ISSN:
1022-1352
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
Polymers 1 of the title monomer, prepared using well-defined molybdenum carbene complexes as catalysts, have been hydrogenated and the structures of the resultant polymers 2 examined by 13C NMR spectroscopy. The hydrogenated polymer made from the all-cis isotactic polymer of (±)-monomer showed a single set of 13C NMR lines as expected for an NX sequence of endo (N) and exo (X) substituents. The hydrogenated polymer made from a cis isotactic polymer of (±)-monomer showed additional fine structure arising from the random incorporation of both enantiomers in the isotactic polymer chain: four equal lines for C-9 (orientational triad sensitivity), two equal lines for C-3, C-4, C-5, and C-1 (dyad sensitivity), but single lines for C-8, C-2, C-7 and C-6 (insensitive to the relative orientation of adjacent repeating units). The hydrogenated polymer made from a trans atactic polymer of (±)-monomer showed fine structure due to the presence of both m and r dyads. That made from a trans atactic polymer of (±)-monomer contains 16 possible triad sequences and gave a more complicated spectrum. A complete assignment was made for the first three polymers and a partial assignment for the fourth. Polymers made using non-carbene catalysts were also examined. Hydrogenation of an all-trans precursor made from (±)-monomer using RuCl3 as catalyst gave an atactic polymer, confirming previous observations. Hydrogenation of a 61% cis, cis/trans blocky precursor, made from (±)-monomer using OsCl3/PhC≡CH as catalyst, gave a syndiotactic-biased stereoblocky polymer, indicating a c/r, t/m correlation in the precursor polymer.
Zusätzliches Material:
4 Ill.
Materialart:
Digitale Medien
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