Single-step preparation of topological gels using vinyl-modified β-cyclodextrin as a figure-of-six cross-linker

Abstract

Herein, we have proposed a single-step preparation of topological gels using vinyl-modified βcyclodextrin (V-β-CyD) and isoprene. Copolymerization of V-β-CyD and isoprene in an aqueous solution resulted in gelation due to V-β-CyD acting as a novel type of copolymer chain cross-linker. The vinyl moiety of V-β-CyD becomes a part of the copolymer, while the β-CyD moiety of V-β-CyD simultaneously incorporates the isoprene component of the copolymer. V-β-CyD is capable of two different modes of cross-linking at each end, i.e., chemically bonding and mechanically interlocking. Due to the shape of the cross-linking point, we refer to it as figure-of-six cross-linking. Nuclear magnetic resonance (NMR) analysis showed that the gel contained V-β-CyD and isoprene in an approximately 1:0.3 stoichiometry. The relatively high content of β-CyD was reflected in the character of the gel; the gel swelled in dimethylformamide (DMF) which is a good solvent of β-CyD. A fluorometric analysis using 6-(p-toluidino)-2-naphthalenesulfonic acid (TNS) showed that the appended β-CyD was able to accommodate guest molecules. Introduction of an additional vinyl monomer into the gel was also successful. Addition of 4-vinylphenylboronic acid to the preparation procedure yielded a sugar-responsive gel that swelled in the presence of D-fructose.

Rotaxa-polymeric-gelation of acrylamides with vinyl-β-cyclodextrin

“…V-β-CyD was prepared according to the previous report [9]. Briefly, 2-isocyanatoethyl methacrylate was reacted to hydroxy group of β-CyD in the presence of dibutyltin dilaurate.…”

“…The mono-modified derivative was confirmed with 1 H-NMR and FAB-MS. The detailed procedure were found in our previous report [9], and the spectra of 1 H-NMR and FAB-MS were in the supporting information (Fig. S1, S2) .…”

“…Nowadays, topological gels have appeared as the third type of gels. They have attracted much attentions because of their special features originated from topological structures in which polymers are cross-linked by mechanically interlocked structures [1][2][3][4][5][6][7][8][9][10].…”

“…Recently, we have reported another type of topological gel using vinyl-modified β-CyD (V-β-CyD in Fig. 1) [9]. When V-β-CyD and isoprene is copolymerized, processes of polymerization, rotaxane formation, and gelation occur simultaneously, thus, we call it rotaxa-polymeric-gelation (RPG).…”

“…In the previous reports of rotaxa-polymerization and RPG [7][8][9], isoprene was the only choice to make an axis polymer covered with β-CyD derivatives. Thus, at the beginning of this study, we investigated the possibility of AAm and NIPAAm to make an axis polymer.…”