Rheological Study of Order to Disorder Transition (ODT) in Microphase Separated Block Copolymer Surfactant-Functional Small Molecule Additive Complexes

Microphase separation is Pluronic® block copolymer surfactants was achieved by blending in small molecules bearing carboxyl or hydroxyl functional groups. The functional group on small molecule selectively hydrogen bonds with the PEO chains of Pluronic thereby effectively increasing X parameter between PEO and PPO and inducing microphase separation. Rheology is used to determine ODT in these complexes with varied amount of small molecule additive and with varied number of functional groups on the additive molecule.  It was found that ODT, and therefore the segregation strength in these microphase separated complexes strongly depend upon the amount of additive added and the number of functional groups present on the additive molecule. The hydrogen bonding capability of the functional group (carboxyl or hydroxyl) also greatly affected the segregation strength in these complexes, as reflected in ODT measurements.