Isostaticity and the solidification of semiflexible polymer melts

CO Plaza-Rivera and HT Nguyen and RS Hoy, SOFT MATTER, 13, 7948-7952 (2017).

DOI: 10.1039/c7sm01442b

Using molecular dynamics simulations of a tangent-soft-sphere bead- spring polymer model, we examine the degree to which semiflexible polymer melts solidify at isostaticity. Flexible and stiff chains crystallize when they are isostatic as defined by appropriate degree-of- freedom-counting arguments. Semiflexible chains also solidify when isostatic if a generalized isostaticity criterion that accounts for the slow freezing out of configurational freedom as chain stiffness increases is employed. The configurational freedom associated with bond angles (theta) can be associated with the characteristic ratio C-infinity = (1 + < cos(theta)>)/(1 - < cos(theta)>). We find that the dependence of the average coordination number at solidification Z(T-s) on chains' characteristic ratio C-infinity has the same functional form Z similar or equal to a bn(C-infinity) as the dependence of the average coordination number at jamming Z(phi(J)) on C-infinity in athermal systems, suggesting that jamming-related phenomena play a significant role in thermal polymer solidification.