Glassy dynamics of poly(2-vinyl-pyridine) brushes with varying grafting density

Soft Matter
Nils NeubauerF Kremer

Abstract

The molecular dynamics of poly(2-vinyl-pyridine) (P2VP) brushes is measured by Broadband Dielectric Spectroscopy (BDS) in a wide temperature (250 K to 440 K) and broad spectral (0.1 Hz to 1 MHz) range. This is realized using nanostructured, highly conductive silicon electrodes being separated by silica spacers as small as 35 nm. A "grafting-to"-method is applied to prepare the P2VP-brushes with five different grafting densities (0.030 nm(-2) to 0.117 nm(-2)), covering the "true-brush" regime with highly stretched coils and the "mushroom-to-brush" transition regime. The film thickness ranges between 1.8 to 7.1 (±0.2) nm. Two relaxations are observed, an Arrhenius-like process being attributed to fluctuations in the poly(glycidyl-methacrylate) (PGMA) linker used for the grafting reaction and the segmental dynamics (dynamic glass transition) of the P2VP brushes. The latter is characterized by a Vogel-Fulcher-Tammann dependence similar to bulk P2VP. The results can be comprehended considering the length scale on which the dynamic glass transition (≤1 nm) takes place.

References

Feb 22, 1991·Science·S T Milner
Mar 5, 2008·The Review of Scientific Instruments·A Serghei, F Kremer
May 18, 2011·Journal of the American Chemical Society·Keewook PaengM D Ediger
May 19, 2009·Macromolecular Rapid Communications·Petra UhlmannManfred Stamm
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Sep 29, 2011·Langmuir : the ACS Journal of Surfaces and Colloids·Cinzia RotellaMichael Wübbenhorst
Sep 17, 2013·Physical Review Letters·Daniele CangialosiJuan Colmenero
Sep 21, 2013·Science·Martin TressFriedrich Kremer

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