Synthesis of Hydrophilic Poly(butylene succinate-butylene dilinoleate) (PBS-DLS) Copolymers Containing Poly(Ethylene Glycol) (PEG) of Variable Molecular Weights

Polymeric materials have numerous applications from the industrial to medical fields because of their vast controllable properties. In this study, we aimed to synthesize series of poly(butylene succinate-dilinoleic succinate-ethylene glycol succinate) (PBS-DLS-PEG) copolymers, by two-step polycondensation using a heterogeneous catalyst and a two-step process. PEG of different molecular weights, namely, 1000 g/mol and 6000 g/mol, was used in order to study its effect on the surface and thermal properties. The amount of the PBS hard segment in all copolymers was fixed at 70 wt%, while different ratios between the soft segments (DLS and PEG) were applied. The chemical structure of PBS-DLS-PEG was evaluated using Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Gel permeation chromatography was used to determine the molecular weight and dispersity index. The results of structural analysis indicate the incorporation of PEG in the macrochain. The physical and thermal properties of the newly synthesized copolymers were also evaluated using water contact angle measurements, differential scanning calorimetry and dynamic thermomechanical analysis. It was found that increasing the amount of PEG of a higher molecular weight increased the surface wettability of the new materials while maintaining their thermal properties. Importantly, the two-step melt polycondensation allowed a direct fabrication of a polymeric filament with a well-controlled diameter directly from the reactor. The obtained results clearly show that the use of two-step polycondensation in the melt allows obtaining novel PBS-DLS-PEG copolymers and creates new opportunities for the controlled processing of these hydrophilic and thermally stable copolymers for 3D printing technology, which is increasingly used in medical techniques.