Protective coating of magnetic nanoparticles

Abstract

Encapsulated particles and methods for manufacturing encapsulated particles and structures are described. Such particles may have a length no greater than 40 nm, and include at least one material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials. A polymeric encapsulant surrounds the particle, the polymeric encapsulant including a phase-separated block copolymer including a glassy first phase and a rubbery second phase, the glassy first phase positioned between the particle and the second rubbery phase. The glassy first phase includes a hydrophobic copolymer having a glass transition temperature of at least 50° C. The rubbery second phase includes a polymer having at least one of (i) a glass transition temperature of no greater than 30° C., and (ii) a tan delta peak maximum of no greater than 30° C. Other embodiments are described and claimed.

What is claimed: 
     
         1 . An encapsulated particle comprising:
 a particle having a length no greater than 40 nm;   the particle comprising at least one material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;   a polymeric encapsulant surrounding the particle, the polymeric encapsulant comprising a phase-separated block copolymer including a glassy first phase and a rubbery second phase, the glassy first phase positioned between the particle and the second rubbery phase;   the glassy first phase comprising a hydrophobic copolymer having a glass transition temperature of at least 50° C.; and   the rubbery second phase comprising a polymer having at least one of (i) a glass transition temperature of no greater than 30° C., and (ii) a tan delta peak maximum of no greater than 30° C.   
     
     
         2 . The encapsulated particle of  claim 1 , wherein the glassy first phase is in direct contact with the particle, and the rubbery second phase is in direct contact with the first phase. 
     
     
         3 . The encapsulated particle of  claim 1 , wherein the particle comprises a material selected from the group consisting of iron cobalt alloys, cobalt platinum alloys, barium ferrite alloys, cobalt, nickel iron alloys, manganese aluminum alloys, iron nickel alloys, manganese aluminum alloys, iron, iron oxide, cobalt oxide, nickel oxide, and spinel ferrites. 
     
     
         4 . The encapsulated particle of  claim 1 , wherein the polymeric encapsulant has a thickness of up to 2 nm. 
     
     
         5 . The encapsulated particle of  claim 1 , wherein the rubbery second phase includes plurality of end groups consisting of reactive functional groups. 
     
     
         6 . The encapsulated particle of  claim 5 , wherein the reactive functional groups include at least one group selected from the group consisting of photoreactive functional groups and chemically reactive functional groups. 
     
     
         7 . The encapsulated particle of  claim 6 , wherein the reactive functional groups include at least one chemically reactive functional group selected from the group consisting of: epoxy functional groups, isocyanate functional groups, anhydride functional groups, carboxylic acid functional groups, and primary alcohol functional groups. 
     
     
         8 . The encapsulated particle of  claim 6 , wherein the reactive functional groups include at least one photoreactive functional group selected from the group consisting of: azo functional groups, vinyl functional groups, allyl functional groups, and acryl functional groups. 
     
     
         9 . The encapsulated particle of  claim 1 , wherein the particle has an aspect ratio that is no less than two. 
     
     
         10 . The encapsulated particle of  claim 1 , wherein the particle has a length dimension of no greater than 20 nm. 
     
     
         11 . The encapsulated particle of  claim 1 , wherein the particle includes an oxide layer, and wherein the glassy phase is formed in contact with the oxide layer 
     
     
         12 . A magnetic tape comprising a plurality of encapsulated particles, comprising:
 a plurality of magnetic particles, each having a length no greater than 40 nm;   the magnetic particles each comprising at one material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;   a polymeric encapsulant surrounding the magnetic particles, the polymeric encapsulant comprising a phase-separated block copolymer including a glassy first phase and a rubbery second phase on each of the magnetic particles, the first phase positioned between the second phase and the magnetic particle;   the glassy first phase comprising a hydrophobic copolymer having a Tg of at least 50° C.; and   the rubbery second phase comprising a polymer having at least one of (i) a glass transition temperature of no greater than 30° C., and (ii) a tan delta peak maximum of no greater than 30° C.   
     
     
         13 . The magnetic tape of  claim 12 , wherein the plurality of particles have a size distribution with a polydispersity of less than 2.0. 
     
     
         14 . The magnetic tape of  claim 12 , wherein a plurality of the magnetic particles are coupled together, wherein for a plurality of the magnetic particles, the second phase on adjacent particles is in direct contact. 
     
     
         15 . The magnetic tape of  claim 12 , further comprising a matrix material positioned between adjacent of the encapsulated particles. 
     
     
         16 . The plurality of particles of  claim 12  wherein the plurality of particles have a polydispersity of less than 1.2. 
     
     
         17 . A method for manufacturing encapsulated particles, comprising:
 forming a first polymer on a magnetic particle; and   performing ligand exchange to attach a second polymer to the first polymer, wherein the first polymer is positioned between the second polymer and the magnetic particle.   
     
     
         18 . The method of  claim 15 , wherein the first polymer comprises a glassy phase comprising a hydrophobic copolymer having a glass transition temperature of at least 50° C. 
     
     
         19 . The method of  claim 16 , wherein the second polymer comprises a rubbery second phase comprising a polymer having at least one of (i) a glass transition temperature of no greater than 30° C., and (ii) a tan delta peak maximum of no greater than 30° C. 
     
     
         20 . The method of  claim 15 , wherein the ligand exchange comprises reacting polystyrene from the first polymer with a carboxylic acid polymer to form the second polymer.