Photochromic Solid Materials Based on Poly(decylviologen) Complexed with Alginate and Poly(sodium 4-styrenesulfonate)

Abstract

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.

Ionic Nanocomplexes of Hyaluronic Acid and Polyarginine to Form Solid Materials: A Green Methodology to Obtain Sponges with Biomedical Potential

“…Aqueous ionic nanocomplexes (INC) are structures formed in water by the association of high-molecular-weight molecules, such as polymers, with complementary charged low- or high-molecular-weight polyions, such as ionic cross-linkers (tripolyphosphate), dyes, oligomers, or polyelectrolytes [1,2,3,4,5,6,7,8,9,10]. INC can be formed following the very simple procedure of mixing aqueous solutions of oppositely charged components at room temperature.…”

“…In addition, the procedure is low cost, both economically and environmentally, which facilitates the adoption of INC at the industrial level. The main nanostructures that are obtained as INC are nanogels, massive nanoprecipitates, or swollen aggregates [8,11,12,13,14]. Opposite to gelation (where only the larger component is able to be allocated in the surface, determining the surfacial charge), ionic complexation between two polymeric species allows the net charge of the INC to be selected by simply varying the ratio between oppositely charged species, thus allowing the production of formulations with tuneable electrostatic characteristics [13].…”

“…Depending on the binding forces between the ionic reactants and the ratio between their corresponding apparent charge concentrations, colloidal suspensions of the INC can be achieved just by tuning the absolute amount of matter in the mixture. At high electroneutralization regimes, the system tends to produce macroprecipitates, so the colloidal suspensions need to be highly diluted to keep colloidal stability [8]. However, an excess of one of the components allows stability of the colloidal suspension at a more concentrated regime, producing colloidal particles charged enough to ensure stability through electrostatic repulsions.…”

“…However, an excess of one of the components allows stability of the colloidal suspension at a more concentrated regime, producing colloidal particles charged enough to ensure stability through electrostatic repulsions. Although the molecule to add in excess is normally of high molecular weight [8], examples are also found in which a low-molecular-weight component is added in excess, which, instead of diffusing out of the colloidal particles, keeps associated to them, determining the net charge of the particle and thus being responsible for the mixture stability [4].…”

“…Interestingly, upon removal of water from colloidal suspensions of INC, a solid material may arise [7,8]. In this sense, freeze-drying appears as a suitable technique to obtain micro- and nanoporous materials from suspensions of INC.…”