Hierarchical assembly of pH-responsive surfactant–cyclodextrin complexes

Abstract

In this work, the inclusion complexes of alkyl ethoxy carboxylates with α-cyclodextrin and β-cyclodextrin were investigated. The thermodynamics of the complexation process was probed by isothermal titration calorimetry (ITC) and...

Thermoresponsive behavior of cyclodextrin inclusion complexes with weakly anionic alkyl ethoxy carboxylates

“…In particular, the experiments evidenced the importance of the presence of charges to induce the crystallization of the layered inclusion complexes. In our previous investigation on the effect of surfactant charge density on the structure of the supramolecular assemblies, 16 we pointed out that a certain degree of ionization of the surfactant is required for the formation of ordered aggregates. We rationalized the finding in terms of electrostatic repulsion between the layers, which promotes the transition from a disordered multilayered structure to a more ordered one.…”

“…Pentaoxyethylene dodecyl ether carboxylic acid (C 12 E 5 Ac) and decaoxyethylene dodecyl ether carboxylic acid (C 12 E 10 Ac) are technical surfactants provided by KAO chemicals under the commercial names AKYPO RLM45CA (444 g mol −1 , 92% purity) and AKYPO RLM100 (686 g mol −1 , 90% purity), with 7.3 and 9.8 wt% water content, respectively. 16 The hydrophobic part of the surfactants is a mixture of C 12 , C 14 and C 16 in approx. Ratio 2 : 1 : 0.25.…”

“…The complex interplay of interactions governing the supramolecular assembly of surfactant-CD inclusion complexes is a widely exploited strategy to design responsive materials relying on environmental conditions. For instance, inclusion complexes which respond to light, [13][14][15] pH, 16 redox potential, [17][18][19] solvent exchanges 20,21 or temperature 22,23 have been prepared for the design of stimuli-responsive assembled materials. 12,24 Because of the large effect on the solubility, molecular vibrational states and strength of interactions, particularly hydrogen bonds, temperature is one of the most common and efficient stimuli employed in controlling molecular conformation and self-assembly processes.…”

“…30,31 In a recent study, we described the properties of inclusion complex formed by cyclodextrins with weakly anionic alkyl ether carboxylic acids (AEC). 16 In particular, the possibility offered by the weakly anionic head group allowed us to probe the effect of surfactant charge density on the formation of inclusion complexes through the pH of the solution without any change in the chemistry of the system. Very interestingly, multilayered aggregates are formed irrespective of the surfactant charge.…”

“…The complex interplay of interactions governing the supramolecular assembly of surfactant–CD inclusion complexes is a widely exploited strategy to design responsive materials relying on environmental conditions. For instance, inclusion complexes which respond to light, 13–15 pH, 16 redox potential, 17–19 solvent exchanges 20,21 or temperature 22,23 have been prepared for the design of stimuli-responsive assembled materials. 12,24…”