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As a kind of smart material, thermoresponsive hydrogels are widely investigated and applied in many fields. Due to the limitation of the freezing temperature of the water, it is a challenge to further broaden their sol-gel transition temperature (T gel ) range, especially below 0 °C. Herein, the lower critical solution temperature type of amphiphilic ABA triblock copolymers, synthesized via two-step reversible addition-fragmentation chain transfer (RAFT) polymerization is demonstrated. The hydrophilic A-block and the hydrophobic B-block are composed of poly(N,N-dimethylacrylamide) (PDMAA) and poly(diacetone acrylamide) (PDAAM), respectively. The degree of polymerization (DP) of both A-block and B-block shows a significant influence on the T gel of triblock copolymer dispersion. By changing the length of these two blocks or physically blending these copolymers dispersions, the T gel can be well adjusted in a temperature range from 45 to -10 °C. Moreover, When the T gel is higher than 4 °C, the triblock copolymer coatings show a good anti-fogging property. And when the T gel is around or lower than the freezing temperature of the water, aqueous dispersions of the triblock copolymer have an ice recrystallization inhibition activity, resulting in the decrease of average maximum grain size (MLGS) of ice crystal., (© 2021 Wiley-VCH GmbH.)

Latex polymers with precisely designed dynamic mechanical behavior are the key for waterborne damping coatings, which are widely desired in noise and vibration reduction with additional environmental benefits. In this work, we synthesized series of polymer latexes with various crosslinking agents (CA) and network distributions through the control on emulsion polymerization processes. We have revealed that the variation on crosslinking can significantly direct the latex behavior under dynamic conditions as well as its films. The variables involve the CA composition, the functionality, the crosslinking manner, the hydrophilic‐hydrophobic feature as well as the feeding method. Although all the latex films showed the damping peaks locating in the range from −10 to 70°C, their damping behaviors were quite different. Suggested by the empirical parameters of LA and TA, the product from sequential monomer feeding method tended to give good extensional damping performance. Especially when the crosslinking of diacetone acrylamide (DAAM)/adipic dihydrazide was applied, there was a linear increase on LA with the increasing dosage of DAAM from 0 to 10 mmol in the final monomer addition batch. Meanwhile, good constrained layer damping is expected on the products from the power monomer feeding method with the maximum CA dosage shown below 7.5 mmol. The best TA was achieved when the CA of divinylbenzene was used in the dosage of 5 mmol. These results would be valuable to be referenced in the engineering on organic damping materials toward modern industrial and vehicles applications. [ABSTRACT FROM AUTHOR]

Inspired by the growing demand for smart and environmentally friendly polymer materials, we employed 2,2′-disulfanediyldianiline (22DTDA) as a chain extender to synthesize a waterborne polyurethane (WPUR). Due to the ortho-substituted structure of the aromatic disulfide, the urea moieties formed a unique microphase structure in the WPUR, its mechanical strength was enhanced more 180 times relative to that of the material prepared without 22DTDA, and excellent self-healing abilities at body temperature in air or under ultrasound in water were obtained. If the self-healing process was carried out at 37 °C, 50 °C or under ultrasound, the ultimate tensile strength and elongation at break of the healed film could reach 13.8 MPa and 1150%, 15.4 MPa and 1215%, or 16 MPa and 1056%, respectively. Moreover, the WPUR films could be re-healed at the same fracture location over three cutting–healing cycles, and the recovery rates of the tensile strength and elongation at break remained almost constant throughout these cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • As far as we know, it is the first report on the HP/polymer composites in aqueous dispersion with the HP content as high as 30phr. • The hindered phenol is well dispersed in the polymer matrix without any special post-treatment. • The TA value is improved from 55.6 to 92.3 with 66.2% enhancement as the consequence of HP content at 30 phr. Abstract The building of polymer composite particles in their confined colloidal-scale space is a highlighted topic, leading to advanced structure complexity and high performance in functional coating applications. Here, we demonstrate a direct emulsion polymerization (EP) approach to synthesize composite latex with hindered phenol (HP), a kind of functional small molecules, successfully loaded inside colloidal polymer particles. Monomer conversion as well as the evolution of droplet/particle size has been traced as a function of polymerization time. The results evidence the smooth running of the polymerization process with high HP loading in situ in the aqueous dispersion which could reach 30 phr. As-synthesized HP/polymer latex could be conveniently used for the formation of coating films. The films are unique for the greatly improved damping properties. With HP content of 30 phr, the effective damping temperature range can be broadened to 112 ℃, and the a maximum loss factor can rise to 2.7. The weak hydrogen bonding is found to be the key for the incorporation of HP with the polymer segments, and contributes to the dissipation of vibration energy in the films. Combined with the environmental benefits, waterborne composite latex here is of potential application for the building of green damping coating systems. [ABSTRACT FROM AUTHOR]

Graphical abstract Schematic illustration for the synthesis of SHH-MIP particles by miniemulsion polymerization Highlights • Miniemulsion polymerization is performed to synthesize MIP particles. • The obtained MIP particles exhibit single hole hollow structure. • MIP show fast adsorption kinetics with the t 1/2 of 4.35 min. • MIP display excellent binding capacities and accurate recognition specificity. Abstract The structural design on the molecularly imprinted polymers (MIP) has been increasingly concerned because of advanced recognition efficiency. We here demonstrate a facile miniemulsion based polymerization to synthesize single hole hollow MIP particles for the recognition of bisphenol A (BPA). Uniform submicron products can be achieved through one-step polymerization in the aqueous dispersion, where the polymer seed has been swelled in the miniemulsion of the cross-linker and functional monomers together with the template molecules of BPA. After the removal of the seed and the template molecules by extraction, the electron microscopy characterization reveals bowl-like particles with a single hole on the concave surface. The unique single hole hollow structure is determined by the polymerization induced phase separation in the miniemulsion droplets and can be altered by monomer components. The characteristic of MIP is illustrated by the molecular recognition in the rebinding tests, where the particles prepared under the optimal formulation exhibit remarkable kinetics and desirable selectivity towards BPA in the mixed solution of methanol and water (20:80, v/v). The MIP particles with single hole hollow structure would be attractive in environmental and analytic fields for BPA decontamination. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate a miniemulsion polymerization strategy to synthesize molecularly imprinted polymer (MIP) submicron particles. Bisphenol A (BPA), an endocrine disrupting chemical, is chosen as the template molecule. The template was dissolved in the mixture of the functional monomer and crosslinking agent. The monomer mixture was emulsified into miniemulsion with the droplet diameter of about 100 nm via sonication. The specific sites were immobilized into polymer particles through the radical polymerization in the droplets. After the extraction of the template, MIP particles were obtained with an average diameter of 138 nm. The formation of recognition sites on the particles was validated by the excellent binding capability towards BPA in the selective and competitive binding experiments. Benefited from the small particle sizes and large surface areas, the MIP particles exhibit accelerated adsorption kinetics. The particles with submicron sizes, excellent BPA recognition accuracy and rebinding efficiency would be attractive in environmental and analytic fields for BPA decontamination. [ABSTRACT FROM AUTHOR]

Abstract: Herein polypyrrole-polystyrene (PPy-PS) hybrid hollow spheres have been prepared by a facile method. In the synthesis, pyrrole was oxidatively polymerized by FeCl3·6H2O in an emulsion of PS latex. The produced PPy deposited onto the surface of the PS particles, which were “dissolved” during the polymerization for the in-situ formation of hollow PPy spheres. The morphology of the hollow spheres was characterized by transmission electron microscope (TEM) and scanning electron microscopy (SEM). The size and size distribution of the hollow spheres were totally depended on that of the PS latex particles which can be adjusted conveniently. The PPy-PS hybrid structure of the shell of the hollow spheres was characterized by selective extraction using tetrahydrofuran (THF) and Fourier transform infrared (FTIR) spectroscopy. The formation process of the hollow spheres was traced by TEM. The probable mechanism for the formation of hollow spheres was also proposed in this work. The influences of the reaction conditions on the formation of the hollow structures have been studied in detail. [Copyright &y& Elsevier]