Percolative effects of poly(vinylidene fluoride) molecules on C[dbnd]O group vibrations in N,N-dimethylformamide in molecular assemblies

Abstract

Poly(vinylidene fluoride) (PVF2) of a linear polymer molecular chain is useful to bridge 1–2 dimensional (D) networks by H-bonding in a dilute medium such as N,N-dimethylformamide (DMF). As a result, a model 1–2D PVF2 molecule tunes selective DMF configurations. This is studied with CO (DMF) group vibration bands which vary in how DMF molecules H-bond through PVF2 as per its dosage and local structure. The PVF2 content is varied in small steps over 0.1 to 100g/L in DMF solutions in attenuating model structures in terms of the IR bands. Virgin DMF has three CO stretching bands ν1CO, ν2CO, and ν3CO of 1652, 1670, and 1724cm−1 of three different configurations. A head-on-H-bonding between CO groups of two DMF molecules strongly H-bonds them in a bismolecular assembly that shares the maximum intensity in the lowest frequency 1652cm−1 band. More molecules add-up giving rise to a promoted value of 1670cm−1, while the third band of 1724cm−1 (poor intensity) briefs only a weak side-by-side H-bonding in a different configuration. These bands change selectively upon adding PVF2 in a polymer solution. The ν2CO peak intensity arises in a sharp peak at 6.5g/L PVF2 at the expense of the ν1CO band, while the integrated intensity varies through two peaks at 1.3 and 20.1g/L PVF2 in a percolative effect on the CO vibrations that converge in association with PVF2 in preferential configurations. Model configurations are proposed based on the various ways the PVF2 probes the ν1–3CO IR bands.