Laetitia Vlaminck

Sustainable thermoplastic elastomers derived from plant oil and their “click-coupling” via TAD chemistry

We report the preparation of plant oil based triblock copolymers based on soybean oil monomers. The monomers were polymerized via atom transfer radical polymerization with subsequent chain extension, resulting in poly(styrene-b-soybean oil acrylate-b-styrene) (PS-b-PSBA-b-PS) and poly(styrene-b-soybean oil methacrylate-b-styrene) (PS-b-PSBMA-b-PS) triblock copolymers. These polymers, ranging from thermoplastics to thermoplastic elastomers (TPEs), were obtained by tuning molecular structures. We employed a “click coupling” strategy using triazolinedione (TAD) chemistry to create chemical junctions between the soft middle blocks of the triblock copolymers, which behave similar to physical chain entanglements. This method helps to overcome the drawbacks of plant oil based polymers, allowing for increase of tensile strength without sacrificing elongation. Cyclic tensile tests show that the “click coupled” triblock copolymers exhibit excellent elastic recovery characteristics.

ADMET and TAD chemistry: a sustainable alliance

A versatile, additive-free post-polymerisation functionalisation method for acyclic diene metathesis (ADMET) derived polymers, utilising 1,2,4-triazoline-3,5-dione (TAD) chemistry, is reported. Several diene monomers have been synthesised starting from 10-undecenoic acid derivatives and subsequently polymerised via ADMET polymerisation reaction. Post-polymerisation functionalisation of the poly-unsaturated macromolecules with several substituted TAD compounds was shown to achieve full conversions within 6 hours. Also, the functionalised polymers could be chemically crosslinked with a bivalent triazolinedione crosslinker. The glass transition temperature of the resulting materials could be tuned by varying the degree of functionalisation, the polymer backbone, the TAD substituent and the crosslinking density.

Sustainable synthesis routes towards urazole compounds

Sustainable synthesis routes towards urazoles, the precursor molecules for triazolinediones, are reported. Not only is the use of isocyanates avoided, but the applied synthetic procedures are also mostly solvent-free, high yielding and performed in an equimolar manner. Two complementary synthesis routes have been developed starting from a wide range of amines, both based on the use of diphenyl carbonate. The first method, which is particularly suitable for the synthesis of bulk urazoles, such as butyl, cyclohexyl or benzyl urazole, is performed in bulk in a one-pot fashion and generally results in yields between 87% and 96%. The second synthesis route, with yields up to 95%, focusses on the implementation of functionalities in the urazole structure and offers the possibility to generate bifunctional urazole compounds.