Functional Group Distribution and Gradient Structure Resulting from the Living Anionic Copolymerization of Styrene and <i>para</i>-But-3-enyl Styrene

Abstract

The functional group distribution along the polymer backbone resulting from the living anionic copolymerization of styrene (S) and <i>para</i>-but-3-enyl styrene (<i>p</i>BuS) was investigated in cyclohexane at room temperature. A variety of copolymers with different comonomer contents <i>x</i>(S) = 0-0.84 have been synthesized with molecular weight dispersities <i>M</i>_w/<i>M</i>_n ≤1.12. All polymers have been characterized in detail by ¹H NMR spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). A detailed understanding of the monomer sequence distribution during the copolymerization was achieved by real-time ¹H NMR spectroscopy. This technique permits us to determine the changing monomer concentration of each monomer in stock throughout the reaction. Consequently, monomer incorporation and thus the probability of incorporation can be determined at any time of the copolymerization, and a precise determination of the functional group density along the polymer chain is possible. To demonstrate accessibility of the olefin side chains of the copolymer for transformations, quantitative thiol-ene addition of a cysteine derivative has been studied.