Electrochemical Quartz Crystal Microbalance Study of the Growth Characteristics of N-Alkylpyrrole: Organic Monolayers as Nucleation Sites for Ordered Polymer Growth

The electrochemical polymerization of the n -alkylpyrrole, N -hexadecylpyrrole (HDPy) to form poly( N -hexadecylpyrrole) (PHDPy) was monitored at both a bare gold electrode surface and a gold surface modified with bis(ω-( N -pyrrolyl)- n -undecyl) sulfide (BPUS). The film growth process was monitored by chronoamperometry and electrochemical quartz crystal microbalance (EQCM). Both techniques revealed that there is a fundamental difference in the nucleation and growth of the polymer films on the modified versus the unmodified electrode surface. EQCM data revealed that the PHDPy film formed on the BPUS-modified electrode was much denser and grew in a more ordered manner than that formed on the bare gold surface. The film formed on the modified electrode was also found to be more resilient than that formed on the bare gold surface, withstanding repeated cycling in an electrolyte solution. These experiments demonstrate that the surface-confined pyrrole units on the modified electrode serve as specific nucleation sites to induce long-range order in the polymer film.