Development of polyurethane-like materials based on proteins

Polymers are now the most widely use man-made substances and have become omnipresent in every aspect of our lives. In particular, polyurethanes (PU), for providing energy savings, safety, lightness and comfort. Nevertheless, their synthesis require the use of petroleum-based polyols and toxic isocyanates, which resulted in increasing efforts on replacing its monomers by those non-toxic and/or made from renewable sources. Nature has repeatedly surpassed engineers when designing functional materials, capable of withstand complex and harsh environmental conditions while maintaining their superior mechanical properties. An abundance of opportunities for designing novel blocks and shaping structural and functional polymers is hidden in Nature’s wide variety of raw materials, for instance proteins. In this thesis, hybrids of protein biopolymers and synthetic polymers were firstly prepared for being a promising new class of soft materials, as the advantages of each component can be complementary. Therefore, elastin-like polypeptide (ELP) was conjugated to poly(ethylene glycol) (PEG) to form multi-block copolymers. The hydrated copolymers preserved the thermoresponsive properties from the ELP block and formed hydrogels with different transition temperatures depending on salt concentration. Small angle scattering indicates that the copolymer hydrogels form sphere-like aggregates with a “fuzzy” interface, while the films form a fractal network of nanoscale aggregates. Afterwards, ELP was combined with poly(lactide) (PLA) and poly(lactideco- glycolide) (PLGA) to produce block copolymers through thiol-maleimide reaction. These copolymers were processed in the form of films via solvent casting and its properties analysed. The results demonstrated that the copolymers prepared formed homogeneous films with better mechanical properties than films from blends of both materials. Additionally, a new and innovative approach to synthesize non-isocyanate polyurethanes (NIPUs) was investigated using proteins as a source of amines to endow unique properties to the final materials. For that, a cyclic carbonate (BCC) was firstly reacted with lysine and small peptides to confirm the formation of the urethane linkage and optimize reaction conditions. Subsequently, different amounts of BCC were combined with ELP and the obtained materials were processed to form thin transparent films. Structural, thermal and thermomechanical characterization confirmed the formation of the urethane linkage and variable behaviours depending on BCC addition. To further improve the sustainability of new NIPUs based on proteins, whey protein isolate (WPI), a widely available agricultural byproduct, was also tested. WPI was reacted with BCC and a NIPU prepolymer based on the same BCC and following characterization provided evidence for the urethane linkage formation. The materials were processed in the form of thin films and final properties showed improved properties compared to other protein films in the literature.

Name thesis:degree_name

Doutoramento em Líderes para as Indústrias Tecnológicas

Grantor

Universidade do Minho

Year dc:date.issued

2018

Author dc:creator

• Araújo, Andreia Isabel da Silva

Advisors dc:contributor.advisor

• Machado, A. V.
• Olsen, Bradley D.

Statement dc:rights

• restrictedAccess

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1822/59039

OAI record oai:identifier

http://repositorium.sdum.uminho.pt/oai/request?verb=GetRecord&metadataPrefix=dim&identifier=oai%3Arepositorium.uminho.pt%3A1822%2F59039