Summary: Experimental and modeling studies of addition–fragmentation chain transfer (AFCT) during radical polymerization of methyl methacrylate in the presence of poly(methyl methacrylate) macromonomer with 2‐carbomethoxy‐2‐propenyl ω‐ends (PMMA‐CO2Me) at 60 °C are reported. The results revealed that AFCT involving PMMA‐CO2Me formed in situ during methyl methacrylate polymerization has a negligible effect on the molecular weight distribution. magnified image

Poly(dimethylsiloxane)‐containing diblock and triblock copolymers were prepared by the combination of anionic ring‐opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) and nitroxide‐mediated radical polymerization (NMRP) of methyl acrylate (MA), isoprene (IP), and styrene (St). The first step was the preparation of a TIPNO‐based alkoxyamine carrying a 4‐bromophenyl group. The alkoxyamine was then treated with Li powder in ether, and AROP of D3 was carried out using the resulting lithiophenyl alkoxyamine at room temperature, giving functional poly(D3) with Mw/Mn of 1.09–1.16. NMRPs of MA, St, and IP from the poly(D3) at 120 °C gave poly(D3‐b‐MA), poly(D3‐b‐St), and poly(D3‐b‐IP) diblock copolymers, and subsequent NMRPs of St from poly(D3‐b‐MA) and poly(D3‐b‐IP) at 120 °C gave poly(D3‐b‐MA‐b‐St) and poly(D3‐b‐IP‐b‐St) triblock copolymers. The poly(dimethylsiloxane)‐containing diblock and triblock copolymers were analyzed by 1H NMR and size exclusion chromatography. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6153–6165, 2005

A detailed investigation of addition-fragmentation chain transfer (AFCT) in the free-radical polymerization of methyl methacrylate (MMA) in the presence of methyl ␣-(bromomethyl)acrylate (MBMA) was carried out to elucidate mechanistic details with efficient macromonomer synthesis as an underlying goal. Advanced modeling techniques were used in connection with the experimental work. Curve fitting of simulated and experimental molecular weight distributions with respect to the rate coefficient for addition of propagating radicals to MBMA (k add ) over 60 -120°C resulted in E add ϭ 21.7 kJ mol Ϫ1 and A add ϭ 2.18 ϫ 10 6 M Ϫ1 s Ϫ1 and a very weak temperature dependence of the chain-transfer constant (E add Ϸ E p ). The rate coefficient for fragmentation of adduct radicals at 60°C was estimated as k f Ϸ 39 s Ϫ1 on the basis of experimental data of the MMA conversion and the concentration of 2-carbomethoxy-2propenyl end groups. The approach developed is generic and can be applied to any AFCT system in which copolymerization does not occur and in which the resulting unsaturated end groups do not undergo further reactions.

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