Comprehensive Mechanistic Analysis of the Ring-Opening Polymerization of [PCl2N]3 Using Quantum Mechanical Calculations

Document Type

Article

Publication Date

3-7-2024

Publication Title

Macromolecules

Abstract

The most popular method to synthesize polychlorophosphazenes, the parent of a prominent class of inorganic polymers, is the ring-opening polymerization (ROP) of [PCl2N](3). In contrast to the accepted (S(N)1-initiated) ROP mechanism that begins with heterolytic P-Cl bond cleavage in [PCl2N](3), our quantum mechanical (QM) calculations suggest that the ROP can proceed through a S(N)2-like route in which one [PCl2N](3) can be attacked by a neighboring [PCl2N](3) and hence transform through a four-center transition state (4C PNPCl TS), yielding a cyclic chlorophosphazene with a linear tail, termed a "tadpole". Meanwhile, two [PCl2N](3) molecules can morph into [PCl2N](6) (RR expansion) through a different four-center transition state (4C PNPN TS) without the assistance of a bridging chlorine. As the activation energy of these processes follows the trend tadpole backbite < chain branching < ROP initiation

Comments

This work was supported by the computational grants from the Ohio Supercomputer Center and the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program (supported by the National Science Foundation grant nos. 2138259, 2138286, 2138307, 2137603, and 2138296) through allocation MCB170023. Y.X. acknowledges the Southeast Conference (SEC) Emerging Scholar Program for the Distinguished Postdoc Fellowship for Year 2023–2024 and the support from the University of Mississippi. This work was partially supported by grants from the National Institutes of Health P01HL147823, R01DK123236, and R01NS124547.

DOI

10.1021/acs.macromol.3c02546

Volume

57

Issue

6

Link to Full Text

Share

COinS