Thermally Stable and Well‐Defined Pentadiene‐Derived Copolymers Prepared by Anionic Alternating Copolymerization and Subsequent Controlled Postmodification

Abstract

AbstractThermally stable and well‐defined hydrocarbon polymers prepared via anionic alternating copolymerization of 1,3‐pentadiene (P monomer: trans (TP) and cis (CP) mixture) and styrene derivatives (S monomer: styrene (St) and 1,1‐diphenylethylene (DPE)) and subsequent hydrogenation and cationic cyclization modifications are reported. The TP/S/CP terpolymerization reveals that an incorporation of S‐alt‐CP sequence into the alternating chain is more favorable, while the S‐alt‐TP insertion is also possible especially under high temperature owing to their competitive energy barriers and thermodynamic properties. Then the resultant copolymers with equimolar amount of the two monomers and predominant linear units are intramolecularly cyclized with CF3SO3H, or hydrogenated with p‐toluenesulfonyl hydrazide, to afford soluble and thermally stable hydrocarbon polymers with controlled Mns and narrow ĐMs. The Tg of cylized polymer increases dramatically (ΔTg > 100 °C) on cyclization between the adjacent CC bond in the P structure and the aromatic ring of S unit through the intramolecular Friedel–Crafts alkylation. On the other hand, the Tg of hydrogenated product slightly decreases (ΔTg ≈ 10 °C) after 98% hydrogenation due to the increasing flexibility of the saturated main‐chain, while the Td increases about 60 °C due to the loss of CC bonds under oxygen atmosphere.