Strong fluorescence of poly(N-vinylpyrrolidone) and its oxidized hydrolyzate.

Discovering fluorescence of existing compounds, which are generally regarded as non-fluorescent, is of important academic and technical significance. This article reports the fluorescence of common compounds containing pyrrolidone ring(s) and their oxidized hydrolyzates. Poly(N-vinylpyrrolidone) (PVP), polymerized from a very weak fluorescent monomer N-vinyl-2-pyrrolidone (NVP), exhibits strong intrinsic fluorescence.

Liquid crystalline behavior of graphene oxide in the formation and deformation of tough nanocomposite hydrogels.

In this paper, we report the formation and transformation of graphene oxide (GO) liquid crystalline (LC) structures in the synthesis and deformation of tough GO nanocomposite hydrogels. GO aqueous dispersions form a nematic LC phase, while the addition of poly(N-vinylpyrrolidone) (PVP) and acrylamide (AAm), which are capable of forming hydrogen bonding with GO nanosheets, shifts the isotropic/nematic transition to a lower volume fraction of GO and enhances the formation of nematic droplets. During the gelation process, a phase separation of the polymers and GO nanosheets is accompanied by the directional assembly of GO nanosheets, forming large LC tactoids with a radial GO configuration.

Self-healing in tough graphene oxide composite hydrogels.

Polymer hydrogels that are capable of spontaneously healing injury are being developed at a rapid pace because of their great potential in biomedical applications. Here, the self-healing property of tough graphene nanocomposite hydrogels fabricated by using graphene peroxide as polyfunctional initiating and cross-linking centers is reported. The hydrogels show excellent self-healing ability at ambient temperature or even lower temperatures for a short time and very high recovery degrees (up to 88% tensile strength) can be achieved at a prolonged healing time.