Olefin Polymerization 475 possibly for PE also. It is beyond the scope of this present study to formulate models more consistent with the observations.Finally, the conclusion that diffusion through PTFE proceeds at least in part along pores and grain boundaries may have a significance far beyond the diffusion process. Other observed properties of bulk PTFE, which have been ascribed to the dense polymer structure itself, may also be due in part to the physical structure of the sintered material. A re-evaluation of PTFE properties on the basis of this model may well be worthwhile.Acknowledgment. M. Christensen assisted in the experimental work and F. J. Martinelli wrote the computer programs. This work was performed for the Jet Propulsion Laboratory, California Institute of Technology, sponsored by the National Aeronautics and Space Administration under Contract No. NAS 7-698.
The infrared analysis of ethylene-propylene copolymers allowed us to confirm that, in the syndiospecific polymerization of propylene, insertion occurs on metal-secondary carbon bonds. The monomer orientation in the insertion is essentially due to steric effects.
Several partially deuterated propylene polymers have been studied by pmr. A partial assignment of the methylene hexad proton resonances is tentatively proposed. The high stereoregularity of the «-heptane-insoluble fraction of isotactic polypropylene prepared using the ERA 3-1(02 5)2 catalyst system and also the methylene proton tetrad resonance assignment have been confirmed. he use of recent developments in proton magnetic resonance techniques has given much information about the microstructure of poly(a-olefins).1-n Detailed information about microstructure is particularly useful in an understanding of the properties of the polymers and the polymerization
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