Method of preparing exfoliated nitropolymer/silicate nanocomposites and the nanocomposites prepared by the method
Disclosed is a preparation method of an exfoliated nitropolymer/silicate nanocomposite by emulsion polymerization of monomers forming the polymer in an aqueous dispersion of non-modified, layered silicate in the presence of a reactive emulsifier having both a radical-polymerizable vinyl group and a functional group with affinity for silicate. In the process of the polymerization, silicate is fully exfoliated and uniformly dispersed in the polymer. Therefore, only a small amount of silicate is sufficient to improve thermal and mechanical properties of the polymer. Further, the method is advantageous in terms of a simple preparation process due to no use of organo-modified silicate, thus achieving an economic benefit.
1. A method of preparing an exfoliated acrylonitrile polymer/silicate nanocomposite, said method comprising the step of emulsion polymerizing at least one monomer constituting said polymer and at least one non-modified, layered silicate in the presence of at least one reactive emulsifier which comprises one or more selected form the group consisting of 2-acrylamido-2-methyl-1-propane sulfonic acid, (3-acrylamidopropyl)trimethylammonium chloride, [2-(acrloyloxy)ethyl]trimethylammonium methyl sulfate, vinylbenzyltrimethylammonium chloride, 3-acrylamido-3-methylbutyltrimethyl-ammonium chloride, N,N-dialkylaminoethyl acrylate, N,N-dialkylaminoethyl methacrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminomethyl acrylamide, N,N-dimethylaminopropyl methacrylamide, 2-methacrylamidopropyltrimethylammonium chloride, and 1,1-(dimethyl-1-(3-methacryloxy-ethyl)-1-(3-sulfopropyl) ammonium betaine.
2. The method according to claim 1 , wherein said monomer comprises acrylonitrile.
3. The method according to claim 2 , wherein said monomer further comprises one or more selected from the group consisting of styrene, vinyl chloride, nethyl methacrylate, butylmethacrylate, butylacrylate, isooctylacrylate, isobutylacrylate, hydroxyethylmethylacrylate, butadiene, and isoprene.
4. The method according to claim 1 , wherein said non-modified, layered silicate has average interlayer space of 7-12 Å.
5. The method according to claim 4 , wherein said silicate comprises one or more selected from the group consisting of montmorillonite, hectorite, saponite, and fluorohectorite.
6. The method according to claim 1 , wherein said emulsion polymerization is initiated by the addition of one or more initiator selected from the group consisting of ammonium persulfate, potassium persulfate, azabisisonitrile, and benzylperoxide.
7. The method according to claim 1 , wherein a particle stabilizer is added at the beginning of or in the process of said emulsion polymerization.
8. The method according to claim 7 , wherein said particle stabilizer is a linear alkylbenzene sulfonate-based anionic emulsifier, a non-ionic emulsifier, a rosin soap, a fatty soap, or a mixture thereof.
9. The method according to claim 8 , wherein said anionic emulsifier comprises one or more selected from the group consisting of sodium dodecyl benzenesulfonate, sodium laurate, sodium decylsulfonate, and sodium dodecylsulfonate.
10. The method according to claim 8 , wherein said non-ionic emulsifier comprises one or more selected from the group consisting of N-triethoxylated nonanamide, decylmethylsulfoxide, and beta-dodecylmaltoside.
11. The method according to claim 1 , wherein said emulsion polymerization is performed in a manner of seeded polymerization, semi-batch polymerization or batch polymerization.
12. An exfoliated acrylonitrile polymer/silicate nanocomposite prepared by the method according to claim 1 .