Photoinduced atom transfer radical polymerization (ATRP) has been proved to be a versatile technique for polymer network formation. However, the slow polymerization rates of typical ATRP limited its application in the field of additive manufacturing (3D printing). In this work, we introduced carbon quantum dots (CQDs) for the first time to the ATRP in aqueous media and developed an ultrafast visible-light-induced polymerization system. After optimization, the polymerization could achieve a high monomer conversion (>90%) within 1 min, and the polydispersity index (PDI) of the polymer was lower than 1.25. This system was then applied as the first example of ATRP for the 3D printing of hydrogel through digital light processing (DLP), and the printed object exhibited good dimensional accuracy. Additionally, the excellent and stable optical properties of CQDs also provided interesting photoluminescence capabilities to the printed objects. We deduce this ATRP mediated 3D printing process would provide a new platform for the preparation of functional and stimuli-responsive hydrogel materials.

Owing to the benefits of using natural or artificial light sources as a stimulus, photoinduced reversible-deactivation radical polymerization (photoRDRP) techniques have been recognized to be a powerful “green” platform for the preparation of well-defined polymers. However, the development of highly efficient visible light-induced photoRDRP processes in aqueous dispersed media remains a challenge due to light scattering and refraction by monomer droplets or colloidal particles. In this work, an efficient green photocatalyst, carbon quantum dots (CQDs), was introduced to visible light-mediated miniemulsion atom transfer radical polymerization (ATRP), leading to highly efficient polymerizations with reaction rates (>80% monomer conversion within 1 h) much higher than in previous studies. This heterogeneous photocatalytic system is presumed to involve three catalytic cycles in (i) the aqueous phase, (ii) the oil–water interface, and (iii) the monomer droplets. The effect of different polymerization parameters on the polymerization reaction was investigated, including the amounts of surfactant and CQDs, CuBr2 dosage, and solid content. Excellent temporal control of the polymerization was illustrated by “ON/OFF” polymerizations, and natural sunlight was also used as an energy source. This novel CQDs-catalyzed miniemulsion photoATRP process may be easily extended to other aqueous dispersion RDRP systems. As an extension of our previous work (J. Am. Chem. Soc. 2022, 144 (22), 9817–9826) we also developed a “one-pot” method for the rapid preparation of heterogeneous hydrogels.

No abstract

Targeting sustainable and eco-friendly polymer synthesis, we demonstrate here a synergistically catalyzed atom transfer radical polymerization (ATRP) induced and controlled by interplay between ball milling (BM) and piezoelectric nanoparticles (piezoNPs). BM-induced electron transfer can be achieved through piezoNPs deformation under impact force, serving as an external stimulus to mediate polymerization. The ppm level of copper loading is sufficient in fabrication of a polymer with well-defined molecular weight and low polydispersity. High-molecular-weight polymers ranging from 33 to 74 kDa were prepared successfully through DMSO-assisted grinding. Besides, its good performance on availability of water as liquid-assisted grinding additive, the recyclability of piezoNPs, and the formation of cross-linker-free composite resin make our ATRP approach a green and practical option alongside the existent heat-, electro-, and photo-induced methods.

No abstract