Preparation of star block copolymers with polystyrene‐block‐poly(ethylene oxide) as side chains on hyperbranched polyglycerol core by combination of ATRP with atom transfer nitroxide radical coupling reaction

Abstract

The star block copolymers with polystyrene-block-poly(ethylene oxide) (PS-b-PEO) as side chains and hyperbranched polyglycerol (HPG) as core were synthesized by combination of atom transfer radical polymerization (ATRP) with the ''atom transfer nitroxide radical coupling'' (''ATNRC'') reaction. The multiarm PS with bromide end groups originated from the HPG core (HPG-g-(PS-Br) n ) was synthesized by ATRP first, and the heterofunctional PEO with a-2,2,6,6-tetramethylpiperidinyl-1-oxy group and x-hydroxyl group (TEMPO-PEO) was prepared by anionic polymerization separately using 4-hydroxyl-2,2,6,6-tetramethylpiperidinyl-1-oxy (HTEMPO) as parents compound. Then ATNRC reaction was conducted between the TEMPO groups in PEO and bromide groups in HPG-g-(PS-Br) n in the presence of CuBr and pentamethyldiethylenetriamine (PMDETA). The obtained star block copolymers and intermediates were characterized by gel permeation chromatography, nuclear magnetic resonance spectroscopy, fourier transform-infrared in detail. Those results showed that the efficiency of ATNRC in the preparation of multiarm star polymers was satisfactory ([90%) even if the density of coupling cites on HPG was high. V V C 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: [6754][6755][6756][6757][6758][6759][6760][6761] 2008

Step‐Growth Radical Addition‐Coupling Polymerization (RACP) for Synthesis of Alternating Copolymers

“…For example, diblock polymer can be prepared by direct ATRC by mono-halogenated polymer [16][17][18] or between mono-halogenated polymer and TEMPO end-functionalized polymer. [19][20][21][22][23] Multiblock polymer can be prepared by ATRC using a,v-dihalogenated polymer, but the block number of the product is not so high and the multiple molecular weight distribution is detected because the the coupling efficiency of ATRC normally does not exceed 95%. [16,18] Only few paper reports synthesis of polymer from small organic molecules by radical coupling reaction.…”

Premature atherosclerosis in pediatric systemic lupus erythematosus: Risk factors for increased carotid intima‐media thickness in the atherosclerosis prevention in pediatric lupus erythematosus cohort

“…There are two reasons for this: (i) besides combination reaction, radicals still can undergo disproportionation and transfer reactions, thus leading to termination of coupling reactions; (ii) the radical combination reaction is not orthogonal; cross‐coupling reaction between radicals of different types generates mixed product with different block sequence. There are a few reports on synthesis of diblock polymer from atom transfer radical coupling (ATRC) reaction, which includes direct coupling of monohalogenated polymer chains,16–18 cross‐coupling between monohalogenated polymer and polymer with a TEMPO end group 19–24. Small organic reagents, such as TEMPO‐based dinitroxide compounds,25 isoprene,26 and nitrone,27 have also been applied to modify the ATRC to increase the coupling efficiency and simultaneously incorporates distinct functional moieties.…”

Optimization of the preparation of a poly(aspartic acid) superabsorbent resin with response surface methodology

“…The trapping of carbon‐centered radicals by stable nitroxide (aminoxyl) radicals at close to diffusion‐controlled rates ( k t ∼ 10 8 L mol −1 s −1 ) to form alkoxyamines has been used to study initiation pathways in free‐radical polymerization 1, 2. This simple reaction has now emerged as a powerful process for the synthesis of macromolecular architectures via the combination of atom transfer radical activation and nitroxide radical coupling (NRC) 3–8. This reaction relies on the formation of carbon‐centered radicals by an atom transfer reaction with Cu(I)Br and subsequent trapping by the persistent nitroxide radical.…”