Phase Separation Induced by Polymerization of 2-Chlorostyrene in a Polystyrene/Dibutyl Phthalate Mixture

Abstract

Phase separation induced by polymerization of 2-chlorostyrene (2ClS) in polystyrene (PSI/ di-n-butyl phthalate (DBP) mixtures was studied by the time-resolved light scattering (TRLS) technique and scanning electron microscopy. Measurements were performed a t a fixed composition of 2ClS:PS: DBP = 45:45:10 by weight in a temperature range from 110 to 180 "C that was above the glass transition temperature of the product. Conversion of 2C1S was estimated by gel permeation chromatography. Two distinct time regions were observed in time dependence of scattered light intensity I , and conversion of 2ClS. In the first region, Z, and conversion increased rapidly, while in the second region, conversion that had reached about 80% changed very little and the growth rate of I , became much smaller than that in the first region. The poly(2-chlorostyrene)-rich phase formed droplets, and droplets of relatively narrow distribution coexisted with much smaller droplets in an early period. Nonspherical domains were formed by coalescence of droplets. At lower temperatures, it was observed for the first time that the droplet domain structure transformed into cocontinuous domains. This morphological change occurred while the conversion changed very little. Acceleration of the phase separation rate associated with the morphological change was observed by TRLS. At higher temperatures, coalescence of droplets occurred only in a very early period, and droplets coarsened without forming cocontinuous domains in the later period. The mechanism of the polymerization-induced phase separation of this system is discussed.

Composition dependence of polymerization-induced phase separation of 2-chlorostyrene/polystyrene mixtures

“…2(b)), at lower two initial compositions, i.e., u ¼ 0:40 and 0.45, acceleration of the intensity growth was observed in a later period of phase separation. Similar acceleration was observed in previous work [11] and was explained by a change in the growth mechanism of phase-separated domains, which will be discussed later.…”

“…2, acceleration of I m growth occurred around the same time. The agreement between these two times was found in a previous study [11] and gave ground for considering that the acceleration of I m was caused by the difference in coarsening rate between droplets and continuous domains. In phase separation of a fluid mixture, phase separation rate depends on the morphological structure of domains: Bicontinuous domains grow much faster than droplets [18].…”

“…In this case, initial morphological structure of phase-separated domains can be explained by a geometrical consideration of the phase diagram of the ternary mixture 2CLS/P2CLS/PS that is schematically illustrated in Fig. 7 [11,14]. Since the life time of a radical can be neglected in the time scale of our observation of phase separation, the proceeding of polymerization corresponds to the increase of number of product polymers.…”

Water uptake, transport and structure characterization in poly(ethylene glycol) diacrylate hydrogels

“…If the water content in the prepolymerization mixture exceeds the maximum equilibrium water uptake of the crosslinked polymer during polymerization, phase separation will occur, forming a polymer-rich phase and a water-rich phase [12,13]. In some cases, the water-rich domains are dispersed in the film in micron sized regions [13][14][15][16]. These regions (i.e., pores) scatter light, resulting in a loss of transparency.…”

Polymerization-Induced Phase Separation. 2. Morphological Analysis

“…[31][32][33][34] In our previous paper, 35 we presented results from a numerical study of PDLC film formation using the PIPS method. An emphasis was placed on the intimate coupling between phase separation and polymerization processes on the droplet size selection mechanism during film fabrication.…”