Cu²⁺ can oxidize amines to generate radicals to initiate radical polymerization of electron-deficient monomers under mild conditions. Here, CuSO₄-catalyzed redox-initiated radical polymerizations of methyl methacrylate from amino-functionalized TiO₂ nanoparticles (TiO₂-NH₂ nanoparticles) was performed to prepare TiO₂ nanoparticles grafted with poly(methyl methacrylate) (TiO₂-g-PMMA hybrid nanoparticles) in dimethylsulfoxide or N,N-dimethylformamide at 90°C. Infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy confirmed the presence of the grafted PMMA and the grafting yield was about 50 wt%. Microscopy and particle-size analysis indicated that TiO₂-g-PMMA nanoparticles had a good affinity to organic media. Because only aminyl radical (NH•) on TiO₂ nanoparticles formed in Cu²⁺-amine redox-initiation step, there was no free PMMA chains formed during polymerization. Thus, our protocol provides a facile strategy to prepare inorganic/organic hybrid nanoparticles via one-pot Cu²⁺-amine redox-initiated free radical polymerization. POLYM. ENG. SCI., 55:735–744, 2015. © 2014 Society of Plastics Engineers

Kinetic results of CuSO₄/2,2'-bipyridine(bPy)-amine redox initiated radical polymerization of methyl methacrylate (MMA) at 70 to 90 °C in dimethylsulfoxide suggest that such initiation is characteristic of a slow rate and a low initiator efficiency, but tertiary amines exhibit a relatively higher rate. UV-Vis spectroscopy confirms the alpha-amino functionality of PMMA chains. CuCl₂/bPy successfully mediates the redox-initiated radical polymerization of MMA with aliphatic tertiary amines in a fashion of slow-initiated reverse atom transfer radical polymerization (ATRP), i.e. both the initiator efficiency of aliphatic tertiary amines and the average molecular weight of PMMA increase gradually, while the molecular weight distribution remains narrow but become broader with the conversions. As the PMMA chains contain alpha amino and omega C-Cl moieties, UV-induced benzophenone-initiated radical polymerization and Cu^ICl/bPy-catalyzed ATRP initiated from PMMA lead to block copolymers from terminal functionalities. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2562-2578

Although the self-condensing atom transfer radical polymerization (SCATRP) of inimers with typical comonomers has been extensively performed, there have been few reports to correlate the reactivity ratio with the growth of the molecular weights (MWs) and the development of branched structures. Thus, the SCATRP of inimers of different reactivity ratios, namely, 4-chloromethylstyrene (CMS) and maleimide (MI) inimers, with a large excess of styrene (St) were carried out, respectively, to examine the effect. The conversion and MW were monitored by gas chromatography, gel permeation chromatography, and multiangle laser light scattering. The results suggested that CMS merely functioned as an initiator for St at the early stage; this led to linear macroinimers, which underwent SCATRP and gave rise to randomly branched polystyrene (PS) only at high conversion. The MI inimers formed charge-transfer complexes with St and underwent the SCATRP to result in hyperbranched copolymers at first; this initiated the atom transfer radical polymerization of St and led to star-shaped PS. With the objective of improving the processability and melt fluidity, the physical properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends with linear, randomly branched, and star-shaped PS were compared. In comparison with those with linear PS, the PPO/branched PS blends exhibited a higher glass-transition temperature, a higher melt flow index, and a comparable thermal stability because of the spherical architecture of the branched PS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011