Phase Separation Kinetics of a Liquid Crystal-Polymer Mixture

Kim, J. Y.; Palffy‐Muhoray, Peter

doi:10.1080/00268949108046049

Cited by 60 publications

(45 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An additional feature of this plot is that S(k m *,t*) grows exponentially during the early stage, but then slows down as the phase separation enters the intermediate stage. This feature has been observed experimentally in PDLCs 8,9 and other polymer systems [31][32][33] formed by the PIPS method. Consequently, the time range of interest in this paper is the early stage and beginning of the intermediate stage of SD.…”

Section: S(k*t*)mentioning

confidence: 73%

See 1 more Smart Citation

Polymerization-Induced Phase Separation. 2. Morphological Analysis

Chan

Rey

1997

Macromolecules

View full text Add to dashboard Cite

A model composed of the nonlinear Cahn-Hilliard and Flory-Huggins theories for spinodal decomposition (SD) and a second-order rate equation for polymerization for the self-condensation of a trifunctional monomer is used to study the polymerization-induced phase separation (PIPS) phenomena. The numerical results are consistent with experimental observations. These observations include the formation and evolution of a droplet-type morphology. In addition, the time evolution of the maximum value of the structure factor S(km,t) exhibits an exponential growth during the early stage but saturates during the intermediate stage of SD. Moreover, the dominant dimensionless wavenumber km* decreases during the intermediate stage. The numerical results, however, also indicate that km* increases during the early stage, which has not yet been observed experimentally. Furthermore, the morphological analysis is also consistent with experimental observations. The droplet size and shape distributions indicate that the average droplet size and shape prevail during the PIPS phenomena, and statistical analysis of the Voronoi polygons indicates that the droplets are randomly positioned within the matrix. Lastly, the characteristic time τ, average dimensionless equivalent droplet diameter 〈d*〉, and droplet number density Nd depend on the magnitudes of a scaled diffusion coefficient D for phase separation and a scaled rate constant K1 for polymerization. Consistent with experimental observations, τ and 〈d*〉 decrease while Nd increases as K1 increases. Similarly, as D increases, τ and 〈d*〉 decrease while Nd increases. The parameters K1 and D have no effect on the average shape factor.

show abstract

Section: S(k*t*)mentioning

confidence: 73%

“…8,9 On the other hand, the increase during the early stage has apparently not been observed experimentally in the formation of PDLCs by the PIPS method. A plausible reason for this is that the phase separation dynamics is too fast to be captured experimentally at early times.…”

Section: S(k*t*)mentioning

confidence: 85%

Polymerization-Induced Phase Separation. 2. Morphological Analysis

Chan

Rey

1997

Macromolecules

View full text Add to dashboard Cite

show abstract

“…Unfortunately, as the first step of their work on this complicated system, the anisotropic characteristics of an LC, let alone the coupling between the concentration and orientation fluctuations, has not been taken into consideration by Lin et al [41][42][43] at all, although PDLC is their central topic. A similar case exists in some experimental observations and theoretical treatments 15,44,45) . In the present paper, a three-dimensional dynamic MC simulation 46) is performed to study the phase separation kinetics in the mixtures of flexible polymers and thermotropic low molecular weight LCs considering the nematic characteristics among rods for the first time.…”

Section: Introductionmentioning

confidence: 57%

Phase separation kinetics in mixtures of flexible polymers and low molecular weight liquid crystals

Zhu

Ding³

et al. 1999

Macromol. Theory Simul.

View full text Add to dashboard Cite

SUMMARY: A dynamic Monte Carlo (MC) simulation is performed to investigate the phase behavior of mixtures of flexible polymers and low molecular weight thermotropic liquid crystals (LCs). The polymer is represented by three-dimensional self-avoiding lattice chains, while the LC is described by the LebwohlLasher nematogen model. The initially homogeneous rod-coil mixture is, following a deep quench, separated into an isotropic phase rich in coils and a nematic phase rich in rods. The underlying spinodal decomposition (SD) process is then simulated and studied extensively. This is the first simulation of SD in a rod-coil mixture where the nematic ordering is included. Concentration fluctuations with a conserved order parameter are thus coupled with orientation fluctuations with a nonconserved order parameter. It is found that the early stage SD in the rod-coil mixture still exhibits the dominant spatial wavelength and that the scalar scattering functions in the late stage of SD obey the Furukawa scaling law. The kinetic difference between the so-called isotropic and anisotropic SD regions is, however, much less pronounced than predicted recently by the mean-field theory.

show abstract

“…Then, the morphologies of the PDLC involve interplay among three kinetic processes: polymerization, phase separation, and phase ordering. These phase separation dynamics have been simulated by some authors [105][106][107][108].…”

Section: Phase Separation Dynamicsmentioning

confidence: 99%

Thermodynamics of Flexible and Rigid Rod Polymer Blends

Matsuyama

2010

Encyclopedia of Polymer Blends

View full text Add to dashboard Cite

Binary mixtures of a flexible polymer and a low molecular weight liquid crystalline molecule, or a rigid rod-like molecule, are of interest because of their important technological applications in high modulus fibers, nonlinear optics, and electro optical devices. These blends are basic materials for recent new technologies of liquid crystal displays [1,2]. The performances of these systems are closely related to phase separations and conformations of polymer chains dissolved in a liquid crystalline phase. One of the main problems is to examine the location of various phases such as isotropic, nematic, and smectic phases, depending on temperature and concentra tion. To understand the thermodynamics and thermal instability of these blends, it is important to consider the co-occurrences between liquid crystalline ordering and phase separations.Generally, polymer chains exhibit a variety of flexibility, from flexible to rigid rodlike polymers. Polymer blends containing a liquid crystalline ordering have received considerable attention. The volume of literature on the theories and experiments of liquid crystallinity in polymer blends is now very extensive. There are many theoretical models for liquid crystalline polymers, such as the Flory lattice model [3][4][5][6][7][8], wormlike chain model [9][10][11], and Onsager virial theory [12] for rigid rods. An example of a recent review of liquid crystalline polymers is the text book of Donald and Windle [13].In this chapter we introduce the thermodynamics, or phase behavior, of binary mixtures of a flexible polymer and a rigid rod-like molecule. Here the flexible polymer means that liquid crystalline ordering does not occur in the constituent pure polymer. We first describe the fundamentals of a nematic phase, based on the Onsager theory for a rigid rod, where the entropy-induced nematic ordering is discussed. This will be the basis of the following sections. In Section 2.3, we focus on the phase separations of mixtures of a flexible polymer and a rigid rod-like molecule, or a low molecular weight liquid crystalline molecule, in a thermal equilibrium state. We introduce recent theoretical models to describe phase behavior, combining the Flory-Huggins Edited by Avraam I. Isayev

show abstract

Phase Separation Kinetics of a Liquid Crystal-Polymer Mixture

Cited by 60 publications

References 6 publications

Polymerization-Induced Phase Separation. 2. Morphological Analysis

Polymerization-Induced Phase Separation. 2. Morphological Analysis

Phase separation kinetics in mixtures of flexible polymers and low molecular weight liquid crystals

Thermodynamics of Flexible and Rigid Rod Polymer Blends

Contact Info

Product

Resources

About