An elegant synthesis…

…of core-shell brush copolymers has just been reported by Wooley et al. (Macromolecules, 40, 2289 (2007)).<img id="image48"

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The exo-norbonene-functionalized raft agent was prepared by esterification of the corresponding alcohol with an acid functionalized raft agent (87 % yield). This was followed by the one pot ROMP and RAFT procedures. The ring-opening metathesis procedure was carried out using a Grubbs catalyst in CH2Cl2 to give a poly(norbonene) derivative with an Mn of 40.6 kDa and a PDI of 1.24.

The RAFT polymerization was then carried out using styrene and maleic acid anhydride as co-monomers and AIBN as the initiator (50 deg C reaction temperature). The comonomer pair was chosen due to their low reactivity ratios, which allows the one-pot preparation of statistical polymers of the type poly(styrene-stat-maleic anhydride)-block-poly(styrene). 1H NMR suggested quantitative conversion of the maleic anhydride after 16 h, but only 8.2 % for styrene. The reaction was allowed to continue for another 16.5 hours and quenched after 12. 8 % styrene conversion to give the desired core-shell brush copolymer (Mn=1200 kDa, PDI = 1.32).

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