WO2005068551A1

WO2005068551A1 - A exfoliated nano-composite from polyaniline graft copolymer/clay

Info

Publication number: WO2005068551A1
Application number: PCT/KR2005/000026
Authority: WO
Inventors: Won-Ho Jo; Yun-Heum Park; Keon-Hyeong Kim; Woo-Jin Bae
Original assignee: Seoul National University Industry Foundation
Priority date: 2004-01-13
Filing date: 2005-01-06
Publication date: 2005-07-28
Also published as: KR100605515B1; KR20050074174A

Abstract

The present invention relates to a method for preparing exfoliated nano-composite from polyaniline graft copolymer/clay and the nano-composite prepared by the same. According to the present invention, a exfoliated polyaniline (PANI)/clay nanocomposites were prepared by in-situ polymerization of aniline onto pre-exfoliated water-soluble poly (styrenesulfonic acid- co - aminostyrene) (P(SSA-co-AMS))/clay nanocomposite or by simple blending of poly (styrenesulfonic acid- g-aniline) (PSSA-g-PANI). When an aqueous mixture of P(SSA-co-AMS) and clay was treated with 1 M HCl (aq.), clay layers are exfoliated into the polymer matrix due to the electrostatic interaction between the positive charge of nitrogen (NH3+) in P(SSA-co-AMS) and the negatively charged surface of clay layers. The electrical conductivity of the nanocomposite is slightly lower than that of pure PSSA-g-PANI but the thermal stability of the nanocomposite becomes better as compared with PSSA- g-PANI.

Description

Description A EXFOLIATED NANO-COMPOSITE FROM POLYANILINE GRAFT COPOLYMER/CLAY Technical Field

[1] The present invention relates to a method for preparing exfoliated nano-composite frcm polyaniline graft copolymer/clay and the nano-composite prepared by the same. Specifically, the present invention relates to a method for preparing a nano-composite of poly(styrenesulfonic aάd-g-aniline) and clay in a manner that after preparing tert- butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aninostyrene(AMS) with tert- butyldicarbonate ((BOC) ), and then the nano-composite may be obtained by reacting 2 said tert-butoxycarbonyl-aninostyrene (BOC-AMS) with sodium stylene- sulfonate(SSNa) to prepare copolymer (P(SSNa-co-BOC-AMS)) and then by penetrating said copolymer (P(SSNa-co-BOC-AMS)) into the gallery of the clay layer swollen by aqueous solution to disperse clay layers in order of nano-scale into the gallery of the clay layers.

[2] Background Art

[3] Polyaniline is essentially one of conducting polymers which have been studying with the most activity, polyaniline has been made conducting by proton-doping or oxidation-doping. It is well known that polyaniline can be combined with high probability frcm comparatively cheap monomer, and it has excellent chemical stability and comparatively high conduction in view of conduction form [MacDiarmid, A.G. In Conjugated polymers and Related Materials, The Interconnection of Chemical and Electronic Structure; Salaneck, W.R.; Lundstrom, I.; Ranby, B., Eds.; Oxford University Press, 1993, PP 73-98].

[4] Polyaniline may be used for application to secondary battery, electro-emitting element, electro chromatic element and sensor owing to the excellent electric, electric- chemical and optical properties. Because polyaniline used in the above applications should be prepared as film or coated shape, a method for preparing polyaniline having self-doped property and capable of being manufactured from a solution may be highly required. But the production from a solution is very difficult in known manner because polyaniline has primary chains with stiff structure and the interaction between the chains with high molecular weight.

[5] For recent more than 10 years the solution process has considerably advanced to develop a method for processing polyaniline dissolved into organic solvent and water, polyaniline may be processed as solution process into a polar Lewis base such as N- methyl pyrrolidone (NMP) [MacDiarmid, A.G. In Conjugated polymers and Related Materials, The Interconnection of Chemical and Electronic Structure; Salaneck, W.R.; Lundstrom, I.; Ranby, B., Eds.; Oxford University Press, 1993], N, N'-dimethyl propylene urea [Tzou, K.T. and Gregory, R.V. Synth. Met. 1995, 69-109] or strong sulphuric acid [Andreatta, A., Cao, Y., Chiang, J.C., Heeger, A.J. and Smith, P. Synth. Met. 1998, 26-383]. More recently, conducting polyaniline can be processed into polar solvent or non-polar solvent using prontoic acid dopant such as dodecylben- zenesulfonic acid or camposulfonic acid [Cao, Y., Smith, P. and Heeger, A.J. Synth. Met. 1992, 48-91].

[6] Methods for preparing soluble polyaniline have been developed. It has been reported that soluble polyaniline can be prepared by substituting alkane sulfonic acid group for nitrogen [Bergeron, J.Y, Chevalier, J.W. and Dao, Le H.J. Chem. Soc, Chem. Cα rnun. 1990, 180; Chen, S.A. and Hwang, G. W. J. Am. Chem. Soc. 1994, 116-7989] or directly polymerizing synthesized aniline-N-alkyl-sulfonate electro- chemically or chemically [Kim, E.M., Lee, M.H., Moon, B.S., Lee, C. and Rhee, S.B.J. Electrochem. Soc.1994,141, L26]. More recently, it has been known that soluble conducting polyaniline containing N-aryl sulfonate can be prepared by directly polymerizing diphenylamine-4-sulfonic acid [DeArmitt, C, Armes, C.P., Winter, J., Uribe, F.A., Gottesfeld, J. and Mombourquette, C. Polymer 1993, 34-158] or oopolymerizing O-aπino benzyl alcohol with diphenylamine-4-sulfonic acid [Nguyen, M. T. and Diaz, A.F. Macrorrolecules 1994, 27, 7003].

[7] Other methods have been reported for preparing soluble polyaniline compounded with high molecular acid by polymerizing aniline with chemical oxidation method under high molecular acid [M. Angelopoulos, N. Patel, J. M. Shaw, N. C. Labianca and S.A. Rishton, J, Vac. Sά. Technol. Bll, 2794(1993); K. Shannon, and J.E. Fernadez, J. Chem. Soc. Chem. Commum., 643(1994)].

[8] Regarding to soluble polyaniline prepared by the above^nentioned methods, it is very difficult to purify product separately from reacting solvent and by-product after reaction. That is, the by-product used as solvent and the residual reagent not activated during reaction are not easily removed from water, and in general dialysis is used for purifying, but it is very difficult to determine degree of purity and also the methods has disadvantage in view of process. Furthermore, the excessive water should be removed disadvantageously for preparing soluble polyaniline with required concentration. [9] In general, if polyaniline in form of film or coated compound prepared by a solution process is to be used for electro-chemical application, then the electro-chemical properties, such as the activity of oxidation and reduction and oxidation-reduction stability (life time) according to the number of repetition are very important. The most important factor for determining the above properties is degree of ion-conduction, for the diffusion of ions affects greatly the reversibility of oxidation-reduction and the lifetime with all the electric-chemical reaction. It has reported that polyaniline substituted for N-alkyl sulfonic acid has the stability of oxidation-reduction more than 100,000 repetitions under acid solution [Kim, E.M., Lee, M.H., Moon, B.S., Lee, C. and Rhee, S.B.J. Electrochem. Soc, 1994, 141, L26], but the acid condition may be not suitable for application of secondary battery, electro-chromic material.

[10] Recently, it has been reported that when the copolymer of poly(styrenesulfonic acid) and oligo ethyleneglycol acrylate were used for the dopant of polyaniline, the electrical property was enhanced [H. Tsutsuπi, S. Fukuzawa, M. Ishikawa, M. Morita, and Y. Matsuda, J. Electrochem. Soc, 142, L168,1995]. In this case, the electrical property was preserved even after the 40 cycles of charging and dis-charging, but the polymerization method is very difficult and the solution process was impossible because the prepared polyaniline film cannot be dissolved in solvent.

[11] Polymer/clay nano-composite corresponds to a next- generation complex material having physical properties such as anti-crushing, and strength, blocking gas, anti- combustion, anti-flaming, anti-wearing and heat stability without impairing transparency and the like by exfoliating and dispersing clay belonging to inorganic particles into polymer material such as thermosetting resin and thermoplastic resin in nanometer scale (nanometer: 10 m) [I.E.P. Giannelis, Adv. Mater. 1996, 8, 29, E.P. Giannelis, R. Krishnαmoorti, and E. Manias, Adv. Polym. Sά. 1999, 138, 107, E.P. Giannelis, Appl. Organomet. Chem.. 1998, 12, 675, R. Xu, E. Manias, A. J. Snyder, and J. Runt, Macromolecules 2001, 34, 337, R. K. Bharadwaj, Macrolecules 2001, 34, 1989, P.B. Messersrrith, and E.P. Giannelis, J. Poly. Sά., Part A, Poly. Chem. 1995, 33, 1047, J. W. Gilman, Chem. Mater. 2000, 12, 1869]. That is, polymer/clay nanocomposite development may include the concept that the lower mechanical property of general ordinary polymer enhances up to that of engineering plastic. And also, polymer/clay composite has given attention as model for studying relating to the con- formational structure of polymer chain molecule and dynamics as well as increasing the physical properties [E. Hackett, E. Manias, and E.P. Giannelis, J. Chem. Phys. 1998, 108, 7410, E. Hackett, E. Manisa, and E. P. Giannelis, Chem. Mater. 2000, 12, 2161, S.H. Anastasiadis, K. Karatasos, G. Nalchos, E. Manis, and E.P. Giannels, Phys. Rev. Lett. 2000, 84, 9].

[12] In molecule level, functional polymer-clay complex material plays an important role in the field of organic-inorganic nano-structural substance. Among such nano- oomposites, it may become a method for preparing new hybrid-high order structural polymer composite representing peculiar electricity to embed a mixture into inter-layer in which the mixture is made from mixing conducting material with phyllosilicates in proportion of 2: 1 [Ozin, G. A. Adv. Mater., 4, 612-649 (1992)]. Substantially, the capability for clay to embed organic material may be used in various fields for representing peculiar properties. Considering the above circumstance, the design and synthesis of nano-composite with conducting material and inorganic material may cause synergy or complement effect of properties which conducting material possess by means of inter-attraction with clay host.

[13] Several methods to prepare PAΝI/clay nano-composite have been reported. One of commonly used methods to prepare the nano-composite is intercalation of aniline into the gallery of clay layers followed by in-situ polymerization. Emulsion polymerization is also used for preparation of PAΝI/clay nano-composite. The emulsifier in emulsion system contribute to maximization of the affinity between hydrophilic host (clay) and hydrophobic guest (aniline) [Kim, J. W.; Kim, S. G.; Choi, H. J.; Jhon, M. S. Macrorrol. Rapid Cαmrnun. 1999, 20, 450, Kim, B. H.; Jung, J. H.; Hong, S. H.; Joo, J.S.; Epstein, A.J; Mizoguchi, K.; Kim, J. W.; Choi, H. J. Macromolecules 2002, 35, 1419].

[14] Although many studies on PAΝI/clay nano-composites have been carried out as mentioned above, they have obtained the intercalative structure. Exfoliated nano- oomposites can attain better physical properties such as stiffness, strength, and barrier property with far less inorganic content than that used in conventionally filled polymer composites. The higher is the degree of exfoliation in polymer/clay nano-composites, the greater is the enhancement of these properties. Recently, it has been reported that PAΝI/clay nano-composites with exfoliated silicate layers are successfully prepared by using an organically modified clay, which show enhancement of corrosion protection and gas barrier property [Yeh, J. M.; Liou, S. J.; Lai, C. Y.; Wu, P. C. Chem. Mater. 2001, 75, 113].

[15] The process using organic agent has some disadvantages that the process is complex and the cost for preparing is high as well as an environmental problem may be caused and the physical properties are poor. In the meanwhile, the method for preparing completely exfoliated polyaniline/clay composite without using organic treatment has not been known.

[16] It is an object of the present invention to provide a method for preparing completely exfoliated polyaniline/clay composite wherein the method makes it possible to process in aqueous solution without organic treatment using aqueous polyaniline graft copolymer.

[17] In a preferred embodiment, there is provided with a method for preparing nanocomposite containing a self-doped aqueous polyaniline graft copolymer represented as following formula (1) and clay (Na -MMT) represented as formula (2):

[18] [Structural formula 1]

[19] aqueous part self-doping part

[20] [Structural formula 2] [21]

[22] Disclosure of Invention

[23] According to the present invention, the nano-composite contains self-doped soluble polyaniline graft copolymer as the above Structural formula 1 and completely exfoliated clay (Na -MMT) as the above Structural formula 2 comprises. [24] According to according to the present invention, the proportion of clay (Na -MMT) and polyaniline preferably may be 1: 1000 to 100: 1. [25] According to the present invention, the number of repeated units in polyaniline graft copolymer may be preferably 1 to 400. [26] According to the present invention, the nano-composite may be self-doped.

[27] According to the present invention, the conductivity of the nano-composite may be 1.0 x 10¹ S/cm to 1.2 x 10 ^"4 S/cm. [28] According to the present invention, there may be provided with an anti- electrification agent comprising the nano-composite. [29] According to the present invention, there may be provided with a material for shielding electroΗiagnetic field containing the nano-composite. [30] According to the present invention, there may be provided with a material for use of secondary battery containing the nano-composite. [31] According to the present invention, there may be provided with a coating membrane containing the nano-composite. [32] According to the present invention, there may be provided with a sensor containing the nano-composite. [33] According to the present invention, a method for preparing the nano-composite, comprising the steps: [34] (a) preparing tert-butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aπinostyrene (AMS) with tert-butyldicarbonate ((BOC) ) 2

[35] (b) preparing copolymer (P(SSNa- co-BOC-AMS)) by said BOC-AMS with sodium styrenesulfonate (SSNa), and penetrating said copolymer (P(SSNa- co-BOC-AMS)) into the gallery of clay layers by immersing said copolymer (P(SSNa- co-BOC-AMS)) into the clay swollen with aqueous solution; [36] (c) preparing copolymer of styrene sulfonic acid and amino-styrene (P(SSA- co - AMS)) by eliminating tert-butoxycarbonyl from said copolymer (P(SSNa- co - BOC-AMS)) penetrated into the gallery of clay layers; and [37] (d) preparing self-doped aqueous conducting polyaniline reacting (P(SSA-co-AMS)) generated in the gallery of clay layers with aniline. [38] According to the present invention, a method for preparing the nano-composite, comprising the steps: [39] (a) preparing tert-butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aπinostyrene (AMS) with tert-butyldicarbonate ((BOC) ); 2 [40] (b) preparing copolymer (P(SSNa- co-BOC-AMS)) by said BOC-AMS with sodium styrenesulfonate (SSNa); [41] (c) preparing copolymer (P(SSNa- co-AMS)) of styrenesulfonic acid and aminostyrene by eliminating tert-butoxycarbonyl (BOC), and penetrating said (P(SSNa-co-AMS)) into the gallery of clay layer by immersing (P(SSNa-co-AMS)) into clay (Na -MMT) swollen by aqueous solution; and [42] (d) preparing self-doped aqueous conducting polyaniline reacting (P(SSA-co-AMS)) generated in the gallery of clay layers with aniline. [43] According to the present invention, a method for preparing the nano-composite, comprising the steps: [44] (a) preparing tert-butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aminostyrene(AMS) with tert-butyldicarbonate ((BOC) ); 2

[45] (b) preparing copolymer (P(SSNa- co-BOC-AMS)) by reacting said BOC-AMS with sodium styrenesulfonate (SSNa); [46] (c) preparing copolymer (P(SSNa- co-AMS)) of styrenesulfonic acid and aminostyrene by eliminating tert-butoxycarbonyl (BOC); [47] (d) preparing aqueous polyaniline graft copolymer(PSSA-g-PANI) by reacting said P(SSNa-co-AMS) with aniline; and [48] (e) penetrating said PSSA-g-PANI into the gallery of clay layers by dissolving said PSSA-g-PANI and clay (Na -MMT) together into aqueous solution to swell the clay. [49] According to the present invention, the weight proportion of clay (Na -MMT) and polyaniline may be 1:1000 to 100: 1 in the above methods. [50] Polyaniline copolymer used in the present invention may be prepared by the method described in Korea patent application No. 10-2003-0051225 as described in the following. [51] tert-butoxycarbonyl-aπinostyrene (BOC-AMS) may be prepared by reacting aminostyrene(AMS) with with tert-butyldicarbonate ((BOC) ), and in turn copolymer 2 (P(SSNa-co-AMS)) of styrenesulfonic acid and aminostyrene may be generated by eliminating tert-butoxycarbonyl(BOC) after preparing copolymer (P(SSNa- co - BOC-AMS)) by reacting said BOC-AMS with sodium styrenesulfonate (SSNa) to prepare self-doped aqueous poly styrenesulfonic acid-g-aniline by reacting said copolymer (P(SSNa- co-BOC-AMS)) with aniline (AM). [52] In a preferred embodiment of the present invention, after preparing tert- butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aminostyrene(AMS) with tert- butyldicarbonate ((BOC) ), which is shown as reaction equation 1 in the following, the 2 nano-composite may be obtained by reacting said tert-butoxycarbonyl-aπinostyrene (BOC-AMS) with sodium stylenesulfonate(SSNa) to prepare copolymer (P(SSNa-co-BOC-AMS)) and then by penetrating said copolymer (P(SSNa-co-BOC-AMS)) into the gallery of the clay layer swollen by aqueous solution to disperse clay layers in order of nano-scale into the gallery of the clay layer, which is shown as reaction equation 2 in the following.

[53] [Reaction equation 1] [54]

BOC-AMS

[55] [Reacting equation 2] [56]

BOC-AMS PfSSNa-co-BOC-A S)

[57] In other preferred embodiment of the present invention, a nano-composite may be prepared by eliminating tert-butoxycarbonyl (BOC) from sodium copolymer (P(SSNa-co-BOC-AMS) of stylenesulfonate to copolymer (P(SSA-co-AMS)) of style- nesulfonic acid and aminostylene, and by penetrating said copolymer (P(SSA-co-AMS)) into the gallery of clay layers swollen by aqueous solution to disperse the clay layers in order of nano-scale, which is shown as reaction equation 3 in the following. [58] In another preferred embodiment of the present invention, a nano-composite may be prepared by reacting copolymer (P(SSA-co-AMA) of stylene sulfonic acid and amino stylene with aniline to prepare self-doped aqueous conducting polyaniline graft copolymer as shown in the above structure formula (1), and then by penetrating said polyaniline graft copolymer into the gallery of clay layers swollen by aqueous solution to disperse the clay layers in order of nano-scale, which is shown in the following reaction equation 4.

[59] The total process for preparing the nano-composite is shown schematically in the following reaction equation 5.

[60] [Reaction equation 3] [61]

[62] [Reaction equation 4] [63]

PtSSA-eo-AMSJ PSSA^Bl**

[64] [Reaction equation 5] [65]

Clay Na* MMT Swelled Clay Na* MMT exfoliation. aniline

PSSA-g-PANI/clay nanocomposite Brief Description of the Drawings

[66] Figure 1 : The process of preparing polyaniline conducting polymer and clay nanocomposite

[67] Figure 2: Illustration of structures for (a) P(SSNa-co-BOC-AMS), (b) P(SSA-co - AMS), and (c) PSSA-g-PANI.

[68] Figure 3: XRD patterns of (a) Na⁺-MMT, (b) P(SSNa-co-BOC-AMS)/clay nanocomposite, (c) P(SSA- co-AMS)/clay nano-composite, (d) in-situ PSSA- g-PANI/clay nano-composite, and (e) simple blending of PSSA- g-PANI and clay.

[69] Figure 4: TEM images of (a) in-situ PSSA- g-PANI/clay nano-composite, (b) simple blending of PSSA-g-PANI and clay, (c) P(SSA-co-AMS)/clay nano-composite and (d) P(SSNa-co-BOC-AMS)/clay nano-composite.

[70] Figure 5: FTIR spectra of (a) PSSA-g-PANI, (b) in-situ PSSA-g-PANI/clay nanocomposite and (c) Na ⁺-MMT.

[71] Figure 6: Comparison of C-N stretching vibration band: (a) PSSA-g-PANI versus in-situ PSSA-g-PANI/clay nanocomposite; (b) P(SSNa- co-BOC-AMS) versus P(SSNa-co-BOC-AMS)/clay nanocomposite and (c) P(SSA- co-AMS) and P(SSA-co - AMS)/clay nanocomposite. Solid line and dashed line represent pure polymer and polymer/clay nanocomposite, respectively.

[72] Figure 7: UV-visible spectra of (a) PSSA- g-PANI, (b) in-situ PSSA-g-PANI/clay nanocomposite, and (c) simple blending of PSSA- g-PANI and clay. [73] Figure 8: TGA curves of (a) in-situ PSSA-g-PANI/clay nanocomposite and (b) PSSA-g-PANI. [74] Mode for the Invention

[75] A method for preparing in-situ PSSA-g-PANI/clay composite according to the present invention will be described more specifically in the following.

[76] Na⁺-MMT (Closite^? Na⁺) and P(SSNa-co-BOC-AMS) in the weight proportion of Na⁺-MMT (Closite⁷ Na⁺) to P(SSNa-co-BOC-AMS) 1:1000 to 100 : 1 were dissolved in aqueous acid solution such as HCL acid solution and then sonicated for 1 to 100 hour using an ultrasonic generator for swelling of the Na -MMT. The swelling procedure not only helps a polymer chain to penetrate into the gallery of clay layers but also eliminates the BOC groups frcm P(SSNa- co-BOC-AMS) to yield P(SSA-co - AMS).

[77] If the proportion of Na⁺-MMT (Closite^? Na⁺) and P(SSNa-co-BOC-AMS) is less than 1 : 1000, then the effect as nano-composite was insignificant, while if more than 100 : 1, then the property of nano-composite was lost because polyaniline couldn't penetrate the gallery of clay layers.

[78] For graft copolymerization of aniline (ANI) the temperature of clay/polymer solution was adjust as 0 to 25 °C, and then the copolymerization was processed using ammonium persulfate as oxidation agent after aniline was dissolved into acid aqueous solution. In such case, equivalent of the oxidation agent and aniline was adjusted as 0.1: 1 to 1: 0.1. After many hours of reaction, a dark green solution was obtained. The dark green solution was purified by dialysis using a seπi-permeable membrane which cutoffs less than molecular weight 3000. The distilled water out of the membrane was changed into new water many times until pH didn't increase for three days. The result solution was concentrated and precipitated into acetone and dried under vacuum.

[79] The method for preparing PSSA-g-PANI/clay by simple blending is described in detail in the following.

[80] Na⁺-MMT and PSSA-g-PANI in proportion of 1 : 1000 to 100: 1 were dissolved in de-ionized water and then sonicated using an ultrasonic generator for swelling of the Na -MMT. The resulting solution was concentrated and precipitated into acetone and then dried under vacuum. If the weight proportion of clay and polyaniline graft copolymer is less than 1: 1000, then the effect as nano-composite was insignificant, on the other hand if more than 100: 1, then the property of nano-composite was lost because polyaniline cannot penetrate the gallery of clay layers. [81] X-ray diffraction (XRD) has often been used for determining the degree of intercalation and/or exfoliation of clay in the polymer matrix. When XRD patterns for pristine clay (Na⁺-MMT), P(SSNa-co-BOC-AMS)/clay, P(SSA-co-AMS)/clay, in-situ composite of PSSA- g-PANI/clay and simple blending of PSSA-g-PANI and clay are compared with each other, as shown in Figure 3. The following facts may be realized. First, the d-spaάng of Na⁺-MMT in P(SSNa-co -BOC-AMS)/clay increased from 9.8 A of pristine clay to 19.4 A , as shown in Figure 3a and 3b, indicating that P(SSNa- co - BOC-AMS) chain is intercalated into the gallery of clay layers. Secondly, P(SSA- co - AMS)/clay does not show any discernible peak in the XRD pattern (Figure 3c), indicating that the clay layers are exfoliated in the polymer matrix. Here, it is noted that P(SSA-co-AMS) is obtained after elimination of BOC group from P(SSNa- co - BOC-AMS) in acidic aqueous media, resulting that P(SSA- co-AMS) has positively charged nitrogen (NH ) in its structure. Therefore, it is considered that the ionic in- 3 teraction between positively charged nitrogen in P(SSA-co-AMS) and negatively charged surface of clay layers, as evidenced from the peak shift of C-N stretching band (Figure 6c), attributes to exfoliation of clay layers in the polymer matrix. Third, both in-situ composite of PSSA- g-PANI/clay shows an exfoliated structure, as can be seen in Figure 3d. This indicates that the exfoliated structure of P(SSA-co-AMS)/clay is preserved even after graft copolymerization of ANI onto P(SSA- co-AMS), considering the fact that in-situ composite of PSSA- g-PANI/clay is prepared by in-situ graft copolymerization of ANI onto P(SS A- co- AMS)/clay. Furthermore, protonated iπine nitrogen in grafted PANE is more favorable to interact with negatively charged surface of clay layers than the positively charged nitrogen in P(SSA-co-AMS). Subsequently, it is expected that the exfoliation of clay layers is easily achieved by simple blending of water-soluble PSSA-g-PANI and Na⁺-MMT, as shown in Figure 3e.

[82]

[83] Figure 4 shows TEM images of (a) in-situ composite of PSSA- g-PANI/clay, (b) simple blending of PSSA-g-PANI and clay, (c) P(SSA-co-AMS)/clay and (d) P(SSNa- co-BOC-AMS)/clay, where dark stripes represent the clay layers and the gray/white area represents the polymer matrix. It is clearly observed from Figure 4 that for in-situ composite of PSSA- g-PANI/clay, simple blending of PSSA-g-PANI/clay and P(SSA- co-AMS)/clay, as can be seen Figure 4a, 4b and 4c, respectively, the nano-sized clay sheets are randomly distributed in the polymer matrix, although some amount of stacked layers are observed. However, the TEM image of P(SSNa- co-BOC-AMS)/clay (Figure 4d) shows that the composite has a larger amount of stacked layers in which polymer chains are intercalated. [84] (1) The FTIR spectrum of in-situ PSSA-g-PANI/clay nano-composite has all the characteristic peaks of PSSA-g-PANI and clay, as shown in Figure 5. Assignments of their peaks are summarized in Table 1. When the spectrum of PSSA- g-PANI is compared with that of PSSA- g-PANI/clay nano-composite, it reveals that the C-N stretching vibration of in-situ PSSA-g-PANI/clay nano-composite at 1301 cm is slightly higher than that of PSSA-g-PANI at 1303 cm , as shown in Figure 6a. This is probably due to physical interaction between PANE chain and silicate layers [Kim, J. W; Kim, S. G.; Choi, H. J.; Jhon, M. S. Macromol. Rapid Commun. 1999, 20, 450; Kim, B. H.; Jung, J. H.; Hong, S. H.; Joo, J. S.; Epstein, A. J.; Mizoguchi, K.; Kim, J. W; Choi, H. J. Macromolecules 2002, 35, 141]. Another important feature to be noted from Figure 6a is that the characteristic peak of PSSA-g-PANI at 1216 cm , as interpreted as C-N stretching vibration in the polaron structure, not only shifts to higher frequency (1230 αn-1) but also becomes stronger in intensity at PSSA- g-PANI/clay nano-composite. These results imply that Coulombic interaction between the positive nitrogen of PSSA-g-PANI and the negatively charged surface of clay layers affects the vibrational motion of PANE. When the C-N stretching vibration of P(SSNa- co - BOC-AMS) is compared with that of P(SSNa- co-BOC-AMS)/clay, it reveals that the C-N vibration peak of P(SSNa-co-BOC-AMS) at 1317 cm^" does not change at its clay nano-composite, as shown in Figure 6b. This is because P(SSNa- co-BOC-AMS) does not have positive charges for ionic interaction with negatively charged surface of clay. Figure 6c shows that the C-N vibration peak of P(SSA-co-AMS) shifts to higher frequency by 4 cm at P(SSA-co-AMS)/clay nano-composite. This is because P(SSA- co-AMS) has positively charged nitrogens (NH ) for interaction with negatively 3 charged surface of clay layer. [85] The UV- visible spectrum of in-situ PSSA- g-PANI/clay nano-composite (or simple blending of PSSA-g-PANI and clay) shows that polaron band transitions take place at 418 nm and 801 nm (or 417 and 797 nm), as shown in Figure 7b and 7c, indicating that the PSSA-g-PANI/clay nano-composite is in a conducting state. The peak observed at 770 nm in PSSA-g-PANI shifts to 797 nm and 801 nm for in-situ PSSA-g-PANI/clay nano-composite and simple blending of PSSA- g-ANI and clay, respectively. The peak shift to higher wavelength indicates the increase of conjugation length, which subsequently results in the decrease of band-gap energy. This is consistent with the delo- calization of electrons in the polaron band. In bulk PANE, the strong interaction between PANE chains may induce defects in π-conjugation. However, the nanometer template in Na -MMT galleries not only eliminates the interaction between different PANE chains, but also limits the contraction of the chains.

[86] The electrical conductivities of in-situ PSSA- g-PANI/clay nano-composite and simple blending of PSSA-g-PANI and clay were 4.7 x 10^" S/cm and 4.2 x 10^" S/cm, respectively, which are lower than the conductivity of PSSA- g-PANI (1.2 10 S/cm). The decrease in conductivity of PSSA-g-PANI/clay nano-composites is not so significant as compared to pure PSSA- g-PANI, considering that the nano-composites have a large content of clay (15 wt%). Here it is noted that the electrical conductivity of intercalated PANI/clay nano-composite decreases by at least two orders of magnitude as compared to PANE.

[87] Figure 8 compares the thermal stability of the PSSA- g-PANI/clay nano-composite with that of the PSSA-g-PANI. The first weight loss around 100 °C is attributed to the loss of water. At the temperature ranging from 200 to 300 °C, both PANE and in-situ PSSA-g-PANI/clay nano-composite do not show any significant weight loss in the TGA curve unlike other PANIs doped with acid dopants. This is probably because the polymeric dopant (backbone PSSA) in this study is covalently bonded to PANE. It is generally known that the PANIs doped with acid dopants decompose at 200 ~ 300 °C. The second weight loss starting at around 300 °C is attributed to the thermal decomposition of backbone PSSA and grafted PANE. When the TGA curve of in-situ PSSA-g-PANI/clay nano-composite is compared with that of PANE, it reveals that in- situ nano-composite is thermally more stable than that of PSSA- g-PANI. This is probably because the attractive Coulombic interaction between the positive nitrogen in PSSA-g-PANI and negatively charged surface of the clay layer improves the thermal stability.

[88]

[89] The present invention will be described more specifically in the following using examples, not limiting the present invention.

[90] Example 1

[91] Preparation of self-doped aqueous polyaniline graft copolymer and exfoliated clay nano-composite

[92] The Na⁺-MMT (0.15 g) and PSSA-g-BOC-PANI (1.0 g) were dissolved in 30 ml of distilled water and then sonicated for 3 h using an ultrasonic generator for swelling of the Na -MMT. The resulting solution was concentrated and precipitated into acetone. Resulting precipitate was filtered and dried under vacuum at 60 °C for 24 h. In the following examples, the condition of experiments will be similar to example 1. [93] The nano-composite prepared according to the present invention without oxidation _3 agent or exterior dopant has conductivity of 4.7 x 10 S/cm with four-probe method, which is sufficient for use of anti-electrification or shielding EMI.

[94] Example 2

[95] Preparation of self-doped aqueous polyaniline graft copolymer and exfoliated clay nano-composite

[96] The Na⁺-MMT (1.0 g) and PSSA-g-PANI (1.0 g) were dissolved in 60 ml of distilled water and then sonicated for 3 h using an ultrasonic generator for swelling of the Na -MMT. The resulting solution was concentrated and precipitated into acetone. Resulting green precipitate was filtered and dried under vacuum at 60 °C for 24 h. In the following examples, the condition of experiments will be similar to example 1.

[97] The nano-composite prepared according to the present invention without oxidation _3 agent or exterior dopant has conductivity of 1.7 x 10 S/cm with four-probe method, which is sufficient for use of anti-electrification or shielding EMI.

[98] Considering example 1 and 2, if the contents of Na -MMT are more than 40 wt% to that of polyaniline graft copolymer, a nano-clay composite penetrated into the gallery of clay layers and exfoliated incompletely was obtained.

[99] And also it is impossible for PSSA-g-PANI to be coated on glass or silicon wafer, but for the nano-composite to be coated excellently, especially when the contents of Na⁺-MMT is between 10 wt% and 20 wt%.

[100] Example 3

[101] Preparation of copolymer (P(SSA-co-AMS)) of styrenesulfonic acid and aminostyrene and exfoliated clay nano-oompositefvariation in the contents of clay

[102] The copolymer (P(SSA-co-AMS)) of styrenesulfonic acid and aminostyrene was prepared by eliminating tert-butoxycarbonyl(BOC) from copolymer(P(SSNa-co-BOC-AMS) of sodium styrenesulfonate, and then the nanocomposite was obtained by dissolving said P(SSA-co-AMS)) into water for immersing clay(0.04 to 4 g) into the aqueous solution (30 to 200 ml of water), and thus penetrating water into the clay layer to disperse the clay layers.

[103] Example 4

[104] Preparation of copolymer (PfSSNa-OD-BOC-AMS of sodium styrenesulfonate and embedded clay nano-oomposite(variation of contents of clay)

[105] The copolymer P(SSNa-co-BOC-AMS) of BOC-AMS and sodium styrenesulfonate was prepared by reacting with sodium styrene sulfonate (SSNa), and then the nanocomposite was obtained by dissolving said P(SSNA-co-BOC-AMS)) (0.8) into water (20 to 200 ml) to immerse clay (0.04 to 4 g) into the aqueous solution, and subsequently penetrating water into the gallery of clay layers to disperse the clay layers.

[106] Example 5

[107] Synthesis of aqueous self-doped polyaniline graft copolymer (Variation in the length of the grafting)

[108] Sodium stylene sulfonate 5 g and BOC-AMS 0.5 g were dissolved into DMSO (Dimethyl Sulfoxide) 60 ml, and then the solution was stirred using 0.5 g AIBN (azobisisobutyronitrile) as an initiating agent for 15 hours at 80 °C. The obtained solution was precipitated into the excessive-amount of acetone with drop-wise addition and precipitate was obtained. The obtained copolymer was washed many times with acetone, and then dried for 24 hours at 60 °C in vacuum. For aniline grafting reaction, the polymerization was performed as following: lowing the temperature as 0 °C; and dissolving 1 g of aniline + P(SSA-co-AMS) into 30 ml of aqueous solution for 30 minutes varying with the molecular ratio of aniline/PS SA-co- AMS 100 to 0.1 wherein ammonium-sulfate was used as an oxidation agent and the equivalent of the oxidation and aniline was adjusted as 1: 1.

[109] Referring the obtained graft copolymer, the average number of aniline was 5 to 20 with each of the length different depending on the condition of experiment, and if the number of aniline was more than 20, then the copolymer is insoluble in water, while if more than 400, then the polymerization was impossible.

[110] The Na⁺-MMT (0.15 g) and PSSA-g-PANI (1.0 g) having aniline more less 20 were dissolved in 30 ml of distilled water and then sonicated for 3 h using an ultrasonic generator for swelling of the Na -MMT. The resulting solution was concentrated and precipitated into acetone. Resulting green precipitate was filtered and dried under vacuum at 60 °C for 24 h. The conductivity increases rapidly until the number of aniline is up to 6, but if the number of aniline was more than 6, the increase rate of conductivity was mitigated. If the number of aniline was between 5 and 20, the range of conductivity varied 7.3 x 10 S/cm to 9.5 x 10 S/cm.

[Ill] As described in detail in the above, the present invention provides exfoliated nanocomposite prepared using aqueous polyaniline graft copolymer in which the composite was processed in solution without organic treatment.

[112] Industrial Applicability

[113] The self doped soluble polyaniline copolymer and the exfoliated clay nanocomposite has advantage that the process for preparing was performed in aqueous solution with organic treatment. And also, a known aqueous polyaniline copolymer is lack of capability for forming film and cleavage or strip of film happens on coating on glass and silicon wafer, but the clay nano-composite has excellent capability to form film and coating on glass or silicon wafer is easy. The exfoliated clay nano-composite according to the present invention can be used for material for shielding EMI, anti-electrification, anti-corrosion, electrodes of se condary battery, electro-chromic element and functional films.

Claims

[1] 1. A nano-composite comprising a self doped soluble polyaniline graft copolymer as structure formula 1 and clay (Na -MMT): [Structure formula 1] aqueous part self-doping part

[Structure formula 2]

O :0 @:OH :Al *F^β, M5 o . • :sι (A

[2] 2. The nano-composite according to claim 1, wherein the proportion of said clay (Na⁺-MMT) and said copolymer is 1: 1000 to 100: 1.

[3] 3. The nano-composite according to claim 1, wherein the repeated units in said poly aniline graft copolymer arel to 400.

[4] 4. The nano-composite according to claim 1, wherein said polyaniline graft copolymer is self-doped.

[5] 5. The nano-composite according to claim 1, wherein said self doped soluble polyaniline graft copolymer and said clay (Na -MMT) has conductivity between 1 4 be 1.0 x 10 S/cm and 1.2 x 10 S/cm by four-probe method without fronting doping or oxidation doping.

[6] 6. A material for anti-electrification comprising the nano-composite according to claim 1.

[7] 7. A material for shielding electromagnetic field comprising the nano-oomposite according to claim 1.

[8] 8 A material for electrodes of secondary battery comprising the nano-oomposite according to claim 1.

[9] 9. A coating film comprising the nano-oomposite according to claim 1.

[10] 10. A sensor comprising the nano-oomposite according to claim 1.

[11] 11. A method for preparing a composite of self-doped soluble conducting polyaniline graft copolymer and clay, comprising the steps of: (a) preparing tert-butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aminostyrene(AMS) with tert-butyldicarbonate ((BOC) ) 2 (b) preparing copolymer (P(SSNa- co-BOC-AMS)) by said BOC-AMS with sodium styrenesulfonate (SSNa), and penetrating said copolymer (P(SSNa- co - BOC-AMS)) into the gallery of clay layers by immersing said copolymer (P(SSNa-co-BOC-AMS)) into the clay swollen with aqueous solution; (c) preparing copolymer of styrene sulfonic acid and aπino-styrene (P(SSA- co AMS)) by eliminating tert-butoxycarbonyl from said copolymer (P(SSNa- co - BOC-AMS)) penetrated into the gallery of clay layers; and (d) preparing self-doped aqueous conducting polyaniline reacting (P(SSA-oo-AMS)) generated in the gallery of clay layers with aniline.

[12] 12. A method for preparing a composite of self-doped soluble conducting polyaniline graft copolymer and clay, comprising the steps of: (a) preparing tert-butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aminostyrene(AMS) with tert-butyldicarbonate ((BOC) ); 2 (b) preparing copolymer (P(SSNa- co-BOC-AMS)) by said BOC-AMS with sodium styrenesulfonate (SSNa); (c) preparing copolymer (P(SSNa- co-AMS)) of styrenesulfonic acid and aminostyrene by eliminating tert-butoxycarbonyl (BOC), and penetrating said (P(SSNa-oo-AMS)) into the gallery of clay layer by immersing (P(SSNa-oo-AMS)) into clay (Na ⁺-MMT) swollen by aqueous solution; and (d) preparing self-doped aqueous conducting polyaniline reacting (P(SSA-oo-AMS)) generated in the gallery of clay layers with aniline.

[13] 13. A method for preparing a composite of self-doped soluble conducting polyaniline graft copolymer and clay, comprising the steps of: (a) preparing tert-butoxycarbonyl-aπinostyrene (BOC-AMS) by reacting aminostyrene(AMS) with tert-butyldicarbonate ((BOC) ); 2 (b) preparing copolymer (P(SSNa- co-BOC-AMS)) by reacting said BOC-AMS with sodium styrenesulfonate (SSNa); (c) preparing copolymer (P(SSNa- co-AMS)) of styrenesulfonic acid and aminostyrene by eliminating tert-butoxycarbonyl (BOC); (d) preparing aqueous polyaniline graft copolymer(PSSA-g-PANI) by reacting said P(SSNa-oo-AMS) with aniline; and (e) penetrating said PSSA-g-PANI into the gallery of clay layers by dissolving said PSSA-g-PANI and clay (Na -MMT) together into aqueous solution to swell the clay.

[14] 14. The method according to any one of claim 11 to 13, wherein the proportion of said clay (Na⁺-MMT) and said polyaniline is 1: 1000 to 100: 1.