Phase behaviour and morphology of polymer/liquid crystal blends

Pracellà, Mariano; Bresci, Bruno; Nicolardi, Concetta

doi:10.1080/02678299308027765

Cited by 11 publications

(5 citation statements)

References 10 publications

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“…The theoretical results have partly been confirmed by corresponding experimental observations 29,32,33) . One of the key arguments is that there are two spinodal curves in the phase diagram of a PDLC 34,35) , following an important finding by Dorgan 36) in the analysis of SD of an LC solution composed of liquid crystalline polymers and isotropic low molecular weight solvents.…”

Section: Introductionsupporting

confidence: 81%

“…Although the phase behaviors of rod-coil mixtures have been dealt with by several researchers [20][21][22][23][24][25][26] , the phase diagram for the mixtures of flexible polymers and thermotropic low molecular weight LCs was proposed by Yang et al [27][28][29] in the formalism of Flory-Huggins lattice theory 30) for isotropic mixing and Maier-Saupe theory 31) for nematic ordering. The theoretical results have partly been confirmed by corresponding experimental observations 29,32,33) . One of the key arguments is that there are two spinodal curves in the phase diagram of a PDLC 34,35) , following an important finding by Dorgan 36) in the analysis of SD of an LC solution composed of liquid crystalline polymers and isotropic low molecular weight solvents.…”

Section: Introductionsupporting

confidence: 72%

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

Zhu

Ding³

et al. 1999

Macromol. Theory Simul.

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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.

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Section: Introductionsupporting

confidence: 81%

Section: Introductionsupporting

confidence: 72%

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

Zhu

Ding³

et al. 1999

Macromol. Theory Simul.

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“…The LC/monomer phase diagram is of the upper critical solution temperature (UCST) type overlapping with the nematic−isotropic transition of the LC. This phase diagram is thermally reversible and similar to that of nematic/linear polymer mixtures. ,− The predicted LC/monomer phase diagram displays various coexistence regions such as liquid + liquid (I + I), nematic + liquid (N + I), and pure nematic phases (N). Below the peritectic line (dotted horizontal line), liquid and nematic phases coexist.…”

Section: Resultsmentioning

confidence: 63%

“…This phase diagram is thermally reversible and similar to that of nematic/linear polymer mixtures. 34,[39][40][41][42][43][44][45][46][47] The predicted LC/monomer phase diagram displays various coexistence regions such as liquid + liquid (I + I), nematic + liquid (N + I), and pure nematic phases (N). Below the peritectic line (dotted horizontal line), liquid and nematic phases coexist.…”

Section: Resultsmentioning

confidence: 99%

Morphology Development and Dynamics of Photopolymerization-Induced Phase Separation in Mixtures of a Nematic Liquid Crystal and Photocuratives

2000

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Dynamics of photopolymerization-induced phase separation (PIPS) and morphology development in mixtures of low molar mass nematic liquid crystal (LC) 4-n-heptyl-4′-cyanobiphenyl (designated K21) and photocuratives (designated NOA65) have been investigated by means of optical microscopy, light scattering, and differential scanning calorimetry. The equilibrium phase diagram of the LC/monomer (uncured NOA65) system was first established theoretically on the basis of the Flory-Huggins/Maier-Saupe theory. The calculated phase diagram displayed isotropic, liquid + liquid, liquid + nematic, and pure nematic coexistence regions in conformity with experiment. The effect of photopolymerization on the phase diagram was examined through comparison of the calculated phase diagrams of LC/linear polymer with LC/cross-linked polymer mixtures. Photopolymerization of the LC/monomer mixtures resulted in phase separation due to instability caused by an increase in molecular weight and subsequent network formation. Photopolymerization initiated in the isotropic phase gave uniformly distributed polygonal-shaped LC droplets in contrast to photopolymerization initiated in the two-phase region. Of particular interest is that the size of the phase-separated LC droplet increases with LC concentration. The network morphology is reminiscent of an interconnected thread seemingly running through the interstices of the polygonal droplets. Temporal evolution of structure factors was analyzed in the context of dynamical scaling law.

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“…The morphology and phase behavior of blends prepared from liquid crystals and polymers are strongly determined by the chemical constitution, molecular structure, and concentration of the components 1, 2. Whereas a low contents of thermoplastic polymers results usually in homogeneous solutions characterized by network morphology, higher concentrations lead to segregation and the formation of LC‐ or polymer‐compartments.…”

Section: Introductionmentioning

confidence: 99%

Display forming polymer/liquid crystal composite layers and their stability against external mechanical distortions

Bauer

Hartmann

Kuschel

et al. 2010

J of Applied Polymer Sci

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The liquid crystal display (LCD) technology is confronted with the task to substitute rigid glass plates enclosing the electro-optically active liquid crystal (LC) material by plastic substrates. In particular, the commercialization of flexible displays requires a sufficient stabilization against external mechanical distortions. To achieve LC layer stabilization, several procedures have been suggested. In this work, the thermal-induced phase separation (TIPS) technique has been applied to generate composite films consisting of LC compartments which are encased by coherent polymer walls after binodal phase separation. Composite films were prepared from a series of poly(methacrylates) and various commercial nematic LC mixtures. Furthermore, the use of copolymers as well as binary blends from ''hard'' and ''soft'' poly(methacrylates) broadens the possibilities to control the film morphology. To compare different polymer/LC composite films regarding their stability under compression load, the samples were investigated by indentation tests using an inverse reflected-light microscope combined with a digital image acquisition technique. The deformation of the composite layers was evaluated by the uniDAC image analysis which relies on the more general method of Digital Image Correlation (DIC). Some of the fabricated composites show a remarkably high indentation resistance, especially such prepared from poly(1-tetralyl methacrylate) and poly(4-tert-butylcyclohexyl methacrylate). The results facilitate the selection of suitable composite systems for the fabrication of mechanically stabilized flexible LC displays.

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Phase behaviour and morphology of polymer/liquid crystal blends

Cited by 11 publications

References 10 publications

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

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

Morphology Development and Dynamics of Photopolymerization-Induced Phase Separation in Mixtures of a Nematic Liquid Crystal and Photocuratives

Display forming polymer/liquid crystal composite layers and their stability against external mechanical distortions

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