3589790

Kinetic investigation on the ring-expansion polymerization of o-phthalaldehyde

Date
August 23, 2021

Poly(phthalaldehyde) is a metastable polymer that has been shown to rapidly depolymerize from the solid state back into its constituent monomer, a consequence of its low ceiling temperature. This depolymerization upon triggering makes it well suited as a chemically recyclable polymer, and sacrificial materials in semiconductor or other manufacturing. Although interest in phthalaldehyde-based polymers has increased in the past several years, there has not been a thorough investigation of the polymerization kinetics since its discovery in 1967. In this work, a continuous flow reactor was utilized to probe the kinetics of this rapid, cationic polymerization in dichloromethane using boron trifluoride diethyl etherate as the Lewis acid catalyst. Under proper catalyst loadings, polymer nominal molecular weights exceed 250 kDa in 10 seconds of reaction time at -78 °C. Molecular weight and time–conversion data supports two polymerization regimes, which has not been observed before in batch polymerizations of this polymer. The initial chain growth regime involves the creation of many polymer chains of moderate molecular weight. At conversions greater than 70%, a kinetic transition is observed as the polymer chains fuse together at higher rates, causing the observed molecular weight to roughly double in the last 20% conversion. These findings provide fundamental kinetic and molecular weight understanding that enable greater synthetic control over depolymerizable poly(aldehydes).

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