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

Abstract

Copolymerizations of three phthalaldehyde isomers (M2) with styrene (M1) were carried out in methylene chloride or in toluene with BF3OEt2 catalyst. The monomer reactivity ratios were r1 = 0.77, r2 = 0 for the meta isomer and r1 = 0.60, r2 = 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.

Stable, High‐Molecular‐Weight Poly(phthalaldehyde)

“…A fast cationic growth mechanism with rapid initiation and exchange of the active propagation site can explain the high Ð values, as seen for BF 3 ‐OEt 2 catalyzed PHA polymerization . Yield fraction, molecular weight, and Ð would be expected to be unchanged with time if the Scheme mechanism was true . The polymer chains quickly mature and reach an asymptotic equilibrium due to the ability of monomer units to be easily removed and inserted.…”

“…In situ 1 H and F nuclear magnetic resonance (NMR) in CD 2 Cl 2 was performed in a Bruker Avance III 400 MHz tool. Temperature was calibrated by the relation of the chemical shift differences of a pure solution of methanol .…”

“…Kaitz et al found that the BF 3 ‐OEt 2 catalyst forms a cyclic polymer with high thermal stability . Previous studies with BF 3 ‐OEt 2 catalyst support the concept that a cationic chain end is produced from a Lewis acid . This cationic end is free to propagate the polymer chain.…”

“…This cationic end is free to propagate the polymer chain. No evidence of the counter‐ion produced to stabilize this propagating chain was provided . Reported values of yield, molecular weight, and polydispersity index for PPHA suggest that cationic addition chain propagation is unlikely.…”

Polymerization of Aromatic Aldehydes. VII. Cyclopolymerization of o-FormylphenylacetaIdehyde and Formation of a Cyclic Trimer

“…All the polymers listed here were white powders and soluble in benzene and carbon tetrachloride. The degree of polymerization was low (about [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. It is interesting to note that the Zieger catalyst gave a soluble cyclopolymer at ooc, in contrast to the cationic polymerization.…”