Synthesis and Self-Assembly of Amphiphilic Bottlebrush Copolymers
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Polymeric materials with nanosized channels can serve as versatile platforms for a variety of applications. Self-assembly of block copolymers into nanostructured morphologies and subsequent removal one of the components provides a reliable route to nanoporous polymers with high pore densities and controlled pore sizes. However in my first approach is hindered by difficult control of morphology orientation and a limited pore size range. Therefore we develop multicomponent bottlebrush copolymers that generate nanoporous membranes with highly aligned channels and controlled pore sizes upon interfacial self-assembly Bottlebrush copolymers are macromolecules with a highly branched architecture containing polymeric side chains on each repeat unit. Steric repulsion between densely grafted polymeric sidechains causes the backbone to stretch out, giving rise to macromolecules with persistent vesicle shapes in solution. The target bottlebrush copolymers were designed to contain core shell hydrophobic domains with a cross linkable shell layer and degradable core layer to generate nanoporous structures, as well as a hydrophilic block to aid in interfacial assembly and vertical alignment of the molecules at the interfaces. The polymers were synthesized by ring opening metathesis of the corresponding macromonomers, which were prepared by a combination of controlled radical and ring opening polymerizations. The assembly of these macromolecules at the aqueous solution.Second approach focus on amphiphilic bottlebrush copolymers with a gradient compositional profile were synthesized by one step ring-opening metathesis copolymerization of exo-norbornene-functionalized polyethylene oxide (PEO) and endonorbornene-functionalized polylactide (PLA) macromonomers. The obtained bottlebrush copolymers featured PLA-rich and PEO-rich domains at each end and gradient interface in the middle. Copolymers with varying degrees of hydrophilicity were obtained by controlled feed ratios of the corresponding macromonomers. Self-assembly of amphiphilic gradient bottlebrush copolymers in aqueous solutions was studied by dynamic light scattering and transmission electron microscopy, and was compared to that of the bottlebrush block copolymers with a sharp interface between the hydrophilic and hydrophobic domains. Uniform micelles were formed by gradient bottlebrush copolymers synthesized by the user-friendly one-step copolymerization of PEO and PLA macromonomers. Critical micelleXIII concentrations of the gradient bottlebrush copolymers were evaluated by the pyrene fluorescence method. The studies have revealed the importance of the gradient interface on polymer self-assembly.