Date of Completion
Polymers, Fluropolymers, block copolymers, controlled radical polymerizations, iodine degenerative transfer
Alexandru D Asandei
Field of Study
Doctor of Philosophy
This thesis focuses on the advancement and development of new polymerization methodologies for the controlled radical polymerizations of 1,3-dienes, (2-methyl-1,3-butadiene, 1,3-butadiene, 2,3-dimethyl-1,3-butadiene) and main chain fluorinated monomers, as well as the ability to synthesize well defined block copolymers thereof. The effect of the reaction variables in the Cp2TiCl-Mediated controlled radical isoprene (2-methyl-1,3-butadiene) polymerizations initiated by epoxide radical ring opening (RRO), was investigated over a wide range of conditions ([Cp2TiCl2]/[epoxide] = 1/1-6/1, [Cp2TiCl2]/[Zn] = 1/0.5-1/8, [isoprene]/[epoxide] = 20/1-1000/1, T = 70-130 °C in THF and dioxane), to reveal a linear dependence of molecular weight on conversion, linear first-order kinetics and moderate polydispersities up to high conversions, with an optimum in initiator efficiency, rate and polydispersity for [epoxide]/[Cp2TiCl2]/[Zn] = 1/3/6-1/4/8 at 90 - 110 °C. NMR studies demonstrated the epoxide initiation and the stereoselectivity of a conventional radical polymerization. Furthermore, random and block copolymers with styrene could also be obtained. This methodology was then expanded, using the optimum conditions, to initiation via single electron transfer (SET) reduction of aldehydes as well as halide abstraction. Subsequently, the three initiating systems were shown to work with both 1,3-butadiene and 2,3-dimethyl-1,3-butadiene. This system was then examined with the main chain fluorinated monomer vinylidene fluoride (VDF), and a series of epoxides, aldehydes, halides and peroxides, known to initiate both styrene and diene polymerizations in the presence of titanocenechloride were tested as potential room temperature VDF initiators. However, regardless of reaction conditions, no polymer was obtained. This is most likely due to the incompatibility of solvents appropriate for Cp2TiCl2 reductions with those conducive of VDF polymerizations. Thus, polar solvents appropriate for Cp2TiCl2 are strong chain transfer agents towards VDF (dioxane, THF, diglyme, acetone), while solvents that limit chain transfer to PVDF react with titanocenechloride. Finally a series of transition metal carbonyl complexes (Re2(CO)10, Mn2(CO)10, Cp2W2(CO)6, Cp2Mo2(CO)6, Fe(CO)5,Cp2Fe2(CO)4, Cp*2Cr2(CO)4,Co2(CO)8 Mo(CO)6, Cr(CO)6) in conjunction with alkyl or perfluoroalkyl halides (CH3(CH2)5Cl, CH3(CH2)5Br, CH3(CH2)5I, CH3I, CCl4, CCl3Br, CF3(CF2)3I Cl(CF2)8Cl, Br(CF2)6Br, and I(CF2)6I) were evaluated in the initiation and respectively control of vinylidene fluoride (VDF) polymerization. Perfluoroalkyl iodides (RFI = CF3(CF2)3I, I(CF2)6I) mediated the VDF controlled radical polymerization (CRP) via iodine degenerative transfer (IDT). The fastest rates were observed with RFI used in conjunction with Re2(CO)10 and Mn2(CO)10. A selection of the metal complexes were then evaluated in the PVDF-I activation, where Re2(CO)10 Mn2(CO)10, Cp2W2(CO)6, Cp2Mo2(CO)6, and Cp2Fe2(CO)4 provided complete activation of both PVDF-CH2-CF2-I and PVDF-CF2-CH2-I chain ends and were subsequently used towards the synthesis of well-defined block copolymers with vinyl acetate, t-butyl acrylate, methyl methacrylate, isoprene, styrene, and acrylonitrile, from their respective metal carbonyls.
Simpson, Christopher P., "Transition Metal Mediated Controlled Polymerizations of 1,3-Dienes, and Main Chain Fluorinated Monomers; Towards the Synthesis of Complex Macromolecular Structures." (2014). Doctoral Dissertations. 508.