Stretching Elasticity and Flexibility of Single Polyformaldehyde Chain

In this work, the single-chain elasticity of polyformaldehyde (POM) is studied, for the first time, by employing atomic force microscopy (AFM)-based single molecule force spectroscopy (SMFS). We find that the single-chain elasticity of POM in a nonpolar organic solvent (nonane) can be described well by a theoretical model (QM-FRC model), when the rotating unit length is 0.144 nm (C-O bond length). After comparison, POM is more flexible than polystyrene (a typical polymer with C-C backbone) at the single-chain level, which is reasonable since the C-O bond has a lower rotation barrier than C-C bond. This result indicates that the flexibility of a polymer chain can be tuned by the C-O bond proportion in backbone, which casts new light on the rational design of new synthetic polymers in the future.