Adamantane-containing poly(dialkyl fumarate)s with rigid chain structures

Abstract

Four dialkyl fumarates containing bulky adamantyl ester groups, i.e., di(1-adamantyl) fumarate (1), bis(3,5-dimethyl-1-adamantyl) fumarate (2), 1-adamantyl isopropyl fumarate (3), and 3,5-dimethyl-1-adamantyl isopropyl fumarate (4), were polymerized to obtain poly(dialkyl fumarate)s (PDRFs) with rigid chain structures. We carried out the conventional radical polymerization of these adamantane-containing DRFs in the presence of a radical initiator either in toluene or in bulk at 80 or 60 °C. Reversible addition-fragmentation chain transfer (RAFT) polymerization was also performed using 1,1′-(1,2-ethanediyl) bis[2-[[(dodecylthio)thioxymethyl]thio]-2-methylpropionate] and 2,2,2-trifluoroethyl 2-[[(dodecylthio)thioxymethyl]thio]-2-methylpropionate as the chain transfer agents (CTAs). Triblock copolymers consisting of rigid and flexible segments were synthesized by the polymerization of 2-ethylhexyl acrylate, which was used as the second monomer, using the PDRFs as the macro-CTA containing trithiocarbonate groups at the chain ends. The excellent thermal stability of the adamantane-containing PDRFs was confirmed by thermogravimetric analysis in a nitrogen stream. The alignment of the rigid PDRF chains in the solid-state was revealed based on the appearance of a peak in the small angle regions of the X-ray diffraction profiles. We carried out the conventional radical polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization of di(1-adamantyl) fumarate, bis(3,5-dimethyl-1-adamantyl) fumarate, 1-adamantyl isopropyl fumarate, and 3,5-dimethyl-1-adamantyl isopropyl fumarate. Triblock copolymers consisting of rigid and flexible segments were synthesized by the RAFT polymerization of 2-ethylhexyl acrylate using poly(dialkyl fumarate)s as the macro-chain transfer agents. The excellent thermal stability of the adamantane-containing poly(dialkyl fumarate)s was confirmed by thermogravimetric analysis. The alignment of the rigid poly(dialkyl fumarate)s chains in the solid-state was revealed by X-ray diffraction.