Premium
On‐Line SEC‐NMR Analysis of the Stereocomplex of Uniform Isotactic and Uniform Syndiotactic Poly(methyl methacrylate)s
Author(s) -
Ute Koichi,
Niimi Ryo,
Matsunaga Morikatsu,
Hatada Koichi,
Kitayama Tatsuki
Publication year - 2001
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/1521-3935(20011001)202:15<3081::aid-macp3081>3.0.co;2-z
Subject(s) - tacticity , acetone , materials science , nmr spectra database , methyl methacrylate , poly(methyl methacrylate) , size exclusion chromatography , polymer chemistry , polymer , analytical chemistry (journal) , elution , proton nmr , spectral line , nuclear magnetic resonance spectroscopy , chemistry , monomer , polymerization , chromatography , organic chemistry , physics , astronomy , enzyme , composite material
Mixtures of uniform isotactic ( it ‐) and uniform syndiotactic ( st ‐) 46mers of methyl methacrylate (C 234 H 378 O 92 ; molecular weight ( M ) = 4 663) in acetone/acetone‐ d 6 at –15°C were analyzed by size exclusion chromatography coupled to 750 MHz 1 H NMR spectroscopy (on‐line SEC‐NMR). Each SEC‐NMR chromatogram of the mixtures showed two elution peaks corresponding to the stereocomplex and the dissociated 46mers. When a detection temperature (the temperature of the flow NMR cell) was adjusted to the column temperature of –15°C, SEC‐NMR spectra of the stereocomplex showed significant broadening of resonances due to the restricted segmental mobility of polymer chains. On the other hand, a detection temperature of 45°C permitted us to observe the it ‐ and st ‐sequences in the OCH 3 and α ‐CH 3 resonances as well‐resolved signals. The st ‐/ it ‐compositions of the stereocomplex were determined to be 1.61–1.94. Accordingly, at least two types of stereocomplexes with different compositions (e. g. st ‐/ it ‐ = 1/1 and 2/1) should coexist in the mixtures. Both the complexes with 1/1 ( M = 9 326) and 2/1 ( M = 13 989) compositions were suggested to have the hydrodynamic volumes corresponding to that of it ‐PMMA with M ≈ 7 000. Multivariate curve resolution was successfully applied to the post‐analysis of the SEC‐NMR experiments to extract component‐resolved spectra of the complex and the dissociated 46mers.