Influence of (1,3-phenylene)bis(3-methyl-1-phenyl pentylidene)dilithium initiator concentration on the modality of polybutadiene

Authors

  • Thodoris C. Vasilakopoulos,

    1. Department of Chemistry, University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece
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  • Nikos Hadjichristidis

    Corresponding author
    1. Department of Chemistry, University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece
    2. Division of Physical Sciences and Engineering, Catalysis Center, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
    • Department of Chemistry, University of Athens, Panepistimiopolis, Zografou, 15771 Athens, Greece
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Abstract

The strong influence of (1,3-phenylene)bis(3-methyl-1-phenyl pentylidene)dilithium initiator (DLI) concentration on the modality of polybutadiene (PBd) in the presence of lithium s-butoxide (s-BuOLi) in benzene, at room temperature, has been studied. The quality of DLI has been evaluated by gas chromatography-mass spectrometry (GC-MS) and 1H NMR. Keeping s-BuOLi/C-Li ratio (R) close to unity, at relatively high DLI concentrations (C > 7 × 10−4 M), monomodal high 1,4-PBds with polydispersity index less than 1.07 were obtained, whereas bimodal ones at lower concentrations (C < 6 × 10−4 M). The effect of C-Li concentration on the modality of PBd has been evaluated using size exclusion chromatography on samples taken during and at the end of the polymerization. Viscosity observations have also been used to further support the results. The bimodality of PBd has been attributed to partially terminated difunctional species because of the inevitable presence of protic impurities in the polymerization solution, although high vacuum technique was used, which becomes more significant at low initiator concentrations. Moreover, the strong influence of s-BuOLi on the microstructure of PBd has been demonstrated by 1H NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

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