Electrostatic interaction is strong but usually diminishes in high ionic-strength environments. Biosystems can use this interaction through adjacent cationic–aromatic amino acids sequence of proteins even in a saline medium. Application of such specific sequence to the development of cationic polymer materials adhesive to negatively charged surfaces in saline environments is challenging due to the difficulty in controlling the copolymer sequences. Here, we discover that copolymers with adjacent cation–aromatic sequences can be synthesized through cation–π complex-aided free-radical polymerization. Sequence controlled hydrogels from diverse cation/aromatic monomers exhibit fast, strong but reversible adhesion to negatively charged surfaces in seawater. Aromatics on copolymers are found to enhance the electrostatic interactions of their adjacent cationic residues to the counter surfaces, even in a high ionic-strength medium that screens the electrostatic interaction for common polyelectrolytes. This work opens a pathway to develop adhesives using saline water.

We report here a zwitterionic copolymer based non-covalently cross-linked hydrogel with intrinsic self-healing nature for potential use in enhanced oil recovery.

We report a multi-stimuli responsive supramolecular hydrogel with great potential for biomedical application, which was composed of the micelle-forming diblock copolymer and physically cross-linked by complexation between ferric ions and carboxylic acid groups, exhibiting gel–sol transition caused by UV irradiation, multidentate ligands (EDTA) and redox agents (Na2S2O4).

Inspired by the toughening mechanism of double-network (DN) gels, tough hydrogel composites with a sandwich structure were fabricated from photoresponsive polymers. By copolymerization of hydrophilic monomers, 2ureidoethyl methacrylate (UM), and photoresponsive hydrophobic monomers, (2-nitrobenzyloxycarbonylaminoethyl methacrylate (NBOC)) at high concentrations, physical hydrogels that are soft and highly stretchable are formed due to the hydrophobic associations of NBOC, serving as dynamic crosslinkers. By UV irradiation, the physical crosslinking switches into chemical crosslinking, and the soft physical hydrogels transform into rigid and less stretchable chemical hydrogels. By UV curing the surface layers of the physical hydrogels, we prepared hydrogel composites having a sandwiched structure with two rigid outer layers and a soft inner layer. The molecular-level continuous interfaces and matched swelling ratios between the layers ensure the macroscale hydrogel composites' high strength and toughness with a DN gel effect. The outer layers fracture preferentially at deformation, playing a role like the first network of a DN gel, while the inner layer maintains the integrity, playing a role resembling the second network. The evolution of the fracture morphology of the rigid layers gives useful insight into the internal fracture process of DN gels.

In this paper, we report a CO 2 /N 2 -switchable sol to gel transition system based on a triblock copolymer of dimethylaminoethyl methacrylate (DMAEMA) and ethylene oxide (EO), with a measured composition DMAEMA 6 -EO 109 -DMAEMA 6 , in aqueous nanoclay dispersions. LAPONITE® is exfoliated and stabilized by Pluronic F127. The aqueous mixture exhibits a strong response to CO 2 , changing from a low viscous sol to a self-healable gel. In the presence of CO 2 , the PDMAEMA blocks are protonated and the positive charged triblock copolymer bridge the negative charged nanoclays, formation of a physical network. As a consequence, a sol to gel transition is observed at the macro level. Upon removal of CO 2 through bubbling with N 2 , a corresponding gel to sol transition occurs due to the deconstruction of the physical network, which is a result of the departure of the deprotonated PDMAEMA blocks from the nanoclays.This sol to gel transition is fully reversible. Furthermore, the formed gel possesses excellent self-healing ability, meaning that this hydrogel is capable of autonomous healing upon damage. Thus, we believe the fundamentals of the present CO 2 -responsive smart hydrogel may hold promise for a wide range of areas, such as intelligent delivery systems and smart biomaterial fields, or a potential CO 2 plugging agent for enhanced oil recovery (EOR) performed by CO 2 flooding.

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A new synthesis method of pH-response superabsorbent hydrogels (SHG) was achieved by direct ultraviolet (UV) photopolymerization, and in particular, the synthesis of SHGs of acrylic acid (AA), sodium acrylate (AANa), and methacrylcholine chloride (MACC) tricomponent copolymer by UV photopolymerization were investigated. The pH value responsive behavior of SHG with different monomer ratios of MACC and AA was researched, and SHG showed large swelling properties at pH value approximately 7. Influences of monomer ratio (mol) of AANa to AA, photoinitiators, crosslinking agents, and exposure time of UV light on the water absorbent properties were studied. The results showed that the water absorbent capacity of SHG based on photoinitiators:Esacure KTO46 or Irgacure 651 can reach comparatively high, N,N 0 -Methylene bisacrylamide and diethylene glycol diacrylate (DEGDA) were high efficient crosslinking agents for its crosslinking the molecular chains through attending the copolymerization with monomers. When the exposure time was 10 min, the distilled water absorbency of SHG was 1503 mL/g under the condition: content of MACC, 14.3 wt %; monomer ratio (mol) of AANa to AA: 5.67; content of DEGDA and Irgacure 651, 0.0025 and 0.25 wt %.