EFFECT OF CHAIN ARCHITECTURE ON ADSORPTION FROM DILUTE-SOLUTION - OMEGA-FUNCTIONALIZED LINEAR AND MONO-OMEGA-FUNCTIONALIZED, DI-OMEGA-FUNCTIONALIZED, AND TRI-OMEGA-FUNCTIONALIZED 3-ARM STAR POLYBUTADIENES

The adsorption behavior of omega-functionalized linear and mono-, di-, and tri-omega-functionalized three-arm star polybutadiene (PB) sample s from the mixed solvent of cyclohexane and toluene (50% by volume) on silicon wafers is investigated by means of null-ellipsometry at 20.0 degrees C. Under these conditions no association of the sulfozwitterio nic functional groups is detected in solution with dynamic light scatt ering, and there is sufficient contrast for in situ ellipsometric adso rption measurements. The adsorbed end-functionalized linear PB chains have a ''brushlike'' conformation. In the case of the functionalized s tar PB, the adsorbed amount increases when the number of functionalize d arms increases from 1 to 3. However, the grafting density is more in fluenced by the molecular weight than by the number of functional grou ps. The adsorbed stars are less stretched than the linear chains. The adsorption energy is calculated as (9 +/- 1)kT. The diffusion coeffici ent and hydrodynamic radius are determined with dynamic light scatteri ng. The adsorption kinetics from time-resolved ellipsometric measureme nts show two regimes: (i) a diffusion-controlled process at the initia l stages and (ii) at longer times, an exponential behavior, where the arriving chains must penetrate a barrier formed by the already adsorbe d chains. The stars penetrate this barrier faster than the linear PB c hains.