Multifunctional hydrophilic poly(vinylidene fluoride) graft copolymer with supertoughness and supergluing properties

Abstract

Here we report the grafting of N,N-dimethylaminoethyl methacrylate (DMAEMA) directly from poly(vinylidene fluoride) (PVDF) backbone in solution phase by atom transfer radical polymerization (ATRP). The graft length is same for different times of polymerization but graft density increases with increasing polymerization time. Four graft copolymers are prepared and depending on the time of conversion they are designated as PD-6, PD-12, PD-18, and PD-24, the number indicates time (h) of polymerization. A maximum of 36% (w/w) conversion with respect to monomer is achieved in the PD-24 sample. Gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and polymerization kinetics study conclude the ATRP nature of the polymerization. The graft copolymer shows induced solubility in water and the effective particle diameter in aqueous medium decreases from PD-6 to PD-24 samples. The enthalpy of fusion values are same in graft copolymers with more than 50% reduction and the melting points reduce by 5-6 °C than that of pure PVDF. WAXS patterns of graft copolymers indicate the formation of mixture of α and β phases in dimethyl formamide cast films and also suggest the existence of self-organized short-range ordering from supramolecular interaction between the >C=O group and the nitrogen atom of the substituted amino group of the grafting component as is evident from the FTIR study. The absence of any lamellar peak than that of pure PVDF in the SAXS data suggests the formation of fringed micelle crystals in the graft copolymers. Storage modulus of graft copolymers decreases more than that of PVDF due to a decrease in crystallinity. The tensile stress-strain experiment of the PD samples indicates 700-750% elongation, which is 45 times higher than that of PVDF. The toughness increases by 1970% in the graft copolymers over that of pure PVDF, and the gluing property is significantly larger. The graft copolymers produce and stabilize gold nanoparticles in aqueous medium; produce amphiphilic membranes and on its modification to trimethyl ammonium ion it shows 2.2 × 10⁻⁶ S/cm dc-conductivity. Because of its water solubility, the polymer promises great use in biotechnology, nanotechnology, energy research, and separation processes.