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Intrinsic Viscosity of Cyclic Polystyrene
Jeong, Youncheol,Jin, Ye,Chang, Taihyun,Uhlik, Filip,Roovers, Jacques American Chemical Society 2017 Macromolecules Vol.50 No.19
<P>The intrinsic viscosity of cyclic polystyrenes (C-PS) and linear polystyrenes (L-PS) with molecular weight (MW) ranging from 16K to 370K was measured in THF using size exclusion chromatography coupled with a triple detection system. The C-PS samples were prepared by a ring-closure reaction of telechelic linear precursor synthesized by anionic polymerization. As-synthesized C-PS samples after the ring closure reaction contain various byproducts, and they were fractionated by liquid chromatography at the critical condition to obtain highly pure C-PS. While the intrinsic viscosity of L-PS agrees well with the literature data, C-PS shows significantly lower value than the literature values. The Mark-Houwink exponent of C-PS is 0.67, somewhat lower than 0.70 for L-PS in the good solvent over the MW range examined. Therefore, the ratio of the intrinsic viscosity of C-PS to L-PS (g' = [eta](C)/[eta](L)) in THF is not MW independent but decreases as MW increases (0.63 >= [eta](C)/[eta](L) >= 0.57). The trend of intrinsic viscosity agrees well with the computer simulation result. The discrepancy in [eta](C) from the literature values can largely be attributed to the contamination of linear byproducts in the earlier studies.</P>
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>