<i>Ab initio</i> molecular dynamics modeling of single polyethylene chains: Scission kinetics and influence of radical under mechanical strain

Ab initio molecular dynamics was used to estimate the response constant imposed strain on a short polyethylene (PE) chain and radical with removed hydrogen atom. Two independent types of simulations were run. In first case, chains strained by expanding periodic cell, restraining length but allowing internal degrees freedom reach equilibrium. From these simulations, average force computed, resulting integrated determine Helmholtz free energy for stretching. second set constrained various lengths, while bond restrained at lengths using umbrella sampling. This provided scission strains. The sum two functions results in an approximation under strains gives realistic new picture effect breaking. Unimolecular rates each type examined as function strain. rate is several orders magnitude larger than that pristine smaller highlights importance formation PE rupture consistent experiments. Constant derive constant-force model demonstrates roll over similar “catch-bond” behavior observed protein membrane detachment