Photoinduced metal-free “grafting from” atom transfer radical polymerization (ATRP) has been successfully applied to the fabrication of renewable cellulose graft copolymers with the aid of 2-bromo-2-phenylacetyl ester-modified ethyl cellulose as the macroinitiator. In the presence of an organic-based photoredox catalyst, “grafting from” polymerization of lauryl methacrylate from ethyl cellulose was efficiently activated and deactivated with UV irradiation, resulting in good control over molecular weight. 1H NMR and MALDI-TOF MS confirmed highly preserved Br chain-end functionality. Furthermore, cellulose graft copolymers with a block side chain architecture were successfully prepared through chain extension by metal-free “grafting from” ATRP. We believe that this work will provide a novel approach to design well-defined cellulose graft copolymers and further expand their application fields.
Photo-induced metal free ATRP method was employed for the synthesis of star-shaped polymers. By using 21-Br-β-CD as the macroinitiator, 10-phenylphenothiazine as the photoredox catalyst, star-shaped PtBA homopolymers were synthesized. The photo-induced ATRP displayed all the characteristics of controlled/living polymerization systems and the good light control over the polymerization process. The successful chain extension with MMA demonstrated the high livingness of PtBA “arms” and good controllability of the Photo-induced metal free ATRP. Finally, the achieved PtBA-b-PMMA star-shaped copolymers were used as templates for the preparation of precisely size-tunable CdSe quantum dots after a simple hydrolyzing process.
Chun-Na Yan,Qian Liu,Lin Xu,Li-Ping Bai,Li-Ping Wang,Guang Li
Well-defined amphiphilic diblock copolymer poly (methyl methacrylate)-b-poly (N-isopropylacrylamide) grafted hollow spheres (HS-g-PMMA-b-PNIPAM) hybrid materials were synthesized via metal-free surface-initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiators α-Bromoisobutyryl bromide (BIBB) were attached onto hollow sphere surfaces through esterification of acyl bromide groups and hydroxyl groups. The synthetic ATRP initiators (HS-Br) were further used for the metal-free SI-ATRP of methyl methacrylate (MMA) and N-isopropyl acrylamide (NIPAM) using 10-phenylphenothiazine (PTH) as the photocatalyst. The molecular weight of the polymers, structure, morphology, and thermal stability of the hybrid materials were characterized via gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS),1H-nuclear magnetic resonance spectroscopy (1H NMR), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA), respectively. The results indicated that the ATRP initiator had been immobilized onto HS surfaces successfully followed by metal-free SI-ATRP of MMA and NIPAM, the Br atom had located at the end of the main PMMA polymer chain, and the polymerization process possessed the characteristic of controlled/“living” polymerization. The thermal stability of the hybrid materials was increased significantly compared to the pure PMMA and PNIPAM.Keywords:hollow spheres;metal-free ATRP;SI-ATRP;10-phenylphenothiazine (PTH);thermal stability
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