Session D40 - Poster Session I.
POSTER session, Monday afternoon, March 12
Exhibit Hall, Washington State Convention Center
The melt structures of linear polyethylene and the isotactic vinyl polymers - polypropylene, poly(1-butene) and poly(4-methyl-1-pentene) - with the corresponding methyl, ethyl and isobutyl side chains, were recently studied with wide-angle X-ray diffraction. As the size of the side-branch increases from zero (PE) to methyl, ethyl and isobutyl, a "pre-peak" appears below the main diffraction peak in the carbon-carbon structure factor. The pre-peak becomes stronger and shifts to lower scattering vectors with increasing bulkiness of the side chain. We present Polymer Reference Interaction Site Model (PRISM) calculations of a melt of vinyl chains as a function of the side chain size. The origin of the pre-peak for vinyl polymers based on experiment and theory will be discussed.