Evidence of Long Two-Dimensional Folding Chain Structure Formation of Poly(vinylidene fluoride) in N -Methylpyrrolidone Solution: Total Form Factor Determination by Combining Multiscattering Data.

Very recently, we proposed that poly(vinylidene fluoride) (PVDF) dissolves in a long rectangular column conformation induced by the formation of a two-dimensional folding chain structure in an N -methylpyrrolidone (NMP) solution based on the results obtained from static light scattering (SLS), small- to wide-angle X-ray scattering (S-WAXS), and viscometric experiments. Small- to wide-angle neutron scattering (S-WANS) experiments were able to provide clear decisive evidence for the presence of such a two-dimensional folding chain structure in a deuterated (d)NMP solution of PVDF samples with two different weight average molar masses ( M w ) of 100 and 1200 kg mol -1 , even under dilute conditions at concentrations less than the overlapping concentrations due to the quite high neutron scattering contrast obtained by using (d)NMP as a solvent. An increase in M w from 100 to 1200 kg mol -1 substantially increases the particle length and width from L = 80 to 350 nm and w 2 = 5.0 to 15 nm, respectively, while the thickness, w 1 , is maintained at 0.3 nm. Since L is much longer than w 2 irrespective of M w , the particles formed by PVDF molecules in NMP simply behave as long rigid rods in a scattering vector ( q ) range covered by SLS measurements. A combination study of S-WANS and S-WAXS experiments covering a higher q range with the SLS techniques could clearly reveal increases in both the L and w 2 values with increasing M w .