Radiopaque organic-inorganic hybrids were prepared by the sol-gel procedure. The hybrid the organic phase is a polyester, poly(1,4-butyleneglutarate), while the inorganic domains are in situ synthesized titania. FT-IR and XPS analyses show that organic and inorganic phases strongly interact mainly because of transesterification reactions involving the polyester chain and Ti atoms during hybrid synthesis. Synthetic parameters, namely solvent, environment acidity and inorganic precursor content, are investigated in order to assess their influence on the solid-state behaviour of the hybrid. The ability of the solvent to solvate, but not complex, Ti atoms and the presence of an inorganic acid in the feed increase interaction between the organic and inorganic phases, thus hindering polymer chain mobility. A similar effect, outlined by T-g increase and crystallization inhibition, is induced by increasing inorganic phase content. All obtained hybrids are optically transparent and opaque to X-rays. (c) 2008 Elsevier Ltd. All rights reserved.