The atom transfer radical polymerizations (ATRPs) of styrene initiated by diselenocarbamates were carried out for the first time. The polymerization showed first-order kinetic with respect to the monomer concentration, and the molecular weights of the obtained polymers increased linearly with the monomer conversions with narrow molecular weight distributions (as low as 1.16). The results of chain extension, ¹H NMR, UV–vis, and MALDI-TOF MS confirmed that the resultant polystyrene possessed some degree of living diselenocarbamates terminal. However, significant amounts of dead polymers (about 53%) were also found. This work offered an alternative type of ATRP initiator, and the seleno-terminated polymers may be useful in biotechnological and biomedical applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1927–1933

A cyclic selenium-based reversible addition-fragmentation chain transfer (RAFT) agent, 5,5-dimethyl-3-phenyl-2-selenoxo-1,3-selenazolidin-4-one (RAFT-Se), was synthesized and utilized in the RAFT polymerizations of vinyl acetate (VAc). Its analog, 5,5-dimethyl-3-phenyl-2-thioxothiazolidin-4-one (RAFT-S), was also used in RAFT polymerizations for comparison under identical conditions. The RAFT polymerizations of VAc with RAFT-Se were moderately controlled evidenced by the increase of molecular weights with conversion, despite the slightly high M_w/M_n (less than 1.90), whereas the molecular weights were poorly controlled in the presence of RAFT-S (2.00 < M_w/M_n < 2.30). Thanks to its unusual cyclic structure of RAFT-Se, one or more RAFT-Se species was incorporated into the resultant poly(VAc) as revealed by the results of cleavage of polymer and atomic absorption spectroscopy. Considering the biorelated functions of both poly(VAc) and Se element, this work undoubtedly provided a successful methodology of how to incorporate high content of Se into a molecular weight controlled poly(VAc). © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

An iodine-based initiator, 2-iodo-2-methylpropionitrile (CPI), was utilized for the single-electron transfer and degenerative chain transfer mediated living radical polymerization (SET-DTLRP) of methyl methacrylate (MMA) in the absence of ligand, at ambient temperature. The CPI-initiated ligand-free polymerizations manifested reasonable control over molecular weights with relatively narrow distributions (M_w/M_n ≤ 1.35). The living nature of the polymers was further confirmed by successful chain extension reaction and ¹H NMR with high chain-end fidelity (∼96%). Screening of the available solvents suggested that the controllability of this polymerization was highly dependent on the kind of solvents, wherein dimethyl sulfoxide was a better solvent for a controlled molecular weight. The proposed ligand-free SET-DTLRP initiated by CPI was intriguing since it would dramatically decrease the concentration of Cu(0) ions both in polymerization system and resultant polymer, and provided a more economical and eco-friendly reversible-deactivation radical polymerization technique. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The combination of zero-valent iron (Fe(0) powder) and copper(II) bromide was used to mediate the polymerization of methyl methacrylate (MMA) or styrene (St) at 25 ° C. The results demonstrated that the solvent played an important role on the polymerization rate and molecular-weight control. The polymerization in toluene displayed a poorly controlled process with remarkably low polymerization rate. With dimethyl sulfoxide (DMSO) as solvent, the polymerization proceeded in a relatively high rate, and the number-average molecular weights were controlled especially at higher conversion. High conversions (80%) of St could be achieved with narrow molecular weight distributions in DMSO at 25 °C. It was supposed that Fe(0) played a dual role, the activator for the generation of active radical and the reducing agent for CuBr₂.

For the first time, ligand-free Cu(0)-mediated polymerization of methyl methacrylate (MMA) was realized by the selection of ethyl-2-bromo-2-phenylacetate as initiator at ambient temperature. The polymerization can reach up to 90% conversion within 5 h with dimethyl sulfoxide (DMSO) as solvent, while keeping manners of the controlled radical polymerization. Extensive investigation of this system revealed that for a well-controlled Cu(0)-mediated polymerization of MMA, the initiator should be selected with the structure as alkyl 2-bromo-2-phenylacetate, and the solvent should be DMSO or N,N-dimethylformamide. The selectivity for solvents indicated a typical single-electron transfer-living radical polymerization process. Scanning for other monomers indicated that under equal conditions, the polymerizations of other alkyl (meth)acrylates were uncontrollable. Based on these results, plausible reasons were discussed. The ligand-free Cu(0)-mediated polymerization showed its superiority with economical components and needless removal of Cu species from the resultant products. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, bimetallic zero-valent metal (Fe(0) powder and Cu(0) powder) was used to mediate the single electron transfer-living radical polymerization (SET-LRP) of methyl methacrylate at 25 °C in dimethyl sulfoxide. Different feed ratios of [Fe(0)]₀/[Cu(0)]₀ (0/1.5, 0.5/1, 0.75/0.75, 1/0.5, and 1.3/0.2) were explored. With the increase of Fe(0) feed, the polymerization rate was mildly depressed with a prolonged induction period. While, the control over the molecular weights was improved upon the increase of Fe(0). A best control (initiation efficiency = 91%) was achieved at [Fe(0)]₀/[Cu(0)]₀ = 1/0.5. A further increase of Fe(0) to the feed ratio of [Fe(0)]₀:[Cu(0)]₀ = 1.3: 0.2 led to a uncontrolled polymerization. Explorations of available solvents and ligands for this polymerization confirmed the SET-LRP mechanism. It was suggested that Fe(0) might act as a dual role in this process: one was the activation agent for Cu(0), which favored a better control over the molecular weights; The other was an alternative catalyst for the activation of R-X or P_n-X to generate radicals, which assured a comparable polymerization rate as that of Cu(0). This work provided an alternative and economical catalyst for SET-LRP, and would eventually reinforce the SET-LRP technique. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, cupric oxide (CuO) or cuprous oxide (Cu₂O) was used as the catalyst for the single electron transfer-reversible addition-fragmentation chain transfer (SET-RAFT) polymerization of methyl methacrylate in the presence of ascorbic acid at 25 °C. 2-Cyanoprop-2-yl-1-dithionaphthalate (CPDN) was used as the RAFT agent. The polymerization occurred smoothly after an induction period arising from the slow activation of CuO (or Cu₂O) and the “initialization” process in RAFT polymerization. The polymerizations conveyed features of “living”/controlled radical polymerizations: linear evolution of number-average molecular weight with monomer conversion, narrow molecular weight distribution, and high retention of chain end fidelity. From the polymerization profile, it was deduced that the polymerization proceeded via a conjunct mechanism of single electron transfer-living radical polymerization (SET-LRP) and RAFT polymerization, wherein CPDN acting as the initiator for SET-LRP and chain transfer agent for RAFT polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, zero-valent iron (Fe(0)) (powder or wire) and elemental bromine (Br₂) were used as the catalysts for atom transfer radical polymerization (ATRP) of styrene (St) without any additional initiator at 110 °C. The polymerizations happened with controlled evidence at appropriate molar ratio of Fe(0) to Br₂: a remarkable increase of molecular weights with St conversions, the narrow molecular weight distributions and living polymer chains end-capped by Br. More Br₂ or less Fe(0) led to a slow polymerization rate but an improved control over molecular weights. After examining the polymer chain ends by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, it was concluded that the polymerization was initiated by thermal self-initiation, and regulated by the in situ generated Fe^IIIBr₃. The results suggested that the Fe(0)/Br₂ catalyzing polymerization was a classical ATRP process with easier operation and more economical components. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, Cu(0)-mediated radical copolymerization of vinyl acetate (VAc) and acrylonitrile (AN) was explored. The polymerization was carried out at 25°C with 2,2′-bipyridine as ligand and dimethyl sulfoxide as solvent. The copolymerization proceeded smoothly producing moderately controlled molecular weights at low VAc feed ratios. The high VAc feed ratios generated low polymerization rate and poorly controlled molecular weights. FTIR, ¹H NMR, and differential scanning calorimetry confirmed the successful obtaining of the copolymers. Based on ¹H NMR spectra, the reactivity ratios of VAc and AN were calculated to be 0.003 and 1.605, respectively. This work conveyed the first example for the Cu(0)-mediated radical polymerization of AN and VAc, wherein VAc cannot be homopolymerized by Cu(0)-mediated radical polymerization technique. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, single electron transfer-living radical polymerization (SET-LRP) was catalyzed by in situ Cu(0) generated from copper sulphate pentahydrate (CuSO₄·5H₂O) and hydrazine hydrate (N₂H₄·H₂O) at 25 °C. The polymerization occurred smoothly with moderate controllability: the polymerization rates increased by the increases of N₂H₄·H₂O, and the initiator concentration had an optimal value on the polymerization rate; the number-average molecular weights (M_n,GPC) increased with monomer conversions and polydispersities were below 1.40. The M_n,GPC deviated much from theoretical ones with about 50% polymer chain-end fidelities. Some side reactions stemming from the strong reduction performance of N₂H₄·H₂O were responsible for the mildly controlled polymerizations. This polymerization can be conducted in SET-LRP unfavorable solvents or in bulk, such as toluene and tetrahydrofuran, owing to the H₂O contained in CuSO₄·5H₂O and N₂H₄·H₂O. On account of the utilization of CuSO₄·5H₂O, an inactive Cu(II) compounds in LRP area, this work confirmed from experimental level that it was Cu(0) which acted as activator and mediator in SET-LRP. This work provided a first example of in situ Cu(0) catalyzing SET-LRP with CuSO₄·5H₂O as a copper source. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011