Get access

Limitations of cyclodextrin-mediated RAFT homopolymerization and block copolymer formation

Authors

  • Martin Hetzer,

    1. Lehrstuhl für Präparative Polymerchemie, Institut für Organische Chemie und Makromolekulare Chemie, Heinrich-Heine Universität, Universitätsstraße 1, Düsseldorf, Germany
    Search for more papers by this author
  • Bernhard V. K. J. Schmidt,

    1. Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
    Search for more papers by this author
  • Christopher Barner-Kowollik,

    Corresponding author
    • Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
    Search for more papers by this author
  • Helmut Ritter

    Corresponding author
    • Lehrstuhl für Präparative Polymerchemie, Institut für Organische Chemie und Makromolekulare Chemie, Heinrich-Heine Universität, Universitätsstraße 1, Düsseldorf, Germany
    Search for more papers by this author

Correspondence to: C. Barner-Kowollik (E-mail: christopher.barner-kowollik@kit.edu) or

H. Ritter (E-mail: h.ritter@uni-duesseldorf.de)

ABSTRACT

The design and synthesis of a new hydrophobic monomer, that is, 4-(tert-butyl)phenyl 6-acrylamidohexanoate (TBP-AA-HO) and its ability to form supramolecular host/guest complexes with β-cyclodextrin (CD) is described. The aqueous CD-mediated reversible addition fragmentation chain transfer (RAFT) polymerization affords molecular masses up to 8600 g mol−1 with polydispersities between 1.2 and 1.4. The surprisingly low molecular weights for higher monomer/chain transfer agent (CTA) ratios are investigated by comparing results obtained from free radical and RAFT radical polymerization in aqueous and organic media. The results indicate a steric hindrance caused by attached CD molecules on the growing polymer chain leading to stagnation of the polymerization process due to a restricted accessibility of the reactive chain end. This hypothesis is supported by matrix-assisted laser desorption/ionization time of flight mass spectrometry. Furthermore, the CD-mediated synthesis of amphiphilic diblock copolymers in variable aqueous media is described. Hydrophilic poly(N,N-dimethylacrylamide) macro-CTAs with different molecular weights are used to polymerize TBP-AA-HO at 50 °C. The diblock copolymers are analyzed by 1H-nuclear magnetic resonance spectroscopy and size exclusion chromatography. The results confirm the polymer structure and reveal similar limitations of chain growth as observed for the CD-mediated homopolymerization with a limit of 7000 g mol−1 for efficient chain extension. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2504–2517

Ancillary