Nanomechanics of Polyphenylacetylene Derivatives by AFM-based SMFS

We quantitatively investigated the effect of iodine and pH on the stability of the helical structure formed by polyphenylacetylene derivatives using atomic force microscopy (AFM) based single-molecule force spectroscopy (SMFS) and circular dichroism (CD). The AFM measurement results showed that the addition of iodine into the system caused the decrease of the plateau heights in the stretching curves recorded during the SMFS experiments. In addition, the pH value increase can weaken the intra. polymer hydrogen bond and interrupt the integrity of the helical structure. However, the CD result did not show any detectable changes upon the addition of iodine and the change of pH value, which indicate that SMFS is a very sensitive and powerful method for subtle structure study.