Observing different dynamic behaviors of weakly and strongly adsorbed polystyrene chains at interfaces.

Understanding the dynamic behavior of polymer chains adsorbed onto a solid surface is of great importance for elucidating polymer-surface interactions. Here by using sum frequency generation (SFG) vibrational spectroscopy, we probed the conformational changes of weakly adsorbed and strongly adsorbed polystyrene (PS) chains on sapphire surfaces perturbed by a nonsolvent (deuterated water, D2O) and a good solvent (carbon tetrachloride, CCl4). The SFG results indicated that the PS chains in the weakly adsorbed state were flexible and the chain conformation could easily be altered. Differently, the PS chains in the strongly adsorbed state were rigid and the chain conformation could not be changed. The local structural variations of the weakly and strongly adsorbed PS chains at the interfaces were also discussed in detail with respect to the SFG spectral characteristics. These intriguing experimental results shed light on our understanding of molecular behaviors of polymer chains adsorbed onto a solid surface.