David J. Duncalf

Bio: David J. Duncalf is an academic researcher from University of Warwick. The author has contributed to research in topics: Radical polymerization & Polymerization. The author has an hindex of 14, co-authored 27 publications receiving 1019 citations.

Atom Transfer Polymerization of Methyl Methacrylate Mediated by Alkylpyridylmethanimine Type Ligands, Copper(I) Bromide, and Alkyl Halides in Hydrocarbon Solution

Abstract: Schiff bases of types 1, 2, and 3, easily prepared by the condensation of primary amines with pyridine-2-carboxaldehyde, glyoxal, or 2-acetylpyridine, respectively, are described as ligands for a copper(I) catalyst in the atom transfer polymerization of a range of methacrylates in toluene and xylene solution. Increasing the length of the alkyl group on ligands of type 1 increases the solubility of the catalyst in nonpolar solvents. The rate of polymerization increases on going from R = ethyl to propyl; however, on increasing the length of R further, we see no effect on the rate. The molecular weight distribution is narrow for all ligands where R = n-alkyl, and the number-average molecular weight (Mn) increases linearly with conversion. A decrease in rate and a loss of control are observed when branching is introduced in the α-position of the side chain. The polymerization is approximately first order in initiator, 0.90 ± 0.22, CuBr, 0.90 ± 0.13, and methyl methacrylate, 0.93 ± 0.01. Polymerization with Cu...

Low-Temperature Living “Radical” Polymerization (Atom Transfer Polymerization) of Methyl Methacrylate Mediated by Copper(I) N-Alkyl-2-Pyridylmethanimine Complexes

Abstract: This paper demonstrates that atom transfer polymerization of methyl methacrylate mediated by CuBr/N-alkyl-2-pyridylmethanimine complexes in toluene proceeds effectively at temperatures as low as 15 °C, while maintaining control over molecular weights and yielding narrow polydispersity indexes. The reaction can even be performed at −15 °C with a number average molecular weight, Mn, of 6980 and a polydispersity, PDI, of 1.28 being achieved in 116 h; however, the molecular weight control is less effective. The polymerizations were performed at 90, 60, 40, and 15 °C with the first-order rate plots, molecular weight vs conversion plots, and final polydispersity indexes consistent with little or no terminationliving/controlled polymerization. Methyl hydroquinone (MeHQ) has been demonstrated to accelerate the polymerization by a factor of 3−4 at temperatures below 40 °C. An activation energy, Ea, for polymerization in the absence of phenol was determined to be 60.3 kJ·mol-1 and is significantly reduced to 44.9 k...

3-aminopropyl silica supported living radical polymerization of methyl methacrylate : Dichlorotris(triphenylphosphine)ruthenium(II) mediated atom transfer polymerization

Abstract: 3-Aminopropyl-functionalized silica support (APSS) has been used as a solid support for the heterogeneous atom transfer polymerization of methyl methacrylate (MMA), to poly(methyl methacrylate) (PMMA), mediated by adsorbed RuCl2(PPh3)3 as catalyst. This system displays characteristics of a living radical polymerization as indicated by (i) an increase in the number-average molecular weight (Mn) with conversion, (ii) relatively low polydispersity indexes (PDI), and (iii) linear first-order rate plots. When PMMA of Mn = 20 000 g mol-1 was targeted, the reaction reached 91% conversion after 4 h with a measured Mn = 21 500 g mol-1 and PDI = 1.49. It was found that polymerization of MMA mediated by RuCl2(PPh3)3 in the presence of APSS does not require the addition of an aluminum alkoxide (e.g., Al(OiPr)3) as an activating reagent. The rate of reaction is higher than for similar homogeneous reactions; however, the polydispersity indexes are also higher. The ruthenium content of polymers thus produced is typicall...

Atom Transfer Radical Polymerization (ATRP): Current Status and Future Perspectives

Abstract: Current status and future perspectives in atom transfer radical polymerization (ATRP) are presented. Special emphasis is placed on mechanistic understanding of ATRP, recent synthetic and process development, and new controlled polymer architectures enabled by ATRP. New hybrid materials based on organic/inorganic systems and natural/synthetic polymers are presented. Some current and forthcoming applications are described.