mz400413v_si_001.pdf (788.91 kB)
Molecular Weight Dependence of Polymer Chain Mobility within Multilayer Films
journal contribution
posted on 2013-10-15, 00:00 authored by Li Xu, Victor Selin, Aliaksandr Zhuk, John F. Ankner, Svetlana A. SukhishviliFluorescence
recovery after photobleaching has been applied to
determine, to our knowledge for the first time, the molecular weight
(Mw) dependence of lateral diffusion of
polymer chains within layer-by-layer (LbL) films. As shown by neutron
reflectometry, polyelectrolyte multilayers containing polymethacrylic
acid (PMAA, Mw/Mn < 1.05) of various molecular weights assembled from solutions
of low ionic strengths at pH 4.5, where film growth was linear, showed
similar diffusion of PMAA in the direction perpendicular to the film
surface. At a salt concentration sufficient for unfreezing electrostatically
bonded chains, layer intermixing remained almost unaffected (changes
<1.0 nm), while the lateral diffusion coefficient (D) scaled with the PMAA molecular weight as D ∼ Mw–1±0.05.