Surface effects in the crystallization process of elastic flexible polymers

Abstract

Investigating thermodynamic properties of liquid-solid transitions of flexible homopolymers with elastic bonds by means of multicanonical Monte Carlo simulations, we find crystalline conformations that resemble groundstate structures of Lennard-Jones clusters. This allows us to set up a structural classification scheme for finite-length flexible polymers and their freezing mechanism in analogy to atomic cluster formation. Crystals of polymers with "magic length" turn out to be perfectly icosahedral.

Identifying transitions in finite systems by means of partition function zeros and microcanonical inflection-point analysis: A comparison for elastic flexible polymers

“…As earlier analyses revealed [1,16], the liquid-solid and solid-solid transitions for system sizes 31 ≤ L ≤ 54 have peculiar characteristics. Except for the special case L = 38 that forms a truncated fcc octahedron, these polymers crystallize in two different ways by cooling down from the liquid phase [16].…”

“…We only analyze here the zero maps for L = 35, 55, 90, and 300, because these system sizes are representative for the various transition behaviors that have been systematically and uniquely identified for polymer chains with lengths in the above mentioned interval in canonical [16][17][18] and microcanonical analyses [1]. From these studies it is known that in this model polymers with "magic" length L = 13, 55, 147, 309, .…”

“…The structural transition behavior was investigated previously by conventional canonical statistical analysis of "peaks" and "shoulders" of fluctuating energetic and structural quantities as functions of the canonical temperature [16,17]. Subsequently, the densities of states of this set of polymers were analyzed systematically by means of microcanonical inflection-point analysis, with particular focus on the typically hardly accessible low-temperature transition behavior (freezing, solid-solid transitions) [1].…”

“…For the study of generic thermodynamic properties of polymers, however, all-atom models can typically be replaced by a simpler coarse-grained representation with effective interactions. We here consider such a generic coarsegrained model for linear, elastic, flexible polymers [16]. Non-bonded monomers interact pairwise via a truncated and shifted Lennard-Jones (LJ) potential…”

“…Most applications of the partition function zero analysis method are considered to be alternative approaches to scaling properties near phase transitions in large systems. However, this method is also promising for the identification and characterization of analogs of phase transitions in finite systems, in particular in finite linear polymer chains that are known to exhibit a variety of structural transitions which sensitively depend on the chain length [1,[16][17][18]. The understanding of these structure formation processes is relevant from both fundamental scientific and applied technological perspectives of molecular building-block systems.…”