María José Clemente

Cristian Lavieja, María José Clemente, Luis Oriol, José Ignacio Peña
The laser marking of acrylonitrile–butadiene–styrene filled with carbon black was studied using either an infrared or ultraviolet laser. The influence of the amount of additive on the final contrast of marks was studied for the two differentiated wavelengths. Both lasers exhibit different marking mechanisms, according to color properties, topography, and spectroscopic analysis of the marks. The infrared laser induced a thermally foaming effect and the ultraviolet laser seemed to induce a photochemical effect with the polymer matrix and removal of carbon black. The highest contrast was achieved with the infrared laser and contents of 0.1% carbon black.

María José Clemente, Cristian Lavieja, José Ignacio Peña, Luis Oriol
Marking of titanium dioxide-containing ABS polymeric samples was accomplished using a UV laser that induces a white to grey color change with only a minor alteration of the plastic material. The characterization of this marking process has been conducted by different techniques to determine the quality of the UV-laser marking and to gain an insight into how the plastic material is affected by laser irradiation. Surface characterization was performed and tests were conducted to evaluate the potential applications of this UV-marking process

María José Clemente, Rosa María Tejedor, Pilar Romero, Juliette Fitremann, Luis Oriol
n the context of exploring new materials based on low molecular weight amphiphiles, we prepared a new series of photoresponsive gelators with azobenzene as photosensitive unit, D-maltose or poly(ethylene glycol) (PEG) as polar head, and L-phenylalanine as linker. The gelation properties of the final amphiphiles and the intermediate molecules have been studied in different solvents. Organogels are obtained for all of them, except for compound with PEG16polar head. Gelation in polar solvents, as DMSO, was achieved. The morphology of supramolecular structures was characterized by electronic microscopy. The chiro-optical properties of gels, due to the supramolecular chirality imposed by the molecular chirality, were also studied. The modifications under irradiation have been monitored by UV-visible spectroscopy and electronic circular dichroism (ECD). Two of the obtained materials showed a gel–sol transition by irradiation with UV light and further thermal cis–trans isomerization to gel state at room temperature.

Nélida Gimeno, María José Clemente, Patricia Forcén, José Luis Serrano and Maria Blanca Ros
Two series of bent-shaped molecules have been synthesized and their supramolecular self-organization at variable temperature has been studied. The majority of these bent-compounds form liquid crystalline phases and the mesomorphic behaviour of them has been fully characterized by polarised optical microscopy, calorimetry, X-ray diffraction and dielectric techniques. A series of bis-4-n-tetradecyloxybenzoyloxybenzoates derived from naphthalene, resulting in a change of the bending angle, have proved that when these cores bend around 120 degrees, a polar lamellar packing (SmC(a)P(A)) can be induced, whereas when the angle was around 60 degrees, an orthogonal lamellar arrangement (SmA) that responded to an electric field, are found to occur. Liquid-crystal order can also be achieved over a significant range of temperatures by using appropriate bis-4,4'-disubstituted phenylene derivatives (-Ar-X-Ar-). Groups such as -CO-, SO- and -CH(2)- connecting the aromatic rings induce the SmC(a)P(A) phase while a sulfide group (-S-) leads to columnar order. Further, the formation of isotropic textures as chiral conglomerates or a field-induced phase transition have also been observed as unusual properties of the self-organizations of these compounds.

María J. Clemente, Rosa M. Tejedor, Pilar Romero, Juliette Fitremann and Luis Oriol
Three light-sensitive amphiphiles, based on azobenzene, have been synthesized as supramolecular gelators. A hydrophobic chain with an azobenzene group incorporated at different positions was click coupled to a maltose polar head by a copper(I)-catalysed azide–alkyne [3 + 2] cycloaddition. The liquid crystalline and gel properties of these azo-amphiphilic materials have been studied. Two of these azo-gelators containing maltose give rise to stable gels in water or in a mixture of water and DMSO at room temperature. The chiral supramolecular assemblies of these gelators have been characterised by NMR, electron microscopy and circular dichroism (CD). The light-response of azo-amphiphiles in supramolecular gels has been studied. Also azo-gels, which contained mixtures of the azo-amphiphilic compounds and a similar structural hydrogelator, have been investigated.

María J. Clemente, Pilar Romero, José L. Serrano, Juliette Fitremann, and Luis Oriol
Supramolecular hydrogelators based on amphiphilic glycolipids have been prepared by clicking different sugar polar heads to a hydrophobic linear chain by copper(I)-catalyzed azide-alkyne [3+2] cycloaddition. The influence of the sugar polar head on the gelation properties in water has been studied and the liquid crystalline properties of the amphiphilic materials have also been characterized. Stable hydrogels at room temperature have been obtained and the fibrillar supramolecular structures formed by the self-assembly have been studied by different microscopic techniques on the dried gel (xerogel) and hydrated conditions in order to characterize the micro and nano-structures. Self-assembly gives rise to supramolecular ribbons with a torsion that is related to a chiral supramolecular arrangement of amphiphiles. The formation of an opposite helical arrangement of the ribbons has been found to depend on the sugar polar head. This fact was confirmed by circular dichroism (CD).

María J. Clemente, Juliette Fitremann, Monique Mauzac, José L. Serrano, and Luis Oriol
Low molecular mass amphiphilic glycolipids have been prepared by linking a maltose polar head and a hydrophobic linear chain either by amidation or copper(I)-catalyzed azide-alkyne [3+2] cycloaddition. The liquid crystalline properties of these amphiphilic materials have been characterized. The influence of the chemical structure of these glycolipids on the gelation properties in water has also been studied. Glycolipids obtained by the click coupling of the two components give rise to stable hydrogels at room temperature. The fibrillar structure of supramolecular hydrogels obtained by the self-assembly of these gelators have been characterized by electron microscopy. Fibers showed some torsion, which could be related with a chiral supramolecular arrangement of amphiphiles, as confirmed by circular dichroism (CD). The sol-gel transition temperature was also determined by DSC and NMR.