Poly(vinylidene fluoride)-block-poly(N-vinylpyrrolidone) diblock copolymers: Synthesis via sequential RAFT/MADIX polymerization and self-assembly behavior

In this contribution, we reported the synthesis of poly(vinylidene fluoride)-block-poly(N-vinylpyrrolidone) (PVDF-b-PVPy) diblock copolymers via a sequential reversible addition-fragmentation chain transfer / macromolecular design via the interchange of xanthate (RAFT/MADIX) approach. First, the radical polymerization of vinylidene fluoride (VDF) was carried out with O-ethyl-S-(1-methoxycarbonyl)ethyldithiocarbonate as the starting chain transfer agent and a xanthate-terminated PVDF was obtained. The xanthate-terminated PVDF was then used as the macromolecular chain transfer agent further to mediate the radical polymerization of N-vinylpyrrolidone (NVP) and the PVDF-b-PVPy diblock copolymers were successfully synthesized. The kinetics of NVP polymerization was investigated by means of gel permeation chromatography (GPC). By controlling the molar ratios of the macromolecular chain transfer agent to NVP, a series of PVDF-b-PVPy diblock copolymers with variable lengths of PVPy were obtained. The PVDF-b-PVPy diblock copolymers displayed the interesting self-assembly behavior. It was found that for the PVDF-b-PVPy diblock copolymers no self-assembly behavior was exhibited in bulks. Nonetheless, the diblock copolymers were capable of self-assembling into the nanoobjects in aqueous solutions. In addition, the diblock copolymers displayed composition-dependent microphase-separated morphologies in their blends with poly(hydroxyether of bisphenol A). The different self-assembly behaviors have been interpreted in terms of differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and atomic force microscopy (AFM).