Natural Rubber: An Old Material for New Applications

The main activity of our research group consists in the modification/ selective degradation of natural rubber to obtain new precursors to employ as building bricks in the synthesis of new materials with tailor-made properties. Two methodologies have been developed two cut the long cis1,4-polyisoprene chains into small oligomers: degradative oxidation with periodic acid and a metathesis reaction using Grubbs II catalysts. The advantage of these controlled degradations is to obtain telechelic functionalized oligomers with a targeted molecular weight, low polydispersity and the stereoregular structure of cis-polyispoprene. A portfolio of oligomers with different chemical functions has been obtained using simple procedures and conditions, in view of industrial applications. After the presentation of the synthesis of some of these reactive oligomers, an overview of the polymers/ materials obtained from them will be given. Among others, oligomers have been modified by adding a RAFT (radical addition-fragmentation chain transfer) agent to the chain ends so that they have been used as macro-RAFT agents in the synthesis of block copolymers. Acrylated chain ends allowed a radical photopolymerization process to generate coatings; ammonium groups were also introduced in the network and biological tests were carried out with different bacteria that are responsible of hospital-acquired infections: the coatings revealed an antibacterial activity that is interesting for future applications in the medical field. Another aspect that has been explored is the synthesis of biobased polymers composed by natural rubber, polyisocyanates, and poly-caprolactone: polyurethane flexible films have been obtained, their thermal and mechanical properties have been studied, and different methods are currently used to study their biodegradation. Finally the synthesis and the characterization of polyurethane foams based on hydroxytelechelic natural rubber oligomers will be described.