Light Scattering in the Course of a Polymerization-Induced Phase Separation by a Nucleation-Growth Mechanism

Abstract

Polymerization-induced phase separation was described using a phase transformation diagram in conversion vs composition coordinates, where metastable and unstable regions were located. Phase separation through a nucleation-growth (NG) mechanism, in the metastable region of the phase diagram, was described with the usual constitutive equations. A distribution of particle sizes was generated as a function of conversion. Different possible composition profiles inside and outside the particles were predicted, leading to refractive index profiles associated with individual particles. Representative sets of particles were properly located in the scattering volume, and the light scattering pattern of the ensemble was generated. A maximum at a wave vector q ≠ 0 was present in the following cases: (a) at low concentrations of dispersed-phase particles when a depletion layer surrounded the particles and (b) at high concentrations of dispersed-phase particles due to the correlation produced by the location of individual scatterers in a constrained space. Both effects generated a maximum in the scattered intensity at q ≠ 0, even for broad particle-size distributions. The position of q max increased with the concentration of dispersed-phase particles. For systems that do not exhibit coarsening effects, the light scattering peak will initially shift to the right and then grow in intensity at a constant value of the wave vector, when nucleation becomes negligible. Coarsening produces a shift of the scattering peak to the left, while increasing its intensity. Therefore, the presence of a maximum in the light scattering pattern should no longer be indicated as the hallmark of spinodal demixing, as is frequently stated in the literature.

Complex coacervation between β-lactoglobulin and Acacia gum: A nucleation and growth mechanism

“…Model simulations based on Mie theory have confirmed this trend [10]. However, a correlation peak can be recorded when a high volume fraction of particles appears, possibly coupled to multiple scattering effects or at low volume fraction when a depletion layer surrounds particles [10,34,35]. A definite difference between SD and NG, in case of the presence of a correlation peak during NG, is the temporal evolution of the maximum wave vector q max corresponding to the maximum scattered light intensity I max .…”

Light scattering of phase separated systems by nucleation-growth mechanisms: a model based on the Fast Fourier Transform

“…1 was obtained in a previous work 5) , using a model of polymerization induced phase separation by a nucleation and growth mechanism. In that publication we considered a pseudobinary system consisting of a solution of a rubber in a stoichiometric diepoxy-diamine reactive solvent.…”

“…This picture is constrained to the generation of a diluted dispersion and may be only used in the initial stages of the phase separation process. The analysis was recently extended to the whole range of the phase separation process occurring by an NG mechanism 5) . In that publication we showed by means of a comprehensive model of a polymerization induced phase separation (PIPS) that a maximum in the light scattering profile at q max m 0 may be also expected by the presence of a spatial correlation effect always present at high volume fractions of particles even for broad distributions of particle sizes.…”

Patterning Semiconductor Nanocrystals in Polymer Films

“…We employed site-specific polymerization-induced phase separation (PIPS) in which a homogeneous liquid mixture of NCs and a monomer separated in the course of monomer polymerization, due to a decrease in the free energy of mixing of the system. [20][21][22][23] In the past, PIPS was successfully used to produce polymer-dispersed liquid crystal films and composite thermoplastic-rubber polymer materials. [24][25][26][27][28][29][30][31] In the course of polymerization, a mixture of a monomer and a non-reactive component (a liquid crystals or rubber) becomes thermodynamically unstable, mostly due to a decrease in the configurational entropy of growing polymer chains.…”