The Sol-Gel Transition and the Liquid-Liquid Phase Separation in Poly(vinyl chloride) Solutions

Abstract

ABSTRACT:The dynamics of the sol-gel transition in poly(vinyl chloride)ly-butyrolactone system was investigated by light scattering. The dynamical studies confirmed that this system has an UCST (upper critical solution temperature). In the phase diagram, temperature vs. concentration, the spinodal curve crosses the sol-gel transition curve. This situation has been predicted by Coniglio et a/. as a result of the site-bond correlated-percolation problem. The gelation takes place both above and under the spinodal curve, suggesting two modes of gelation: one is accompanied by a spinodal decomposition and the other takes place without liquid-liquid phase separation. In the former case, the dynamics of phase separation at an early stage of gelation is well described within the framework of Cahn's linearized spinodal decomposition theory. It is noted that, in order to understand the entire mechanism of sol-gel transition, one should clarify the three dynamical aspects on the liquid-liquid phase separation, percolation-type association, and liquid-solid transition.

Dynamic heterogeneity, cooperative motion, and Johari–Goldstein $$\beta $$-relaxation in a metallic glass-forming material exhibiting a fragile-to-strong transition

“…[133]] and the change in miscibility due this physical cause is particularly significant when one of the components self-assembles upon heating, as in the case of S. This type of additive is predicted with the classical molecular dynamics of our Al-Sm metallic GF liquid. This type of phase behavior, involving a line of polymerization or self-assembly line of transitions that terminates near the critical point of the phase boundary for liquid-liquid phase separation, is ubiquitous in complex fluids in which molecular assembly occurs, micelle formation [174,175], living polymers [57], thermally reversible gelation of polymers in solution [176,177], etc. Liquid-liquid thermodynamic transitions, accompanied by significant changes in fluid structure and viscoelastic properties in the two liquid states, are thus very common in complex fluids, even if this phenomenon is not always overtly recognized.…”

Heat-Induced Gelation of Globular Proteins. 1. Model for the Effects of Time and Temperature on the Gelation Time of BSA Gels

“…Experimental studies on this type of state diagram were carried out by several workers, e.g. by Kawanishi et al 25 and Tan et al 26 for synthetic polymers, and by Tanaka et al for biopolymers. 27 In the latter studies the gelation curves, or sol/gel boundaries, were determined by use of rheological techniques such as rheometry and viscometry.…”

Spatiotemporal Evolution in Morphogenesis of Thermoreversible Polymer Gels with Fibrillar Network

“…Figure shows the Ornstein−Zernike plot and the speckle pattern before the fibril nucleation. The point to observe is that the characteristic fluctuation length-scale (∼0.5 μm) was also shown in other polymer gel systems. − This would be considered later.…”

“…From a phase transition point of view, the experimentalists attempt to answer the origin of the polymer fibrillar network. − , − A fundamental understanding of the thermodynamics, the kinetics, and the mechanism of the gelation is therefore of great importance. However, recent studies on thermodynamic equilibrium microstructures (junctions) and morphologies (networks) − and on global kinetics − do not fill the gap in our knowledge on the formation mechanism.…”

“…The point to observe is that the characteristic fluctuation length-scale (∼0.5 μm) was also shown in other polymer gel systems. [36][37][38][39][40][41] This would be considered later. Figure 7 shows the result of a systematic stepwise survey of the time-resolved scattering patterns.…”