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Multi-functional copolymers based on NIPAM and thienoviologens with different numbers of thiophene units (n = 1, 2 and 3) were synthesized and their absorption/emission properties were systematically studied. The thienoviologens exhibited significantly decreased energy band gaps (2.21–2.80 eV) compared with methyl viologen (3.70 eV) as well as intense fluorescence emission with up to 92% quantum yield. Different numbers of thiophene units effectively changed the electrochromic and electrofluorochromic behavior of the devices because of the varied conjugation degree. The PNIPAM chains contribute to the thermo-responsive properties which could be observed simultaneously with electrochromic and electrofluorochromic behavior when the temperature varied below and above the LCST (32 °C). By combining the thermo-responsive, electrochromic and electrofluorochromic properties of poly(NIPAM-co-TV), multi-responsive smart windows were developed. The thienoviologen units also demonstrate photodynamic antimicrobial activities due to their ability to generate singlet oxygen species upon photo irradiation. With the contribution of thermo-responsive PNIPAM fragments, poly(NIPAM-co-terthienoviologen) is endowed with thermo-controlled antimicrobial activity (CFU reduction = 99.6% for T > LCST and CFU reduction = 63.0% for T < LCST). This discovery successfully integrated thermo-responsive, electrochromic, electrofluorochromic and photodynamic antimicrobial properties into one system and will be greatly beneficial to expand the potential applications of viologen derivatives.

The chemical structures and topologies of the crosslinks in supramolecular networks play a crucial role in their properties and functions. Herein, the preparation of a type of poly(N-isopropylacrylamide) (PNIPAAM)-based supramolecular networks crosslinked by emissive hexagonal metallacycles is presented. The topological connections in these networks greatly affect their properties, as evidenced by their differences in absorption, emission, lower critical solution temperature, and modulus along with the variation of crosslinking densities. The integration of PNIPAAM and metallacycles in the networks benefits them improved bioavailability, making them serve as reagents for bacterial imaging and killing. This study provides a strategy to prepare cavity-crosslinked polymer networks for antibacterial applications.

Graphene oxide–poly(urea–formaldehyde) (GUF) composites were prepared by anchoring a prepolymer of urea–formaldehyde resin onto graphene oxide (GO) sheets through in–situ polycondensation. Five GUF composites with 2.6, 4.3, 8.6, 20.8, and 34.6 wt.% GO sheets were synthesized and added into epoxy resin by ball milling. Results of sedimentation test, transmission electron microscopy, and cross–sectional microstructural analysis showed that GUF/EP coatings with 8.6 wt.% GO sheets were compatible with the polymer matrix. Electrochemical impedance spectra further revealed the optimal corrosion protection of GUF composites with 8.6 wt.% GO sheets.

Four kinds of graphite derivatives in different exfoliation degrees were synthesized via modified Hummers’ method by controlling the mass ration of graphite and KMnO4 . The modified graphite derivatives (GUF) were synthesized through chemical modification with the prepolymer of urea–formaldehyde. Results of Raman spectroscopy (Raman) and Scanning electron microscopy (SEM) revealed that the layer exfoliation was affected by oxidation degree during the preparation of graphene oxide (GO). The highly exfoliated GO was fully modified by UF resin and presented excellent compatibility with epoxy resin. The data of electrochemical impedance spectra (EIS) verified the optimal corrosion resistance of GUF/EP composite coating with the highly exfoliated GO sheets. The data of localized electrochemical impedance spectroscopy (LEIS) demonstrated that the highly exfoliated modified GO exhibited slight galvanic corrosion in the defective coatings.