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    Rheological Behavior of Precursor PPV Monolayers

    Year: 2004

    Journal: Langmuir 2004, 20, 11517-11522, 20111221

    Authors: J. W. Luinge, G. W. Nijboer, J. G. Hagting, E. J. Vorenkamp, G. G. Fuller, and A. J. Schouten

    Organizations: Department of Polymer Chemistry and Materials Science Centre, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025

    The rheological behavior of different precursor poly(p-phenylene vinylene) (prec-PPV) monolayers at the air-water interface was investigated using an interfacial stress rheometer (ISR). This device nicely reveals a transition of the precursor poly(2,5-dimethoxy-1,4 phenylene vinylene) (prec-DMePPV) monolayer from Newtonian to elastic behavior with increasing surface pressure. The transition is accompanied by an increase in the modulus. This behavior coincides with the coagulation of different 2D condensed domains as revealed by Brewster angle microscopy (BAM). However, partly converted prec-DMePPV monolayers show elastic behavior even at low surface pressures, although a sudden increase of the moduli does occur. This phenomenon is attributed to enhanced hydrophobic interactions between the conjugated moieties in the partly converted polymers. The latter also explains the stretching behavior of the partly converted prec-DMePPV upon transfer in Langmuir-Blodgett-type vertical dipping. The increase of the moduli which is observed is much more gradual in the precursor poly(2,5-dibutoxy-1,4-phenylene vinylene), prec- DBuPPV, a monolayer which is in agreement with the expected expanded state of the latter monolayer.