Monolayer properties of uronic acid bicatenary derivatives at the air–water interface: effect of hydroxyl group stereochemistry evidenced by experimental and computational approaches

Abstract

By screening uronic acid-based surfactant interfacial properties, the effect of the hydroxyl group stereochemistry (OH-4) on the conformation of bicatenary (disubstituted) derivatives at the air-water interface has been evidenced by experimental and computational approaches. Physical and optical properties of a monolayer characterized by Langmuir film balance, Brewster angle microscopy, and ellipsometry at 20 °C reveal that the derivative of glucuronate (C(14/14)-GlcA) forms a more expanded monolayer, and shows a transition state under compression, in the opposite to that of galacturonate (C(14/14)-GalA). Both films are very mechanically resistant (compression modulus > 300 mN m(-1)) and stable (collapse pressure exceeding 60 mN m(-1)), while that of C(14/14)-GalA exhibits a very high compression modulus up to 600 mN m(-1) like films in the solid state. Computational approaches provide single and assembly molecular models that corroborate the molecule expansion degree and interactions data from experimental results. Differences in the molecular conformation and film behaviours of uronic acid bicatenary derivatives at the air-water interface are attributed to the intra-H-bonding formation, which is more favourable with an OH-4 in the axial (C(14/14)-GalA) than in the equatorial position (C(14/14)-GlcA).

Reversible pH‐ and Photocontrollable Carbohydrate‐Based Surfactants

“…Model fits to the experimental SANS data (shown as solid lines in Figure 2) indicate that the anionic glucuronic acid-based surfactants GlcU-Azo (7) and GlcU-Tz-Azo (8) exhibit relatively small, oblate spheroidal and squat cylindrical micelles, respectively. As expected from previous studies of structure-function relationships [24] for uronic acid-derived surfactants, [20] the anionic form produces significantly smaller micelles than the protonated, non-ionic variants. Detailed fitting parameters from SANS measurements (Table S1, Supporting Information) provide additional information that helps to rationalize the aggregate morphologies for these amphiphiles.…”

“…In addition to neutral carbohydrates, a d-glucuronic acid (GlcU) was also targeted, since it would give rise to pH-responsive materials and could be readily synthesized by oxidation of the 6-OH alcohol of Glc-based surfactants. [20,21] Having acquired surfactants 1-8, we next set about examining the effect of the size, polarity and stereochemical configuration of the carbohydrate head-group, the rigid triazole linker, and the pH-dependent ionization of the GlcU head-group on the surface and aggregation properties. This was achieved using tensiometry, small-angle neutron scattering (SANS) and UV-visible spectroscopy.…”

Conversion of Carbohydrates Under Microwave Heating

“…Microwave has progressively emerged as an attractive heating source allowing energy savings and improved yields and selectivity. Recent developments in the field have been reviewed by Richel in 2011(Richel, 2011b. They include the use of heterogeneous catalysts in various media (organic solvents, water, ionic liquids or biphasic systems).…”

“…These monosubstituted glucuronolactones are not easily attainable using other conventional protocols and required multi-step synthesis. These original products find special relevance in the field of surface-active agents and emulsifiers (Razafindralambo, 2011).…”

“…Several parameters are found to influence the (stereoselective) formation of glycosyl linkages such as solvent, catalyst, additives, nature of both leaving groups and surrounding protecting groups. In particular, the formation of alkyl-and aryl-glycosides has find special attention in both academic and industrial worlds, due to the importance of these molecules as non-toxic and biodegradable surfactants, liquid crystals, and pharmaceutical agents (Razafindralambo 2011(Razafindralambo & 2012. Under microwave conditions, the introduction of alkyl substituents on the OH1 position is the most extensively developed, notably for the large-scale production of surface-active agents, and relies on the reaction of an alkyl alcohol with unprotected saccharide (Fischertype glycosylation) or with completely O-protected carbohydrate compounds (Helferichtype glycosylation).…”