Layer-by-Layer assembly of two polyacrylate derivatives: Effect of solvent composition and side-chain structure

We fabricated Layer-by-Layer (LbL) assemblies of poly(8-(4-carboxy-phenoxy)-octyl acrylate) (PCPOA) and poly(3-(4-pyridyl)-propyl acrylate) (PPyPA) in solvent mixtures of tetrahydrofuran (THF) and ethanol with different compositions. It was confirmed by FT-IR spectroscopy that the driving force for the assembly was mainly hydrogen bonding. Effect of solvent composition on the assembly was investigated using UV-vis spectroscopy. The amount of polymers in the film initially decreased with increase of THF content in solvent mixture, reaching a minimal value in the range between 45% and 70%, and then increased with increase of THF content. Combined with the polymer radius of gyration obtained from Dissipative Particle Dynamics simulation, we found that the adsorption amount of polymer is small when conformation of polymer is extended in a solution. We also investigated the effect of the number of methylene groups in polymer side chains on LbL assembly. When poly(2-(4-carboxy-phenoxy)-ethyl acrylate) (PCPEA) was used instead of PCPOA, we found that more polymers were adsorbed onto the substrate. In addition, we compared the normalized growth curves of both assemblies and found that the deviation of (PCPEA/PPyPA)n from linear growth was larger than that of (PCPOA/PPyPA)n.