Resumen de Crystallization, processing and applications of new polyesters
Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. The most of these polymers can be prepared from biobased diols and dicarboxylic acids. In the present thesis two different groups of poly(alkylene dicarboxylate)s were synthesized by thermal policondensation. The first group concerns to polymers derived from 1,9-nonanediol and different ratios of pimelic and azelaic acids. Different techniques such as OM, DSC, SAXS and FTIR were used in order to characterize the copolymers. The crystalline structure of these polyesters has been investigated by means of electron and X-ray diffraction. Single crystal of homopolymers and the copolymer with the intermediate composition were easily degraded by enzymes. The second group is constituted by poly(alkylene dicarboxylate)s derived from 1,4-butanediol and succinic and azelaic acids. Physicochemical techniques were combined to understand the thermal properties and the different factors that influenced the crystallization process. Morphological changes occurring during crystallization were evaluated by time resolved SAXS/WAXD experiments using synchrotron radiation. Lauritzen and Hoffman analysis was performed from spherulite growth rates and also considering overall crystallization rates determined from DSC experiments. Enzymatic degradability was clearly dependent on the composition and logically on the crystallinity. Interestingly constituent spherulites of copolymer samples were highlighted during degradation. Ultrasounds technology has been proved as an useful method to mould biodegradable polylactide and poly(nonamethylene azelate). Minimum material loss and degradation was found when materials were processed under appropriate operating conditions (i.e. time, amplitude and force). The technology was also appropriate to prepare nanocomposites, being assayed the use of clay and silica nanoparticles. In the first case, the achievement of exfoliated structures was clearly demonstrated by X-ray diffraction and TEM observations and using N757, C20A, C25A, and N848 clays. Crystallization behavior of exfoliated PLA nanocomposites was evaluated, being found a highly peculiar behavior since clay particles had an antinucleating effect. The contrary effect was observed for nanocomposites derived from the poly(alkylene dicarboxylate) sample. The possibility of using ultrasound micro-molding to get materials with a homogeneous dispersion of particles has also been explored considering both, micro and nano-sized silica particles using poly(nonamethylene azelate) as a matrix. The wide versatility of polyesters and their derivatives provides advantageous technological applications as those for example reported in the biomedical field. Three different applications for polyesters have been specifically evaluated in this work. The first was the study of polyester derivatives that incorporate urea groups. These poly(ester urea)s showed good properties and were highly soluble in most organic solvents, an interesting feature that facilitated the electrospinning process and the effective incorporation of drugs with bactericide activity, enzymes and bacteriophages. In the second application, polyethylene glycol grafted poly(lactide-r-trimethylene carbonate) copolymers were employed to prepare homogenous drug loaded microspheres. New polymers were degradable and biocompatible.Finally, crystallization of multiarm star polymers was studied due to their wide applications (for example the development of epoxy coatings). Specifically, the study was focused on multiarm star systems constituted by a commercial core of poly(ethyleneimine) and arms of poly(e-caprolactone) with degrees of polymerization of 50, 30 and 10.
