Molecular Dynamics of Swollen Poly(2-vinylpyridine) Brushes

The influence of swelling on the molecular dynamics of poly­(2-vinylpyridine) (P2VP) brushes is measured by broadband dielectric spectroscopy (BDS) in a broad temperature (350–420 K) and spectral (0.1 Hz–1 MHz) range with nanostructured, highly conductive silicon electrodes, separated by 35 nm high insulating silica spacers. A “grafting-to” method is applied to prepare P2VP brushes with a grafting density σ = 0.12 nm^–2 and a film thickness <i>d</i> = 7.3 nm as measured by ellipsometry. Swelling of the P2VP brushes is realized with tetrahydrofuran (THF) vapor using a flow cell. In the dry state, the segmental dynamics of the P2VP brushes coincides with the dynamic glass transition of the bulk system while in the swollen state it becomes faster by up to 1–2 decades due to the plasticizing effect of THF