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The development and fabrication of high-performance renewable 3D objects with moderate elongation and high mechanical strength via 3D printing are highly desirable in the ongoing transition toward ...

The fabrication of polystyrene-grafted nanosilica (SiO 2 − g −PS) via nitroxide radical coupling (NRC) reaction was presented in this study. First, nanosilica anchored with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-based nitroxide radicals was synthesized by hydrolysis-condensation reaction between TEMPO-based nitroxide radical functional triethoxysilyl coupling agents and nanosilica. Then, the pre-synthesized, well-defined PS with bromide end group which was obtained by atom-transfer radical polymerization (ATRP) was grafted onto the functionalized nanosilica in the presence of CuBr/PMDETA. The structure, surface morphologies and particle size of the obtained hybrid nanoparticles were investigated by characterization methods The grafting yield by this method achieved up to 37.5% in the given conditions, which is approximated to the ones obtained by ‘grafting to’ route. A comprehensive study of UV-curable formula based on acrylates/polymer-grafted nanosilica were also discussed to find a possible correlation among the viscosity, curing kinetics, mechanical and thermal properties of the final hybrid organic-inorganic coatings.

A series of UV-curable flexible hyperbranched polyurethane acrylate (F-HBPUA) with various generation numbers and soft chains are successfully developed by modifying different generations of hydroxyl terminated hyperbranched polyurethane (HBPU-OH) with diverse soft chains contained semiadduct urethane monoacrylate. The influence of generation number and soft chain on the performances of F-HBPUA and its UV-cured freestanding film is studied. The degree of branching of F-HBPUA from the second to the fifth generation is proved to be 0.74, 0.79, 0.82 and 0.94, respectively. The glass transition temperature of F-HBPUA increases with increasing generation number but it decreases with the increase of soft chain length. The thermal stability of F-HBPUA improveswith higher generations while the longer soft chain is only beneficial to the heat resistance at below 300 °C. As the increase of generation number and chain length, the UV-curing time of F-HBPUA film is significantly shortened from 12 s to 3 s, the flexibility of the UV-cured film is greatly increased from 4 mm to 1 mm, adhesion is improved to 3 grades. This novel flexible hyperbranched polyurethane acrylates can be applied to coatings, membranes and 3D print parts with excellent flexibility.

In this study, we prepared a novel triblock copolymer, PDMS-b-(PMAEBB-co-PDMAEMA)2 (tri-PI) bearing side-chain benzophenone (BP) and coinitiator amine, as a macro-photoinitiator via reversible addition-fragmentation chain transfer (RAFT) copolymerization of the polymerizable photoinitiator 2-(methacryloyloxy)ethyl-2-benzoylbenzoate (MAEBB) and the unsaturated coinitiator amine 2-(dimethylamino)ethyl methacrylate (DMAEMA) with a bifunctional polydimethylsiloxane (PDMS) macro-chain transfer agent (macro-CTA). The structure of synthesized copolymer was confirmed by Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (1H NMR), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC). The effects of the photoinitiator/coinitiator ratio, concentration, and photoinitiator systems on the photopolymerization kinetics of tri(propylene glycol) diacrylate (TPGDA) were investigated by real-time FT-IR. The mobility of the tri-PI chain segments was proven by X-ray photoelectron spectroscopy (XPS), and the surface morphology of TPGDA curing coatings was studied by scanning electron microscopy (SEM). Results showed that tri-PI strongly suppressed the effect of oxygen inhibition on the photopolymerization system. Tri-PI was also used in the curing of UV-curable waterborne polyurethane acrylate (UV-WPUA) resin to determine its versatility.

Two types of photoactive polymers with an alkoxyphenyl ketone moiety at their backbone centers were synthesized through atom transfer radical polymerization. A facile protocol for preparing α,ω-heterotelechelic polymers was developed, employing nitroxide with different functional groups (e.g., hydroxyl, propargyl, glycidyl, and polyethylene glycol) coupled with macromolecular radicals generated via the Norrish-type I photoreaction under mild UV irradiation from the said polymers. Experimental conditions such as solvent effects and irradiaton time were investigated to optimize the efficiency of reaction functionality. The number-average molecular weights of the photoactive polymers and α,ω-heterotelechelic polymers were determined by gel permeation chromatography. Material structures were further confirmed by 1H NMR and FT-IR spectroscopy. The end group activity of α,ω-heterotelechelic polymers obtained from this reaction was further demonstrated using the Cu-catalyzed azide–alkyne click reactions between PS-N3 and polystyrene capped with a propargyl group.

In this study, spiropyran (SP)-containing fluorinated polyacrylate (F-PA–SP) latex was prepared by emulsion polymerization using fluorinated and SP-based acrylic monomers as raw materials. Fourier transform infrared and 1H NMR demonstrate that the F-PA–SP copolymer has been successfully synthesized, and dynamic light scattering and transmission electron microscopy analyses indicate that the synthesized latex has presented a uniform particle size of approximately 200 nm. X-ray photoelectron spectroscopy, atomic force microscopy, and water contact angle (WCA) analyses were used to investigate the surface properties of the F-PA–SP coating and demonstrate that its hydrophobicity is enhanced by the addition of a fluorinated acrylic monomer. The photochromic properties of the coating were investigated by UV/vis spectroscopy, and the results reveal that the F-PA–SP coating possesses better photoresponsiveness, fatigue resistance, and photoreversibility under UV/vis irradiation than the coating prepared using flu...

A novel UV-curable hyperbranched polyurethane acrylate (FHBPUA) with excellent flexibility is successfully synthesized based on a reaction of hydroxyl terminated hyperbranched polyurethane (regarded as core) with flexible semiadduct urethane monoacrylate (regarded as arms). The structure and property of FHBPUA is firstly analyzed and then utilized as functional additives to ameliorate the UV-curing and mechanical properties of epoxy acrylate resin. The degree of branching of FHBPUA turns out to be 0.82. Its thermal decomposition process consists of three different stages, and the glass transition temperature is around 65 °C. The freestanding FHBPUA film (~30 μm thickness) can be UV-cured within 3 s, and its flexibility is up to 1 mm. With the increase of FHBPUA content to 10 wt %, the UV-curing time of UV1000 film decreases from 6 to 3 s, flexibility strikingly increases from 10 to 1 mm, and adhesive force also improves from 5 to 3 grades, meanwhile its glossiness is not influenced by FHBPUA. In addition, a certain amount of FHBPUA can improve the tensile strength and elongation at break of UV1000 film. This novel FHBPUA can be used not only to develop flexible UV-curable freestanding films but also as functional additives to perfect other UV-curable compositions like coatings, inks and 3D printed parts.