Free Radically Derived Polymeric Shells on Magnetic Particles for Magnetic Tape Storage

University of Arizona
posted on 05/26/2010

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Background:  The use of dipolar particles as building blocks to prepare organized hierarchical materials is an emerging area of great potential in materials chemistry.  Control of structure on the molecular, nano- and macroscopic regimes offers the possibility of designing specific properties into materials that are otherwise inaccessible. This invention particularly focuses on compatabilizing interfaces between organic and inorganic matter as a route to combine the advantageous properties of both components. Ferromagnetic colloids are of interest as the inherent dipole moment of these materials enables one- and two-dimensional assembly into novel mesostructures.

Sub-micron sized magnetic metal particles suitable for forming a recording layer on a flexible magnetic medium or tape are commonly manufactured in sintered clusters of oxide coated metal particles. The oxide layer imparts chemical stability to the metal particles. The oxide layer also stabilizes the metal core, but reduces the volume fraction of the magnetic particle available to contribute to the magnetic domain which is needed to store information. The oxide layer is formed in a sintering process that also cements individual magnetic particles into clusters held together by the hard oxide material. This makes dispersion of the particles into the individual magnetic particles very difficult, if not impossible. As a result, processing of these particles into suspensions suitable for creation of a useful recording layer on a flexible substrate is becoming increasingly difficult to achieve as the particles become smaller. Agglomeration of magnetic particles can occur, resulting in poor tape performance and limiting the maximum achievable information density.

Invention:  This invention relates to polymer coated magnetic nanoparticles for application in magnetic tape. The invention describes methods for making the particles and magnetic tape compositions comprising coated particles. This invention imparts greatly enhanced handling and processing characteristics to the magnetic nanoparticles, ultimately yielding improved performance and greater information density to the magnetic media.

Applications:
* Commercial applications are in high-density information storage, such as magnetic tape or flexible magnetic storage media.

Advantages:
* Magnetic nanoparticles that are not subject to flocculation and agglomeration;
* Well-defined, end-functional or side-chain-functional copolymers easy to attach as an overcoat to the surface of commercial, metallic, magnetic nanoparticles;
* Simple free radical polymerization process.

Status:  Well-defined, end-functional or side-chain-functional copolymers have been prepared using free radical polymerization, and then attached as an overcoat to the surface of commercial, metallic, magnetic nanoparticles (aka "core-shell" nanoparticles). The polymer synthetic methods are based on free radical polymerization and controlled radical polymerization, namely, atom transfer radical polymerization (ATRP). This work is continuing in collaboration with industry: in order to evaluate the capabilities of these materials for information storage media. The UA Office of Technology Transfer filed a US Utility Patent application with the USPTO. We seek development partners and industrial manufactures of magnetic tape.

Lead Inventor:  Jeffrey Pyun

Licensing Information:  Please contact Eugene Cochran for further information referencing UA Case No.:UA09-087.