Amphiphilic branched block copolymers as responsive materials

The ultimate goal of this project is to understand the fundamental relationships between the architecture and chemical design of highly branched multifunctional block copolymers and their supramolecular organization, physical behavior, and microscopic properties at surfaces and interfaces. The present work is focused on synthesis of linear and branched macromolecules with specific topology, using different types of polymerization methods, such as anionic, atom transfer radical polymerization (ATRP), nitroxide mediated polymerization (NMP) and reversible addition-fragmentation chain transfer polymerization (RAFT). The chemical composition of the macromolecules is confirmed by nuclear magnetic resonance (NMR), Fourier transform infra-red (FTIR) spectroscopy, and gel permeation chromatography (GPC). The physical properties of the polymers are analyzed with differential scanning calorimetry (DSC) and X-ray diffraction techniques. The behavior of the amphiphilic macromolecules at the air-water interface and on a solid surface is characterized by X-ray reflectivity and atomic force microscopy (AFM). As concluded in this research for star block copolymers with low number of arms, increasing the number of PS arms stabilized the circular morphology of the Langmuir monolayer. Introducing of ionic amino or carboxyl terminal groups of arms is found to be effective in creating stable and very fine circular domain morphology. Furthermore, adding ionic blocks containing tertiary amino groups allowed tuning their surface properties by changes in both pH and temperature. On the other hand, different surface morphologies ranging from peculiar stripes and net-like patterns to a highly ordered 2D assembly of fine circular domains and peculiar dendritic superstructures were observed for the multiarm star polymers with high number of arms (16-38). Finally, for the hyperbranched block copolymers, AFM revealed morphology transition from very smooth monolayer to formation of nonuniform bilayer structure followed by second collapse and creation of uniform polymeric multilayers. As an outcome of research, fundamental relationships between architecture/chemical composition and resulting structures are suggested. This research expands a range of potential technologies to improve the control over interfacial behavior of the nanoscale polymeric films