Synthesis and characterization of β-myrcene/styrene copolymers

In recent years, there has been an increasing effort to move away from fossil sources as raw materials for monomer production. Terpenes can be used as raw materials for synthesizing new classes of polymers to make the best use of available biodiversity and to follow the principles of green chemistry. A new class of materials that reflects these criteria is represented by myrcene-styrene copolymers. These copolymers are known for their unique and versatile properties. Myrcene, an olefinic monomer obtained from biomass, is combined with styrene, an aromatic monomer, to produce copolymers with a wide range of adjustable properties, depending on the composition and polymerization conditions. Styrene-myrcene copolymers combine the flexibility, impact resistance, and good compatibility of myrcene-based polymers with the rigidity, thermal resistance, and transparency of polystyrene. The copolymerization was conducted using a titanium complex as catalyst activated with MAO. Polymerizations were carried out at 70°C under nitrogen atmosphere [1]. Samples with myrcene/styrene ratios 30/70, 50/50, 70/30 and 80/20 mol/mol were synthesized and characterized. The glass transition temperature (Tg) increases with increasing styrene content. Differential scanning calorimetry thermograms show relaxation phenomena close Tg, attributed to styrene sequences, as highlighted by annealing experiments at different temperatures. All samples are amorphous. They show X-ray powder diffraction profiles characterized by a double halo typical of polystyrene, and remain amorphous even after annealing treatments. Copolymers with styrene content higher than or equal to 30 mol% show a highly rigidity and experience viscous flow upon stretching at 70°C. The sample with 20mol% appears as a soft material, able to flow even at 40 °C, having a high potential to behave as a rubber upon vulcanization.