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

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 C=0 (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 100 g/L in DMF solutions in attenuating model structures in terms of the IR bands. Virgin DMF has three C = O stretching bands v(1)c = 0, v(2 =)o, and v(3) c = o of 1652, 1670, and 1724 cm(-1) of three different configurations. A head-on-H-bonding between C=0 groups of two DMF molecules strongly H-bonds them in a bismolecular assembly that shares the maximum intensity in the lowest frequency 1652 cm-1 band. More molecules add-up giving rise to a promoted value of 1670 cm-1, while the third band of 1724 cm-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 v(2)c = o peak intensity arises in a sharp peak at 6.5 g/L PVF2 at the expense of the v(1)c = 0 band, while the integrated intensity varies through two peaks at 1.3 and 20.1 g/L PVF2 in a percolative effect on the C=0 vibrations that converge in association with PVF2 in preferential configurations. Model configurations are proposed based on the various ways the PVF2 probes the V(1-3)c = o IR bands. (C) 2013 Elsevier B.V. All rights reserved.