Abstract
A simple model for polyethyleneoxide (PEO) is introduced and
analyzed by
Monte Carlo simulation. The occurrence of a solvation shell of
PEO in water
is modeled by two internal states of the monomers with an energy
difference
P. In the solvated state the monomer excluded volume
increases due
to the bound water and prevents the collapse of the poor-solvent
backbone. As
a function of P, which can be positive or negative,
we find for
P≲0.7kBT a first-order collapse transition,
while for
P ≳ 0.7kBT the standard Θ-point is
recovered. Thus, if
the solvation shell is accompanied by a lower internal energy
(P < 0 as for PEO), the transition is always of first
order.