Folding mechanism of a polymer chain with short-range attractions

C Leitold and C Dellago, JOURNAL OF CHEMICAL PHYSICS, 141, 134901 (2014).

DOI: 10.1063/1.4896560

We investigate the crystallization of a single, flexible homopolymer chain using transition path sampling. The chain consists of N identical spherical monomers evolved according to Langevin dynamics. While neighboring monomers are coupled via harmonic springs, the non- neighboring monomers interact via a hard core and a short-ranged attractive potential. For a sufficiently small interaction range., the system undergoes a first-order freezing transition from an expanded, disordered phase to a compact crystalline state. Using a new shooting move tailored to polymers combined with a committor analysis, we study the transition state ensemble of an N = 128 chain and search for possible reaction coordinates based on likelihood maximization. We find that typical transition states consist of a crystalline nucleus with one or more chain fragments attached to it. Furthermore, we show that the number of particles in the crystalline core is not well suited as a reaction coordinate. We then present an improved reaction coordinate, which includes information from the potential energy and the overall crystallinity of the polymer. (C) 2014 AIP Publishing LLC.

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