In this paper, the preparation of PBS-ran-PCL copolyesters by enzymatic ring opening polymerization is presented for the first time. The copolyesters were produced in a wide composition range and free of metallic contaminants, so they may be regarded as potential biomaterials. The copolymers have been characterized by proton and carbon nuclear magnetic resonance (1 H and 13 C NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM) and wide angle X-ray scattering (WAXS). The PBS-ran-PCL copolyesters were able to crystallize in the entire composition range and displayed a pseudo-eutectic region. Most copolymers away from the pseudo-eutectic region exhibited a single crystalline phase (PBS-rich or PCL-rich crystalline phase), while within the pseudoeutectic region the copolymers were double crystalline. Observations by PLOM, during isothermal crystallization showed that both nucleation density and spherulitic growth rate of the copolyesters are determined by the component that constitutes the majority phase. WAXS studies revealed that d spacings of selected crystallographic planes depend on composition. Therefore, both DSC and WAXS results suggest that the copolymers are probably isodimorphic, as the PBS-rich crystalline phase may contain small inclusions of PCL co-units, while the PCL-rich crystalline domains may also contain a minor quantity of PBS co-units inside.

Poly(butylene 2,5-furandicarboxylate-co-succinate) copolyesters (coPBFxSy) have been synthesized by\ud ring opening polymerization (ROP). Cyclic butylene 2,5-furandicarboxylate and butylene succinate\ud oligomer mixtures, to be used as monomers for ROP, were prepared by high dilution condensation\ud and enzymatic cyclization reactions, respectively. Two different catalytic systems, tin dioctanoate and\ud supported Candida antarctica lipase B (CALB), were used for polymerization. Thus two series of copolyesters\ud covering the whole range of compositions were prepared and their properties comparatively\ud examined. In both cases, random copolyesters with compositions close to those used in their respective\ud feeds were obtained. The influence of composition on reaction kinetics with respect to time and\ud temperature was evaluated for the two series. Chemically catalyzed ROP rendered copolyesters with Mw\ud in the ~50 000–65 000 g mol-1 range, whereas values between 15 000 and 45 000 g mol-1 were attained\ud when the ROP reaction was assisted by CALB. The thermal behavior of coPBFxSy obtained by ROP was\ud similar to that reported for such copolymers prepared by melt polycondensation. They all start to decompose\ud above 300 °C and display melting enthalpy and temperatures that decrease with copolymerization,\ud attaining minimum values when the comonomer contents are approximate to balance. On the\ud contrary, the glass-transition temperature increased almost linearly with the content of butylene furandicarboxylate\ud units, covering the whole range of values between those of the two parent homopolyesters.\ud Small deviations in thermal properties observed between the two series could be attributed to their differences\ud in molecular weights. Hydrolytic and enzymatic degradation studies revealed that coPBFxSy\ud became more degradable with increasing content of succinic units, whereas the homopolyester PBF\ud remained practically unaffected when incubated under similar conditions.Peer ReviewedPostprint (author's final draft

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Aiming the obtainment of materials with useful properties for bio-applications, as thermal and mechanical (in particular flexibility), chitosan and low molecular weight poly(lactic acid) were chosen due to their biodegradability and biocompatibility in various bio-environments. Networks formed by oligo(DL-lactic acid) segments linked to the chitosan chains were prepared, in which the ratio between the components varied systematically. A thorough structural characterization was performed, including the degree of crosslinking and the size of the crosslinking blocks. The thermal and mechanical properties varied according the ratio between the components in a non-linear way, which was discussed in terms of the macromolecular architecture. The data were compared with previous results obtained for grafts with the same composition aiming to verify the effect of the macromolecular architecture on the macroscopic properties.

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