Spray-assisted layer-by-layer assembly of decorated PEI/PAA films: morphological, growth and mechanical behavior

The development and study of new smart materials is an emergent research area with high potential applications. In this study, we have fabricated poly(ethyleneimine)/poly(acrylic acid) multilayer films on glass substrates by automated spray-layer-by-layer (spray-LbL) technique. By analyzing the changes in thickness, roughness and elasticity, with fine-tuning of the operational parameters of the spray-LbL system, evident trends of its effect on the multilayer construction were observed. In the case of its mechanical properties, the stability of Young’s modulus (up to 8.25 GPa) from film thickness at this scale was detected, making it variable for other factors such as pH and molecular weight. This work also identified the healability phenomenon that is present in the exponentially grown PEI/PAA samples, based on the reduction in viscosity of the polymer complexes and the interdiffusion of polyelectrolytes at the damaged zones in the presence of water. These properties allow for the assembly of a highly electrically conductive multilayered film by dispersion of a top layer of silver nanowires whose sheet resistance is increased around 5% after multiple damaging events. These experimental results provide new data for the evaluation and design of polyelectrolyte multilayers assembled with a spin-assisted automated spray deposition system to serve as substrates for mechanoelectrical devices which can benefit from its self-healing and modulated mechanical capabilities.