Synthesis and characterization of inorganic–organic polymer microgels for catalytic reduction of 4‐nitroaniline in aqueous medium

Abstract

Poly(N‐isopropylacrylamide‐co‐acrylic acid) [p(NiPA‐co‐AAc)] microgel particles were synthesized by free radical precipitation polymerization in aqueous medium. Silver nanoparticles (Ag NPs) were fabricated inside the microgels by in situ reduction method. UV–visible, Fourier transform infrared (FTIR), and dynamic light scattering techniques were used for characterization of pure microgels. The Ag‐p(NiPA‐co‐AAc) hybrid microgels were characterized by UV–visible, FTIR, X‐ray diffraction, and transmission electron microscopy. The hybrid microgel system was used as a catalyst for reduction of 4‐nitroaniline (4‐NA) in aqueous medium. The kinetics of the catalytic reduction of 4‐NA under various conditions of concentration of hybrid microgels, sodium borohydride (NaBH4), and 4‐NA was monitored by UV–visible spectrophotometry. It was found that the value of apparent rate constant (kapp) increases with increase of concentration of NaBH4 and catalyst dosage while it remains constant at various concentrations of 4‐NA. The kinetic data were used to elaborate the conversion of 4‐NA into p‐phenylenediamine on the basis of electron relaying effect of Ag NPs present inside the microgels. POLYM. COMPOS., 39:645–653, 2018. © 2016 Society of Plastics Engineers

Silver Nanoparticles Engineered Polystyrene‐Poly(N‐isopropylmethacrylamide‐acrylic acid) Core Shell Hybrid Polymer Microgels for Catalytic Reduction of Congo Red

“…Results showed that value of k app was increased from 0.40 × 10 −2 to 0.78 × 10 −2 s −1 with the increase of catalyst dose from 0.146 to 0.390 mg mL −1 , respectively, as given in Table 1 . Actually, high amount of catalyst provides large surface area for the adsorption of reactants and as a result, the value of k app for CR reduction was increased . Tang and coworkers evaluated the effect of catalyst dose on the value of k app for the reduction of methylene blue (MB) using Ag NPs impregnated poly(N‐isopropylacrylamide‐co‐2‐(dimethylamino) ethyl methacrylate) [p(NIpmam‐EMa)] composite microgels catalyst using NaBH 4 reducing agent .…”

“…Although, different metal nanoparticle (MNp) catalysts have been reported for CR reduction, naked MNps possess high surface energy due to which they coagulate rapidly and lose their catalytic activity . Various stabilizing systems like micelles, dendrimers, and microgels have been reported to prevent the aggregation and coagulation of MNps as well as to prolong their life span. Among them, smart polymer microgels are superior supporting materials due to their responsive behavior, tunable particle size, and easy recoverability by centrifugation and ultrafiltration .…”

“…Various stabilizing systems like micelles, dendrimers, and microgels have been reported to prevent the aggregation and coagulation of MNps as well as to prolong their life span. Among them, smart polymer microgels are superior supporting materials due to their responsive behavior, tunable particle size, and easy recoverability by centrifugation and ultrafiltration . Porous structure of hybrid microgel catalysts supports the access of reactants to MNps surface.…”

Ag‐nanoparticle embedded p(AA) hydrogel as an efficient green heterogeneous Nano‐catalyst for oxidation and reduction of organic compounds

“…[41] The value of ΔS # was calculated from the intercept of plot of ln(k app /T) vs. 1/T and was found as −196.17 J mol −1 K −1 .The negative value of ΔS # shows that the reduction of 4-NP is entropically unfavorable which can be made favorable by adding catalyst. [40] The value of ΔG # was calculated from the following equation, [7] and it needs an input energy to proceed which is provided by the addition of the catalyst.…”

“…[6] However, the aggregation of these nanoparticles due to their high surface charge and surface to volume ratio, decreases their surface area, [7] which results in a decrease in their catalytic activity. [8] To overcome this problem, silver NPs are usually loaded or dispersed in a solid matrix, such as polymeric matrices e.g.…”