated intense absorption bands in the near-UV spectral region and one fluorescence centre with emission at 365 nm. The refractive index increased with the number of naphthyl groups up to a value of 1.6205. The diffraction efficiency was about 8.7% for diffraction grating of cured films. (C) 2003 Society of Chemical Industry.