Characterization of Organometallic Polymers by Chromatographic Methods and Nuclear Magnetic Resonance. Part 2

摘要

Continuing research into the analytical methodology for characterization of organometallic polymers (OMPs) has produced improved methods of characterization by size exclusion chromatography (SEC) and Fourier transform nuclear magnetic resonance (FTNMR). Molecular weight (MW) and MW dispersion (MWD), as well as the amount of tin associated with fractions of various MW can now be reliably determined by SEC coupled with various detectors: differential refractive index (delta RI), ultra-violet (UV), and graphite furnace atomic absorption (GFAA) spectroscopy. Configurational sequencing in terms of both tacticity and sequencing of monomer units can be determined by FTNMR, as well as certain tin-containing impurities. Removal of tributyltin groups to produce a metal-free copolymer allows much more informative FTNMR spectra to be obtained. All of the polymers examined are approximately 80 percent racemic (r) and 20 percent meso (m) in tacticity (i.e., predominantly syndiotactic). The growing chain end in the copolymer adds either of the monomer units approximately in proportion to its instantaneous concentration in the mixture (i.e., at random).