Crystallinity and Microstructure of Plasticized Poly(vinyl chloride). A ¹³C and ¹H Solid State NMR Study

Abstract

The combination of 13C solution NMR and 13C solid-state NMR (CP/MAS and MAS) is used to reveal the relative amount of rigid (crystalline) PVC in two PVC/DOP (50/50 wt % of poly(vinyl chloride)/di-2-ethylhexyl phthalate) samples with tacticities, α, of 0.52 and 0.575, respectively. For both samples the crystallinity decreases with increasing temperature, from about 30% at 90 °C to approximately 6% at 180 °C. By means of a careful spectral deconvolution of the 13C solid-state NMR spectra, the relative amounts of different triad sequences in the crystallites of PVC were obtained. The relative fractions of rr and rm sequences, about 0.5 and 0.4 respectively, are found to be constant as a function of temperatures above 90 °C. On the basis of proton low resolution T 2 experiments the mean average amorphous chain length between crystals was estimated at 50 monomer units at 160−180 °C. All results can be well understood by assuming the existence of crystallites which on average consist of only a few syndiotactic sequences in the chain direction.

Heterogeneous structure of poly(vinyl chloride) as the origin of anomalous dynamical behavior

“…1͒ and to recent NMR estimates in plasticized PVC. 36 There, the plasticizer did not seem to effect the degree of crystallinity but merely acts to disperse the crystals. In view of the rather featureless scattering curves obtained for PVCd-besides the peak structure-no further microscopic details have revealed themselves.…”

Phase Composition and Molecular Mobility in Nylon 6 Fibers as Studied by Proton NMR Transverse Magnetization Relaxation

“…[24][25][26][27][28][29]40,41] A study of 1 H T 2 relaxation as a function of temperature provides information about molecular motions and phase transitions. Local chain motions (b-and g-relaxations) below the glass transition temperature (T g ) cause a slight increase in T 2 .…”

“…For example, WAXD determines only large crystals consisting of several crystal unit cells, whereas NMR-determined crystallinity includes both large and small nano-size crystals, and crystals with a large fraction of defects. [23][24][25][26] Therefore, the term ''phase composition'' is perhaps more appropriate than simply ''crystallinity'' to emphasize the multi-phase nature of semicrystalline polymers. However, when the term crystallinity is used in connection with the solid-state NMR technique, this will mean to denote the rigid fraction, i.e., the fraction of material possessing the lowest molecular mobility, and to distinguish this material from semi-rigid and soft non-crystalline materials (either oriented or non oriented).…”

The effect of annealing of linear and branched polyamide 46 on the phase composition, molecular mobility and water absorption as studied by DSC, 1H and 2H solid-state NMR

“…For example, WAXD detects only large crystals consisting of several crystal unit cells, whereas NMR crystallinity includes both large and small nano-size crystals, as well as disordered crystals. 47,52,53 As far as the NMR crystallinity is concerned, the method determines the low mobile (rigid) mass fraction of semi-crystalline polymers which is usually close to the crystallinity that is determined by traditional methods if the NMR experiment is performed at temperatures largely exceeding the T g of the amorphous phase. 34 (c) The two-phase model, which is traditionally used for determining crystallinity, is rather simplified for describing semicrystalline polymers due to the presence of a crystal-amorphous interface, which can be detected either as crystalline or amorphous fraction, depending on the method used.…”