Biobased polyurethanes with tunable properties through covalent and non-covalent approaches

Identifier:  TDX:2614

Handle: https://hdl.handle.net/20.500.11797/TDX2614

Authors:  Comí Bonachí, Marc

Abstract:
This Thesis is addressed to the development of side-chain functionalized polyurethanes (FPU)s, with enhanced properties, made from fatty acid-based functional diols and two different diisocyanates; isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI). The novel FPUs present tertiary amine and alkyl, allyl, propargyl moieties or the combination of these, as side-chain positions groups. The FPUs were further modified via two post-polymerization mechanisms based on covalent or non-covalent bonds. In the first case, photoinitiated thiol-ene/yne coupling reaction between allyl, propargyl-functionalized PUs (based on IPDI) and thioglycerol was carried out. Obtained hydroxyl-PUs exhibit different thermal and mechanical properties in comparison with precursor PUs. Moreover, the incorporation of hydroxyl groups leads to PUs with enhanced hydrophilicity. Alternatively, the FPU (based on IPDI) containing only tertiary amine pendant group was mixed with different carboxylic acids in an acid-base reaction. Supramolecular ionic PUs were characterized by spectroscopic tools to verify the presence of ionic hydrogen bond as ionic interaction. Correlation between structure and thermal and mechanical properties was demonstrated. Samples show rapid thermal reversibility and recyclability thanks to the reversible bonds. In addition, elastomeric supramolecular PUs networks were prepared from HDI and aminodiol. The resulting materials exhibit some promising adaptive material properties such as effective energy dissipation upon deformation through unzipping the ionic hydrogen bonding network, combined with good shape-regeneration property and recycling/reshaping capability arising from their recoverable nature. More importantly, the resulting biobased elastomers possess the inherent self-healing ability, which can be seen as an upgrade of their sustainability.A novel thermo-reversible network is constructed by the thiol-ene functionalized polyurethane via dynamic ionic hydrogen bonds and covalent cross-links. By varying the covalent cross-linking density, the mechanical properties and the stimuli-responsive behaviour can be systematically tuned. This synthesis demonstrates a simple and effective pathway to fabricate multifunctional polyurethanes with desired functions.