Investigation of bulk properties and monolayer behaviour of amphiphilic mesogens: structural variations of the head group

Joachimi, Detlev; Öhlmann, André; Rettig, W.; Tschierske, Carsten

doi:10.1039/p29940002011

Cited by 15 publications

(4 citation statements)

References 18 publications

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“…Here, the molecular order is largely the result of the parallel alignment of rigid anisometric units − or disk-shaped units in amphiphiles on their mesogenic properties as well as on their organization at the air−water interface was studied. Those compounds with rodlike rigid units usually carry the polar substituent at one of the termini of their rigid core (type I in Figure ).…”

Section: Introductionmentioning

confidence: 99%

Influence of the Position of the Hydrophilic Group on the Monolayer Properties of Rigid Amphiphiles with Laterally Attached Headgroups

1999

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The π/A isotherms of rodlike 4,4‘ ‘-didecyloxy-p-terphenyl derivatives incorporating hydrophilic 1,2-diol groups in different lateral positions were recorded with dependence on the temperature, and the thin films were investigated by Brewster angle microscopy. Depending on the position of the hydrophilic groups and on the type of spacer between the hydrophilic group and the rigid core, different types of isotherms with different temperature dependences have been found. Two sharp breaks separated by a large plateau occur along the π/A isotherms of the 2-substituted and 2‘-substituted compounds. In the plateau region a defined formation of a triple layer is proposed. For the 3-substituted compounds with a peripheral position of the hydrophilic groups, the type of isotherm largely depends on the type and the length of the spacer unit between the hydrophilic group and the rigid core. Two transition regions can be found in the slope of their isotherms. A tentative model of the organization of these molecules with dependence on the lateral pressure is proposed. Accordingly, the first transition is attributed to a transition of the rigid cores from a flat arrangement on the surface to a tilted arrangement. In the second transition region either formation of a defined triple layer (short spacer) or transition to a more densely packed monomolecular film with the rigid cores arranged parallel or tilted to the surface normal (long polyether chains) should take place. If the hydrophilic groups are coupled via lipophilic alkyl chains, the molecules are organized immediately after spreading and π/A isotherms similar to those of amphiphiles with terminal hydrophilic groups have been found. Thus, by slight changes of the molecular structure completely different supermolecular organizations at the water surface can be realized.

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Section: Introductionmentioning

confidence: 99%

Influence of the Position of the Hydrophilic Group on the Monolayer Properties of Rigid Amphiphiles with Laterally Attached Headgroups

1999

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“…The aggregation of amphiphiles in aqueous media and at interfaces and the organization of anisometric compounds with formation of liquid crystalline phases are important examples of molecular self organization, and therefore they are intensively investigated. More recently both structural concepts have been combined and, for example, the influence of anisometric (rod-shaped [1][2][3][4][5][6][7][8] or disk-shaped [9][10][11] ) units in amphiphiles on their monolayers was studied. Those compounds with rodlike mesogenic units usually carry the polar substituent at one of the termini of their rigid cores (structure A; Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Monolayer Properties of a New Family of Amphiphiles with an Unusual Head-Group Topology

Schröter¹,

Plehnert²,

Tschierske³

et al. 1997

Langmuir

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Several rodlike 4,4‘‘-bis(decyloxy)-p-terphenyl derivatives incorporating nonionic hydrophilic groups in the lateral 2‘-position (2-oxa-4,5-dihydroxypentyl, 2,5-dioxa-7,8-dihydroxyoctyl, 2,5,8-trioxa-10,11-dihydroxyundecyl, and 2,5,8,11-tetraoxa-13,14-tetradecyl groups) and 2‘-(2-oxa-4,5-dihydroxypentyl)-4,4‘‘-diundecyl-p-terphenyl form well-ordered thin films when spread at the air−water interface. One observes two sharp breaks in the pressure/area isotherms separated by a large plateau. The first break occurs at an area of ca. 0.90 nm2/molecule, an area which corresponds to a side-on arrangement of the terphenyl units at the interface. The plateau corresponds to a first-order phase transition. The surface pressure related to this transition significantly rises with an increasing number of oxyethylene units in the hydrophilic lateral groups. Brewster angle microscopic investigations indicate the formation of fluid domains in this region. In some cases these domains coalesce to a homogenous layer. The surface potential is nearly constant in the region of the plateau, which can be explained by a defined collapse due to the formation of a triple layer consisting of a bilayer on top of the monolayer.

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“…Long and linear alkyl chains push the molecule to tilt, favoring the formation of SmC mesophase due to entropic pressure . Polyfunctional as well as highly flexible groups as oligo(dimethylsiloxane) or perfluoroether at the chain end are important functionalization of LC which can lead to suppression of out‐of‐layer fluctuations, favoring Vries‐type smectic phases materials . Additionally, polar terminal groups have been reported to stabilize lamellar mesophase in particular SmA mesophase in some cases, but not in others .…”

Section: Introductionmentioning

confidence: 99%

“…SmA and SmC mesophases were predominant for rod‐shape amphotropic materials in bulk and polar (protic/aprotic) solvents. Their ability to form stable monolayers at the air/water interface were also investigated . Most impressive is that columnar and cubic mesophases by calamitic molecules were obtained by the increasing of polar character by glycerol‐ether alkyl chain .…”

Section: Introductionmentioning

confidence: 99%

Insight into Out‐of‐Layer Fluctuations in the Smectic A Stability of 3,5‐Diarylisoxazole Liquid Crystals

et al. 2020

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Polar‐terminated 3,5‐diarylisoxazole liquid crystals (ILCs) were synthetized and characterized. ILCs are composed by rigid core 3,5‐diarylisoxazol, alkyl chain and polar‐terminated flexible spacer. Hydroxyl‐, ketal‐ and 1,2‐diol‐terminated ILCs rendered smectic C and A mesophase, while bromine‐terminated ILCs showed smectic A and B mesophase, for monosubstituted and linear ILCs. For branched alkyl chain monotropic SmA was detected and for disubstituted ILCs no mesophase was detected. Out‐of‐layer fluctuations (OLFs) are discussed based on X‐ray diffraction date and textures. The OLFs are dependent on the bromine atom hardness, hydrogen bonding through collective actions and conformational effects at the interface between layers. Smectic translational order parameter (TOP) Σ was also obtained for orientated bromine‐ and hydroxyl‐terminated ILCs and related it with OLFs. For 1,2‐diol‐terminated ILCs two SmC sublayers were founded, probably related to the intramolecular hydrogen bond favoring the 5‐membered and 6‐membered formation.

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Investigation of bulk properties and monolayer behaviour of amphiphilic mesogens: structural variations of the head group

Cited by 15 publications

References 18 publications

Influence of the Position of the Hydrophilic Group on the Monolayer Properties of Rigid Amphiphiles with Laterally Attached Headgroups

Influence of the Position of the Hydrophilic Group on the Monolayer Properties of Rigid Amphiphiles with Laterally Attached Headgroups

Monolayer Properties of a New Family of Amphiphiles with an Unusual Head-Group Topology

Insight into Out‐of‐Layer Fluctuations in the Smectic A Stability of 3,5‐Diarylisoxazole Liquid Crystals

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