Polyphosphazenes for polymeric micelles and optical applications

The synthesis and characterization of polymeric micelles and dendrimers based on polyphosphazene materials were systematically investigated. In addition, this dissertation is concerned with the novel polymeric optical waveguide materials based on the polyphosphazene cyclomatrix structure.Amphiphilic triblock copolymers (PN-PPG-PN) were synthesized with two hydrophobic poly[bis(2,2,2-trifluoroethoxy)phosphazene] blocks linked to a central poly(propylene glycol) block. These were synthesized via the cationic polymerization of chlorophosphoranimines and coupling of these blocks to a diamine functionalized poly(propylene glycol) followed by macromolecular substitution. The micellar characteristics of these amphiphilic triblock copolymers were examined using fluorescence techniques, dynamic light scattering, and transmission electron microscopy. The critical micelle concentrations (cmcs) of PN-PPG-PN polymeric micelles determined by a fluorescence technique were in the range of 9.5-12.4 mg/L. The mean diameters of the micelles of the PN-PPG-PN polymeric micelles, measured by dynamic light scattering, were between 197-364 nm.Hydrophobic block copolymers with adamantyl-polyphosphazene and polystyrene blocks were synthesized via the controlled cationic living polymerization of a phosphoranimine at ambient temperature. beta-Cyclodextrins (beta-CDs) were then complexed with the adamantyl side groups in aqueous media to generate amphiphilic block copolymers. These underwent micelle formation in an aqueous environment. The micellar behavior of these complexes was monitored using fluorescence techniques, transmission electron microscopy (TEM), and dynamic light scattering. The critical micelle concentration of the adamantyl polyphosphazene-polystyrene block copolymer complexes was 0.925 mg/L. TEM imaging revealed spherically shaped micelles. A mean diameter of 193 nm was measured by dynamic light scattering. It was possible to control micelle formation by changing the amount of beta-CD in the aqueous medium at constant block copolymer concentration.Three novel polyphosphazene-functionalized diaminobutane poly(propyleneimine) dendrimers have been prepared and investigated for their properties as prospective hydrophobic drug delivery systems. The solubilization and release properties of these functionalized dendrimers have been investigated by absorption and fluorescence spectroscopy by using pyrene as a probe. The introduction of amphiphilic phosphazene groups at the external surface of the dendrimers affects the solubilization and guest release properties compared to the behavior of the parent dendrimers. The release of encapsulated guest molecules is triggered by the addition of sodium chloride solution. It has been established that these novel dendrimeric compounds exhibit useful protective and targeting properties. These properties render the new molecules promising candidates for salt-responsive controlled-release systems, possibly including prospective drug delivery applications.Novel cyclophosphazenes containing aryl trifluorovinyl ether functional units together with the corresponding perfluorocyclobutane (PFCB) phosphazene polymers have been synthesized and characterized. These polymers have desirable properties for low optical loss waveguide applications. The monomers used in this study were prepared from sodium 4-(trifluorovinyloxy)phenoxides and cyclophosphazenes with fluorinated alkoxy or aryloxy side groups. The resulting polymers, produced by 2pi + 2pi cyclopolymerization of the aromatic trifluorovinyl ether moieties, showed good chemical stabilities and high thermal stabilities (Td up to 330°C). Tough and transparent thin films of these polymers were readily prepared by solvent-free processes using spin-coating of the monomers. By adjusting the ratio of monomers, the refractive index of the polymers could be controlled from 1.4528 to 1.5187 at 1550 nm, with exceptionally low birefringence of Deltan = 0 to 0.0003 +/- 0.0002. A propagation optical loss lower than &sim0.25 dB/cm at 1550 nm was determined from the polymer films, for the TE polarization by measuring the scattered light intensity along the slab waveguide length. Such good thermal and optical properties demonstrate that these novel PFCB-based phosphazene polymers are promising candidates for optical waveguide or optical device materials.Amphilic triblock copolymers with varying ratios of hydrophilic poly[bis-(methoxyethoxyethoxy)phosphazene] (MEEP) and relatively hydrophobic poly-(propylene glycol) (PPG) blocks were synthesized via the controlled cationic-induced living polymerization of a phosphoranimine (Cl3P=NSiMe3) at ambient temperature. A PPG block can function as either a classical hydrophobic block or a less hydrophobic component by varying the nature of a phosphazene block. The aqueous phase behavior of MEEP-PPG-MEEP block copolymers was investigated using fluorescence techniques, TEM, and dynamic light scattering. The critical micelle concentrations (cmcs) of MEEP-PPG-MEEP block copolymers were determined to be in the range of 3.7-16.8 mg/L. The mean diameters of MEEP-PPG-MEEP polymeric micelles, measured by dynamic light scattering, were between 31 and 44 nm. The equilibrium constants of pyrene in these micelles ranged from 4.7 x 104 to 9.6 x 104.