One-Shot Preparation of Polyacrylamide/Poly(sodium styrenesulfonate) Double-Network Hydrogels for Rapid Optical Tissue Clearing

Abstract

In this study, we propose a convenient method for the synthesis of double-network gels by the one-shot radical polymerization for their application to rapid optical tissue clearing. Double-network gels were produced during the radical polymerization of acrylamide (AAm) and sodium styrenesulfonate (SS) in the presence of N,N′-methylenebisacrylamide and sodium divinylbenzenesulfonate as the cross-linkers by simultaneous addition, that is, one-shot polymerization accompanying the delay of polymerization for a second network monomer. We analyzed the polymerization process based on the consumption rates of each monomer during the reactions in the absence of the cross-linkers in order to estimate the repeating unit structure of the resulting polymers. We then fabricated the AAm/SS gels by the polymerization of AAm and SS in the presence of the cross-linkers. We analyzed the swelling, viscoelastic, and mechanical properties of the produced gels to investigate their network structure. Finally, we demonstrated the validity of the double-network gels for the application to rapid optical tissue clearing.

One‐shot radical polymerization of vinyl monomers with different reactivity accompanying spontaneous delay of polymerization for the synthesis of double‐network hydrogels

“…2). In the polymerization of AAm and SS, the consumption of AAm proceeded slowly after some SS was consumed in the early stage of the reaction (Figs 2(a) and 3(a)), as previously reported 30 . SS was preferentially consumed because of the highly conjugated structure of the monomer.…”

“…This is because the presence of the α ‐methyl group in SPM increased the stability of the polymer radical. Similar effects of the α ‐methyl group on copolymerization reactivity have been reported for several copolymerization systems; 33–35 for example, while SS has a large monomer reactivity ratio (a large r 1 value) for copolymerizations with acrylamide 30 and N ‐vinylpyrrolidone, 36 an acrylate monomer and an acrylamide monomer exhibit similar monomer reactivity ratios, 37 as summarized in Table 1. Similar reactivity was also observed for the copolymerization of an acrylate (M 1 ) with N ‐vinylpyrrolidone (M 2 ) ( r 1 = 0.52 and r 2 = 0.03) 38 .…”

“…In contrast, few studies have been reported of a simple one‐shot (one‐pot) polymerization method for the fabrication of gels having a structure in which both networks are connected by chemical crosslinking. We recently reported DN hydrogels synthesized by radical polymerization with the simultaneous addition of monomers and crosslinkers with different reactivity, that is, AAm and sodium p ‐styrenesulfonate (SS) as the monomers, and N , N '‐methylenebisacrylamide (bisAA) and sodium divinylbenzenesulfonate (DVBS) as the corosslinkers 30 . By the one‐shot polymerization method, after the highly reactive SS forming the first network is almost consumed, the less‐reactive AAm forming the second network starts to react with a delay of time, so that a DN gel is efficiently formed.…”

“…In the polymerization of AAm and SS, the consumption of AAm proceeded slowly after some SS was consumed in the early stage of the reaction (Figs 2(a) and 3(a)), as previously reported. 30 SS was preferentially consumed because of the highly conjugated structure of the monomer. For the copolymerization of AAm with SPA instead of SS, no significant difference was observed in the time-conversion curves ( Fig.…”

Synthesis of hydrogels with a gradient crosslinking structure by electron beam radiation to an aqueous solution of poly(sodium acrylate)

“…Hydrogels containing water have various functions, such as water absorption, water retention, absorbability, separability, permeability, high strength, controlled release, biocompatibility, transparency, and so on. [1][2][3][4][5][6][7][8][9][10][11][12][13] Therefore, they have been used in a wide range of fields from fundamental biological and medical researches to practical superabsorbent polymers and industrial membrane separation processes. Polymer gels can be classified into chemically crosslinked gels, whose crosslinking structure is formed by covalent bonds, and physically crosslinked gels, which are formed by intermolecular interactions, such as van der Waals forces or hydrogen bonding.…”