Force Spectroscopy on Dendronized Poly(p-phenylene)s: Revealing the Chain Elasticity and the Interfacial Interaction

Single-chain manipulation of two second-generation dendronized polymers, hydrophobic and amphiphilic poly( p -phenylene), was performed by using single-molecule force spectroscopy on the basis of atomic force microscopy. In tetrahydrofuran (THF) buffer, the individual amphiphilic dendronized polymer chain exhibits larger elasticity than the corresponding hydrophobic dendronized polymer chain does. The larger elasticity of the single amphiphilic polymer chain is probably from the collapse of oligoethyleneoxy chains in THF, which is a poor solvent for them. While using CH 2 Cl 2 as a buffer, all the side groups can be expanded; the elasticity of the amphiphilic polymer chain is therefore smaller than that in THF. The individual hydrophobic polymer exhibits the same elasticity in THF and CH 2 Cl 2 because of the similar polymer chain conformation in the two buffers. Moreover, the adhesion−force measurements in a poor solvent at the interface reveal that the poor solubility of the polymer side groups as well as the hydrophobic interaction between the surface and the polymer side groups enhances the adhesion force.