Phase-behavior, rheology and erosion behavior of hydrogels of fluorocarbon end-capped PEG

Hydrogels formed by association of PEG with fluoroalkyl end-groups can exhibit three different types of behavior as a function of concentration depending on the relative hydrophilicity of the midblock compared to the hydrophobicity of the end blocks. For polymers with relatively long PEG chains compared to the fluoroalkyl groups the aggregation behavior follows the typical single-phase, continuous transition from sol to gel that is widely observed in associative thickeners. As the PEG length is reduced relative to fluoroalkyl length the phase behavior to sol-gel coexistence (`two-phase' type) behavior. This correlates with changes in the rheological characteristics of the gel and in its erosion behavior.