Bringing D-limonene to the scene of bio-based thermoset coatings via free-radical thiol-ene chemistry: macromonomer synthesis, UV-curing and thermo-mechanical characterization
2014 (English)In: Polymer Chemistry, ISSN 1759-9954, Vol. 5, no 9, 3245-3260 p.Article in journal (Refereed) Published
The increasing pursuit for bio-based plastic materials led us to investigate the potential use of the monoterpene limonene in thermoset synthesis using the free-radical mediated thiol-ene reaction. The high efficiency of this reaction to prepare multifunctional ene-terminated resins, as intermediary macromolecular precursors, for thermosets synthesis was demonstrated under thermal and photoinitiated conditions. Although an excess of terpene favors formation of well-defined macromonomers in organic solution, the characteristic low-vapor pressure of limonene hinders its simple removal (or recycling) via evaporation after synthesis. Alteration to an initial thiol-ene stoichiometry of 1 : 0.5 enables production of high molecular weight resins in the form of 'hyperbranched oligomeric-like' structures having moderate polydispersity. UV-curing of these polyfunctional resins combined with equal mole compositions of multifunctional alkyl ester 3-mercapto propionates yields highly sticky, amorphous and flexible elastomers with different thermo-mechanical properties. These can be further modulated by varying the amount of unreacted thiol occluded within the networks working as a plasticizer. Introduction of a renewable cycloaliphatic structure into the materials offers a convenient way to enhance the glass-transition temperature and stiffness of traditional thiol-ene networks. The materials synthesized may be considered potentially useful as sealants and adhesives in a wide variety of applications including organic coatings. The versatility of UV-irradiation over thermal initiation makes this method particularly suitable for green industrial synthesis processes via thiol-ene chemistry using limonene and multifunctional thiols. The thiol-ene system evaluated herein serves as a model example for the sustainable incorporation of natural diolefinic monomers into semisynthetic thiol-ene networks exhibiting a range of thermo-mechanical properties.
Place, publisher, year, edition, pages
2014. Vol. 5, no 9, 3245-3260 p.
Characterization, Curing, Mechanical properties, Monomers, Monoterpenes, Organic coatings, Resins, Sealants
IdentifiersURN: urn:nbn:se:kth:diva-144970DOI: 10.1039/c3py01302bISI: 000333581400014ScopusID: 2-s2.0-84897538614OAI: oai:DiVA.org:kth-144970DiVA: diva2:716097
FunderSwedish Research Council, 621-2007-5723
QC 201405082014-05-082014-05-052014-05-08Bibliographically approved