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Article Dans Une Revue Recueil des Travaux Chimiques des Pays-Bas Année : 1993

α, ω-Dipolar amphiphiles: Influence of rigid and flexible units on aggregation behavior

Résumé

Mono-and \alpha,\omega-dipolar amphiphiles with hydrophilic pyridinium head groups, and flexible and rigid hydrophobic parts have been synthesized. Surface tension and conductivity measurements proved that micellar aggregates for amphiphiles 1-4 are formed. The incorporation of rigid units leads to a decrease in the critical micellar concentration (CMC): the rigid monopolar amphiphile 2 aggregates at lower concentration than the flexible monopolar amphiphile 1. A similar decrease was observed when chain ends were connected: the flexible a,w-dipolar amphiphile 3 has a lower CMC than the flexible monopolar amphiphile 1. The more flexible amphiphiles 1-3 allow the formation of micelles of different shape leading to both CMC and C, values. For the a,w-dipolar amphiphile 4 with a rigid azoxybiphenylene core, the possibility of different micellar shapes is reduced, leading only to a CMC value (CMC = C,). For the flexible \alpha-\omega-dipolar amphiphile 3, only a small, but linear viscosity increase with concentration is found. Very viscous solutions were measured for the rigid \alpha-\omega-dipolar amphiphile 4 above a certain concentration. Phase diagrams of amphiphiles 3 and 4 were detefmined using polarization-microscopy and X-ray measurements. Flexible \alpha-\omega-dipolar amphiphile 3 shows a lyotropic mesophase only at very high concentration (83 mass %). In contrast, rigid analog 4 forms stable lyotropic mesophases at 16 mass %. Both nematic and higher ordered mesophases (probably lamellar) are found for the rigid \alpha-\omega-dipolar amphiphile 4.

Dates et versions

hal-04191555 , version 1 (30-08-2023)

Identifiants

Citer

V. Hessel, H. Ringsdorf, R. Laversanne, Frédéric Nallet. α, ω-Dipolar amphiphiles: Influence of rigid and flexible units on aggregation behavior. Recueil des Travaux Chimiques des Pays-Bas, 1993, 112 (6), pp.339-346. ⟨10.1002/recl.19931120606⟩. ⟨hal-04191555⟩

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