Ionic material
The present invention relates to a material containing ionic groups that form an ionic pair with a free radical catalyst. In particular, the invention relates to materials that are magnetic, and to the methods of forming such materials. For example, a method of forming paramagnetic particles is disclosed, the method comprising contacting a substance having cationic groups with an aqueous solution of Fe 3+ so that all the cationic groups are exchanged for Fe 3+ , adjusting the pH of the solution to between 9 and 10 , to form Fe(III) hydroxide, reducing a portion of the Fe(III) hydroxide to Fe(II) hydroxide to obtain a blend of the Fe(III) hydroxide the Fe(II) hydroxide, and crystallizing the two iron hydroxides to form paramagnetic particles comprising magnetite. The invention also discloses the formation of polymers from the ionic groups within the material. Various applications of the resulting materials are also disclosed.
1. A method of preparing superparamagnetic particles attached to a polymer chain comprising the steps of:
(a) providing particles comprising ionic groups;
(b) utilizing the ionic groups for the capture of Fe cations;
(c) inducing nanocrystallization of magnetite or ferrite to form superparamagnetic particles; and
(d) introducing free radical catalysts and subsequent polymer using site directed polymerization.
2. The method of claim 1 , wherein the particles in step (a) are polymeric or non-polymeric.
3. The method of claim 1 , wherein the ionic groups are selected from sulfates, sulfonates, phosphates, carboxylates, or phenolics.
4. The method of claim 1 , wherein the particles in step (a) comprising ionic groups are selected from sulfonated polystyrene or poly(meth)acrylate particles.
5. The method of claim 1 , wherein step (b) comprises:
contacting the particles comprising ionic groups with an aqueous solution Fe 3+ or Fe 2+ so that all the cations are exchanged for an Fe 3+ or an Fe 2+ ion.
6. The method of claim 5 , wherein step (c) comprises:
adjusting the pH of the solution of Fe 3+ to between 9 and 10 to precipitate Fe(III) hydroxide;
reducing at least some of the Fe(III) hydroxide to Fe(II) hydroxide; and
crystallizing the two iron hydroxides to form magnetite (Fe 3 O 4 ).
7. The method of claim 5 , wherein step (c) comprises:
adjusting the pH of the solution of Fe 2+ to between 9 and 10; and
oxidizing the Fe 2− ions to form paramagnetic particles by aerating the particles at 65° C.
8. The method of claim 1 , wherein the steps (b)-(c) are carried out a plurality of times.
9. The method of claim 6 , wherein said reducing is carried out using hydrazine.
10. The method of claim 5 , wherein the solution containing Fe 2+ ions further comprises additional metal 2−ions.
11. The method of claim 10 , wherein the additional metal 2+ ions are Ni 2+ or Mn 2+ or a combination thereof.
12. The method of claim 1 , wherein step (d) comprises the following steps:
loading the ionic groups with the free radical catalyst;
adding one or more monomers to the particles;
generating free radicals by the catalyst; and
forming a polymer from the catalyst attached to the ionic groups.
13. The method of claim 12 , wherein the free radical catalyst is capable of thermal or redox initiation.
14. The method of claim 13 , wherein the free radical catalyst capable of thermal initiation is selected from 2,2′-azobis (2 amidinopropane) dihydrochloride, 2,2′-azobis [2-(2-imidazolin-2-yl) propane) dihydrochloride, 4,4′-azobis (4-cyanopentanoic acid), ammonium persulfate or sodium persulfate.
15. The method of claim 13 , wherein the free radical catalyst capable of redox initiation is Iron III in conjunction with a peroxide catalyst.
16. The method of claim 1 , wherein the polymer is selected from styrene, (meth)acrylate, (meth)acrylamide, or vinyl acetate.
17. The method of claim 1 , wherein the polymer chain further comprises chemical groups suitable for ligand binding.