RAFT Polymerization of a Biorenewable/Sustainable Monomer via a Green Process

A biorenewable polymer is synthesized via a green process using the RAFT principle for the first time in supercritical CO₂ at 300 bar and 80 °C. α-Methylene-γ-butyrolactone polymers of various chain lengths and molecular weights are obtained. The molecular weights vary from 10 000 up to 20 000 with low polydispersity indexes (PDI <1.5). Furthermore, the monomer conversion in supercritical CO₂ is substantially higher, respectively 85% for ScCO₂ compared to ≈65% for polymerizations conducted in dimethyl formamide (DMF) solvent. Chain extensions are carried out to confirm the livingness of the formed polymers in ScCO₂ . This opens up future possibilities of the formation of different polymer architectures in ScCO₂ . The polymers synthesized in ScCO₂ have glass transition temperature (T_g ) values ranging from 155 up to 190 °C. However, the presence of residual monomer encapsulated inside the formed polymer matrix affects the glass transition of the polymer that is lowered by increasing monomer concentrations. Hence, additional research is required to eliminate the remaining monomer concentration in the polymer matrix in order to arrive at the optimal T_g .