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Conformational Changes of a Surface-Tethered Polymer during Radical Growth Probed with Second-Harmonic Generation

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posted on 12.04.2017, 00:00 by Steven Deckers, Maarten Bloemen, Guy Koeckelberghs, Christ Glorieux, Thierry Verbiest, Monique A. van der Veen
The surface-induced polymerization of a chromophore-functionalized monomer was probed in situ for the first time using a nonlinear optical technique, second-harmonic generation. During the first hours of the polymerization reaction, dramatic changes in the tilt angle of the chromophore-functionalized side groups were observed. Following evaluation of the nonlinear optical data with those obtained from atomic force microscopy and ultraviolet–visible, we conclude that second-harmonic generation efficiently probes the polymerization reaction and the conformational changes of the surface-grafted polymer. With polymerization time, the conformation of the surface-tethered polymer changes from a conformation with the polymer backbone and its side groups flat on the surface, i.e., a “pancake” conformation, to a conformation where the polymer backbone is stretched away combined with tilted side groups or an enlarged tilt angle distribution, i.e., a “brush-type” conformation.

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