WO2006055372A2

WO2006055372A2 - Photoinitiator anchored to silicate and use thereof to prepare polymer exfoliated silicate nanocomposite

Info

Publication number: WO2006055372A2
Application number: PCT/US2005/040611
Authority: WO
Inventors: Dostsevi Y. Sogah; Jianbo Di; Xiao-Ping Chen
Original assignee: Cornell Research Foundation Inc
Current assignee: Cornell Research Foundation Inc
Priority date: 2004-11-17
Filing date: 2005-11-09
Publication date: 2006-05-26
Anticipated expiration: 2007-05-17
Also published as: US7659321B2; US20090012199A1; WO2006055372A3

Abstract

Photoinitiator modified silicate and ethylenically unsaturated monomer are reacted in solvent to cause living polymerization of monomer and exfoliation of silicate layers and cause attachment of silicate layers to polymer chains, thereby providing dispersed homopolymer or block copolymer silicate nanocomposites.

Description

PHOTO1MTIATOR ANCHORED TO SILICATE AND USE THEREOF TO PREPARE POLYMER EXFOLIATED SILICATE NANOCOMPOSITE

The invention was made in pait with United States Government support under National Science Foundation Grant Numbers DMR-0079992, DMR-9632275 and DMR-8314255. The Unites States Government has certain rights in the invention.

Cross-Reference to Related Applications

This application claims the benefit of U.S. Provisional Patent Application No. 60/628,172, filed November 17, 2004, the whole of which is incoiporated herein by reference.

Technical Field

The invention is directed at photoinitiator modified silicate, method for forming dispersed polymer photoinitiator modified silicate nanocomposite, admixture for use in the method and nanocomposites produced by this method.

Background of the Invention

Direct synthesis of dispersed polymer silicate nanocomposites has been carried out by living polymerization of styrene using a silicate anchored to 2,2,6,6 tetramethylpiperdine alkoxyamine, Weimer, M W , et al, J. Am. Chem. Soc. 121, 1615-1616 (1999). This reaction has limitations since the initiator there is not efficient enough to polymerize methacrylates with reasonable conversion rates at acceptable temperatures.

Muhlebach et al WO 2004/000809A1 indicates that it improves upon the method described in the above paragraph to effectively produce dispersed polymer silicate nanocomposites where the polymer is obtained from acrylates or methacrylates or styrene by using certain different alkoxyamines anchored to natural or synthetic clay by a cationic anchor group. Examples of the anchoring compounds are set forth at pages 34 and 35 of WO 2004/000809A1. The process described in WO 2004/000809A1 has the disadvantages that the anchoring compounds are all very complicated and the polymerizations are carried out in the working example of WO 2004/000809A1 at HO⁰C.

Summary of the Invention

It has been discovered herein that the ubiquitous nature of WO 2004/000809 Al so far as monomeis are concerned can be duplicated by using initiators anchored to silicate which are not required to be alkoxyamines and which can be much simpler in chemical structure than those of Muhlebach et al and can initiate polymerization at room temperature by using as initiator modified silicate, photoinitiator modified silicate or partially photoinitiator modified silicate,

In summary, photoinitiator modified silicate or paitially photoinitiator modified silicate and ethylenically unsaturated monomer are reacted in solvent to cause living polymerization of monomer and dispersion of silicate layers and ionic attachment of polymer chains to silicate layers thereby providing dispeised polymer silicate nanocomposite

In one embodiment of the invention herein, denoted the first embodiment, there is provided a photoinitiator for cation exchange attachment to a nanoclay comprising a photoinitiating moiety and a moiety for attaching to nanoclay by cation exchange.

In another embodiment of the invention herein, denoted the second embodiment, there is provided a nanoclay cation exchanged with the photoinitiator of the first embodiment or a nanoclay partially cation exchanged with (a) photoinitiator of the first embodiment and partially cation exchanged with (b) organic cation that does not contain photoinitiating moiety.

In still another embodiment of the invention herein, denoted the third embodiment, there is provided a method of preparing dispersed homopolymer or copolymer silicate nanocomposite from ethylenically unsaturated monomer and photoinitiater modified silicate or partially photoinitiator modified silicate comprising photopolymerizing ethylenically unsaturated monomer in organic solvent containing photoinitiator modified silicate or partially photoinitiator modified silicate to cause living polymerization of the monomer, and formation of nanocomposite with polymer chains ionically attached to exfoliated silicate layers dispeised in a polymer matrix.

In still another embodiment of the invention herein, denoted the fourth embodiment, there is piovided an admixture for polymerization comprising ethylenically unsaturated monomer and photoinitiatoi modified silicate or partially photoinitiator modified silicate in a weight ratio of monomer to photoinitiator modified silicate or partially photoinitator modified silicate ranging from 400:1 to 1:2.

In still another embodiment of the invention herein, denoted the fifth embodiment, there is provided a dispersed poly(ethylenically unsaturated monomer) photoinitiator modified silicate or partially photoinitiatoi modified silicate nanocomposite wheie polymer chains aie attached to photoinitiator modified silicate, where the weight ratio of polymer to photoinitiatoτ modified silicate or partially photoinitiator modified silicate ranges from 400:1 to 1 :2, hi still another embodiment of the invention herein, denoted the sixth embodiment, there is provided a dispersed poly(ethylenically unsatuiated rnonomer)- block-poly(different entylenically unsatuiated monomei) photoinitiator modified silicate or paitially photoinitiated modified silicate nanocomposite wheie one end of first block polymer chain is attached to photoinitiator modified silicate and where the weight ratio of block copolymer to photoinitiator modified silicate or partially photoinitiator modified silicate ranges from 400:1 to 1:2, and where the volume ratio of poly(ethylenically unsaturated monomer) to poly(different ethylenically unsaturated monomei) ranges from 1 :5 to 5:1

As used herein, the term "nanoclay" means clay having nanometer thickness silicate platelets that can be modified to make clay complexes compatible with organic monomers and polymers.

As used herein, the term "nanocomposite" means composition of nanoclay in a polymer matrix. The term "dispersed" used in the term "dispersed polymer silicate nanocomposites" means that silicate platelets of the nanoclay aie exfoliated into single layers (denoted "silicate layers" herein) which are randomly dispersed in a polymer matrix The terra "photoinitiatoi" is used herein to mean a photoactive living radical initiator that induces free radical polymerization that pioceeds via initiation, propagation, piimary radical termination and transfei to initiator

The term "photoinitiatoi modified silicate" is used heiein to mean that photoinitiator is ionicaily or covalently attached to exfoliated silicate layers

The term "partially photoinitiatoi modified silicate" is used herein to mean that (a) photoinitiatoi is ionicaily or covalently attached to pait ol the exfoliated silicate layers and (b) organic cation which does not contain photoinitiating moiety is ionicaily or covalently attached to another part of the exfoliated silicate layers, where the mole ratio of a:b ranges ftom 10: 1 to 1 : 10 and, for example, ranges fiom 2:1 to l :2, e.g , is l : l

Weight aveiage molecular weight (MJ, number average molecular weight (M_n) and polydispeisity indexes (PDl) herein aie determined by size extrusion chromatography (SEC) in tetrahydrofuran (THF) using Wateis HPLC Ultrastyragel (Waters Associates) columns unless otheiwise noted. Retention times were converted to polymer moleculai weights using a calibration cuive built from narrow molecular weight distribution polystyrene standards

Detailed Description

We tuin now to the Hist embodiment

The photoinitiating moiety of the photoinitiatoi is piefcrably a benzyl dithiocarbamatc moiety and the attaching moiety is preferably a benzyl trimethyl ammonium moiety

The photoinitiatoi of the first embodiment is very piefeiably;

)

The compound 4-(N,N-diethyldithiocarbamylmethyl)benzyl trimethylammonium bromide can be made as described in Woiking Example I hereinafter We turn now to the second embodiment

The product of the second embodiment which is nanoclay cation exchanged with photoinitiator of the fiist embodiment can be prepared by cation exchanging nanoclay, e.g., as obtained in inorganic cation foπn, e g , in the sodium form, with the composition of the first embodiment. The product of the second embodiment which is nanoclay partially cation exchanged with photoinitiator can be prepared by cation exchanging nanoclay, e.g , as obtained in inorganic cation form, e g., in the sodium form concuπently with (a) the composition of the first embodiment and (b) with organic cation that does not contain photoinitiating moiety where the mole ratio of a:b ranges from 10:1 to 1 :10, e.g , from 2:1 to 1 :2, eg , is 1 :1. The nanoclay is preferably montmorillonite (a natural clay) or fluoiohectoiite or Iaponite (synthetic clays) Other useful nanoclays include bentonites, beidellites, hectorites, saponites, nontronites, sauconites, vermiculites, ledildtes, magadiites, kenyaites and stevensites The nanoclays are noimally purchased in the sodium foim although some clays may contain othei cations Any alkali metal cation (e. g., Li+, Na+, or K+) present in the clay is exchangeable with other cations. Exchanging the interlayer inorganic cations present with organic cation rendeis the nanoclay (silicate) more hydrophobic so the nanoclay is more readily swellable in organic media (so the silicate layers therein are more readily accessible to monomei) and renders the silicate layers more miscible with the polymer of the nanocomposite. which is formed in the third embodiment herein.

Preferably, the composition of the second embodiment is montmorillonite in an inorganic cation form cation exchanged with photoinitiator (I) oi paitially cation exchanged with photoinitiatoi (I) and partially cation exchanged with organic cation which does not contain photoinitiating moiety Compositions of the second embodiment can be made as described in Working Examples II and Ha hereinafter.

We turn now to the first case of the third embodiment where dispersed homopolymer photoinitiator modified silicate or partially modified silicate nanocomposite is prepared.

The photoinitiator modified silicate can be any of the cation exchanged nanoclays of the second embodiment Preferably, lhe photoinitiator modified silicate is the montmorillonite whose interlayer alkali cations have been exchanged with (1) winch is a preferred composition of the second embodiment

Pteferably also, the partially modified silicate is the montmorillonite whose interlayer alkali cations have been partially exchanged with (a) photoinitialor (I) and partially cation exchanged with (b) tiimethylbenzyl ammonium chloride, when the mole ratio of a:b is 1 :1

The ethylenically unsatuiated monomer is, for example, selected from the group consisting of styrene, methyl metliacrylate, tert-bulyl methaciylate, n-butyl metliacrylate, 2-hydroxyethylmethacι ylate 1 , 1 ,1 ,2,2 -pentafluoi opropyl metliacrylate, (2-trimethysilyloxy)-ethy]-rnelhacrylate, and tertbutyl aciylale

The photopolymei ization can be caπied out on admixture of photoinitiator modified silicate oi partially photoiπitiatoi modified silicate, ethylenically unsaturated monomei and oiganic solvent by positioning the admixture so it receives ultraviolet iπadiation (e.g., from a UV lamp), very suitably at ioom temperature. Preferably, the solvent is a dipolar aprotic solvent, very prefeiabiy, tetrahydrofliraπ, less preferably, dimethyl formamide, N-methyl pyπ olidone or dimethyl sulfoxide The weight ratios of monomei :photoinitiatoi modified silicate or partially photoinitiator modified silicate, can be, for example, 400: 1 to 1 :2 Working examples of the first case of the thiid embodiment aie Working Examples III, IV, IVA, V and VI below. Resulting polymer chains include those set foith below

where R is, for example, 2-hydroxyethyl. 2-trimethylsiloxyethyl, tert-butyl, 2- hydroxyethyl, hydiogen, methyl oi n-butyl. or the corresponding polyacrylates- Poly(acrylic acid) chains can be formed from poly(tcrt-butyl acrylate) chains by hydrolysis under mild acidic conditions, Poly(2-tiϊmcthylsiloxyeth_,yl methaciylate) chains can be converted to hydroxyethyl methaciylate chains by tteatment under mild acidic conditions The admixtuie for polymerization is the admixture of the fourth embodiment of the invention

The nanocomposite produced by the method of the fust case of the third embodiment is the nanocomposite of the fifth embodiment of the invention herein.

We turn now to the second case of the third embodiment where the method of the third embodiment is modified to make dispersed block copolymer photoinitiator modified silicate or partially photoinitiator modified silicate nanocomposite In this case, living homopolymer nanocomposite made as described above is admixed with ethylenically unsaturated monomer for the second block and organic solvent and photopolymerization is carried out, e.g., as described above, e g , at room temperature, with total monomer to modified silicate weight ratio ranging from 400:1 to 1 :2. The one end of the block which is attached to photoinitiator modified silicate provides photoinitiator functionality to piovide living polymerization of the second block. No silicate becomes dispersed in the second block. Dispersed block copolymer silicate nanocomposites have been made employing sequential monomei addition either fust producing silicate-polystyrene living block and then canying out polymerization of methyl methacrylate or by first producing silicate-poly(m ethyl methacrylate) living block and then carrying out polymerization of styrene. Working Example of the second case of the third embodiment is set forth in Working Example VII below.

The nanocomposite produced by the method of the second case of the third embodiment is the nanocomposite of the sixth embodiment of the invention herein.

The nanocomposites produced herein have significantly higher dynamic storage modulus than the neat homopolymer or copolymer (i.e., without nanoclay) at temperatures below the T₁, of the neat polymer or copolymei so they are deformed less compared to neat homopolymer oi copolymer at the same stress at said temperatures

The invention is illustrated in the following working examples Synthesis of the Photoinitiator 4-rN.N-DiethyldithiocarbamylmethyI)benzyl Trimetliylammonium Bromide (2)

4-(N,N-diethyldithiocarbamyImethyl)benzyl trimethylammoπium bromide (2), To a 1000-mL flask equipped with a stirring bar were added 4- (bromomethyl)benzyl trimetliylammonium bromide (1) (prepaied as described in Rammo, J., et al., Chimica Acta 251, 125-134 (1996) (8.60 g, 26.6 mmol), sodium N,N-diethyldithiocarbamate trihydrate (Aldrich) (12.0 g, 53.3 mmol), and acetone (200 mL). The mixture was stiired at room temperature for 24 hours. A white precipitate formed gradually. The precipitate was filteied and washed with technical acetone (500 mL x 3). By-product NaCl can be removed as a solid by extraction with dry CHCl₃ foi five hours. The white powder product was dried in a vacuum oven overnight. Yield: 104 g, (98.0%), ¹H NMR: d(DMSO-dr,) 1 14-1.20 (m, 6H), 2.98 (s, 9H), 3.70-3.72 (q, 2H), 3-94-3.96 (q, 2H)₁ 4.47 (s, 2H), 4.56 (s, 2H), 7,44-7.52 (q, 4H).

WORIONG EXAMPLE II Synthesis of Photoinitiator 2 Modified Montmorillonite

A mixture of 4.97 g of montmorillonite in the sodium form (Cloisite® Na⁺, 92 meq/100 gm clay of cation exchange capacity (CEC); Southern Clay Products, Gonzeles, TX), in 500 mL of distilled water was ultrasonicated overnight and stirred for one hour. 2.0 g of 4-(N,N-diethyldithiocarbamylmethyl)benzyl trimethylammonium bromide prepared as in Working Example I in 100 mL of distilled water was added. The leactive mixture was stirred for 48 h at RT and the resultant photoinitiator modified montmorillonite became a precipitate in water. The modified montimorillonite was obtained after filtration; washed with water till no precipitate was formed when 0.1 N Of AgNO₃ aqueous solution was added to the filtrate; and freeze-dried. The loading of the organic photoinitiator component was 15.5% by weight based on the weight loss of the modified montmorillonite on TGA. WORIONQ EXAMPLE HA Synthesis of Partially Photoinitiator Modified Montmorillonite (MMT)

A mixture of 10.0 g of MMT in 250 mL of distilled water was ultrasonicated for half an hour and stiired at 5O⁰C overnight. A mixture of 1,45 g of 4-(N,N- diethyldithiocarbamylmethyl)benzyl trimethylammonium bromide (photoinitiator) and 1.37 g of trimethylbenzyl ammonium chloride (Bz) (photoinitiator:Bz=l ;2, molar ratio) in 200 mL of distilled water was dissolved at 50C° and then added to the clay suspension with rigorous stirring. The reaction mixture was stirring for 6h at 5O⁰C and overnight at RT. The modified MMT λvas obtained after filtration; washed with water till no precipitate was formed when 0.1 N of AgNO₃ aqueous solution was added in the filtrate; and dried by freeze-drier. Photoinitiator loading: 27,5meq./100g clay (photoinitiator:Bz=l : 1 ). When the solvent was a mixture of ethanol :H,O (80:20,v/v), photoinitiator loading: 20meq./100g clay (photoinitiator:Bz-l :2).

WORICING EXAMPLE III Preparation of Polystyrene Silicate Nanocomposites

To a 3 -neck round bottom flask equipped with a stirring bar were added the desiied amounts of photoinitiator modified silicate made as described in Working Example II, styrene monomer, and THF (200 mL). Nitrogen gas was bubbled into the mixture with stirring for 30 min. A UV lamp positioned 10 cm away from the flask was turned on and left on for 48 hours. The temperature of the reaction flask was kept around room temperature by the air flow in the hood, Nitrogen gas was kept on throughout the whole process, At the end of the polymerization, the UV lamp was turned off and the mixture was diluted with THF (about 150 mL). The product was precipitated into methanol (10-fold excess). The while solid was filtered and dried in a vacuum oven. Amounts of photoinitiator modified silica and styrene (S) and polymerization results are given in Table 1 below: Table 1

1

Silicate-PS- 2 50 20.0 44.0 5 9 13 6 1.52 27.1 λ

Silicate-PS- 1.70 20 0 48.1 9 5 19 0 1.54 20.5

5 Silicate-PS- 5 00 50.0 42.0 7 1 28.3 1 53 17.2

4 A Silicate-PS- 0.60 40.0 30.3 34.0 41 3 1 80 7.2 j Silicate-PS- 0 50 80.0 45 5 122.5 102 0 2.02 0 7 6 ^a Calculated value based on monomer conversion and equivalent of initiator sites. ^b Deteirained by SEC in THF using a Waters HPLC with Ultrastyragel (Waters Associates) columns. Retention times were converted to polymer molecular weights using a calibiation curve built from nairow moleculai weight distribution PS standards. ^c Determined by TGA under N₂ on a Seiko theimogravimetric differential thermal analyzer using a heating rate of 5.0 ⁰C /min

WORKING EXAMPLE IV

Pieparation of Polymethylmethacrylate) Silicate Nanocomposites Polymerizations weie earned out as in Working Example III except that the monomer was methyl methacrylate Amounts of photoinitiator modified silicate and methyl methacrylate (MMA) monomer and polymerization results are given in Table 2 below: Table 2

Photoinitiator M_n" M_n ^b

Entry modified MMA Yield (CAL) (SEC) PDl^b Silicate silicate (g) (mL) (%) xlθ° xlO"³ weight%^c

Silicate- 4.00 30.0 73.8 9.6 48.2 1.56 15,6

PMMA-I

SiIi cate- 3.00 40 0 73.4 17.0 644 1 ,23 10.7

PMMA-2

Silicate- 2.70 60.0 75.6 29.0 70.4 1,7.3 7.5

PMMA-3

"Silicate- 4.10 40.0 72.6 12.3 96.8 1.27 12.8

PMMA-4 ^dSilicate- 3.00 100.0 65.5 37.8 146.9 1.46 5.6

PMMA-5

" Calculated value based on monomer¹ conversion and equivalent of initiator sites. ^b Deteimined by SEC in THF using a Waters HPLC with Ultrastyragel (Waters Associates) columns. Retention times were converted to polymer molecular weights using a calibration curve built from narrow molecular weight distribution PS standards, ^c Deteimined by TGA under N₂ on a Seiko theimogravimetric differential thermal analyzer using a heating rate of 5 0 ⁰C /min. ^d Bulk polymerization.

WORKING EXAMPLE IVA

Preparation of Poly(methylmethacrylate) Silicate Nanocomposites Using Partially

Photoinitiator Modified Silicate

The polymerization was earned out in bulk. A mixture of 0 29g of partially modified MMT (photoinitiator:Bz=I :l) and 13 6 g of MMA was ultrasonicated for 0.5h and stirred overnight. After flushing with a N₂ flow for 2 h, the reaction mixture was irradiation under UV light for 3 days The resultant solid polymer was dissolved in THF and precipitated from hexanes, dried in a vacuum oven at 5O⁰C over night. 13.0 g of polymer nanocomposile was obtained with 1 ,9 % of silicate. M_n was 394,000 and PDI was 3.2. XRD spectrum was silent indicating the product could be an exfoliated polymer layered silicate nanocomposite. Preparation of Polyft-butyl aciylate) Silicate Nanocomposites

PolyiΩerizations were caπied out as in Working Example III except that the monomer was t-butyl acrylate and the pmificalion procedure was different ftom that of Working Example III in that the polymer/THF mixture was kept under vacuum for 24 hours to lemove all the solvent and the un-reacted monomer. The resulting yellowish solid was ground into powder while being cooled in liquid nitrogen. Amounts of photoinitiatox modified silicate, t-butyl acrylate monomer (PtBA) and polymerization results are given in Table 3 below:

Photoinitiator M_n"

Entry modified /BA Yield (CAL) (SEC) PDI^b Silicate

Silicate (g) (mi) (%) xlO ¹ Xl(T* weight⁰/,⁰

Silicate- 3 50 30 0 71 2 10 0 12 6 1 63 17 8

P/BA-1

Silicate- 2 00 20 0 65 3 10 6 18.4 1 67 12 5

P/BA-2

Silicatc- 2 00 50 0 68 2 27 6 30 5 1 67 5.7

P/BA-3 ^a Calculated value based on monomer conversion and equivalent of initiator sites. ^b Determined by SEC in THF using a Waters HPLC with Ultrastyiagel (Waters Associates) columns Retention times were converted to polymer molecular weights using a calibration curve built from naπow molecular weight distribution PS standards. ^Q Determined by TGA under N₂ on a Seiko Ihermogravimetric differential thermal analyzer using a heating rate of 5 0 ⁰C /min,

WORKING EXAMPLE VI Preparation of polyfn-butyl methaciylate) (;?BMA) Silicate Nanocomposites

LO g of inifeiter (photoinitiator) modified clay, p. epared as described in Working Example II, was added in 30 mL of dry THF and flushed with a flow of N₂ for 1 h, and then ultrasonicated for half an hour. Then /ΪBMA was added. The mixture was stirred for 2h under a flow of N₂. The polymerization was carried out for 48h at RT under UV irradiation with around 10 cm of distance between the UV lamp and the flask The resultant polymer silicate nanocomposite in THF was precipitated from MeOH, and dried in a vacuum oven at 5O⁰C overnight Amounts of 7ΪBMA and clay (IC) and polymerization results are given in Table 4 below:

Table 4

'Iniferter modified clay

²The time of UV irradiation

''Nanocomposite initiation efficiency of initiator

'Percentage of clay in nanocomposite by TGA

'Weight of benzyl diethyldithiocarbamate (BDC) Entry 4 was carried out in bulk without THF

"Homopolymer Poly(n-butyl melhacrylate) (PnBMA)

Entry 4 was carried out with BDC (without clay)

Instrom testing results on PnBMA silicate nanocomposite films are set forth in Table 5 below where MMT stands foi montmorillonite and NC means nanocomposite.

Table 5

'The film samples were measured at 7OF with 65% of humidity; the samples were stored for 3 days before measurement

¹TTIe control sample is the commeicial PnBMA with M_Λ(GPO - 337,000 after purification by precipitation in

MeOH from THF solution of PnBMA

^ΛThe blending with overall 1 5w% or MMT consists of PnBMA silicate nanocomposite (40wt% MMT, M_llCrc ^:

10,710, PDI = 1 7) and the puriiied commercial PnBMA

⁴PnBMA silicate nanocomposite with PnBMA of M_niαrø = 30,300, PDI = 1 6

WORKING EXAMPLE VII Preparation of Block Copolymer Silicate Nanocomposites

In this example PS means polystyrene and PMMA means poly(methyl methacrylate).

To a 3-neck round bottom flask equipped with a stirring bar were added either silicate-PS or silicate-PMMA (1.00 g) nanocomposite (depending on the desired first block) prepared respectively by the procedure of Woiking Example III or Working Example IV, monomer (MMA or styrene, 5.50 ml,) (depending on the desired second block), and THF (100 mL). Nitrogen gas was bubbled into the mixture with stirring for 30 min. A UV lamp positioned 10 cm away from the flask was turned on and left on for 48 hours. The temperature of the reaction flask was kept around room temperature by the air¹ flow in the hood. Nitrogen gas was kept on throughout the whole process. At the end of the polymerization, UV lamp was turned off. The product was precipitated into methanol (10-fold excess). The white solid was filtered and dried in a vacuum oven. Yield for silicate-PS-PMMA was 65.5%, and for silicate- PMMA-PS, 43.2%. Amounts and results are set forth in Table 6 below.

Table 6

Starting Second M," polymei Monomer Yield (CAL) (SEC)

Entry (niL) (%) X l O^"3 X lO-³ PDI^b

Silicate-PS — — — — 11.0 1.60

Silicate-PS-PMMA 0 50 20 0 65.5 192.6 25.8 1.56

Silicate-PMMA — — — — 29.1 1.43

Silicate-PMMA-PS 0.50 20 0 43.2 145.4 47.8 1.59

° Calculated value based on monomer conversion and equivalent of initiator sites ^b Determined by SEC in THF using a Waters HPLC with Ultrastyragel (Waters Associates) columns Retention times were converted to polymer molecular weights using a calibration curve built from narrow molecular weight distribution PS standards

Variations

The foregoing description of the invention has been presented describing certain opeiable and piefeπed embodiments. It is not intended that the invention should be so limited since variations and modifications thereof will be obvious to those skilled in the art, all of which are within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. Photoinitiator for cation exchange attachment to a nanoclay composing a photoinitiating moiety and a moiety for attaching to nanoclay by cation exchange

2. The photoinitiator of Claim 1 where the photoinitiating moiety is a benzyl dithiocaibamate moiety and the attaching moiety is a benzyl tiimethyl ammonium moiety

3 The photoinitiator of Claim 2 which is

4. Nanoclay cation exchanged with the photoinitiator of Claim 1

5 The nanoclay of Claim 4 where the photoiniliating moiety of the photoinitiator is a benzyl dithiocarbamate moiety and the attaching moiety of the photoinitiator is a benzyl trimethylammonium moiety.

11

The nanoclay of Claim 5 where the cation exchange is with

)

7. Nanoclay partially cation exchanged with (a) photoinitiatoi of Claim 1 and partially cation exchanged with (b) oiganic cation that does not contain photoinitiating moety where the mole ratio of a:b ranges from 10: 1 to 1 :10

8. The nanoclay oi Claim 7 wheie (a) is

)

and (b) is trimethylbenzyl ammonium chloride

9. A method for preparing homopolymei oi copolymer dispersed silicate nanocomposite from ethylenically unsaturated monomer and photoinitiator modified silicate or partially photoinitiator modified silicate comprising photopolymerizing ethylenically unsaturated monomei in solvent containing photoinitiator-modified silicate to cause living polymerization of the monomer, with polymer chains in a nanocomposite ionically attached to exfoliated silicate layers dispersed in a polymer matrix.

10 The method of Claim 9 where the solvent is a dipolar aprotic solvent.

1 1 The method of Claim 10 where photoiπitiator modified silicate is present and is nanoclay cation exchanged with photoinitiatoi comprising a photoiπitiating moiety and a moiety for attaching to nanoclay by cation exchange

12. The method of Claim 10 wheie photoinitiator modified silicate is present and is nanoclay cation exchanged with

13. The method of Claim 10 wheie paitially photoinitiatoi modified silicate is piesent and is nanoclay partially cation exchanged with (a)

)

and partially cation exchanged with (b) organic cation that does not contain photoinitiating moiety, where the mole ratio of a:b ranges from 10:1 to 1 :10

14. The method of Claim 10 where the ethyl enically unsaturated monomer is selected from the group consisting of styiene, methyl methacrylate, tert- butyl methacrylate, n-bulyl methacrylate, 1,1,1 ,2.2-pentafluoropropyl methacrylate, (2-trimethylsilyloxy)-ethyl-methacrylate and tert-butylacrylate.

15. The method of Claim 14 where sequential monomer addition is employed either first pioducing silicate-polystyrene living block and then polymerizing methyl methacrylate from it or first producing silicate-poly(methyl methacrylate) living block and then polymerizing styrene from it.

16. Admixture for polymerization comprising ethylenically unsaturated monomer and photoinitiator modified silicate or partially photoinitiator modified silicate, in a weight ratio ranging from 400:1 to 1 :2.

17. Dispersed poly( ethylenically unsaturated monomer) photoinitiator modified silicate or partially photoinitiator modified silicate nanocomposite where polymer chains aie attached to photoinitiatoi modified silicate, where the weight ratio of polymer to photoinitiator modified silicate or paitially photoinitiator modified silicate ranges from 400:1 to 1 :2.

18. Dispersed poly(ethylenically unsaturated monomer)-block- poly(different ethylenically unsaturated monomer) photoinitiator modified silicate or¹ partially photoinitiator modified silicate nanocomposite where one end of the first block polymer chain is attached to photoinitiator modified silicate and where the weight ratio of block copolymer to photoinitiator modified silicate or partially photoinitiator modified silicate ranges from 400:1 to 1 :2, and where the volume ratio of poly(ethyl enically unsaturated monomer) to poly(different ethylenically unsaturated monomer) ranges from 1 :5 to 5: L