Insights into the Thermal Response of a Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) Triblock Polymer in Water

A thermal responsive block copolymer
made up of ethylene oxide
(EO) and propylene oxide (PO) blocks was simulated with optimized
atomistic potentials and enhanced sampling methods over a range of
temperatures. The results for the L42 pluronic polymer (EO)4(PO)22(EO)4, which is known to undergo a transition
in this temperature range, and the similarly sized (EO)30 polymer, which does not, are compared. The thermal responsive L42
polymers in a dilute solution tend to aggregate, and this tendency
gets stronger as temperature increases. The poly­(ethylene oxide) polymer
shows no such tendency. The aggregation is stabilized by the hydrophobic
contact of the propylene oxide methyl groups, which outweighs a small
loss in hydrogen bonds between the ether oxygens and water.