UV Polymerisation of Surfactants Adsorbed at the Nematic Liquid Crystal–Water Interface Produces an Optical Response

Fletcher, Paul D. I.; Kang, Nam Lyong; Paunov, Vesselin N.

doi:10.1002/cphc.200900405

Cited by 35 publications

(35 citation statements)

References 46 publications

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“…These studies provide support for the hypothesis that the interaction of the LC with the amphiphiles is mediated primarily via the tail of the lipid 52, 61, 64. For example, one study used two forms of dodecylbenzenesulfonate(DBS) (linear L-DBS and branched BR-DBS, shown in Figure 5E) to investigate the effects of surfactant tail structure on the ordering of the LC 52.…”

Section: Section 2: Aqueous Interfaces Of Thermotropic Liquid Crystalsmentioning

confidence: 81%

“…al . using UV-polymerizable surfactants showed that polymerization of the hydrophobic tail of a surfactant at the LC-aqueous interface changes the ordering of the LC from homeotropic to planar, whereas polymerization of the hydrophilic head region does not produce a similar LC ordering transition 61. These results combined indicate that the surfactant head group does not have a large effect on the orientation of 5CB, whereas the aliphatic tail structure, length, and conformation greatly affect the ordering of the LC.…”

Section: Section 2: Aqueous Interfaces Of Thermotropic Liquid Crystalsmentioning

confidence: 95%

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Recent Advances in Colloidal and Interfacial Phenomena Involving Liquid Crystals

2010

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This article describes recent advances in several areas of research involving the interfacial ordering of liquid crystals (LCs). The first advance revolves around the ordering of LCs at bio/ chemically functionalized surfaces. Whereas the majority of past studies of surface-induced ordering of LCs have involved surfaces of solids that present a limited diversity of chemical functional groups (surfaces at which van der Waals forces dominate surface-induced ordering), recent studies have moved to investigate the ordering of LCs on chemically complex surfaces. For example, surfaces decorated with biomolecules (e.g. oligopeptides and proteins) and transition metal ions have been investigated, leading to an understanding of the roles that metal-ligand coordination interactions, electrical double-layers, acid-base interactions, and hydrogen bonding can have on the interfacial ordering of LCs. The opportunity to create chemically-responsive LCs capable of undergoing ordering transitions in the presence of targeted molecular events (e.g., ligand exchange around a metal center) has emerged from these fundamental studies. A second advance has focused on investigations of the ordering of LCs at interfaces with immiscible isotropic fluids, particularly water. In contrast to prior studies of surface-induced ordering of LCs on solid surfaces, LC-aqueous interfaces are deformable and molecules at these interfaces exhibit high levels of mobility and thus can reorganize in response to changes in interfacial environment. A range of fundamental investigations involving these LC-aqueous interfaces have revealed that (i) the spatial and temporal characteristics of assemblies formed from biomolecular interactions can be reported by surface-driven ordering transitions in the LCs, (ii) the interfacial phase behaviour of molecules and colloids can be coupled to (and manipulated via) the ordering (and nematic elasticity) of LCs, and (iii) confinement of LCs leads to unanticipated size-dependent ordering (particularly in the context of LC emulsion droplets). The third and final advance addressed in this article involves interactions between colloids mediated by LCs. Recent experiments involving microparticles deposited at the LC-aqueous interface have revealed that LC-mediated interactions can drive interfacial assemblies of particles through reversible ordering transitions (e.g., from one-dimensional chains to two-dimensional arrays with local hexagonal symmetry). In addition, recent single nanoparticle measurements suggest that the ordering of LCs about nanoparticles differs substantially from micrometer-sized particles and that the interactions between nanoparticles mediated by the LCs are far weaker than predicted by theory (sufficiently weak that the interactions are reversible and thus enable self-assembly). Finally, LC-mediated interactions between colloidal particles have also been shown to lead to the formation of colloidin-LC gels that possess mechanical properties relevant to the design of materials to interface with li...

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Section: Section 2: Aqueous Interfaces Of Thermotropic Liquid Crystalsmentioning

confidence: 81%

Section: Section 2: Aqueous Interfaces Of Thermotropic Liquid Crystalsmentioning

confidence: 95%

Recent Advances in Colloidal and Interfacial Phenomena Involving Liquid Crystals

2010

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“…Subsequently, Kuhnau et al used differential scanning calorimetry (DSC) to determine that LCs penetrate into dipalmitoylphosphatidylcholine (DPPC) bilayers, leading to a change in the ordering of the acyl chains of DPPC 50,51. Finally, in a recent and elegant experiment, Fletcher et al reported that UV polymerization of the tails of surfactants at aqueous-LC interfaces frustrates homeotropic ordering of the LC whereas polymerization of the headgroup does not perturb the system from the homeotropic orientation 19. All these experiments support the view that homeotropic anchoring of LCs on lipid-decorated surfaces is induced by the interdigitation (or penetration) of mesogens into the aliphatic chains of the amphiphiles.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, early work by Hiltrop and Stegemeyer demonstrated that the ordering of LCs at surfaces can be influenced by the presence of monolayers of lecithin transferred onto the surfaces by the Langmuir-Blodgett (LB) technique 15,16. More recently, the influence of surfactants and phospholipids self-assembled at aqueous-LC interfaces on the ordering of LCs has been reported 11,17-19. These past studies, when combined, suggest a physical picture in which monolayer films of phospholipids organize to present their hydrophobic tails towards the LC phase, thus leading to interdigitation of mesogens and lipid acyl chains with the subsequent homeotropic (perpendicular) ordering of the LCs.…”

Section: Introductionmentioning

confidence: 99%

Ordering Transitions in Nematic Liquid Crystals Induced by Vesicles Captured through Ligand−Receptor Interactions

Tan

Bertics²,

Abbott

2010

Langmuir

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We report that phospholipid vesicles incorporating ligands, when captured from solution onto surfaces presenting receptors for these ligands, can trigger surface-induced orientational ordering transitions in nematic phases of 4′-pentyl-4-cyanobiphenyl (5CB). Specifically, whereas avidin-functionalized surfaces incubated against vesicles comprised of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were observed to cause the liquid crystal (LC) to adopt a parallel orientation at the surfaces, the same surfaces incubated against biotinylated vesicles (DOPC and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (biotin-DOPE)) caused homeotropic (perpendicular) ordering of the LC. The use of a combination of atomic force microscopy (AFM), ellipsometry and quantitative fluorimetry, performed as a function of vesicle composition and vesicle concentration in solution, revealed the capture of intact vesicles containing 1% biotin-DOPE from buffer at the avidin-functionalized surfaces; subsequent exposure to water prior to contact with the LC, however, resulted in rupture of the majority of vesicles into interfacial multilayer assemblies with a maximum phospholipid loading set by random close-packing of the intact vesicles captured initially on the surface (5.1 ± 0.2 phospholipid molecules/nm2). At high concentrations of biotinylated lipid (> 10% biotin-DOPE) in the vesicles, the limiting lipid loading was measured to be 4.0 ± 0.3 phospholipid molecules/nm2, consistent with the maximum phospholipid loading set by spontaneous formation of a bilayer during incubation with the biotinylated vesicles. Independent of the initial morphology of the phospholipid assembly captured on the surface (intact vesicle, planar multilayer), we measured homeotropic ordering of the LC on the surfaces. We interpret this result to infer reorganization of the phospholipid bilayers either prior to or upon contact with the LCs such that interactions of the acyl chains of the phospholipid and the LC dominate the ordering of the LC, a conclusion that is further supported by quantitative measurements of the orientation of the LC as a function of surface density of phospholipid (>1.8 molecules/nm2 is required to cause homeotropic ordering of the LC). These results and others presented herein provide fundamental insights into the interactions of phospholipid-decorated interfaces with LCs, and thereby provide guidance for the design of surfaces on which phospholipid assemblies captured through ligand-receptor recognition can be reported via ordering transitions in LCs.

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“…1 For this class of adsorbates, the steric interactions of the tails of the amphiphiles and the mesogens of the thermotropic LC have been shown to couple the interfacial organization of the amphiphiles to the orientational ordering of the LC. 9–14 For example, contact of an aqueous dispersion of vesicles of dilauroylphosphatidylcholine (DLPC) with the interface of a micrometer-thick film of nematic 4′-pentyl-4-cyanobiphenyl (5CB) has been observed to result in spontaneous formation (via fusion) of a monolayer of DLPC on the interface of the LC, resulting in a discontinuous orientational ordering transition in which the LC changes from an orientation that is parallel to the interface (prior to lipid adsorption) to perpendicular to the interface (after lipid adsorption). 9 In addition, it was observed that, at interfacial densities of DLPC below saturation coverage, the DLPC monolayer exhibited coexisting lipid-rich and lipid-lean domains which gave rise to patterned orientations of the LC.…”

Section: Introductionmentioning

confidence: 99%

Ordering Transitions Triggered by Specific Binding of Vesicles to Protein-Decorated Interfaces of Thermotropic Liquid Crystals

2012

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We report that specific binding of ligand-functionalized (biotinylated) phospholipid vesicles (diameter = 120 ± 19 nm) to a monolayer of proteins (streptavidin or anti-biotin antibody) adsorbed at an interface between an aqueous phase and an immiscible film of a thermotropic liquid crystal (LC) (nematic 4′-pentyl-4-cyanobiphenyl (5CB)) triggers a continuous orientational ordering transition (continuous change in the tilt) in the LC. Results presented in this paper indicate that, following the capture of the vesicles at the LC interface via the specific binding interaction, phospholipids are transferred from the vesicles onto the LC interface to form a monolayer, reorganizing and partially displacing proteins from the LC interface. The dynamics of this process are accelerated substantially by the specific binding event relative to a protein-decorated interface of a LC that does not bind the ligands presented by vesicles. The observation of the continuous change in the ordering of the LC, when combined with other results presented in this paper, is significant as it is consistent with the presence of sub-optical domains of proteins and phospholipids on the LC interface. An additional significant hypothesis that emerges from the work reported in this paper is that the ordering transition of the LC is strongly influenced by the bound state of the protein adsorbed on the LC interface, as evidenced by the influence on the LC of (i) “crowding” of the protein within a monolayer formed at the LC interface and (ii) aging of the proteins on the LC interface. Overall, these results demonstrate that ordering transitions in LCs can be used to provide fundamental insights into the competitive adsorption of proteins and lipids at oil-water interfaces, and that LC ordering transitions have the potential to be useful for reporting specific binding events involving vesicles and proteins.

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UV Polymerisation of Surfactants Adsorbed at the Nematic Liquid Crystal–Water Interface Produces an Optical Response

Cited by 35 publications

References 46 publications

Recent Advances in Colloidal and Interfacial Phenomena Involving Liquid Crystals

Recent Advances in Colloidal and Interfacial Phenomena Involving Liquid Crystals

Ordering Transitions in Nematic Liquid Crystals Induced by Vesicles Captured through Ligand−Receptor Interactions

Ordering Transitions Triggered by Specific Binding of Vesicles to Protein-Decorated Interfaces of Thermotropic Liquid Crystals

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