Ceren Ozdilek

Publications (2)8.22 Total impact

• Article: Phase separation as a tool to control dispersion of multiwall carbon nanotubes in polymeric blends.

  Suryasarathi Bose, Ceren Ozdilek, Jan Leys, Jin Won Seo, Michael Wübbenhorst, Jan Vermant, Paula Moldenaers
  [show abstract] [hide abstract]
  ABSTRACT: Conducting polymeric materials with stable phase microstructures have a range of potential applications. In this work, it is investigated whether phase separation in polymer blends can be used as a tool to create well dispersed conducting filler rich domains in 3D with controlled morphology, potentially resulting in more effective percolation. The effect of amine functionalized multiwall carbon nanotubes (NH(2)-MWCNTs) on the thermally induced phase separation processes in poly[(alpha-methyl styrene)-co-acrylonitrile]/poly(methyl methacrylate) (PalphaMSAN/PMMA) blends was monitored by melt rheology, conductivity spectroscopy, and microscopic techniques. Electron microscopic images revealed that the phase separation resulted in a heterogeneous distribution of NH(2)-MWCNTs in the blends. The migration of NH(2)-MWCNTs is controlled by the thermodynamic forces that drive phase separation and led to an increase in their local concentration in a specific phase resulting in percolative "network-like" structure. Conductivity spectroscopy measurements demonstrated that the blends with 2 wt % NH(2)-MWCNTs that showed insulating properties for a one phasic system revealed highly conducting material in the melt state (two phasic) as a result of phase separation. By quenching this morphology, a highly conducting material with controlled dispersion of MWCNTs can be achieved. Furthermore, the role of NH(2)-MWCNTs in stabilizing the PMMA droplets against flow induced coalescence in 85/15 PalphaMSAN/PMMA blends was also established for the first time. It was observed that at a typical loading of 1.25 wt % NH(2)-MWCNTs the coalescence was completely suppressed on a practical time scale.
  ACS Applied Materials & Interfaces 03/2010; 2(3):800-7. · 4.53 Impact Factor
• Article: Complex phase separation in poly(acrylonitrile-butadiene-styrene)-modified epoxy/4,4'-diaminodiphenyl sulfone blends: generation of new micro- and nanosubstructures.

  P Jyotishkumar, Joachim Koetz, Brigitte Tiersch, Veronika Strehmel, Ceren Ozdilek, Paula Moldenaers, Rudiger Hässler, Sabu Thomas
  [show abstract] [hide abstract]
  ABSTRACT: The epoxy system containing diglycidyl ether of bisphenol A and 4,4'-diaminodiphenyl sulfone is modified with poly(acrylonitrile-butadiene-styrene) (ABS) to explore the effects of the ABS content on the phase morphology, mechanism of phase separation, and viscoelastic properties. The amount of ABS in the blends was 5, 10, 15, and 20 parts per hundred of epoxy resin (phr). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to investigate the final morphology of ABS-modified epoxy blends. Scanning electron microscopic studies of 15 phr ABS-modified epoxy blends reveal a bicontinuous structure in which both epoxy and ABS are continuous, with substructures of the ABS phase dispersed in the continuous epoxy phase and substructures of the epoxy phase dispersed in the continuous ABS phase. TEM micrographs of 15 phr ABS-modified epoxy blends confirm the results observed by SEM. TEM micrographs reveal the existence of nanosubstructures of ABS in 20 phr ABS-modified epoxy blends. To the best of our knowledge, to date, nanosubstructures have never been reported in any epoxy/thermoplastic blends. The influence of the concentration of the thermoplastic on the generated morphology as analyzed by SEM and TEM was explained in detail. The evolution and mechanism of phase separation was investigated in detail by optical microscopy (OM) and small-angle laser light scattering (SALLS). At concentrations lower than 10 phr the system phase separates through nucleation and growth (NG). However, at higher concentrations, 15 and 20 phr, the blends phase separate through both NG and spinodal decomposition mechanisms. On the basis of OM and SALLS, we conclude that the phenomenon of complex substructure formation in dynamic asymmetric blends is due to the combined effect of hydrodynamics and viscoelasticity. Additionally, dynamic mechanical analysis was carried out to evaluate the viscoelastic behavior of the cross-linked epoxy/ABS blends. Finally, apparent weight fractions of epoxy and ABS components in epoxy- and ABS-rich phases were evaluated from T(g) analysis.
  The Journal of Physical Chemistry B 04/2009; 113(16):5418-30. · 3.70 Impact Factor