ELITE NETZWERK BAYERN

English  Sprachen Icon  |  Gebärdensprache  |  Leichte Sprache  |  Kontakt


Forschungsarbeit


Carbonnanotubes with Triblock Terpolymers as Efficient Compatibilizer in Polymer Blends

von Thomas Gegenhuber

Carbon nanotubes (CNTs) are an excellent material class, representing one of the allotropes of carbon. Due to poor miscibility and a lack of dispersion of CNTs, their handling is rather difficult. We utilized tailored and well-defined polymers to tackle this issue.

In the framework of my project at the University of Bayreuth, I was investigating the usage of triblock co- and terpolymers as surface decoration of carbon nanotubes (CNT) for enhancement of CNT dispersion in organic media or polymer blends. [1,2] Therefore, we utilized the polymers polystyrene-block-polyethylene-block-poly(methyl methacrylate) (SEM) and polystyrene-block-polyethylene-block-polystyrene (SES) for surface coating of the CNTs (Figure 1A). According to our investigations, the polyethylene (PE) block absorbs onto the surface of the CNT, leaving the polystyrene (PS) and poly(methyl methacrylate) (PMMA) block as soluble corona brushes (Figure 1B). By utilizing SEM triblock terpolymers, the immiscibility of PS and PMMA chains causes microphase separation of the polymer brushes, [3,4] illustrating a compartmentalized corona structure (Figure 1B and C) on the surface of the CNTs in transmission electron microscopy (TEM) micrographs. In case of symmetric triblock copolymers SES, no corona phase separation is present and a uniform outer corona is obtained (Figure 1D). As we could show successfully, such surface decorations enhance the CNT dispersion stability drastically. Furthermore, we employed the SEM decorated CNTs as additive to compatibilize and reinforce polymer blends. In polymer blending, immiscibility of polymers impedes a simple mixing of two polymers, due to high interfacial tension causing a collapse of the interface as a result of poor attractive interactions between the polymers. Therefore, the polymer blend remains macrophase separated, leaving the material unfeasible for application. Hence, surfactants are employed, in order to decrease interfacial tension. Further, CNTs are commonly employed as reinforcing materials, however, their tendency of aggregation and poor interfacial attraction complicates their utilization in homopolymers and polymer blends. For our CNT materials, the surface decoration prevents CNT aggregation and in particular good compatibility to the polymer matrix. Benefiting from the corona phase segregation, the dispersed phase size of an asymmetric PS/PMMA blend could be decreased. In addition, the size distribution was narrowed due to decreasing interfacial tension caused by the microphase separted CNTs with SEM. Underpinning the ease of the method, we are convinced that such CNT based materials are an excellent class to overcome issues in terms of macrophase separation and enhance polymer material strength in general.

References:

[1] T. Gegenhuber, M. Krekhova, J. Schöbel, A. H. Gröschel and H. Schmalz, ACS Macro Lett., 2016, 5, 306-310.

[2] T. Gegenhuber, A. H. Gröschel, T. I. Löbling, M. Drechsler, S. Ehlert, S. Förster and H. Schmalz, Macromolecules, 2015, 48, 1767-1776.

[3] H. Schmalz, J. Schmelz, M. Drechsler, J. Yuan, A. Walther, K. Schweimer and A. M. Mihut, Macromolecules, 2008, 41, 3235-3242.

[4] J. Schmelz, M. Karg, T. Hellweg and H. Schmalz, ACS Nano, 2011, 5, 9523-9534.

 

 

Zur Person

Thomas Gegenhuber studierte zunächst von 2008 an Polymer- und Kolloidchemie B. Sc. an der Universität Bayreuth, und beendete sein Studium im Masterstudiengang Polymer Science, ebenda. Seit Ende 2011 ist er Mitglied im studienbegleitenden Elitestudiengang Macromolecular Science an der Universität Bayreuth. Nachdem erfolgreichen Abschluss seines Masterstudiums Ende 2013, wechselte er von der Universität Bayreuth an das Karlsruher Institut für Technologie (KIT) zu Prof. Christopher Barner-Kowollik (inzwischen Queensland University of Technology, QUT, Brisbane, Australien) um seit 2014 im Rahmen seiner Promotion spezielle Stufenwachstumsprozesse zu behandeln. In der zweiten Jahreshälfte 2017 war er im Rahmen des Elitestudiengangs für drei Monate an der University of New South Wales (UNSW) in Sydney, Australien, bei Prof. Per Zetterlund. (08.09.2017)

 

Figure 1. Patchy SEM@CNTs and uniform PS-coated SES@CNTs. A) Schematic representation of SEM@CNT with a patchy, compartmentalized PS/PMMA corona and SES@CNT with a uniform PS shell obtained by ultrasound-assisted, non-covalent grafting of multi-walled CNTs with PS-b-PE-b-PMMA and PS-b-PE-b-PS, respectively. B,C) TEM micrograph and tomography of the patchy SEM@CNT hybrid. D) TEM micrograph of the SES@CNT. Reprinted from T. Gegenhuber, M. Krekhova, J. Schöbel, A. H. Gröschel and H. Schmalz, ACS Macro Lett., 2016, 5, 306–310, Copyright 2016© with permission from American Chemical Society.[1]

veröffentlicht am