Polymer fluids star-branched

Two PBs of different molecular weight provided by Michelin were also studied. One is linear (PB) and the other star-branched (PBb). These fluids are also molten at ambient temperature. Moreover they are reputed to be well-defined polymers. Finally, they are highly birefringent, making it possible to study the local stress field during flow, thanks to the use of flow birefiingence methods. 

The PRISM theory has recently been generalized and apfdied by Grayce and Schweizer [101] to treat star-branched polymer soluticms and melts. For such systems the equivalent site approximation must be abandtmed, and non-ideal conformational effects become particularly important near the crowded central brmidi point. Generalization of their new methods to treat complex fluids composed polymer-coated colloidal particles is also feasiUe and presently under study. 

Highly stereoregular PMMA macromonomers, 14, prepared by Hatada and coworkers, have recently been fractionated by supercritical fluid chromatography into completely uniform fractions with no structural distribution [20,21]. They have been oligomerized with a radical (AIBN) or an anionic initiator (3,3-dimethyl-1,1-diphenylbutyllithium). After a new fractionation by SEC comb or star polymers of completely uniform architecture are obtained. No doubt, these samples will be most promising to investigate the branched structure-property relationship. 

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