Valdivia, Chile
Valdivia, Chile

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Sanhueza L.,Institute Ciencias Quimicas | Castro J.,Austral University of Chile | Urzua E.,Institute Ciencias Quimicas | Barrientos L.,Metropolitan University of Educational Sciences | And 8 more authors.
Journal of Physical Chemistry B | Year: 2015

Photochromic solid materials based on the cationic polymer poly(decylviologen) are reported. The solids were obtained by freeze-drying colloidal suspensions of nanocomplexes obtained by mixing aqueous solutions of the polycation with different solutions of polyanions such as poly(sodium 4-styrenesulfonate) or sodium alginate, at a cationic/anionic polymeric charge ratio of 0.7. The photochromic responses of the solid materials fabricated with alginate as complementary charged polyelectrolyte of the cationic polyviologen are faster than those of the solid materials fabricated with poly(sodium 4-styrenesulfonate), achieving coloration kinetics in the order of minutes, and discoloration kinetics in the order of hours for the former. Aromatic-aromatic interactions between the latter polyanion and the polyviologen may stabilize the dicationic form of the viologen derivative, increasing the necessary energy to undergo photoreduction, thus decreasing the reduction kinetics. © 2015 American Chemical Society.

Iturriaga L.B.,Institute Ciencias Quimicas | Lopez de Mishima B.,Institute Ciencias Quimicas | Anon M.C.,National University of La Plata
LWT - Food Science and Technology | Year: 2010

Rate of the retrogradation process of five new argentine genotypes rice starches with different amylose contents and gelatinization temperatures during storage at 4.5 ± 0.5 °C was studied using differential scanning calorimetry (DSC). Significant differences were not found among transition temperatures, i.e., T0 (onset temperature), Tp (peak temperature) and Tc (conclusion temperature), of non-waxy genotypes when studied using DSC. An increased retrogradation enthalpy (ΔH, mJ/mg) with the storage time occurred with all non-waxy samples. The waxy genotype, W4109, did not show a retrogradation peak for the period under study. Genotypes with high total amylose content (TAM) retrograded more than those with lower content. The kinetic parameters "k" and "n" were evaluated using the Avrami model appearing to be related to the water-soluble amylose (SAM) content. Relationship between the retrogradation degree (%R) and the water-insoluble amylose (IAM) content was found. Gelatinization temperature of the starch (TG) seemed to affect the retrogradation rate. © 2009 Elsevier Ltd. All rights reserved.

Orellana S.L.,Institute Ciencias Quimicas | Giacaman A.,Institute Anatomia | Pavicic F.,Institute Anatomia | Vidal A.,Institute Anatomia | And 2 more authors.
Journal of Biomedical Materials Research - Part A | Year: 2016

The study of biomaterials by electrical charge scaling to explore the role of net charge on biocompatibility and suitability for tissue regeneration has been limited as has the search for products that could improve this first-rate variable. In the present study, we prepared sponges composed of chitosan/alginate (CS/ALG) with or without hyaluronic acid (HA) by mixing polymer stock solutions of different net electric charge ratios (n+/n-), and then lyophilizing them to obtain porous materials. The electric charge ratios n+/n- studied were 0.3, 0.8, 1.0, and 2.5 for CS/ALG and 0.3, 1.0, 1.9, and 3.7 for CS/ALG/HA sponges. Under these conditions a role for net electric charge balance over sponge microstructure rearrangement, protection to dissolution, cellular proliferation, and cell-cell interactions was apparent, effects that were enhanced by copolymer modification with HA. Mass balance, electric charge, and specific products that influence both such as HA, have a potential in biomaterials for wound healing. © 2016 Wiley Periodicals, Inc.

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