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The paper presents the mechanism of lactide polymerization initiated with zinc (II) acetylacetonate monohydrate. However, the actual initiator of this reaction is the complex containing a metal–oxygen bond, formed by the exchange reaction of acetylacetonate ligand with deprotonated lactide derivative. The described reaction results in the release of free acetylacetonate and formation of transitional zinc complex with metal–oxygen bond connecting the zinc atom with derivative of lactide, incorporated – as a new, active in polymerization ligand. Polylactide chain propagation process, which constitutes the following stage of the reaction, is caused by a typical, well known, coordination-insertion ring opening polymerization. The proceeding polymerization maximum yield at the applied conditions does not exceed about 70% in benzene solution and 90% at bulk.

The aim of this paper is to present a new method of copolymerization of glycolide with l -lactide with the use of low toxic iron compounds. The use of Fe(acac) 3 and Fe(OEt) 3 initiators enabled one to obtain copolymers with yields up to 100% and possessing good mechanical properties. The chain propagation process and the influence of the transesterification was examined. On the basis of NMR examination and DSC thermograms, it was shown that the samples obtained at the temperature of 100 °C with the use of the initiators have quasi-segmental chain microstructure.

The use of butyllithium and butylmagnesium in the polymerization of racemic lactide leads to the formation of polylactide with a partially disyndiotactic structure. A coefficient of stereoselectivity p2 which describes the content of disyndiotactic structures appears to be higher for the lithium initiator; however an increase in the concentration of this initiator tends to enhance an intermolecular transesterification process thus leading to the formation of totally random structures in a polylactide chain. In contrast, in the case of butylmagnesium, an increase in the initiator concentration does not induce the intermolecular transesterification processes.

The application of heteronuclear chemical shift correlation (HETCOR) NMR allowed us to correlate the homodecoupled methine proton with the methine carbon signals of poly( rac -lactide) and poly( meso -lactide), and made it possible to perform a detailed analysis of 1 H NMR spectra (homodecoupled) and to ascribe the signals to configurational pentads. The assumption made by Chisholm and coworkers [Chisholm et al., Chem. Comm. 1997, p. 1999] that the previous assignment of methine carbon signals in 13 C NMR spectra was incorrect appeared to be wrong.

Acoustooptical parameters in a mixture of polyvinyl alcohol (PVA) polymers with modified polyvinyl alcohol (MPA) were investigated as functions of the MPA content, time of exposure and temperature. The maximum value of the acoustooptical quality coefficient was achieved for values of the MPA content above 70%. It was proposed to use the polyvinyl alcohol photopolymers as acoustooptical modulators and deflectors. An essential influence of the polyvinyl alcohol modifications on the acoustooptical parameters was unambiguously shown. Also, a critical dependence of the acoustooptical coefficients on the sample thickness was revealed. The data on the acoustooptical quality coefficient correlate well with the data obtained for the sound losses coefficient.

The 13C nuclear magnetic resonance (n.m.r.) spectra were found to provide a means for direct observation of the structures formed along the glycolide/lactide copolymer chain upon transesterification. Nevertheless 1H n.m.r. spectroscopy appeared to be more convenient and useful in the analysis of chain microstructure. The glycolide methylene group region of the proton spectra exhibits several signals which can be ascribed to longer sequences (as compared to those giving rise to 13C resonances) as well as to the sequences which can appear only as a result of the second mode of transesterification. The analysis revealed that the longest blocks were in the copolymers prepared with A1(acac)3 as the initiator and the shortest blocks were in the copolymers obtained with tin initiators. A decrease in temperature was found to reduce the extent of the second mode of transesterification.