Fabrication and Characterization of Multilayer Films from Amphiphilic Poly(p-phenylene)s

Over the past two decades, considerable efforts have been devoted to the development of conjugated polymeric materials for electronic applications due to the tunability of their properties through variation of their chemical structure. The LB technique is one of the most effective and precise methods for controlling the organization and thereby the properties of polymer films at the nanoscale for device fabrication. A detailed study was performed on the Langmuir−Schaefer (LS) monolayer and Langmuir−Blodgett−Kuhn (LBK) multilayer formation of newly designed conjugated poly(p-phenylene)s (C_nPPPOH), incorporated with alkoxy groups with different chain lengths (C₆H₁₃O-, C₁₂H₂₅O-, and C₁₈H₃₇O-) and hydroxyl groups on the polymer backbone. The monolayer formed at the air−water interface was characterized using surface pressure−area isotherms, including hysteresis measurements. The films were then transferred to different hydrophilic solid substrates and analyzed using surface plasmon resonance spectroscopy, UV−vis spectroscopy, fluorescence spectroscopy, and AFM measurements. The results showed that the polymer with a short alkoxy chain (C₆PPPOH) forms uniform monolayers at the air−water interface and can be transferred as multilayer films compared to C₁₂PPPOH and C₁₈PPPOH. The observed film thicknesses measured by SPR and AFM studies were similar to the theoretical value obtained in the case of C₆PPPOH, whereas this was not the case with the other two polymers. The present study shows that the polymer C_nPPPOH with short alkoxy chain can be transferred onto different solid substrates for device fabrication with molecular level control.