Synthesis of well-defined block copolymers and star-branched polymers by using terminal 1,3-butadiene functionalized polymers as reactive building blocks

Terminal 1,3-buadiene (Bd) functional polymers are stoichiometrically reacted with living anionic polymers in a monoaddition manner in THF at −78 °C, but neither polymerization nor oligomerization occurs under the conditions. By utilizing this reactive but non-polymerizable character of the Bd function toward living anionic polymers, a variety of block copolymers and regular and asymmetric star-branched polymers were successfully synthesized. In these syntheses, the terminal Bd functionalized polymers work effectively as reactive building blocks, namely polymeric efficient linking agents, to construct such architectural polymers. Since all the polymer segments used for the syntheses were derived from living anionic polymers and the linking reactions quantitatively proceeded, the architectural polymers herein synthesized were well-defined in structure and were precisely controlled in chain length. A new protocol based on iterative approach by repeating a two reaction sequence involving linking reaction and re-introduction of Bd group was proposed and developed to successively synthesize asymmetric star-branched polymers up to a 6-arm ABCDEF type. The terminal Bd functionalized polymers were readily and quantitatively converted to anhydride or diepoxide functionalized polymers by Diels-Alder or oxidation reactions. Because of their high reactive termini, the resulting polymers are also usable as reactive building blocks to synthesize the core-functionalized star-branched polymers with carboxylic acids or hydroxyl groups. The reactions between terminal anhydride and amine functionalized polymers were carried out in bulk at 180 °C to examine the synthetic possibility of star-branched polymers under such conditions.