Interfacial morphology and behavior of rod-dendrons and carbosilane dendrimers

Self assembly of polymer molecules offers a simple and efficient means of creating surfaces on the nanoscale. By utilizing polymer molecules with specific properties, the formation of supramolecular structures can be predicted. Here we investigate the ability of amphiphilic dendron-rod molecules with three hydrophilic polyethylene oxide (PEO) branches attached to a hydrophobic octa-p-phenylene rod stem to form organized micellar structures on a solid surface, as well as the surface organizational tendencies of carbosilane dendrimers with mesogenic terminal groups. The asymmetric shape of the dendron-rod molecules is a major factor in the formation of non-planar micellar structures in solution and in the bulk state (cylindrical and spherical). However, the question of their organization at the planar interfaces, which are unfavorable for such highly curved structures, remains open. We observed that the novel dendritic-rod amphiphilic molecules bearing hydrophobic terminal groups can assemble themselves in dense and thick monolayers with multiple intra-layer transitions due to the hydrophobic terminal groups serving as anchors, preventing the PEO dendrons from completely submerging in the water subphase. We observed these molecules forming planar ribbon-like structures as well as two dimensional micellar structures under lateral compression at the air/water interface. We also observed these molecules undergoing crystallization into ribbon-like nanofiber structures. Prepared films of carbosilane dendrimers were also shown to exhibit nanoscale assembly into locally organized lamellar structures with d-spacing of 5-7nm. We propose the strong intermolecular interactions between terminal mesogenic groups along with the hydrophilic silicon substrate causes these molecules to assume an oblate, pancake-like conformation on the surface with interdigitating terminal groups creating lamellae with alternating cores