CPC C08J 3/075 (2013.01) [C08K 3/22 (2013.01); C09K 8/032 (2013.01); C09K 8/588 (2013.01); C08J 2301/02 (2013.01); C08J 2305/12 (2013.01); C08J 2329/04 (2013.01); C08J 2333/08 (2013.01); C08J 2333/26 (2013.01); C08K 2003/2275 (2013.01); C08K 2201/003 (2013.01); C08K 2201/01 (2013.01)] | 11 Claims |
1. A polymer gel in a gelled or non-gelled state, the polymer gel comprising:
a polymer gel base material comprising at least water and polymer; and
superparamagnetic nanoparticles having a bimodal size distribution and each having a diameter of less than 100 nm, where:
at least 25 wt. % of the superparamagnetic nanoparticles have diameters in a first size range between a first diameter and a second diameter, where the first diameter is less than the second diameter, where the difference between the first diameter and the second diameter is 4 nm, and where the diameter of the particles in the first size range is measured as the core diameter;
at least 25 wt. % of the superparamagnetic nanoparticles have diameters in a second size range between a third diameter and a fourth diameter, where the third diameter is less than the fourth diameter, where the difference between the third diameter and the fourth diameter is 8 nm, and where the diameter of the particles in the second size range is measured as the hydrodynamic diameter;
the second diameter is less than or equal to the third diameter;
the Brownian relaxation time of the portion of the superparamagnetic nanoparticles in the first size range is at least 5 times the Neel relaxation time of the portion of the superparamagnetic nanoparticles in the first size range; and
the Neel relaxation time of the portion of the superparamagnetic nanoparticles in the second size range is at least 5 times the Brownian relaxation time of the portion of the superparamagnetic nanoparticles in the second size range.
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