Phase Behavior of Liquid Crystalline Polymer/Model Compound Mixtures: Theory and Experiment

Lee, Suk Min; Oertli, Alfred G.; Gannon, Mark A.; Liu, Andrea J.; Pearson, Dale S.; Schmidt, Hans‐Werner; Fredrickson, Glenn H.

doi:10.1021/ma00092a040

Cited by 18 publications

(17 citation statements)

References 13 publications

(17 reference statements)

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“…Phase diagrams of our current system, as well as closely related systems, have been found with similar topology as the diagrams that we present in this section. 22,46,47 Assuming a given temperature dependence of the parameters in the model, these phase diagrams can be reproduced more accurately with our current SCF method. However, rather than an exhaustive listing of the types of phase diagrams, we will only discuss three phase diagrams, as examples of the application of our SCF method and to discuss certain issues not emphasized in previous studies.…”

Section: A Phase Behaviormentioning

confidence: 95%

“…14,20 However, the addition of a second component ͑whether another polymer species or small nonmesogenic solvent͒ produces new qualitative features in the phase behavior as shown by Liu and Fredrickson. 21,22 In addition, in the approach by Warner and co-workers, the mean-field approximation is introduced as an ansatz instead of being derived as the lowest order approximation in a systematic approach. Furthermore, by restricting the interaction to a spatially independent scalar form using the second Legendre polynomial P 2 ()ϭ3u z 2 ()/2Ϫ1/2, the approach can only treat the homogeneous state.…”

Section: Introductionmentioning

confidence: 99%

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Semiflexible polymer solutions. I. Phase behavior and single-chain statistics

Spakowitz

Wang

2003

The Journal of Chemical Physics

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We study the thermodynamics and single-chain statistics of wormlike polymer solutions with Maier-Saupe-type interactions using self-consistent-field ͑SCF͒ theory. The SCF equations are derived using a systematic field-theoretical approach which yields the SCF equations as the lowest order approximation, but permits fluctuation corrections to be incorporated. We solve the SCF equations using the spheroidal functions, which provides a nonperturbative description of the thermodynamics and single-chain statistics in the nematic state for arbitrary degrees of nematic order. Several types of phase diagrams are predicted, with an emphasis on the limit of metastability ͑spinodal͒ associated with each phase. The shape and location of these spinodals suggest interesting scenarios for the phase transition kinetics. A large but finite persistence length is shown to significantly decrease the isotropic-nematic transition temperature relative to that for rigid rods. In the nematic state, the mean-square end-to-end distance in the parallel and perpendicular directions are governed by two separate correlation lengths. An exact relationship between these correlation lengths and the eigenvalues of the spheroidal functions is provided, which reproduces the analytical expressions predicted from earlier studies in the limit of large nematic strength. The dominant contribution to the single-chain thermodynamics is shown to arise from small amplitude undulations in the directions perpendicular to the nematic direction; the presence of hairpins, though crucial for determining the dimensions of the polymer, has insignificant consequences on the single-chain thermodynamics.

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Section: A Phase Behaviormentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Semiflexible polymer solutions. I. Phase behavior and single-chain statistics

Spakowitz

Wang

2003

The Journal of Chemical Physics

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“…Lee et al [15] found that films made from evaporated solutions of a liquid crystalline model compound below 0.4 weight fraction incorporation in a liquid crystalline polymer also showed no phase separation. The absence of phase separation seen in DSC and optical microscopy suggests that the POSS fillers were soluble in all three polymer matrixes.…”

Section: Discussionmentioning

confidence: 99%

“…OctaSilane-POSS ® or 1, 3,5,7,9,11,13,15-Octakis(dimethylsilyloxy)pentacyclo[9.5.1.1 3,9 .1 5,15 .1 17,13 ]octasiloxane was purchased from Hybrid Plastics. The remaining chemicals were purchased from Aldrich, Fisher, or Acros Organics and used as received unless otherwise noted.…”

Section: Materials Characterization and Processing Conditionsmentioning

confidence: 99%

Nanocomposites of Liquid Crystalline Polyhedral Oligomeric Silsesquioxane Particles and Liquid Crystalline Polymers

2003

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A new liquid crystalline nanoparticle has been synthesized by the reaction of a cyanobiphenyl derivative with polyhedral oligomeric silsesquioxane (POSS ® *). Two POSS nanoparticles, liquid crystalline POSS (LC POSS 3) and a non-LC isooctyl POSS (OPOSS), were then compounded at 2.5 wt % into thermotropic polyester liquid crystalline polymers (LCPs) poly(hexamethylene 4,4'-bibenzoate), poly(diethylene glycol 4,4'-bibenzoate) as well as a frustrated LCP 45:55 poly(ethylene terephthalate-co-4,4'-bibenzoate). These polymers are currently being studied for potential use in high performance fibers and high barrier packaging materials. A comprehensive study of LCP/LC POSS 3 nanocomposites will focus on any changes in the thermal and mechanical properties of the LCPs with increasing LC POSS 3 concentration. It will be determined how incorporation of LC POSS 3 affects the liquid crystalline phases of an amorphous and crystalline LCP. Of special interest is the incorporation of LC POSS 3 into a frustrated LCP. It is proposed that the LC POSS 3 might help to unfrustrate the LCP.

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“…Phase‐transition temperatures were measured by differential scanning calorimetry by the method of Lee et al14…”

Section: Methodsmentioning

confidence: 99%

Synthesis of low‐shrinkage polymerizable methacrylate liquid‐crystal monomers

2005

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As a part of the continuous pursuit to develop an ideal resinous dental restorative material for use in large posterior cavity restorations, this article reports the easy, high-yield synthesis and the incredibly low polymerization shrinkage property of a new bifunctional liquid crystal (LC) monomer. This new polymerizable nematic liquid crystal is the next higher homolog of the acrylate monomer reported in a previous work.1 It remains liquid crystalline between room and mouth temperatures and can be polymerized to isotropic polymer with the use of the same visible light inhibitor system as used with conventional monomers. The structure of this new monomer has been confirmed to be 2-(t-butyl), 1,4-bis-[4-(6-methacryloxy-hexan-1-oxy)-benzoyloxy]-benzene. Unlike the synthesis of its acrylate homolog, when the same procedure is adopted for the synthesis of this compound, the recovery of the product is not split by a sizable amount of the by-product. Therefore, the reaction is cleaner, with high yield and a less labor-intensive purification procedure. Thus, the synthetic methodology has the potential for easy commercial scale-up. The monomer (V) polymerizes at room temperature with a shrinkage of about 2 vol %, as compared to > 8 vol % for conventional control (GTE), at similar degrees of conversion.

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Phase Behavior of Liquid Crystalline Polymer/Model Compound Mixtures: Theory and Experiment

Cited by 18 publications

References 13 publications

Semiflexible polymer solutions. I. Phase behavior and single-chain statistics

Semiflexible polymer solutions. I. Phase behavior and single-chain statistics

Nanocomposites of Liquid Crystalline Polyhedral Oligomeric Silsesquioxane Particles and Liquid Crystalline Polymers

Synthesis of low‐shrinkage polymerizable methacrylate liquid‐crystal monomers

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