Macromolekulare Chemie II: Publications: Synthesis and Direct Topology Visualization of ...

219. Xue, L.; Agarwal, U.S.; Zhang, M.; Staal, B.B.P.; Müller, A.H.E.; Bailly, C.M.E.; Lemstra, P.J.: Synthesis and Direct Topology Visualization of High Molecular Weight Star PMMA, Macromolecules 38, 2093 (2005)

Abstract:
We report synthesis and direct topology visualization of single molecules of six-arm star
poly(methyl methacrylate) (PMMA). We synthesized two hexafunctional initiators, 2,3,6,7,10,11-triphenylene
hexa-2-bromo-2-methylpropionate (fused-core initiator) and ethylene glycol bis[3,4,5-tri(2-bromo-
2-methylpropionate)] benzoylate (linear-core initiator). Their structures differ in the linking arrangement
of the initiating sites. Atom transfer radical polymerizations (ATRP) of methyl methacrylate (MMA) from
these initiators using CuCl as the catalyst and 4,4`-di-n-nonyl-2,2`-bipyridine as the ligand at 90 °C
produced six-arm star PMMAs with very high molecular weight (M_w> 2 million) and narrow molecular
weight distribution (polydispersity index |≈|. A high initiation efficiency (>90%) of the initiating sites
is inferred from a good match of the M_w of the star PMMA with the expected value based on M_w of the
cleaved arms. SEC-LS analysis confirmed the compact structure of the star PMMA compared to linear
PMMA and the absence of star-star coupling. Tapping mode scanning force microscopy of a dip-coated
sample on mica enabled resolution of the individual arms linked to the initiating core and allowed clear
identification of predominantly six-arm star molecules.

Prof. Dr. Axel Müller

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