Synergistic Ordering of Side‐Group Liquid Crystal Polymer and Small Molecule Liquid Crystal: Order and Phase Behavior of Nematic Polymer Solutions

Scruggs, Neal R.; Kornfield, Julia A.

doi:10.1002/macp.200700342

Cited by 6 publications

(19 citation statements)

References 41 publications

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“…Whereas, as noted above, the behaviors of amphiphilic polymers and monomers have been widely studied at LC interfaces, − oligomers have not been investigated. Past studies have established, however, that the interactions of adsorbates/absorbates with nematic LCs are strongly dependent on the configurational degrees of freedom of the adsorbates/absorbates and the extent to which configurational degrees of freedom are modified by the orientationally ordered environment of the LCs. ,,− For example, it is well-known that flexible polymers segregate from nematic LCs because the orientational order of the LC reduces the configurational degrees of freedom of the polymer chain (entropic penalty). , Accordingly, we hypothesized that the degree of oligomerization may impact the miscibility of amphiphiles with LCs and thus the response of LCs to exposure to oligomers.…”

Section: Introductionmentioning

confidence: 99%

“…7,29,37−40 For example, it is well-known that flexible polymers segregate from nematic LCs because the orientational order of the LC reduces the configurational degrees of freedom of the polymer chain (entropic penalty). 41,42 Accordingly, we hypothesized that the degree of oligomerization may impact the miscibility of amphiphiles with LCs and thus the response of LCs to exposure to oligomers.…”

Section: ■ Introductionmentioning

confidence: 99%

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Oligomers as Triggers for Responsive Liquid Crystals

et al. 2018

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We report an investigation of the influence of aqueous solutions of amphiphilic oligomers on the ordering of micrometer-thick films of thermotropic liquid crystals (LCs), thus addressing the gap in knowledge arising from previous studies of the interactions of monomeric and polymeric amphiphiles with LCs. Specifically, we synthesized amphiphilic oligomers (with decyl hydrophobic and pentaethylene glycol hydrophilic domains) in monomer, dimer, and trimer forms, and incubated aqueous solutions of the oligomers against nematic films of 4'-pentyl-4-biphenylcarbonitrile (5CB). All amphiphilic oligomers caused sequential surface-driven orientational (planar to homeotropic) and then bulk phase transitions (nematic to isotropic) with dynamics depending strongly on the degree of oligomerization. The dynamics of the orientational transitions accelerated from monomer to trimer, consistent with the effects of an increase in adsorption free energy. The mechanism underlying the orientational transition, however, involved a decrease in anchoring energy and not change in the easy axis of the LC. In contrast, the rate of the phase transition induced by absorption of oligomers into the LC decreased from monomer to trimer, suggesting that constraints on configurational degrees of freedom influence the absorption free energies of the oligomers. Interestingly, the oligomer-induced transition from the nematic to isotropic phase of 5CB was observed to nucleate at the aqueous-5CB interface, consistent with surface-induced disorder underlying the above-reported decrease in anchoring energy caused by the oligomers. Finally, we provided proof-of-concept experiments of the triggering of LCs using a trimeric amphiphile that is photocleaved by UV illumination into monomeric fragments. Overall, our results provide insight into the rational design of oligomers that can be used as triggers to create responsive LCs.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Oligomers as Triggers for Responsive Liquid Crystals

et al. 2018

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“…64,63 Indeed, the SCLCP was found to dissolve very well in the LMWLC, and the biphasic region in the phase diagram was observed to be very narrow. 30 We thus use A = 0 and a small negative value of B = −0.5/k B for the χ parameter to ensure the good solvent quality. Since the SCLCP backbone chain in the Scruggs−Kornfield experiment is long, we set N = 100 in our calculation.…”

Section: Resultsmentioning

confidence: 99%

“…25−27 While this approach can yield good agreement with the observed phase diagrams for some systems, 22,28,29 it does not consider the conformation of the SCLCP backbone and any effects originating from the coupling between the polymer backbone and the nematic order. 30,31 Another popular approach, proposed by Wang and Warner, 32 describes the SCLCP backbone using a worm-like chain model and the coupling between the backbone and side groups using a term of the Maier−Saupe form. However, this theory predicts first-order phase transitions between nematic phases with different chain conformations, but such abrupt transitions have not been observed experimentally.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Concentration Effects on Phase Behavior and Nematic Order in Mixtures of Side-Chain Liquid Crystal Polymers and Low-Molecular-Weight Liquid Crystals

Zhuang

Wang

2012

Macromolecules

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We study the anomalous concentration effects in mixtures of side-chain liquid crystalline polymers (SCLCPs) and low-molecular-weight liquid crystals (LMWLCs) by modifying the theory of Brochard, Jouffroy, and Levinson (BJL) to include the effects of the polymer backbone. Our new theory considers both the interaction of the polymer backbone with the global nematic field, as well as the local steric constraints due to the grafting of the side groups onto the polymer backbone. In addition, we consider the enhancement in the coupling between the pedant mesogens and the LMWLC molecules as the SCLCP concentration increases. The resulting phase diagram and nematic order parameters are in qualitative agreement with experimental observations, but drastically different from the predictions by the BJL theory.

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“…Later on, Finkelmann et al have shown that the block copolymer segment containing the mesogenic moieties feature a selective solubility in the low molecular weight liquid crystals, whereas the isotropic block is not soluble in the LC solvent [13]. As a result, the flexible segments of an AB-diblock copolymer associate and form a micelle core that is surrounded by a corona of soluble liquid crystalline blocks [14][15][16].…”

Section: Introductionmentioning

confidence: 97%

Structure-Property Relations of Liquid Crystalline Gels with ABA-Triblock Copolymers as Gelators

Pettau

Müller

Khazimullin

et al. 2012

Zeitschrift Für Physikalische Chemie

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This paper reports on the influence of the structure of tailored ABA-triblock copolymers on physical gelation of the nematic liquid crystal 4 -n-pentyl-4-cyanobiphenyl (5CB), rheological properties, and the electro-optical response of the gels. The block copolymer gelators, comprised of two polystyrene A-blocks connected to a cyanobiphenyl-functionalized polyhydroxystyrene B-block, were synthesized by living anionic polymerization and functionalized by polymer analogous reactions. These block copolymers feature selective solubility. The B-block is soluble in the nematic and isotropic state of 5CB, whereas the polystyrene A-blocks are only soluble in the isotropic state. Consequently, upon cooling liquid crystalline gels are formed due to the controlled microphase-separation of the A-blocks. We show that the polymer composition and the different block lengths are important to vary the gel properties and the electro-optical response. It is confirmed that the gel formation correlates to the isotropic to nematic transition of 5CB for block copolymer gelators with sufficiently long A-blocks. Higher gel elasticity is obtained if gelators with short B-blocks are employed. The influence of the polymer network on the switching behavior of these liquid crystalline gels is investigated with respect to the electro-optical response in light scattering experiments. Intriguingly, these indicate a rearrangement of the nodes formed by the A-blocks under a strong electric field for block copolymers with short A-blocks.

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Synergistic Ordering of Side‐Group Liquid Crystal Polymer and Small Molecule Liquid Crystal: Order and Phase Behavior of Nematic Polymer Solutions

Cited by 6 publications

References 41 publications

Oligomers as Triggers for Responsive Liquid Crystals

Oligomers as Triggers for Responsive Liquid Crystals

Anomalous Concentration Effects on Phase Behavior and Nematic Order in Mixtures of Side-Chain Liquid Crystal Polymers and Low-Molecular-Weight Liquid Crystals

Structure-Property Relations of Liquid Crystalline Gels with ABA-Triblock Copolymers as Gelators

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