Atom transfer radical polymerization.

Atom transfer radical polymerization (ATRP) of tert-butyl acrylate is reported. Controlled polymerizations were performed using a CuBr/N,N,N‘,N‘ ‘,N‘ ‘-pentamethyldiethylenetriamine catalyst system in conjunction with an alkyl bromide as the initiator. Low molecular weight polymers with narrow molecular weight distributions were obtained by the addition of a solvent to create a homogeneous catalytic system. The addition of the solvent was necessary to decrease the polymerization rate and afford low polydispersity materials. This differs from the ATRP of methyl or n-butyl acrylate using this catalytic system, which do not require the addition of a solvent to obtain well-defined polymers. Subsequent hydrolysis of the polymer in refluxing dioxane with addition of HCl afforded poly(acrylic acid). Characterization using 1H NMR and FT-IR confirmed complete hydrolysis of the ester group. Further use of poly(tert-butyl acrylate) as a macroinitiator for block copolymerizations followed by hydrolysis of the ester g...

Atom Transfer Radical Polymerization of tert-Butyl Acrylate and Preparation of Block Copolymers

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...

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

The efficient, controlled polymerization of 2-hydroxyethyl methacrylate (HEMA) is achieved using atom transfer radical polymerization in methanol/water mixtures or pure methanol at 20 °C. The evolution of molecular weight with conversion is linear; polydispersities are around 1.1 for polymerization in methanol and around 1.2−1.3 for syntheses in 50:50 methanol/water mixtures, indicating good living character.

Controlled polymerization of 2-hydroxyethyl methacrylate by ATRP at ambient temperature

The homopolymerization and block/statistical copolymerization of 2-hydroxyethyl methacrylate (HEMA) using atom transfer radical polymerization (ATRP) in methanol at 20 °C has been investigated. For the homopolymerizations, both high conversions and low polydispersities (Mw/Mn < 1.25) were obtained over a wide range of target degrees of polymerization. According to the literature, HEMA homopolymer is usually described as only water-swellable, but in this work low molecular weight HEMA oligomers (target degrees of polymerization, DPn, less than 20) exhibited water solubility over a wide temperature range (no cloud point behavior). Furthermore, for actual DPn's between 20 and 45, HEMA homopolymers exhibited inverse temperature solubility in dilute aqueous solution at pH 6.5, and their cloud points increased systematically as the DPn was reduced. Gravimetric studies indicated that “water-insoluble” HEMA homopolymers with DPn's higher than 50 were actually partially soluble:  GPC studies confirmed that fractio...

Stimulus-responsive water-soluble polymers based on 2-hydroxyethyl methacrylate

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...

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

and Alex M. Heming

Papers

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