| Biodegradable polymers made from renewable resources ("green" polymers) are an interesting alternative to recycling in a world more and more turned towards environmentally-friendly solutions.;Poly(lactide) is a biodegradable, biocompatible material coming from renewable resources. Such properties, added to a more and more competitive cost makes it an interesting material for current industries. Coupled with other materials, properties can be tuned for different fields, ranging from construction materials to biomedical applications.;Poly(lactide) was grown on the surface of various particles through ring-opening polymerization of lactide, using lactic acid as surface modifier. The aim was to determine what materials were compatible with this method to make cost-efficient materials with new properties. To this end, a simple, one-pot reaction under very mild conditions was developed and tested with various materials.;Particles containing about 40% polymer were successfully obtained from silica gel particles. Poly(lactide) growth was confirmed through Fourier-transform infrared and solid state 13C nuclear magnetic resonance analyses. Scanning electron microscopy showed polymer growth on the particles, although it was shown part of the growth comes from the surface initiator polymerizing on its own. It was also shown that polymer did not smoothly coat the particles but rather grew in random pattern.;White quartz, basic alumina, titanium oxide and montmorillonite all successfully grew poly(lactide), while iron oxide, cobalt oxide, barium titanate and starch did not within the chosen reaction conditions. It is also possible to vary the monomer being used or the surface modifier, as was shown by growing poly(caprolactone) or by using glycolic acid on silica gel particles.;Poly(propylene oxide) is widely used in polymer industry, in particular in the process of making polyurethanes, which can be found in many aspects of our daily lives. It is made from propylene oxide, a petroleum-based molecule, and it is not biodegradable. However, it can be copolymerized with CO 2 or natural succinic anhydride to make biodegradable polyesters.;Propylene oxide was copolymerized with succinic anhydride in a reaction catalyzed by aluminum porphyrins. Molecular weights of around 4000 Da were obtained, with polydispersity indexes as low as 1.03. The turnover frequency was found to be almost twice as high as that of the homopolymerization of propylene oxide, and a high regioselectivity was observed, although stereoselectivity could not be determined. Kinetic studies showed that the reaction is first order in propylene oxide and in metal center.;Variations of this reaction were investigated. Chromium was found to be faster than aluminum, while cobalt reacted similarly. Changing the electron-donating ability of the porphyrin was shown to influence the rate of the reaction. And it was shown that the copolymerization can be done with substituted or unsaturated anhydrides, allowing to tune the properties of the final polymer. Finally, chain extension of the polymer was investigated to increase the molecular weight, although unsuccessfully.;Overall, it was shown that "green" polymers can be tuned and modified in various ways. This shows environmentally-friendly polymers can eventually replace petroleum-based polymers, if the right combination of materials can be found to make them competitive. |
