Carlos Sánchez-Somolinos

Engineering of Complex Order and the Macroscopic Deformation of Liquid Crystal Polymer Networks

Rise or fall: Complex-structured freestanding polymer films with molecular order in three dimensions were prepared through photoalignment of polymerizable liquid crystals. The resulting films deform into cone and saddle shapes upon heating.

Light induced molecular release from vesicles based on amphiphilic linear-dendritic block copolymers

We report on the synthesis and characterization of new amphiphilic linear-dendritic block copolymers (LDBCs) as well as their self-assembly in water to form polymeric vesicles. We have also investigated the encapsulation of both hydrophilic and hydrophobic fluorescent probes by these stimuli-responsive polymeric vesicles and the use of light as an external stimulus to trigger the release of the probes. The LDBCs are composed of a 2000 g mol−1 poly(ethylene glycol) (PEG) linear segment linked to a fourth generation 2,2-di(hydroxymethyl)propionic acid (bis-MPA) based dendron with 4-isobutyloxyazobenzene units at the periphery. By tuning the chemical structure of the azobenzene moieties, a specific LDBC has been identified that forms stable vesicles in water as it is clearly revealed by TEM and Cryo-TEM images. Encapsulation of both hydrophobic and hydrophilic molecules by these vesicular self-assemblies has been investigated by fluorescence analysis as well as the release of the loaded probes triggered by low intensity UV illumination, which is related to trans-to-cis isomerisation of the azobenzene moieties. Thus, the potential of these photo-responsive vesicles as light-responsive nanocarriers is demonstrated.

A polymer network prepared by the thiol-yne photocrosslinking of a liquid crystalline dendrimer

A polymer network is prepared by the thiol-yne photopolymerization of multifunctional dendrimer with a tetrathiol crosslinker. The network obtained shows a liquid crystalline phase at room temperature, which has been characterized by optical microscopy, differential scanning calorimetry, and X-ray diffraction. Photoinduced deformation of uniaxially aligned free-standing films of the photocrosslinked material has been demonstrated.

Angular deficits in flat space: remotely controllable apertures in nematic solid sheets

Recent attention has been given to the realization of angular deficits and surpluses in the local ground-state geometry of thin sheets of nematic solids as out-of-plane deformations. Such systems exhibit conical or anti-conical curvature sites, or possibly arrays of such polyhedral corners, in order to satisfy the materials spontaneous strain-generated metric requirements. Here, we turn the angular deficit requirement on its head, and show theoretically and experimentally that by appropriately altering the topology of the initially flat sheet—for example, by cutting it in carefully chosen regions—the same angular deficits and surpluses may manifest simply in-plane by changing the geometry of the cut region. Such a mechanism offers a route to apertures or arrays of apertures that may be reversibly opened and closed by applying spontaneous strain with heat, light or chemical potential.

Anisotropic light emissions in luminescent solar concentrators-isotropic systems

In this paper we develop a model to describe the emission profile from randomly oriented dichroic dye molecules in a luminescent solar concentrator (LSC) waveguide as a function of incoming light direction. The resulting emission is non-isotropic, in contradiction to what is used in almost all previous simulations on the performance of LSCs, and helps explain the large surface losses measured in these devices. To achieve more precise LSC performance simulations we suggest that the dichroic nature of the dyes must be included in the future modeling efforts.

3D Orientational Control in Self‐Assembled Thin Films with Sub‐5 nm Features by Light

While self-assembled molecular building blocks could lead to many next-generation functional organic nanomaterials, control over the thin-film morphologies to yield monolithic sub-5 nm patterns with 3D orientational control at macroscopic length scales remains a grand challenge. A series of photoresponsive hybrid oligo(dimethylsiloxane) liquid crystals that form periodic cylindrical nanostructures with periodicities between 3.8 and 5.1 nm is studied. The liquid crystals can be aligned in-plane by exposure to actinic linearly polarized light and out-of-plane by exposure to actinic unpolarized light. The photoalignment is most efficient when performed just under the clearing point of the liquid crystal, at which the cylindrical nanostructures are reoriented within minutes. These results allow the generation of highly ordered sub-5 nm patterns in thin films at macroscopic length scales, with control over the orientation in a noncontact fashion.

Holographic storage and multiplexing in azopolyester blends using low energy pulses down to 2 ms

Three different blends containing side-chain azobenzene polyesters and poly(methyl methacrylate) homopolymers have been prepared for recording volume holographic polarization gratings using 488 nm light pulses. The final azo content in the blends has been decreased down to 0.2 wt. %, and their morphologies have been investigated by transmission electron microscopy. Stable and rewritable polarization gratings have been recorded, and 20 gratings have been multiplexed using 2 ms pulses of low energy (4 mJ/cm2). The equilibrium values of the diffraction efficiency were higher than 5 × 10−5.

Smart polymers for optical data storage

Abstract: Smart polymers based on photoresponsive azobenzene moieties have been extensively explored as potential materials for high capacity optical storage. This chapter reviews different strategies to incorporate azobenzenes into polymeric structures as well as their photoresponse properties. The potential of this type of materials as volume holographic media is summarized with special emphasis on block copolymers and blends. Although side-chain azopolymers has been the most investigated, new macromolecular architectures have been recently proposed and will be briefly presented.

Engineered complex molecular order in liquid crystals towards unusual optics and responsive mechanics

Defects in liquid crystals have been studied over decades to disclose information and knowledge on the structure of LC phases. More recently, LC defects have been identified as a tool to implement new physical functions useful in optical films for polarization conversion or mechanical actuators able to adopt novel exotic shapes. In the present paper we describe a general methodology to engineer different defect patterns by combining the use of linear photopolymerizable polymers and liquid crystals.

Anisotropic light emissions in a luminescent solar concentrator

The emission of randomly oriented dichroic dyes illuminated with a collimated beam results in a non-isotropic emission distribution. We demonstrate this can have significant impact on the surface losses and edge output of luminescent solar concentrators.