Self-assembly of surfactants and phospholipids at interfaces between aqueous phases and thermotropic liquid crystals

Lockwood, Nathan A.; Abbott, Nicholas L.

doi:10.1016/j.cocis.2005.06.002

Cited by 83 publications

(116 citation statements)

References 29 publications

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“…For example, the Abbott group has investigated the use of hybrid aligned LC films confined between air and water as a novel sensor system [8]. Here, by varying surfactant concentration at the LC-water interface, it has proved possible to switch in and out of the hybrid aligned state, so giving an easy-to-read surfactant detector.…”

Section: Introductionmentioning

confidence: 99%

Simulation and theory of hybrid aligned liquid crystal films

et al. 2009

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We present a study of the effects of nano-confinement on a system of hard Gaussian overlap particles interacting with planar substrates through the hard-needle-wall potential, extending earlier work by two of us [D. J. Cleaver and P. I. C. Teixeira, Chem. Phys. Lett. 338, 1 (2001)]. Here, we consider the case of hybrid films, where one of the substrates induces strongly homeotropic anchoring while the other favours either weakly homeotropic or planar anchoring. These systems are investigated using both Monte Carlo simulation and density-functional theory, the latter implemented at the level of Onsager's second virial approximation with Parsons-Lee rescaling. The orientational structure is found to change either continuously or discontinuously depending on substrate separation, in agreement with earlier predictions by others. Theory is seen to perform well in spite of its simplicity, predicting the positional and orientational structure seen in simulations even for small particle elongations.

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Section: Introductionmentioning

confidence: 99%

Simulation and theory of hybrid aligned liquid crystal films

et al. 2009

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“…[1][2][3] Subtle changes in interfacial structure result in long-range consequences in the director field of the LC; the resulting amplification was used by Gupta et al to enable facile detection of antigen binding at solid/ LC interfaces. 4 More recently, environmentally-responsive aqueous/LC interfaces [5][6][7][8][9][10][11][12][13][14][15] have been shown to control the orientational order of the LC, responding actively and/or reversibly to a broad range of stimuli. Examples of such systems are the assembly of amphiphiles, such as phospholipids 7,9,15 and surfactants, 6,8,11,12 at an aqueous/LC interface leading to changes in the alignment of the LC that can be observed in real time using the birefringence of the LC.…”

Section: Introductionmentioning

confidence: 99%

pH-responsive aqueous/LC interfaces using SGLCP-b-polyacrylic acid block copolymers

et al. 2010

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Block copolymers that combine a side-group liquid crystalline polymer (SGLCP) block and a pH-responsive hydrophilic block, poly(acrylic acid) (PAA), are shown to confer pH-dependent anchoring of the director orientation at the aqueous/LC interface. The SGLCP block, poly-(4-cyanobiphenyl-4-oxyundecylacrylate), was chosen based on its ability to influence the director field of the 5CB (4-cyano-4 0 -pentylbiphenyl). At low pH the PAA block collapses and the inherent, planar alignment tendency of 5CB at a water interface prevails. As pH increases, the polyelectrolyte block becomes increasingly charged and expands, producing a change to homeotropic anchoring. The change in anchoring occurs as quickly as the buffer can be changed (within $2 s) and is reversible, with a response that is repeatable over as many cycles as were tested (approximately 20 cycles). The polymer-mediated anchoring persists for 6 days, indicating that the SGLCP block secures the self-assembled layer on the 5CB, even under conditions that cause repulsive interactions among the PAA blocks. Thus, SGLCP blocks can translate conformational changes of a responsive hydrophilic block into rapid, reversible changes in the director field.

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“…Past studies have shown that the interaction between the aliphatic chains of lipids and the LCs can cause the homeotropic orientation of 5CB at the aqueous-LC interface. [19][20][21][22][23] Although optical images darkened immediately after the introduction of the lipid mixture, the aqueous solution was maintained for 1 hour to allow for equilibration. We should point out that an unstable monolayer of lipids would appear if the copper grid was not completely clean or if the interface of 5CB and aqueous phase was not flat.…”

Section: Resultsmentioning

confidence: 99%

“…Past studies have demonstrated that this approach permits the formation of stable and approximately planar interfaces between water immiscible LC and an aqueous phase that can be readily exchanged. [19][20][21][22][23] Before the aqueous solution was immersed into the optical cell, 5CB confined in the copper grid was directly contacted with air. The dark appearance of the LC between crossed microscopic polarizers was observed because OTStreated glass slides anchor the 5CB in a homeotropic orientation (perpendicular orientation to the surface) at the interface.…”

Section: Resultsmentioning

confidence: 99%

“…18 Abbott et al have shown that phospholipids assembled at aqueous-LC interfaces couple strongly to the orientation of the LC, and the binding of proteins at these interfaces induces ordering transitions in the LC. [19][20][21][22][23] The activities of the proteins could be easily observed between crossed polarizers because the longrange orientational order in the LC couples to the organization of the proteins and phospholipids at the interface.…”

Section: Introductionmentioning

confidence: 99%

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Liquid Crystal-based Imaging of Enzymatic Reactions at Aqueous-liquid Crystal Interfaces Decorated with Oligopeptide Amphiphiles

Hu¹,

Jang²

2010

Bulletin of the Korean Chemical Society

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In this study, we investigated the use of liquid crystals to selectively detect the activity of enzymes at interfaces decorated with oligopeptide-based membranes. We prepared a mixed monolayer of tetra(ethylene glycol)-terminated lipids and carboxylic acid-terminated lipids at the aqueous-liquid crystal (LC) interface. The 17 amino-acid oligopeptide SNFKTIYDEANQFATYK was then immobilized onto this mixed monolayer through N-hydroxysuccinimide-activation of the carboxylic acid groups. We examined the orientational behavior of nematic 4-cyano-4'-pentylbiphenyl (5CB) after conjugation of the 17 amino-acid oligopeptide with the mixed monolayer assembled at the interface. Immobilization of the oligopeptide caused orientational transitions in 5CB, with a change from homeotropic (perpendicular) to tilted alignment, which was primarily due to the reorganization of the monolayer. The orientation of the 5CB molecules returned to its homeotropic state after contacting the interface containing α-chymotrypsin, which can cleave the immobilized oligopeptide. Control experiments confirmed that the enzymatic activity of α-chymotrypsin triggered the ordering transitions in the LC. These results suggest that the LC can provide a facile method for selective detection of enzymatic activity.

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Self-assembly of surfactants and phospholipids at interfaces between aqueous phases and thermotropic liquid crystals

Cited by 83 publications

References 29 publications

Simulation and theory of hybrid aligned liquid crystal films

Simulation and theory of hybrid aligned liquid crystal films

pH-responsive aqueous/LC interfaces using SGLCP-b-polyacrylic acid block copolymers

Liquid Crystal-based Imaging of Enzymatic Reactions at Aqueous-liquid Crystal Interfaces Decorated with Oligopeptide Amphiphiles

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