Blob Size Controls Diffusion of Free Polymer in a Chemically Identical Brush in Semidilute Solution

Abstract

The diffusion of rhodamine-labeled poly(ethylene glycol) (r-PEG) within surface-grafted poly(ethylene glycol) (s-PEG) layers in aqueous solution at 18 °C was measured by fluorescence correlation spectroscopy. The diffusion coefficient of r-PEG within s-PEG was controlled by the grafting density, σ, and scaled as σ–1.42±0.09. It is proposed that a characteristic blob size associated with the grafted (brush) layer defines the region through which the r-PEG diffusion occurs. The diffusion coefficients for r-PEG in semidilute solution were found to be similar to those in the brushes.

Lateral diffusion of single poly(ethylene oxide) chains on the surfaces of glassy and molten polymer films

“…50 That PEO takes up a pancake structure has been questioned for hydrophobic surfaces 51 but force spectroscopy has revealed that adsorption as a pancake does occurs on some surfaces. 23 Bulk measurements of PEO diffusion have a diffusion coefficient similar to the maximum surface diffusion values reported here, 22,26,28 and so it may be argued that the conformational transition just below the glass transition amounts to desorption. Nevertheless, the relative contributions of adsorption and desorption are important in some diffusion mechanisms.…”

“…The maximum diffusion coefficients are similar to those in bulk solution for PEO of similar molar mass. 22,26,28 The blend data reveal two peaks in the diffusion coefficient: one corresponding to the glass transition temperature of the PBMA-rich phase and the other to that of the PMMA-rich phase. In both cases, the peaks are located ~10 K below the corresponding expansivity change measured using ellipsometry (Figure S1b).…”

“…21 A polymer that is fully adsorbed in a 'pancake' configuration 22 on the surface is constrained and exhibits less movement than one that has fewer contact points on the surface. 23 The diffusion of PEO on surfaces is a function of other parameters such as the concentration of adsorbed polymer [24][25][26][27] or the presence of topographic constraints. 28,29 All of these experiments concern the diffusion at the solid-liquid interface.…”

Surface-Grafted Poly(ionic liquid) that Lubricates in Both Non-polar and Polar Solvents

“…The surface interactions acquired when the borosilicate colloidal probe was approaching the PIL samples were analyzed to validate the hypothesis that the PIL is solvated to lubricate in water, but is collapsed on the surface to form a compact layer in dodecane with minimal surface interaction. As demonstrated in previous studies, such a method offers both a qualitative judgment on the solvation state of the surface-grafted polymer and a quantitative approach to evaluate the thickness of the brush layer by measuring the onset of repulsion upon contact. ,,− Figure shows representative plots of the approaching curves of all the PIL samples acquired in water and dodecane.…”

“…As demonstrated in previous studies, such a method offers both a qualitative judgment on the solvation state of the surface-grafted polymer and a quantitative approach to evaluate the thickness of the brush layer by measuring the onset of repulsion upon contact. 16 , 45 , 51 − 54 Figure 6 shows representative plots of the approaching curves of all the PIL samples acquired in water and dodecane.…”