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RISS 인기검색어
- 검색키워드
- 저자 : Pierre J. Lutz (검색결과 2 건)
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Branched Polyethylenes Fractionated in Supercritical Propane
Frédéric Pelascini,Simoni Plentz-Meneghetti,Pierre J. Lutz,Val Krukonis,Kara Williams 한국고분자학회 2010 Macromolecular Research Vol.18 No.5
A series of polyethylenes (PEs), were synthesized in the presence of a palladium catalyst containing bulky diimine ligands (VERSIPOLTM) yielding amorphous PEs. The different PE samples were characterized by Size Exclusion Chromatography (SEC) with on line light scattering, NMR, viscometry or small angle neutron scattering (SANS) techniques to assess the molar mass, molar mass distribution (MMD), radius of gyration (or hydrodynamic radius) and degree of branching. Selected PE samples were fractionated in supercritical propane by isothermal increasing the pressure profile. In most cases, PE fractions with a sharper MMD than the original PEs were obtained. The average absolute molar masses of the resulting fractions increased steadily with increasing extraction pressure. Their dilute solution properties were compared with those of unfractionated PEs. Structural analyses confirmed the homogeneity of the degree of branching within a raw PE sample.
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Influence of the Solvent Quality on Ring Polymer Dimensions
Gooßen, Sebastian,Brá,s, Ana R.,Pyckhout-Hintzen, Wim,Wischnewski, Andreas,Richter, Dieter,Rubinstein, Michael,Roovers, Jacques,Lutz, Pierre J.,Jeong, Youncheol,Chang, Taihyun,Vlassopoulos, Dimi American Chemical Society 2015 Macromolecules Vol.48 No.5
<P>We present a systematic investigation of well-characterized, experimentally pure polystyrene (PS) rings with molar mass of 161 000 g/mol in dilute solutions. We measure the ring form factor at θ- and good-solvent conditions as well as in a polymeric solvent (linear PS of roughly comparable molar mass) by means of small-angle neutron scattering (SANS). Additional dynamic light scattering (DLS) measurements support the SANS data and help elucidate the role of solvent quality and solution preparation. The results indicate the increase of ring dimensions as the solvent quality improves. Furthermore, the experimental form factors in both θ-solvent and linear matrix behave as ideal rings and are fully superimposable. The nearly Gaussian conformations of rings in a melt of linear chains provide evidence of threading of linear chains through rings. The latter result has implications for the dynamics of ring–linear polymer mixtures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2015/mamobx.2015.48.issue-5/ma502518p/production/images/medium/ma-2014-02518p_0004.gif'></P>
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