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

Abstract

In this work, we developed a fast, highly efficient, and environmentally friendly catalytic systemfor classical freeradical polymerization (FRP) utilizing a high-pressure (HP) approach. The application of HP for thermallyinduced, bulk FRP of 1-vinyl-2-pyrrolidone (VP) allowed to eliminate the current limitation of ambientpressure polymerization of ‘less-activated’ monomer (LAM), characterized by the lack of temporal control yielding polymers of unacceptably large disperisites and poor result reproducibility. By a simple manipulation of thermodynamic conditions (p ¼ 125–500 MPa, T ¼ 323–333 K) and reaction composition (twocomponent 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 (Mn ¼ 16.2–280.5 kg mol 1, Đ ¼ 1.27–1.45) have been produced. We have found that HP can act as an ‘external’ controlling factor that warrants the first-order polymerization kinetics for classical FRP, something that was possible so far only for reversible 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 been confirmed 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.