Graft and block copolymers, formation of nano structures, controlled synthesis

Prof. Brigitte Voit, Dr. Doris Pospiech

    • Controlled synthesis of nanophase separated di- and triblock copolymers, segmented block copolymers and graft copolymers, partially with inline- monitoring
    • Examination of nanophase separation supported by mean field modelling

    • Investigation of the influence of nanophase separation on macroscopic properties, particularly wettability:

      • The macroscopic wetting behaviour of polymers determines significantly the applicability in microelectronics, nanolithography, as templates etc.

    • Block copolymers / Hybrids

    Controlled radical polymerization techniques allow to combine functionality in polymers with well controlled architecture and control over molar mass. The following techniques are used:

    • ATRP (atom transfer radical polymerization)
    • NMRP (nitroxide mediated radical polymerization)
    • RAFT (reversible addition fragmentation transfer)

    Via both, ATRP and NMRP, functional end groups are incorporated in methacrylate and styrene based polymers; ATRP is also used to functionalize branched structures with linear chains. Via NMRP a variety of hydroxystyrene based block copolymer structures have been synthesized which show interesting and well controllable nanostructures in thin films. For the preparation of special functionalized block copolymers and rod-coil-like structures NMRP has been combined with highly effective polymer analogous reactions, e.g. 1,3-dipolar cycloaddition reactions.
    The RAFT process is specially suited for the synthesis of polar and amphiphilic polymers which are expected to be used in biomedical applications. Here, first block copolymer structures could be realized having a thermoresponsive poly(NiPAAm) segment and a bioactive glycomonomer segment.

    The copper-mediated 1,3-dipolar cycloaddition reaction of azides and alkynes, since Sharpless also known as “click chemistry”, is a highly selective as well as regioselective and very efficient reaction which leads usually to complete conversion and no side reactions under very mild  reaction conditions. Thus, the reaction is especially well suited to modify complex architectures (dendritic structures) as well as linear block copolymers highly effectively and also selectively tolerating the presence of additional functional groups. In the Dept. Polymer Structures a variety of alkyne modified random and block copolymer structures has been prepared which were effectively modified with a broad range of functional and also dendritic features by click chemistry. The highly selective reaction of the cylcoaddition step is here the base for the introduction of multi-functionality in a cascade modification reaction. This allows also the introduction of photo- and thermolabile units as well as of anchoring groups (e.g. for surface immobilization). Also, rod-coil like structures with a chain exhibiting dendritic units were prepared under mild conditions and in very high yields.
    Alkyne and azide units at the chain end, originated from functional initiators, have also been used to introduce more complex end functions (e.g. fluorescence labels) and to couple different polymer chains to new types of block copolymers.
    In addition, cycloaddition reactions allow also the preparation of totally new linear and branched polymer structures with triazole units in the backbone. Perfectly branched dendrimers as well as new types of hyperbranched polymers have been prepared in this way. For the first time, also kinetic studies on the formation of hyperbranched polymers by click chemistry have been presented.

    Polymers for nanostructured functional films

    controlled radical polymerization (NMRP)anionic polymerization

    1/11, Mn=61400 g/mol, PD=1.2
    21 nm thick film on Si wafer

    vertical cylinders
    (proven by GISAXS)

    67/33, Mn=84700 g/mol, PD=1.2
    20 nm thick film on Si wafer

    New nanostructured bulk materials

    water contact angle > 120°
    • bulk polymer with low surface free energy by phase separation and segregation
    • new TPE with bifunctional coupling agents

    Selected Publications

    1. Chakraborty, S. ; Jähnichen, K. ; Komber, H. ; Basfar, A. A. ; Voit, B. Synthesis of magnetic polystyrene nanoparticles using amphiphilic ionic liquid stabilized RAFT mediated miniemulsion polymerization more Macromolecules 47 (2014) 4186-4198
    2. Riedel, M. ; Voit, B. Synthesis of multifunctional polymers by combination of controlled radical polymerization (CRP) and effective polymer analogous reactions more Pure and Applied Chemistry 85 (2013) 557-571
    3. Stadermann, J. ; Riedel, M. ; Voit, B. Nanostructured films of block copolymers functionalized with photolabile protected amino groups more Macromolecular Chemistry and Physics 214 (2013) 263-271
    4. Huang, X. ; Hauptmann, N. ; Appelhans, D. ; Formanek, P. ; Frank, S. ; Kaskel, S. ; Voit, B. Synthesis of hetero-polymer functionalized nanocarriers by combining surface-initiated ATRP and RAFT polymerization more Small 8 (2012) 3579.3583
    5. Heuken, M. ; Komber, H. ; Erdmann, T. ; Senkovskyy, V. ; Kiriy, A. ; Voit, B. Fullerene-Functionalized Donor–Acceptor Block Copolymers through Etherification as Stabilizers for Bulk Heterojunction Solar Cellsheterojunction solar cells more Macromolecules 45 (2012) 4101-4114
    6. Voit, B. ; Riedel, M. ; Stadermann, J. Nanoscale functional patterning of thin films using block copolymers prepared through CRP more ACS Publisher 1101 (2012) Chapter 9, 127-139
    7. Huang, X. ; Appelhans, D. ; Formanek, P. ; Simon, F. ; Voit, B. Synthesis of well-defined photo-cross-linked polymeric nanocapsules by surface-initiated RAFT polymerization more Macromolecules 44 (2011) 8351-8360
    8. Pötzsch, R. ; Fleischmann, S. ; Tock, C. ; Komber, H. ; Voit, B. Combining RAFT and Staudinger ligation: a potentially new synthetic tool for bioconjugate formation more Macromolecules 44 (2011) 3260-3269
    9. Gaitzsch, J. ; Appelhans, D. ; Gräfe, D. ; Schwille, P. ; Voit, B. Photo-crosslinked and pH sensitive polymersomes for triggering the loading and release of cargo more Chemical Communications 47 (2011) 3466-3468