| This thesis describes the preparation of stimuli-responsive molecular brushes with complex architectures. In chapter 2, the preparation of molecular brushes with a spontaneous gradient along the backbone is described. Gradient brushes have the unique topological arrangement of the branched structure, leading to broken symmetry. They are particularly interesting, since the rod-globule transition occurs at the end where the brush is densely grafted, leaving a molecule with a globular "head" and an extended "tail" upon compression due to their broken symmetry. In chapter 3, the preparation of cylindrical core-shell brushes by a combination of ring opening polymerization (ROP) and ATRP is described. These brushes have block copolymer side chains, i.e., a crystalline poly(epsilon-caprolactone) (PCL) core with an amorphous poly(n-butyl acrylate) (PBA) shell. In chapter 4, the preparation of hetero-grafted A-B type brush-block-brush copolymers is described. AB-type brush-block -brush copolymers with PCL and PBA side chains were synthesized for the first time by entire 'grafting from' technique. In chapter 5, 6 and 7, I describe comprehensive rational approaches to impart smartness in molecular brushes by integrating all the knowledge of brush architectures. In chapter 5, light-induced reversible formation of polymeric micelles is described. I investigated stimuli-responsiveness in polymeric micelles as a model system before getting into more complex molecular brush systems. An amphiphilic block copolymer, consisting of a polymethacrylate block with hydrophobic spiropyran (SP) moieties and a hydrophilic poly(ethylene oxide) (PEO) block, was prepared. In chapter 6, the preparation and properties of photo-tunable temperature-responsive molecular brushes are described. In chapter 7, pH-Induced conformation changes of the loosely-grafted molecular brushes are described. A series of the water-soluble loosely-grafted poly(acrylic acid) (PAA) brushes with four different grafting densities were synthesized by the "grafting from" approach using ATRP. In chapter 8, I describe the preparation of polymer brushes from a functionalized PDMS surface to generate molecular scale roughness.; Appendix 1 includes the preparation of molecular brushes with long side chain brushes. Another aspect of controlling molecular architectures of the brush molecules, control of the length of the side chains, is briefly discussed. Appendix 2 covers additional research that was conducted for the preparation of supersoft elastomeric materials using chemical or physical crosslinking of the molecular brushes. Appendix 3 includes solution properties of the molecular brushes using NMR relaxation dynamics. |
