Supramolecular gel formation and self-correction induced by aggregation-driven conformational changes

The formation of self-assembled fibrillar networks by low molecular weight peptidomimetics containing a Pro-Val moiety is reported; insight into the aggregation mechanism is provided revealing that it is associated to an unfolding process and that a fibrillar network formed under kinetic control can self-correct into a thermodynamically stable on

A supramolecular hydrogel as a reusable heterogeneous catalyst for the direct aldol reaction

An L-proline based supramolecular hydrogel is used as an efficient heterogeneous organocatalyst for the direct aldol reaction with high stereoselectivity (up to 90% ee) and recyclability (up to 3 runs). The reversible nature of this self-assembled supramolecular system allows for easy recovery and regeneration of the catalys

Remarkable increase in basicity associated with supramolecular gelation

L-Proline derivatives which are able to form supramolecular gels show an amazing basicity increase in the aggregated (gel) state as compared to solution. As a result they behave as enantioselective catalysts for the aldol reaction in solution but produce a base-catalyzed aldol racemisation in the gel stat

Structure and adhesion properties before and after hydrolytic ageing of polyurethane urea adhesives made with mixtures of waterborne polyurethane dispersions

Several waterborne polyurethane urea dispersions (WPUUs) were prepared by mixing different amounts of two waterborne polyurethane urea dispersions made with polyester (WPUU-Polyester) and polycarbonate diol (WPUU-PCD). Their crystallinity, thermal, rheological, viscoelastic and adhesion properties depended on the segmented structure and degree of phase separation which were determined by the different content of the parent dispersions. The PUU films made with WPUU-Polyester+WPUU-PCD mixtures containing more than 50 wt% of WPUU-PCD showed higher hard segments content and lower degree of phase separation, and the addition of 25 wt% of WPUU-Polyester imparted crystallinity to the polyurethane urea due to the interactions between the carbonate groups in the soft segments. The differences in the degree of phase separation and crystallinity of the PUU films made with WPUU-Polyester+WPUU-PCD mixtures were evidenced by the increase in the glass transition temperature associated to the alpha relaxation of the soft segments, and the higher modulus at the cross-over between the storage and loss moduli. Excellent adhesion was obtained in plasticized PVC/WPUU/plasticized PVC joints, and a cohesive failure of PVC was always obtained, irrespective of the composition of WPUU-Polyester+WPUU-PCD mixtures. Furthermore, the adhesion of surface-chlorinated vulcanized styrene-butadiene (SBR) rubber/WPUU+5 wt% hardener/roughened leather joints were high and similar in all joints and a dominant cohesive failure in the rubber substrate was produced. The accelerated ageing by immersion in water at 70 °C during different times showed that the polyurethane urea film and the surface-chlorinated vulcanized SBR rubber/WPUU+5 wt% hardener/roughened leather joint made with WPUU-PCD dispersion were not affected, but noticeable hydrolytic degradation of the ester units in the soft segments was produced in PUU-Polyester and, to a less extent, in PUU-50Polyester/50PCD films and adhesive joints.Financial support by UBE CHEMICAL EUROPE (Grant no. UBE1-15ID) is acknowledged

HRMAS 1H NMR as a tool for the study of supramolecular gels

HRMAS 1H NMR is reported for the first time as a useful technique to gain insight into the dynamic properties of aggregates present in supramolecular gels. The study of several low molecular weight gelators with this technique in toluene and acetonitrile is described

Selective and highly efficient dye scavenging by a pH-responsive molecular hydrogelator

A structurally simple low molecular weight hydrogelator derived from isophthalic acid forms robust pH-responsive hydrogels capable of highly efficient and selective dye adsorption

Geles supramoleculares: estudios fundamentales y aplicación en organocatálisis

En la presente tesis se describen los resultados del estudio estructural de gelantes supramoleculares basados en moléculas de bajo peso molecular. Además, se describen sus propiedades catalí­ticas en diferentes reacciones

Switchable Perfomance of an l-Proline-Derived Basic Catalyst Controlled by Supramolecular Gelation

An l-proline-derived low molecular weight gelator forms gels in nitromethane and nitroethane and acts as a basic catalyst for the Henry nitroaldol reaction of these solvents with 4-nitrobenzaldehyde and 4-chlorobenzaldehyde. The reported catalyst is efficient only upon aggregation into self-assembled fibrillar networks. The formation of the gels is associated to a basicity boost of the l-proline residues. Gel dissociation blocks the catalytic efficiency for the nitroaldol reaction but enhances a reaction pathway leading to alkenes. Because of the reversible nature of supramolecular gels, subtle temperature changes allow for a reversible sol−gel transition associated to an activation of the catalyst. The catalytic gel from nitroethane is significantly more active than the one from nitromethane probably because of its different structure as revealed by X-ray diffraction and thermal stability studies. The results shown indicate that in solution the l-proline moiety catalyzes the reaction of nitroalkanes with aldehydes via iminium intermediates while efficient nitroaldol reactions are promoted in the gel phase through an ionic pair type mechanism. The fact that upon aggregation the amino acid-based molecule used as gelator plays both a structural (gel formation) and catalytic role is interesting for the point of view of life origin studies

Supramolecular gels as active media for organic reactions and catalysis

Supramolecular gels have attracted an enormous amount of interest from scientists in the last decade because of their potential applications proposed up to now in fields of great social impact like biomedicine or materials science. However, their potential in organic transformations and catalysis has been only scarcely explored. In this review we describe the state-of-the-art as well as the contribution of our group to the field of reactive and catalytic supramolecular gels