Synthesis and Characterization of Well Defined AB, ABA Block Copolymers of Polyvinylidene Fluoride By Photomediated Controlled Radical Polymerization

Polyvinylidene fluoride (PVDF) is a fluoropolymer of high interest because of its versatility and unique properties, allowing for its contributions in membrane, coating as well as paint applications. PVDF is well known for its piezoelectric, pyroelectric and dielectric properties, which allows for its versatility. The controlled architecture of the block copolymers of PVDF and its comonomers are pertinent due to the fact that the most practical applications of PVDF are in the form of homo or random copolymers. Through our study, we could produce PVDF monofunctional or bifunctional macroinitiators from the highly reactive Vinylidene Flouride (VDF, B. pt - 84°C) monomer via Iodine Degenerative Transfer (IDT) controlled radical polymerization using metal carbonyl (Mt)_x(CO)_y halide abstractors. However, there is a great challenge in synthesizing well defined PVDF block copolymer architecture. The challenge is the result of using IDT to synthesize PVDF macroinitiators. The PVDF macrointiators synthesized in this way can initiate and have two different chain ends, both with vastly varying reactivities depending on the degree of polymerization as well as conversion. Through various methods, we were able to demonstrate activation of both chain ends of the macroinitiators by using stoichiometric amounts of metal carbonyls such as dimanganese decacarbonyl (Mn₂CO₁₀) and dirhenium decacarbonyl (Re₂CO₁₀). Investigation continued by varying PVDF compositions with other commercially significant monomers such as styrene, Vinyl Acetate, Methyl Acrylate and Isoprene, to name a few. The synthesized macroinitiators and block copolymers were studied and characterized via 1H, 19F, 2D AAHF COSY Nuclear Magnetic Resonance (NMR), Gel Permeation Chromatography, Differential Scanning Calorimetry, Small Angle X-ray Scattering, Atomic Force Microscopy, and Contact Angle analysis. From the results obtained from the characteristic analysis, we were able to understand the preliminary morphology of the blocks, as well as the hydrophobicity and hydrophilicity of the copolymers depending on composition of the blocks. Such characterizations help identify the wide variety of applications for these well-defined block copolymers.