Rd. Groot et Wgm. Agterof, MONTE-CARLO STUDY OF ASSOCIATIVE POLYMER NETWORKS .1. EQUATION OF STATE, The Journal of chemical physics, 100(2), 1994, pp. 1649-1656
The equation of state of associative polymer networks has been studied
by Monte Carlo simulation. To describe the associations, an algorithm
is introduced which for dilute monatomic systems reduces to the well-
known mass action law. For the polymers, the simple bead spring model
was employed. The incorporation of a finite volume of the beads is ess
ential to prevent phase separation once the associative interaction is
turned on, and the system is quenched into the gel state. The excess
pressure of this quenched state is well described by two exponents of
the density p. The repulsive part of the excess pressure scales propor
tional to p(alpha), the attractive part is proportional to p(8). For t
he nonassociating polymers we measured the first exponent as alpha=2.3
39 +/- 0.006, and for associating polymers far away from the critical
point we found beta=2.06 +/- 0.05. For certain values of the density a
nd the association constant the measured pressure was negative, in the
se cases we find microphase separated configurations. The simulations
also enabled the establishment of the percolation transition. The asso
ciation constant at the gel point has been obtained as a function of d
ensity and polymer length. Together with the equation of state this re
sulted in a phase diagram for polymer gels.