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•The incorporation of azobenzene moieties into a bridged silsesquioxane led a material with light-induced healing ability.•The photoisomerization of the azobenzene increases the ...mobility and allows the material to flow in the damaged area.•A complete recovery of the damage was observed after only 30 s of UV irradiation.
Intrinsic healable polymers are materials capable of repairing itself through its chemical nature, in order to improve stability and durability and to restore the lost functionalities or properties.
In this study, azobenzene (AZO) moieties were incorporated into a previously reported bridged silsesquioxane based on the reaction of isocyanatepropyltriethoxysilane (IPTS) with bisphenol A (BPA), by replacing a small fraction of BPA by a bisazophenol (4,4′-dihydroxyazobenzene, AZOH). The incorporation of these AZO moieties led to a material with UV light-induced healing abilities. The underlying healing mechanism is attributed to the intra-molecular conformational changes of the azo-chromophores that are induced by the trans to cis photoisomerization of the azobenzene. These changes temporary increased its mobility and allowed the material to flow in the damaged area, followed by a process of restoring the physical hydrogen bonds. This process was monitored following the viscoelastic properties during successive cycles of turning ON and OFF the UV irradiation. Remarkably, the resultant healed material has not significant observed mechanical differences with the original one.
Dynamics of water in the hydration shells of proteins in the no man's land temperature region is a currently debated topic. Previously 1, we proposed the use of lysine aqueous solutions as a model ...system to study the dynamics of water in a genuine biological solution at any temperature. We found that lysine can be completely dissolved in water without crystallization, making it possible to access the dynamics of amorphous water in a biological environment. By contrast, in this work we studied proline aqueous solutions, which partially crystallize upon cooling. We found similar results in the two systems: the presence of three water relaxations where the two slowest processes (processes 2 and 3) resemble the behavior of normal glasses. Moreover, we observed the change of a cooperative (α-like) water relaxation to a more local β-like water relaxation with decreasing temperature whereas a faster water relaxation process is also present. In addition, we studied amorphous samples in a restricted temperature interval, and also found three different dynamics (processes 3, 4 and 5). As in the case of the hydrated protein powders, the two faster dynamics (3 and 4) are coupled or slaved.
•Water dynamics at supercooled temperatures in a biological solution of amino acids•Below Tg, three dynamical processes as due to the relaxation of water molecules•Above Tg, dynamics of water and proline are extremely coupled as observed in proteins.
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•Polymers containing azobenzene units and alkyl side chains were synthesized.•Azobenzene groups contribute to light response, alkyl chains form physical crosslinks.•Domains of alkyl ...chains are an alternative for optimizing photoinduced anisotropy.
The influence of physical crosslinks on the photoinduced anisotropy in epoxy linear polymers with azobenzene and alkyl side groups was studied. Two series of linear epoxy-based polymers were synthesized by reaction between diglycidyl ether of bisphenol A (DGEBA), Disperse Orange-3 (DO3), and dodecylamine (DA). Two strategies of synthesis were employed in order to analyse the optical behavior of the polymers with their architecture. As a result, a polymer with randomly distributed amine groups (one-step polymerization), and another with both amines forming blocks (two-step polymerization) were synthesized. The experimental evidence derived from different techniques confirmed that isothermal annealing at several temperatures produced association of DA alkyl chains. The rate of this physical gelation process could be varied with the annealing temperature and the polymer architecture. The association strength of the alkyl chains was higher for the block polymer. The rate of the physical gelation process increased as the annealing temperature did. UV–visible spectroscopy showed interactions between the azo groups and aggregated alkyl chains only for the polymer prepared in two steps. For the same chromophore content, block polymers yielded higher birefringence than random ones did. The increment in the information stored (remnant birefringence) for annealed samples was considerable only for block polymers. This study demonstrates the importance of the polymer architecture and the presence of domains of alkyl chains on its potential photo responsiveness.
A comparative study of the influence of the competitive reactions that can take place in epoxy–isocyanate based azo systems over optical behavior was developed.
Diverse disperse red 19 (DR 19) azo ...urethane oligomers (PUs) were synthesized and characterized using size exclusion chromatography (SEC), Fourier transform infrared (FTIR), and UV–visible spectroscopy. Based on these urethane oligomers, epoxy-PU networks having isocyanurate and oxazolidone rings in their structures were prepared in different isocyanate/epoxy stoichiometric ratios, r=eq. NCO/eq. epoxy (0.5, 1, and 2).
Photoinduced anisotropy (Δn), remnant birefringence (RB) and dichroism were measured for the resulting polymers and evaluated as function of their Tgs and chemical structures. Final materials exhibited very high values of Δn and RB being promised materials for using in optical storage information devices.
•Two different solvents (toluene and chloroform) were used to prepare Langmuir films of PS-b-P4VP(DO13) copolymers.•For toluene, which is a selective solvent for one of the blocks of the copolymer, a ...higher film-forming ability was observed.•A pronounced effect on the optical storage capability of LS and LB films was observed.•Higher photoinduced birefringence for the films prepared with toluene was developed.•The enhanced properties in toluene are ascribed to the formation of micelles.
Langmuir films of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with an azo dye, 4-4-(phenylazo)-1-naphthylazophenol (Disperse Orange 13, DO13), hydrogen-bonded to the pyridine group of P4VP blocks were investigated. The surface pressure isotherms were considerably different for the copolymer dissolved in a nonselective (chloroform) and selective (toluene) solvents. The Langmuir–Blodgett (LB) and Langmuir–Schaefer (LS) films produced with PS-b-P4VP(DO13) copolymers displayed higher optically induced birefringence than the cast films owing to their nanostructured nature. The photoinduced birefringence properties were particularly enhanced when toluene was used owing to the confinement of azo chromophores in micelles consisting of a P4VP core and a PS corona.
The prognostic role of cerebrospinal fluid biomarkers in patients with incidental radiological findings of white matter abnormalities or radiologically isolated syndromes (RIS) has yet to be defined. ...Matute-Blanch et al. report that RIS patients with oligoclonal bands and high neurofilament light chain levels have increased risk of clinical conversion.
Abstract
The prognostic role of cerebrospinal fluid molecular biomarkers determined in early pathogenic stages of multiple sclerosis has yet to be defined. In the present study, we aimed to investigate the prognostic value of chitinase 3 like 1 (CHI3L1), neurofilament light chain, and oligoclonal bands for conversion to clinically isolated syndrome and to multiple sclerosis in 75 patients with radiologically isolated syndrome. Cerebrospinal fluid levels of CHI3L1 and neurofilament light chain were measured by enzyme-linked immunosorbent assay. Uni- and multivariable Cox regression models including as covariates age at diagnosis of radiologically isolated syndrome, number of brain lesions, sex and treatment were used to investigate associations between cerebrospinal fluid CHI3L1 and neurofilament light chain levels and time to conversion to clinically isolated syndrome and multiple sclerosis. Neurofilament light chain levels and oligoclonal bands were independent risk factors for the development of clinically isolated syndrome (hazard ratio = 1.02, P = 0.019, and hazard ratio = 14.7, P = 0.012, respectively) and multiple sclerosis (hazard ratio = 1.03, P = 0.003, and hazard ratio = 8.9, P = 0.046, respectively). The best cut-off to classify cerebrospinal fluid neurofilament light chain levels into high and low was 619 ng/l, and high neurofilament light chain levels were associated with a trend to shorter time to clinically isolated syndrome (P = 0.079) and significant shorter time to multiple sclerosis (P = 0.017). Similarly, patients with radiologically isolated syndrome presenting positive oligoclonal bands converted faster to clinically isolated syndrome and multiple sclerosis (P = 0.005 and P = 0.008, respectively). The effects of high neurofilament light chain levels shortening time to clinically isolated syndrome and multiple sclerosis were more pronounced in radiologically isolated syndrome patients with ≥37 years compared to younger patients. Cerebrospinal fluid CHI3L1 levels did not influence conversion to clinically isolated syndrome and multiple sclerosis in radiologically isolated syndrome patients. Overall, these findings suggest that cerebrospinal neurofilament light chain levels and oligoclonal bands are independent predictors of clinical conversion in patients with radiologically isolated syndrome. The association with a faster development of multiple sclerosis reinforces the importance of cerebrospinal fluid analysis in patients with radiologically isolated syndrome.
