Dual Temperature and Metal Salts-Responsive Interpenetrating Polymer Networks Composed of Poly (N-isopropylacrylamide) and Polyethylene Glycol

Abstract

Novel interpenetrating polymer networks (IPNs) composed of poly(N-isopropylacrylamide) (poly-NIPAM) and polyethers—namely, polyethylene glycol (PEG) and poly(tetramethylene oxide)—were synthesized in the absence and presence of polysiloxane containing a silanol residue. Gelation was accomplished using end-capped polyethers with trimethoxysilyl moieties and proceeded through simultaneous radical gelation of NIPAM and condensation of the silyl groups to form siloxane linkages. Thus, a novel one-step method constructing an IPN structure was provided. The obtained IPNs showed a gentle temperature-responsive volume change in water owing to the constructed poly-NIPAM gel component. In addition, a specific color-change response to chemical stimuli, such as CuCl2 and AgNO3 in water, was observed only when both components of poly-NIPAM and PEG existed in a gel form. For example, a single network gel composed of poly-NIPAM or PEG was isolated as a pale blue hydrogel, whereas IPNs composed of poly-NIPAM and PEG components turned yellow after swelling in an aqueous CuCl2 solution (0.1 M, pale blue). Dual-responsive functionalities of the synthesized hydrogels to temperature and metal salts, along with volume and color changes, were demonstrated.

Smart Hydrogel Reactor of Poly(N-isopropylacrylamide)/Polyethylene Glycol Interpenetrating Polymer Networks for Oxidative Coupling of 2-Naphthol

“…The SEM images showed that the IPN cryogels have sponge-like porous structures with significantly different pore sizes between each other and that of G NIPAM . 6 Notably, the pore size was considerably smaller in IPN PEG11k 3 and IPN PEG11k 4 (Table 1, entries 4 and 5), relative to that of the other gels, such as…”

“…Thus, it was a smart hydrogel with dualresponsive functionalities. 6 Herein, we report preliminary results of a novel strategy for organic reactions in water and the function of the IPN PEG hydrogel as a reactor vessel/flask, which does not show any catalytic activity but effectively promotes an oxidative coupling reaction. The large surface area inside the hydrogel could provide organic conditions even in aqueous media.…”

“…12 The synthetic procedure for IPN PEG has been previously reported. 6 Herein, for the synthesis of DS-PEG, PEG with a large molecular weight of 11000 (PEG 11k ) was used to pro-duce gels with flexible network structures by decreasing the crosslinked points. Table 1 lists the yields of the IPNs synthesized by using DS-PEG 11k , NIPAM, a crosslinker (BIS), and a radical initiator (AIBN).…”

“…5 Recently, we reported a novel simultaneous procedure that affords IPN gels, IPN PEG , composed of poly(Nisopropylacrylamide) (poly-NIPAM) and polyethylene glycol (PEG) networks (Scheme 1). 6 During gelation, the radical polymerization of NIPAM with a crosslinker and the condensation of trialkoxysilyl [-Si(OR) 3 ] groups that end-cap PEG (DS-PEG) to form a siloxane linkage 7 proceed simultaneously.…”