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The polymerization of phenyl vinyl sulfoxide in blocks of increasing enantiomeric excess was carried out. Portions of the polymer were removed after each charge of monomer was consumed. The poly(pheny1 vinyl su1foxide)s were characterized by gel permeation chromatography and nuclear magnetic resonance spectroscopy. Reduction of the poly(pheny1 vinyl su1foxide)s to poly(pheny1 vinyl sulfide)s permitted assignment of the polymer stereochemistry and verification that stereogradient polymers were formed.

1509mosphere. The crude product was obtained by distillation under a reduced pressure. It was purified carefully by fractional distillation at 58 "C (2 mmHg) [lit.15 61 "C (0.3 mmHg)] to give 8.9 g (55 mmol, 83%) of colorless liquid 1: CCl& 6 7.58, 7.17 (4 H, m, phenyl), 6.67 (1 H, 2d, vinyl CH), 5.69,5.19 (2 H, 2d, J = 11, 18 Hz, vinyl CH,), 4.40 (1 H, m, SiH), 0.33 (6 H, d, SiCH3).In order to remove impurities in monomers, benzylmagnesium chloride (5 mL, 0.5 M solution in THF) was added to 1 (5.0 g) at 0 "C under a nitrogen atmosphere, and the mixture was stirred for 10 min. It was then degassed and distilled on the vacuum line into the ampules fitted with breakseals. Thus, 1 distilled from THF solution was obtained and stored at 0 "C until ready for use. Similarly, styrene, a-methylstyrene, and isoprene were purified and stored in the ampules with breakseals.Polymerization Procedure. All the polymerizations were carried out at -78 "C with shaking under high vacuum conditions (-lo4 mmHg) in an all-glass apparatus equipped with breakseals. The polymerization of 1 was usually completed within less than 5 min and was terminated with methyl iodide after 5-10 min of the polymerization. The polymers were precipitated by adding a large excess of methanol. They were redissolved in THF, precipitated into methanol 2 additional times, and freeze-dried.Block copolymerizations and the treatment of the resulting copolymers were also performed in a similar manner as above.Determination of Actual Anion Content by Titration. The concentration of 2 was determined by colorimetric titration with the standardized methyl iodide in a sealed reactor through breakseals under vacuum. The operations were conducted by the method as previously reported.13Instruments for Measurements. 'H NMR (60-MHz) spectra were recorded with a JEOL-PMX 60 instrument. Gel permeation chromatograms (GPC) were obtained with a Toyo Soda HLC-802 instrument with UV or refractive index detection, THF being the elution solvent. Vapor-pressure osmometry ( W O ) measurements for the number-average molecular weight determination were made with a Corona 117 instrument in benzene solution. IR spectra were run with a Jasco IR-G spectrophotometer.ABSTRACT: The oligomerization and polymerization of racemic and highly optically enriched vinyl phenyl sulfoxide (3) were carried out in THF at -78 "C. Dimer and trimer stereochemistry was consistent with the stereospecific addition of 3 to an ion pair epimer of 1-lithio(phenylsulfiny1)ethane (2) or l-lithio-1,3-bis-(phenylsulfiny1)butane (4), where the stereoelectivity for one enantiomer of 3 over the other was large. The polymerization of racemic 3 resulted in the formation of an apparently atactic polymer. In contrast, the polymerization of highly optically enriched 3 resulted in the formation of an apparently highly stereoregular polymer. These results are shown to be consistent with a process where many chain-end epimers may participate in the polymerization and each epimer undergoes vinyl addition stereospecifically an...

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The preparation of oligocyclosiloxanes via hydrosilation reactions has been investigated. Hydrosilation reactions employing heptamethylcyclotetrasiloxane and vinyl‐containing silanes and siloxanes yielded a variety of oligocyclosiloxanes with various numbers of cyclosiloxane rings connected through tri‐, tetra‐, penta‐, hexa‐, hepta‐, or octafunctional junctions. The oligocyclosiloxanes were characterized by gas chromatography, IR spectroscopy, 29Si‐, 1H‐, and 13C‐NMR spectroscopy, elemental analysis, and vapor phase osmometry. The polycyclics were redistributed with hexamethyldisiloxane and the resulting fragments analyzed by gas chromatography. All results were consistent with the formation of isomeric oligocyclosiloxanes due to a lack of absolute regioselectivity of the hydrosilation reaction. © 1993 John Wiley & Sons, Inc.