(243h) Probing the Rheology of Block Polymer Liquid Crystals Via Diffusion of Nanometric Tracer Particles | AIChE

(243h) Probing the Rheology of Block Polymer Liquid Crystals Via Diffusion of Nanometric Tracer Particles

Authors 

Walker, L. - Presenter, Carnegie Mellon University
Valentine, C. S., Carnegie Mellon University
Dispersion of nanometric particles in block copolymer micellar crystals provides a method to control the spatial organization of the dispersed phase. This approach can be used to protect nanometric material against aggregation and develop templated materials. Pluronic [PEOm-PPOn-PEOm] liquid crystals provide a thermoreversible and versatile template for development of these applications. Particles (globular proteins) are first dispersed in an aqueous unassembled solution, which are liquid at low temperature (T < ~ 10°C). On heating to near room temperature and higher the block copolymers self-assemble into micelles, which arrange into ordered crystalline lattices. The aqueous continuous phase of these crystals acts as a nanostructured template which hinders the mobility of the dispersed proteins - the proteins are confined to the aqueous interstitial pockets. The properties and size of the aqueous pockets between micelles can be engineered by changing polymer architecture, concentration, additives, and temperature. The mobility of the proteins within this aqueous phase will depend on more than geometry of the dynamic, nanostructured material. Fluorescence Recovery After Photobleaching (FRAP) is used to quantity the mobility of fluorescently labeled proteins within the continuous phase of micellar liquid crystals. Diffusion in these systems cannot be explained as transport through a bulk viscous media. The properties of the micellar corona impact the proteins’ ability to move through micellar brushes as they diffuse between interstitial sites. Here, we use a simple hopping model to analyze the diffusivity of the dispersed phase.