Novel near-infrared (NIR) light-responsive poly(N-isopropylacrylamide)/graphene oxide (PNIPAM-GO) nanocomposite hydrogels with ultrahigh tensibility are prepared by incorporating sparse chemical cross-linking of small molecules with physical cross-linking of graphene oxide (GO) nanosheets. Combination of the GO nanosheets and thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) polymeric networks provides the hydrogels with an excellent NIR light-responsive property. The ultrahigh tensibility of PNIPAM-GO nanocomposite hydrogels is achieved by simply using a very low concentration of N,N'-methylenebis(acrylamide) (BIS) molecules as chemical cross-linkers to generate a relatively homogeneous structure with flexible long polymer chains and rare chemically cross-linked dense clusters. Moreover, the oxidized groups of GO nanosheets enable the formation of a hydrogen bond interaction with the amide groups of PNIPAM chains, which could physically cross-link the PNIPAM chains to increase the toughness of the hydrogel networks. The prepared PNIPAM-GO nanocomposite hydrogels with ultrahigh tensibility exhibit rapid, reversible, and repeatable NIR light-responsive properties, which are highly promising for fabricating remote light-controlled devices, smart actuators, artificial muscles, and so on.

Here we report a simple and versatile strategy for the in situ fabrication of nanogel-containing smart membranes in microchannels of microchips. The fabrication approach is demonstrated by the in situ formation of a chitosan membrane containing poly(N-isopropylacrylamide) (PNIPAM) nanogels in a microchannel of a microchip. The PNIPAM nanogels, that allow temperature- and ethanol-responsive swelling-shrinking volume transitions, serve as smart nanovalves for controlling the diffusional permeability of solutes across the membrane. Such self-regulation of the membrane permeability is investigated by using fluorescein isothiocyanate (FITC) as a tracer molecule. This approach provides a promising strategy for the in situ fabrication of versatile nanogel-containing smart membranes within microchips via simply changing the functional nanogels for developing micro-scale detectors, sensors, separators and controlled release systems.

Back Cover: γ‐CD‐recognition responsive characteristics of poly(N‐isopropylacrylamide‐co‐benzo‐12‐crown‐4‐acrylamide) (PNB12C4) hydrogels are investigated. The formation of stable γ‐CD/B12C4 complexes induces positive shift of the volume phase transition temperature of PNB12C4 hydrogels. Increase of γ‐CD concentration in solution or B12C4 content in PNB12C4 copolymer networks can dramatically enhance the γ‐CD‐recognition sensitivity of the PNB12C4 hydrogels. This is reported by Yun‐Yan Wei, Zhuang Liu, Xiao‐Jie Ju,* Kun Shi, Rui Xie, Wei Wang, Zhengdong Cheng, and Liang‐Yin Chu* in article number 1600386.

Molecular-recognition-responsive characteristics of a novel poly(N-isopropylacrylamide-co-benzo-12-crown-4-acrylamide) (PNB12C4) hydrogel have been investigated. In the prepared PNB12C4 hydrogel, benzo-12-crown-4 (B12C4) groups act as guest molecules and γ-cyclodextrin (γ-CD)receptors, and poly(N-isopropylacrylamide) (PNIPAM) networks act as phase-transition actuators. The formation of stable γ-CD/B12C4 complexes enhances the hydrophilicity of the PNB12C4 hydrogel networks, and induces positive shift of the volume phase transition temperature (VPTT) of PNB12C4 hydrogel. Moreover, the PNB12C4 hydrogel also shows thermoresponsive adsorption property selectively towards γ-CD. The γ-CD-recognition sensitivity of PNB12C4 hydrogel can be dramatically improved by increasing γ-CD concentration in solution or B12C4 content in PNB12C4 copolymer networks. The results in this study provide valuable information for developing crown ether-based smart materials in various applications.properties triggered by various external stimuli, such as pH, [1][2][3] temperature, [4][5][6] light, [7,8] certain molecules, [9][10][11] or ions. [12][13][14][15] Such hydrogels show great promise in many applications including switches, adsorbents, sensors, and

A novel poly(N‐isopropylacrylamide‐co‐acryloylamidobenzo‐12‐crown‐4) (PNB) microgel with rapid γ‐cyclodextrin (CD)‐responsive characteristics and adsorption property is developed. The microgel is composed of benzo‐12‐crown‐4 (B12C4) units as molecule‐recognition receptors and poly(N‐isopropylacrylamide) networks as phase‐transition actuators as well as adsorbent backbone chains. The PNB microgels significantly increase their volumes induced by γ‐CD, and adsorb γ‐CD molecules within PNB networks because of formation of γ‐CD/B12C4 inclusion complexes. Detection of γ‐CD‐concentration and the molecule‐specific adsorption processes of the microgels are investigated systematically. The PNB microgels provide a new tool for rapid concentration measurement and effective separation of γ‐CD.