Functional polymeric assembly materials via non-transition metal iodide catalyzed controlled radical polymerization

• Main Author: Sarkar, Jit
• Other Authors: Goto Atsushi
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: DRNTU::Science::Chemistry
• Online Access: https://hdl.handle.net/10356/106450; http://hdl.handle.net/10220/47972
• Institution: Nanyang Technological University

Chapter 1 introduces the advantages and disadvantages of the well-known living radical polymerization (LRP) systems. The advantages of reversible complexation mediated polymerization (RCMP) over other LRPs have been discussed. The self-assembly methods of block copolymers for generating self-assemblies and their influencing parameters have been discussed in brief. The motivations and aims for the works in this Thesis are discussed. In Chapter 2, Alkali metal iodides, NaI, KI, and CsI, and alkaline earth metal iodides, MgI2 and CaI2, were systematically studied as catalysts. Among the five catalysts, NaI exhibited a particularly high reactivity. NaI is also amenable to styrene, acrylonitrile, and functional methacrylates. In addition to homopolymers, NaI also afforded well-defined block copolymers, telechelic polymers, and a star polymer. The high monomer versatility and accessibility to a wide range of polymer architectural designs are desirable features of this polymerization system. In Chapter 3, NaI-catalyzed RCMP was combined with polymerization induced self-assembly (PISA) to generate self-assemblies. Poly(methacrylic acid) (PMAA) and poly(methyl methacrylate) (PMMA) were used as hydrophilic and hydrophobic segments, respectively, to generate self-assemblies. Micelles (nano-particles), worms (nano-cylinders), and vesicles (nano-capsules) were generated in ethanol at 5-9 wt% solid content. In Chapter 4, biocompatible polymer nano-capsules (or vesicles) were prepared using aqueous emulsion PISA (polymerization induced self-assembly) catalyzed by NaI. The hydrophilic and hydrophobic monomers used in this study were poly(ethylene glycol) methyl ether methacrylate (PEGMA) and methyl methacrylate (MMA), respectively. Spheres and vesicles were generated depending on the degrees of polymerization (DPs) of the hydrophilic and hydrophobic segments in the block copolymers. The nano-capsules (or vesicles) were successfully obtained with relatively high (8-9%) solid concentrations. The encapsulation property of the obtained vesicles was studied using a hydrophilic dye, i.e., Rhodamine-B. In a typical example loading capacity was 0.28% and the encapsulation efficiency 48%. In Chapter 5, we carried out RCMP of a macromonomer, i.e., poly(dimethylsiloxane) methacrylate (PDMSM), and prepared a bottlebrush polymer via a grafting-through approach. The obtained bottlebrush polymer (PPDMSM-I) was further used as a macroinitiator in the polymerization of a divinyl crosslinkable monomer, i.e., ethylene glycol dimethacrylate (EGDMA), yielding a bottlebrush particle. For comparison, we also synthesized particle whose shell consisted of a linear (non-bottlebrush) polymer, i.e., poly(methyl methacrylate) (PMMA). In tetrahydrofuran (THF), above a critical overlapping concentration (5 wt%) of the particle, the viscosity of the PMMA particle significantly increased because of the entanglement of the linear shell polymers, and the viscosity of the PPDMSM particle became much lower than that of the PMMA particle, demonstrating a better lubrication property of the bottlebrush particle. The observed lower viscosity of the PPDMSM particle is ascribed to the entropic repulsion of the sterically hindered bottlebrush polymer shell.