Pressure-assisted solvent- and catalyst-freeproduction of well-defined poly(1-vinyl-2-pyrrolidone) for biomedical applications

In this work, we developed a fast, highly efficient, and environmentally friendlycatalytic system for classical free-radical polymerization (FRP) utilizing a high-pressure (HP) approach. The application of HP for thermally-induced, bulk FRP of 1-vinyl-2-pyrrolidone (VP) allowed to eliminate the current limitation of ambient-pressure polymerization of‘less-activated’monomer (LAM), characterized by the lack of temporal controlyielding polymers of unacceptably large disperisites and poor result reproducibility. By a simple manipulationof thermodynamic conditions (p¼125–500 MPa,T¼323–333 K) and reaction composition (two-component system: monomer and low content of thermoinitiator) well-defined poly(1-vinyl-2-pyrrolidone)s(PVP) in a wide range of molecular weights and low/moderate dispersities (Mn¼16.2–280.5 kg mol1,Đ¼1.27–1.45) have been produced. We have found that HP can act as an‘external’controlling factor thatwarrants thefirst-order polymerization kinetics for classical FRP, something that was possible so far only forreversible deactivation radical polymerization (RDRP) systems. Importantly, our synthetic strategy adopted for VP FRP enabled us to obtain polymers of very high Mn in a very short time-frame (0.5 h). It has also beenconfirmed that VP bulk polymerization yields polymers with significantly lower glass transition temperatures (Tg) and different solubility properties in comparison to macromolecules obtained during the solvent-assisted reaction.