BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Keynote 5 - Combining in-situ\, time-resolved SANS\, SAXS/WAXS and SALS\, to study molecular and crystal alignment in bottlebrushes polymers during uniaxial deformation DTSTART;VALUE=DATE-TIME:20181211T080000Z DTEND;VALUE=DATE-TIME:20181211T084000Z DTSTAMP;VALUE=DATE-TIME:20260523T211633Z UID:indico-contribution-88-484@lindico453.srv.lu.se DESCRIPTION:Speakers: Carlos Lopez-Barron (ExxonMobile Chemical Company\, USA)\nMolecular bottlebrushes are branched polymers with very high graft d ensity which results in very rigid backbones. This conformation provides u nique rheological properties compared to linear polymer melts. For instanc e\, their very large entanglement molecular weight (Me) results in very lo w elastic modulus\, which could be used to produce super-soft elastomers [ Pakula et al.\, Polymer 47\, 7198 (2006)]. Despite the growing interest in bottlebrush polymers\, very few studies have been devoted to their linear viscoelastic response\, whereas\, to our knowledge\, no study has been re ported on their extensional rheology or their response to cold-drawing. We synthesized a series of ultra-high molecular weight (UHMW) a-olefin molec ular bottlebrushes by organometallic coordinative insertion polymerization of 1-alkenes with lengths ranging from 8 to 18 carbons. The molecular wei ght of these polymers are in the order of a few million g/mol\, which allo ws accurate measurement of their rubbery plateau modulus (GN0) and their M e values. The latter is an increasing function of the side chain length (N sc) and takes values ranging from 25 kg/mol (for poly(1-octene)) to 115 kg /mol (for poly(1-octadecene)). Therefore\, our bottlebrush polymers are hi ghly-entangled and have sufficient melt strength to perform extensional rh eology measurements using a commercial Sentmant extensional rheometer (SER ). Bottlebrush chain alignment was measured using a novel method that comb ines the use of a SER with time-resolved small-angle neutron scattering (S ANS) measurements [López-Barrón et al.\, J Rheol. 61\, 697 (2017)]. The latter uses state of the art methods of neutron time stamping in the SANS detector and deconvolution protocols that yields scattering data with time resolutions of the order of seconds [López-Barrón et al.\, Phys. Rev. L ett. 108\, 258301\; Calabrese et al.\, Soft Matter 12\, 2301 (2016)]. Thos e measurements were used to confirm the direct correlation between extensi onal stress and bottlebrush chain alignment. Complementary\, in situ wide- and small-angle X-ray scattering measurements reveal that chain alignment is concomitant of self-assembly of the bottlebrush molecules into hexagon al packed cylinder (HEX) phases induced by uniaxial extension. This work r eports the first direct evidence of strain-induced alignment and packing o f molecular bottlebrushes and their relation with the macroscopic rheologi cal and mechanical responses.\n\nhttps://lindico453.srv.lu.se/event/67/con tributions/484/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/484/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 7 - Spherical Harmonics Expansion show Chain Retractio n DTSTART;VALUE=DATE-TIME:20181211T090000Z DTEND;VALUE=DATE-TIME:20181211T092000Z DTSTAMP;VALUE=DATE-TIME:20260523T211633Z UID:indico-contribution-88-486@lindico453.srv.lu.se DESCRIPTION:Speakers: Anine Borger (Niels Bohr Institute\, University of C openhagen)\nThe mechanical properties of polymer melts under deformation a re well described by the tube model developed in the 1970s by de Gennes an d Doi and Edwards. In the model\, the restricted motion of a chain due to its neighbors is modeled as if the chain ia confined to a tube. However\, the validity of the tube model for rapid deformations compared to the mole cular relaxation was recently questioned [1]. They proposed a new analysis method for anisotropic 2D small angle (neutron) scattering\, SANS\, data for uniaxially extended polymer melts expanding the data in spherical harm onics to ease the separation of the isotropic and anisotropic contribution s. Using this method\, they looked for the signature of chain retraction\, see below\, during relaxation after deformation which is a cornerstone of the tube model. The signature was absent in their data which lead them to conclude that chain retraction either does not occur or that it is shield ed by some other non-linear effect not yet included in the model. However\ , we employ the same analysis also on SANS data for a polystyrene melt of about a factor of five lower molar mass stretched more than a factor of te n more\, and we do see the proposed signature in the harmonics: The minimu m in the expansion coefficient of the leading anisotropic contribution to the scattering pattern shifts towards larger q as the relaxation times app roaches the Rouse time\, τR. We therefore conclude that the relaxation of the molecular stretching and orientation are decoupled\, or in other word s that the chain retracts\, which supports the tube model.\nChain retracti on arises during relaxation if the deformation is fast enough to not only orient the chains but also stretch them. The hypothesis of the tube model is that the relaxation of the stretching of the molecule happens on a fast time scale\, τR\, through a Rouse-like process whereas the relaxation of the orientation happens on a much slower timescale through repetition. Th at these timescales are well separated causes the molecule to shrink in al l dimensions for t∼τR does it relax back to its equilibrium shape.\n\nh ttps://lindico453.srv.lu.se/event/67/contributions/486/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/486/ END:VEVENT BEGIN:VEVENT SUMMARY:Contr. Talk 6 - Dynamics and morphological fingerprinting of nano- filled polymer systems subjected to nonlinear deformations DTSTART;VALUE=DATE-TIME:20181211T084000Z DTEND;VALUE=DATE-TIME:20181211T090000Z DTSTAMP;VALUE=DATE-TIME:20260523T211633Z UID:indico-contribution-88-485@lindico453.srv.lu.se DESCRIPTION:Speakers: Roland Kádár (Industrial and Materials Science\, E ngineering Materials\, Chalmers University of Technology\,)\nNonlinear def ormations are a key ingredient for applications of rheologically complex m aterials\,\ne.g. for the processing of polymeric materials stretching\, or ientation\, dissentaglement of\npolymer chains occurs\, with the interacti ons between flow field and constituents dictating the\noverall flow dynami cs and subsequent material properties/performance. In this framework\, we\ nfocus mainly on nano-filled suspensions and polymer composites in oscilla tory and steady\nshear for a various nanofillers\, e.g. graphene\, nanocel ulose etc.. Of particular importance is the\nanalysis of the oscillatory s hear stress output signal analysis in the framework of Fourier-\nTransform (FT) analysis and Tchebyshev polynomial decomposition. The effects of ori entation\ndynamics and morphological fingerprinting are highlighted\, with rheological percolation\nthresholds determined with superior sensitivity using nonlinear material parameters and\nnonlinear features hinting at the filler morphology of percolated network dynamic response.\n\nhttps://lind ico453.srv.lu.se/event/67/contributions/485/ LOCATION:Elite Hotel Ideon Tera URL:https://lindico453.srv.lu.se/event/67/contributions/485/ END:VEVENT END:VCALENDAR