Ionic copolyesters and their nanocomposites: synthesis, characterization and properties
A polymer containing small amounts of ionic groups either along the polymer backbone chains or as pendant groups is defined as ionomer. As originally proposed by Eisenberg, the interaction between ionic groups leads to the formation of multiplets containing a small number of ion pairs, and also to i...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/319440 |
| Acceso en línea: | http://hdl.handle.net/10803/319440 https://dx.doi.org/10.5821/dissertation-2117-95801 |
| Access Level: | acceso abierto |
| Palabra clave: | 544 66 |
| Sumario: | A polymer containing small amounts of ionic groups either along the polymer backbone chains or as pendant groups is defined as ionomer. As originally proposed by Eisenberg, the interaction between ionic groups leads to the formation of multiplets containing a small number of ion pairs, and also to ionic clusters, which constitute a second phase made of many multiplets as well as portions of the hydrocarbon chains. These ionic structures have been shown to act as strong electrostatic cross-links, which provide altered physical properties, such as enhanced mechanical properties and high melt viscosity, among others. Both aromatic polyesters as aliphatic are polymeric materials widely used today. Their most familiar applications are in clothing, food packaging and water and carbonated soft drinks bottles. Major part of biodegradable synthetic polymers are polyesters, and in particular, aliphatic polyesters. Monomers for the latter can be synthesized from renewable resources. Biodegradable polyesters play a key role in medical applications due to their biodegradability and versatile synthesis able to afford tailored properties; they are currently employed as biomaterials for medical purposes such as surgical sutures, scaffolds, screws and reinforcing plates as well as controlled release drug carriers, since they are biocompatible and nontoxic. This thesis is focused to the chemical modification of aromatic and aliphatic polyesters through the incorporation of various concentration and different ionic groups. We synthesized poly(hexamethylene terephthalate) and poly(butylene succinate)-based ionomers and investigated the effects of the ionic substitution on physical properties, crystallization rates and hydrodegradability of these polyester ionomers. In addition, we also studied the influence of the ionic interaction with nanoclays in the formation of ionomers-based nanocomposites. This thesis embodies a multidisciplinary task work that includes synthesis, spectroscopy characterization, evaluation of thermal and mechanical properties, hydrolytic degradation and nanocomposites preparation: the synthesis procedure of copolyesters was made in all cases by polycondensation in melt-phase. Different conditions of temperature, catalyst and time required were used for each family of copolyesters depending on both the stability and the reactivity of the comonomers involved in the synthesis. The copolyesters synthesized incorporated sulfonated, ammonium, trimethylamonium and tributylphosphonium ionic groups into their chains. The hydrolytic degradation results suggest that the insertion of sulfonated groups in the copolyesters make them more hydrophilic allowing better solvation and an easier attack of water on the ester groups. Nanocomposites with nanoclays were obtained by using different approaches for mixing and in some cases by making use of compatibilizers. Octadecyltrimethylammonium, 1,12-dodecylenediammonium salts and a terpolyester ionomer were used for compatibilization. The clay was used either unmodified or modified with alkylammonium soaps. Results obtained by the different procedures were compared and the effect of the compatibilizers on the mixing efficiency and composite properties were evaluated. Characterization was carried out by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, FTIR spectroscopy, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). The changes in crystal structure upon copolymerization were followed by X-ray diffraction (XRD). |
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