Physical gels from PVC: molecular structure of pregels and gels by low-angle neutron scattering

Abstract

In this paper we report on investigations into the short-range molecular structure of pregels (aggregates formed in dilute solutions) and gels as a function of ageing time, temperature and solvent type. In some solvents (diethyl oxalate and bromobenzene) it is found that the structure of the pregels is cylinder-like or ellipsoidlike. The structure is seen to be the same for the gels and the pregels in the investigated range of transfer momentum which leads us to conclude that the gels are probably fiber-like, a statement in agreement with the morphology observed by Yang and Geil. The fiber section is also about the same order of magnitude as that reported by these authors. Also, further evidence is given for the existence of a second type of physical knot, different from those formed by the more syndiotactic sequences. The validity of the molecular structures deduced from these experiments is discussed in the light of macroscopic properties such as compression modulus and swelling.

Small‐angle x‐ray scattering study of thermoreversible poly(vinyl chloride) gels

“…These experimental data clearly showed that the PVC/DOP gels were constructed from the fibrillar structure and that the structure interacted to form gel structures at high concentrations or low temperatures. This morphological model is in qualitative agreement with the fibrillar structure models proposed by Abied et al15 and Dahmani et al,17 although the experimental methods are different.…”

“…The morphology revealed a network, with a mesh size of about 100 nm, that consisted essentially of fiberlike objects, the diameters of which were roughly 10–20 nm. Abied et al15 studied the molecular structure of the pregels and gels of PVC/solvent systems with neutron scattering. The structure of the pregels (sol) and gels was cylinder‐like or ellipsoid‐like, and they concluded that the gels were probably fiberlike.…”

Influence of the physical characteristics of the polymer on the glass transition of various chemically modified PVCs

“…See for instance Chalykh et a1.20 and Guenet et a1. 21,22 Neither we found appreciable differences in the Tg of VC-VTB copolymers when the reaction is carried out at diluted or more concentrated solutions (from 2 to 32 g/L).…”

Light-Scattering Study of Thermoreversible Aggregates from Chemically Modified PVCs: Outcomes for the Gel State

“…2,7,11,12 Under these conditions, the radius of gyration is written: in which 〈R L 2 〉 z is the z-averaged radius of gyration related to the long axis, and 〈r L 2 〉 z the z-averaged cross- …”