Magnetic Field Induced Ordering Of Block Copolymers

Poloxamers are amphiphilic ABA type triblock co-polymers that act like a surfactant in water, creating a micelle with a “B” type polypropylene oxide core and “A” type polyethylene oxide coronas. They are widely applicable as hydrogels, which are notably utilized in biocatalysis, drug delivery, and drug stability. In this project, we probed an atypical response of disordered poloxamer solution to ordered gel transition in response to magnetic fields. The behavior of a poloxamer solution in presence of an applied magnetic field (B = 0.5T) was investigated using magnetorheology, where the rheological characteristics of the samples were studied while exposed to an in situ magnetic field. Specifically, the time required by the poloxamers to transition from their disordered to gel state under magnetization, referred to as critical time, was tracked as a function of block ratio and molecular weight. The gels were characterized using small-angle x-ray scattering (SAXS), which revealed their structural information. The critical time decreased exponentially and the modulus remained relatively consistent when increasing the molecular weight of the poloxamer. These results demonstrate the tunability of magnetically-induced poloxamer gels for wide-ranging applications.