Star polymers by ATRP of styrene and acrylates employing multifunctional initiators

Abstract

Multifunctional initiators for atom transfer radical polymerization (ATRP) are prepared by converting ditrimethylolpropane with four hydroxyl groups, dipentaerythritol with six hydroxyl groups, and poly(3‐ethyl‐3‐hydroxymethyl‐oxetane) with ∼11 hydroxyl groups to the corresponding 2‐bromoisobutyrates or 2‐bromopropionates as obtained by reaction with acid bromides. Star polystyrene (PS) is produced by using these macroinitiators and neat styrene in a controlled manner by ATRP at 110 °C, employing the catalytic system CuBr and bipyridine. Mn up to 51,000 associated with narrow molecular weight distributions (PDI < 1.1) are obtained with conversions up to 32%. Hydrolysis of the star‐PS leads to linear chains having the expected Mn values. The star‐PS polymers based on dipentaerythritol degrade thermally in nitrogen in a two‐step process in which the first low‐temperature step involves scission of the ester linkages and the second step corresponds to the normal PS degradation. Star poly(methyl acrylates) with various cores are likewise prepared in a controlled manner by ATRP of methyl acrylate in bulk and in solution at 60–80 °C with the 1,1,4,7,7‐pentamethyldiethylene triamine ligand. Under these conditions, higher conversions were possible still maintaining low PDI signaling controlled star growth. Multiarm stars of poly(n‐butyl acrylate) and poly(n‐hexyl acrylate) with controlled characteristics have also been prepared. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3748–3759, 2005

Novel polymers based on atom transfer radical polymerization of 2‐methoxyethyl acrylate

“…Elemental analysis of halogen content (no discrimination between Br and Cl) was performed after sample oxidation in oxygen atmosphere as previously described. 13 …”

“…Especially, application of atom transfer radical polymerization (ATRP), in numerous cases, 10,11 has extended the materials engineering potential of methacrylate monomers by use of the macroinitiator concept. 12,13 A monomer somehow related to 2-methoxyethyl acrylate (MEA), methoxy-capped oligo(ethylene glycol) methacrylate, has both been polymerized in aqueous media at ambient temperature 14 and in toluene at 90 8C 15 by ATRP. In recent years, numerous different acrylate monomers have also been homo-and block copolymerized by ATRP.…”

Efficient metal‐free coupling of polystyrene chains using silane radical atom abstraction

“…a Apparent number-average molecular weight based on analysis using a GPC calibrated with polystyrene standards. M n values calculated by 1 H NMR using integration of the methine end group with aromatic protons agreed within 5% in each case. b Method used to couple the polystyrenes.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Regardless of the specific CRP method being utilized, the essential phenomenon is the reversible trapping of active polymer radicals, temporarily transforming them into dormant species and thus minimizing bimolecular radical reactions that polymer radicals are susceptible to, such as radical-radical coupling, chain transfer, or disproportionation.…”

“…The synthesis of the PStBr precursors with narrow PDI values was successfully accomplished using established ATRP methods, 31 with the bromine chain terminus verified by 1 H NMR in conjunction with gel permeation chromatography (GPC). The metal catalyst was removed from the polymers by passing them through an alumina column, giving ultra white powder after precipitation in cold methanol, prior to use in coupling reactions.…”