Polymerization of aromatic aldehydes. II. Cationic cyclopolymerization of phthalaldehyde

Abstract

Phthalaldehyde was found to undergo cyclopolymerization with ease by several cationic catalysts and by γ‐ray irradiation. The polymer was composed entirely of the dioxyphthalan unit, as confirmed by infrared spectroscopy and ready decomposition to monomer. The enhanced polymerizability of phthalaldehyde as compared with other aromatic aldehydes was explained in terms of the intermediate‐type or, preferably, concerted propagation scheme. The conversion reached a saturation value of 87% in about 1 hr in methylene chloride at −78°C, indicating an equilibrium polymerization. The ceiling temperature of the polymerization was −43°C, as estimated from the relation between the saturation yield and polymerization temperature. The enthalpy and entropy of propagation were −5.3 kcal/mole and −23.0 eu, respectively. Since the molecular weight of the polymer was proportional to conversion, the propagating chain end was considered to be “living” in this system. The rate constant for propagation was calculated to be 0.18 1/mole‐sec in methylene chloride at −78°C with BF3OEt2 catalyst.

Controlled cationic copolymerization of benzaldehyde with isobutyl vinyl ether using base‐assisting system

“…These results indicated that the copolymers had no BzA-BzA sequences, and were consistent with previous reports that BzA homopolymerization did not proceed. [10][11][12][13] On the other hand, copolymerization failed in polar solvents such as dichloromethane, at 0 C, and/or in the absence of an added base. In these cases, only IBVE homopolymers were obtained, as confirmed by 1 H NMR analysis.…”

“…Homopolymerization of aromatic aldehydes is known to be especially difficult. [10][11][12] In fact, their homopolymerizations have never been achieved except in the case of benzaldehyde (BzA) derivatives with special structures. 10,12,13 In contrast, polymers were obtained from both BzA and a simple derivative in copolymerizations with styrene (St) or isoprene.…”

“…[10][11][12] In fact, their homopolymerizations have never been achieved except in the case of benzaldehyde (BzA) derivatives with special structures. 10,12,13 In contrast, polymers were obtained from both BzA and a simple derivative in copolymerizations with styrene (St) or isoprene. 10,11,14 However, no copolymers of BzA and its derivatives with vinyl ethers (VEs), which have high cationic polymerizability, have been obtained, 11 although carbocation from BzA derivatives were proven to initiate living polymerization of alkyl vinyl ethers.…”

“…10,12,13 In contrast, polymers were obtained from both BzA and a simple derivative in copolymerizations with styrene (St) or isoprene. 10,11,14 However, no copolymers of BzA and its derivatives with vinyl ethers (VEs), which have high cationic polymerizability, have been obtained, 11 although carbocation from BzA derivatives were proven to initiate living polymerization of alkyl vinyl ethers. [15][16][17] One of the methods that allows living cationic polymerization is the base-assisting reaction with a Lewis acid.…”

Determination of ceiling temperature and thermodynamic properties of low ceiling temperature polyaldehydes

“…Aso et al were successful in developing an in situ IR method for monitoring the monomer concentration for poly(phthalaldehyde) polymerization, but were limited by the temperature control. 12,13 The variable temperature NMR method for measuring monomer concentration and polymer thermodynamics has been disclosed before but has not been applied to very low ceiling temperatures polymers such as polyaldehydes. [14][15][16][17][18] In this paper, variable temperature 1 H NMR was used to measure the polymer ceiling temperature and to provide additional insight into the thermodynamics of polymerization for several low ceiling temperature polyaldehydes.…”