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Full-Text Articles in Chemistry
Form Factor Of Pnipam Microgels In Overpacked States, U. Gasser, J. S. Hyatt, J.- J. Lietor-Santos, E. S. Herman, L. Andrew Lyon, A. Fernandez-Nieves
Form Factor Of Pnipam Microgels In Overpacked States, U. Gasser, J. S. Hyatt, J.- J. Lietor-Santos, E. S. Herman, L. Andrew Lyon, A. Fernandez-Nieves
Biology, Chemistry, and Environmental Sciences Faculty Articles and Research
We study the form factor of thermoresponsive microgels based on poly(N-isopropylacrylamide) at high generalized volume fractions, ζ, where the particles must shrink or interpenetrate to fit into the available space. Small-angle neutron scattering with contrast matching techniques is used to determine the particle form factor. We find that the particle size is constant up to a volume fraction roughly between random close packing and space filling. Beyond this point, the particle size decreases with increasing particle concentration; this decrease is found to occur with little interpenetration. Noteworthily, the suspensions remain liquid-like for ζ larger than 1, emphasizing the importance of …
Bulk Modulus Of Poly(N-Isopropylacrylamide) Microgels Through The Swelling Transition, B. Sierra-Martin, Y. Laporte, A. B. South, L. Andrew Lyon, A. Fernandez-Nieves
Bulk Modulus Of Poly(N-Isopropylacrylamide) Microgels Through The Swelling Transition, B. Sierra-Martin, Y. Laporte, A. B. South, L. Andrew Lyon, A. Fernandez-Nieves
Biology, Chemistry, and Environmental Sciences Faculty Articles and Research
We report measurements of the bulk modulus of individual poly(N-isopropylacrylamide) microgels along their swelling transition. The modulus is determined by measuring the volume deformation of the microgel as a function of osmotic pressure using dextran solutions. We find that the modulus softens through the transition, displaying a nonmonotonous behavior with temperature. This feature is correctly reproduced by the theory of Flory for polymer gels, once the concentration dependence of the solvency parameter is properly incorporated.