The adsorption behavior of ω-functionalized linear and mono-, di-, and tri-ω-functionalized three-arm star polybutadiene (PB) samples from the mixed solvent of cyclohexane and toluene (50% by volume) on silicon wafers is investigated by means of null-ellipsometry at 20.0 °C. Under these conditions no association of the sulfozwitterionic functional groups is detected in solution with dynamic light scattering, and there is sufficient contrast for in situ ellipsometric adsorption measurements. The adsorbed end-functionalized linear PB chains have a "brushlike" conformation. In the case of the functionalized star PB, the adsorbed amount increases when the number of functionalized arms increases from 1 to 3. However, the grafting density is more influenced by the molecular weight than by the number of functional groups. The adsorbed stars are less stretched than the linear chains. The adsorption energy is calculated as (9 ± 1)kT. The diffusion coefficient and hydrodynamic radius are determined with dynamic light scattering. The adsorption kinetics from time-resolved ellipsometric measurements show two regimes: (i) a diffusion-controlled process at the initial stages and (ii) at longer times, an exponential behavior, where the arriving chains must penetrate a barrier formed by the already adsorbed chains. The stars penetrate this barrier faster than the linear PB chains.
|Original language||English (US)|
|Number of pages||7|
|State||Published - Mar 20 1996|
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces