Polymerization of aromatic aldehydes. IV. Cationic copolymerization of phthalaldehyde isomers and styrene

Abstract

Abstract Copolymerizations of three phthalaldehyde isomers (M 2 ) with styrene (M 1 ) were carried out in methylene chloride or in toluene with BF 3 OEt 2 catalyst. The monomer reactivity ratios were r 1 = 0.77, r 2 = 0 for the meta isomer and r 1 = 0.60, r 2 = 0 for the para isomer. The second aldehyde group of both isomers did not participate in polymerization and acted simply as the electron‐withdrawing group, thus reducing the cationic reactivity of these monomers. Copolymerization behaviors of the ortho isomer (o‐PhA) were quite different between 0°C and −78°C. At −78°C, o ‐PhA preferentially polymerized to yield “living” cyclopolymers, until an equilibrium concentration of o ‐PhA monomer was reached. Then, styrene propagated from the living terminal rather slowly. The block structure of the copolymer was confirmed by the chemical and spectroscopic means. In the copolymerization at 0°C, the o ‐PhA unit in copolymer consisted both of cyclized and uncyclized units. This copolymer seemed to contain short o ‐PhA sequences. The variation of the o ‐PhA‐St copolymer structure with the polymerization temperature was explained on the basis of whether the polymerization was carried out above or below the ceiling temperature (−43°C) of the homopolymerization of o ‐PhA.