STEREOSELECTIVE (CO)POLYMERIZATION OF BIO-BASED CONJUGATED DIENES DERIVED FROM NATURAL ALDEHYDES USING [OSSO]-TITANIUM CATALYSTS

THE TRANSITION TOWARD A SUSTAINABLE POLYMER INDUSTRY REQUIRES THE DESIGN OF NEW MATERIALS DERIVED FROM RENEWABLE RESOURCES, CAPABLE OF COMBINING HIGH PERFORMANCE WITH ENVIRONMENTAL RESPONSIBILITY. IN THIS CONTEXT, THIS WORK FOCUSES ON THE SYNTHESIS AND STEREOSELECTIVE POLYMERIZATION OF NOVEL BIO-BASED CONJUGATED DIENES OBTAINED FROM NATURAL ALDEHYDES SUCH AS CINNAMALDEHYDE, PERILLALDEHYDE, AND CITRAL. SPECIFICALLY, THREE MONOMERS, TRANS-1-PHENYL-1,3-BUTADIENE (1PB), S-4-ISOPROPENYL-1-VINYL-1-CYCLOHEXENE (IVC), AND (E)-4,8-DIMETHYL-1,3,7-NONATRIENE (DMNT), WERE SYNTHESIZED AND SUBSEQUENTLY POLYMERIZED UNDER OPTIMIZED CONDITIONS USING TITANIUM [OSSO]-TYPE COMPLEXES BEARING DIFFERENT SUBSTITUENTS ON THE AROMATIC RINGS OF THE LIGAND BACKBONE. ALL POLYMERIZATIONS AFFORDED HIGHLY REGIO- AND STEREOREGULAR POLYMERS WITH REMARKABLE ISOTACTICITY, HIGH YIELDS, AND SIGNIFICANT MOLECULAR WEIGHTS. THE RESULTING POLYMERS WERE THOROUGHLY CHARACTERIZED BY NMR SPECTROSCOPY AS WELL AS THERMAL AND MECHANICAL ANALYSES TO ELUCIDATE THE RELATIONSHIPS BETWEEN MICROSTRUCTURE AND PROPERTIES. MOREOVER, THE MONOMERS WERE COPOLYMERIZED EITHER AMONG THEMSELVES OR WITH TWO LINEAR TERPENES, Β-MYRCENE AND Β-OCIMENE, TO OBTAIN FULLY RENEWABLE COPOLYMERS EXHIBITING TUNABLE ELASTOMERIC BEHAVIOR. THESE COPOLYMERIZATIONS WERE PERFORMED EMPLOYING THE SAME CATALYTIC SYSTEMS UNDER THE OPTIMAL CONDITIONS IDENTIFIED FOR THE HOMOPOLYMERIZATIONS. OWING TO THE PRESENCE OF RESIDUAL CARBON-CARBON DOUBLE BONDS IN THE POLYMER BACKBONE, POLY(IVC) WAS USED AS A MODEL POLYMER TO INVESTIGATE BOTH REVERSIBLE AND IRREVERSIBLE CROSS-LINKING REACTIONS AIMED AT ENHANCING MECHANICAL PERFORMANCE. IN ADDITION, KINETIC STUDIES AND MONOMER REACTIVITY ORDER ANALYSES WERE CONDUCTED FOR EACH HOMO- AND COPOLYMERIZATION SYSTEM THROUGH IN SITU NMR TECHNIQUES, PROVIDING INSIGHT INTO THE MECHANISTIC ASPECTS OF THE POLYMERIZATION PROCESSES. OVERALL, THIS RESEARCH DEMONSTRATES THE POTENTIAL OF TITANIUM [OSSO]-CATALYZED STEREOSELECTIVE POLYMERIZATION AS A POWERFUL STRATEGY FOR CONVERTING NATURAL BUILDING BLOCKS INTO HIGH-PERFORMANCE, RENEWABLE POLYMERS, PAVING THE WAY TOWARD SUSTAINABLE ELASTOMERIC MATERIALS WITH CONTROLLED MICROSTRUCTURES AND TAILORED PROPERTIES.