In this work, a novel kind of temperature-responsive core cross-linked star (CCS) polymer, composing of poly(methoxypolyethylene glycol-co-di(ethylene glycol) ethyl ether acrylate) (P(PEGA-DEGA)) as thermo-responsive arm and poly(2-(dimethylamino)ethyl methacrylate) as functional core, was developed as nanoreactor for immobilizing gold nanoparticles for smart catalyst with facile recovery. The protonated imino groups in CCS polymer core could capture AuCl 4 - and simultaneously reduce it to Au NPs in aqueous solution, leading to the formation of P(PEGA-DEGA) CCS@Au composite. The whole procedure was carried out in aqueous media without using any toxic reducing agent, which is facile, efficient and green. The as-prepared CCS@Au composite exhibit a superior high catalytic activity for the reduction of 4-nitrophenol (4-NP), owing to that the soluble polymeric arms of the CCS polymers provides a homogeneous reaction system with fast mass transfer and thus facilitates interactions between Au NPs in the core and 4-NP. In addition, temperature-responsive catalyzing behavior was observed for the CCS@Au composite: the reaction rate enhanced with the elevation of the reaction temperature at first, but decreased when the temperature increased close to the LCSTs of the CCS@Au catalysts.
Qian Li,Tong Wang,Qu Wang,Kaihao Wang,Li Wang,Wantai Yang
Engineering advanced thermochromic smart windows capable of simultaneously addressing multifaceted performance, durability, and multifunctionality requirements is crucial for their practical applications. Herein, a mini library of lower critical solution temperature (LCST) copolymers with well-defined structure and programmed hydrophile-lipophile balance (HLB) is synthesized by the reversible addition-fragmentation chain transfer (RAFT) copolymerization of highly hydrophilic N-vinylpyrrolidone (NVP) and four maleimide derivative (MI) monomers with descending hydrophilicity. MI-NVP copolymers afford a copolymer composition-dependent phase transition temperature tunable over an ultra-wide range of 20–67 °C and efficient UV shielding capability. By ingeniously doping MI-NVP copolymers into non-thermoresponsive polyacrylamide hydrogel, smart windows with outstanding thermochromic properties, solar modulation performance, inherent stability (1000 cycles), and fast response rate (14 ± 2 s) are obtained. Further integration with photothermal Cs x WO 3 or electrothermal indium tin oxide (ITO) glass delivers enhanced spectral selectivity or active-mode regulation. Overall, by meticulously tailoring the multilevel structure of thermochromic hydrogels, this strategy establishes a novel MI-NVP copolymer platform for thermochromic smart windows that significantly advances energy conservation and occupant comfort.
The “graft onto” method is used to obtain the “stimuli-responsive water-soluble polymer” with low concentration, where 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and n-hydroxysulfosuccinimide sodium salt as catalyst and sodium polyacrylate as backbone chain. The molecular structure of the polymer is characterized by Nuclear Magnetic Resonance ( 1 H NMR). The influence of temperature on polymer rheological properties and aggregation is studied by rheometer and fluorescence probe respectively. The results show that when the polymer concentration is higher than 1500 mg/L, the thickening properties can be controlled by diacetoneacrylamide, thermal-responsive monomer , NaCl and polymer concentration, where the apparent viscosity max / viscosity min (η max /η min ) changes from 18.3 to 39.4, from 2.6 to 45.5, from 9.3 to 36, from 7.8 to 36.9 respectively and the lower critical solution temperature (LCST) changes from 60 °C to 40 °C. The reason for the polymer with controllable thickening properties is that the thermal-responsive monomers change from hydrophilicity to hydrophobicity , thus forming aggregations. At this time, the polymer chains form network structures. Because of controllable thickening properties at low concentration, it has potential application prospects.
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