AD-AOS7 1B2 PENNSYLVAN A UNV PHILADELPHIA DEPT OF CHEMISTRY F/S 7/3ORGANIC METALS AND SEMICONDUCTORS: THE CHEMISTRY OF POLYACETYLE-ETC(U)OCT 79 A 6 MACDIARMID, A .J HEESER N00016-75-C-0962

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Technical report No. 79-8 Z4. TITLE (end Subtitle) S. TYPE OF REPORT & PERIOD COVERED

Organic Metals and Semiconductors: The Chemistryof Polyacetylene, (CH) , and its Derivatives

S. PZRFO)4114 ORG. REPORTNUMO-ER

7. AUTHOR(a) 41. CONTRACT OR GRANT NUMBER(e)*

Alan G. MacDiarmid and Alan 3. Heeger N00014-75-C-0962

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Departments of Chemistry and Physics AREA & WORK UNIT NUMBERS

University of Pennsylvania NR-356-602Philadelphia, Pa. 19104

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18. SUPPLEMENTARY NOTES

Paper given at Advanced Study Institute on the Physics and Chemistry..of Low-Dimensional So-lids, Tomar, Portugal, August 1979

lS. KEY WORDS (Continue on ,.verfa aide It neceae.' and Id*nttfy by block numbetjOrganic metals; organic semiconductor-; polyar-etylene.chemistry; cis-polyacety-

lene; trans-polyacetylene; semiconducting films; stretch aligned flims; (CH) x;chemical doping; electrochemical doping; n-type polymer; p-type polymer; photo-electrochemical photovoltaic cells; (CH)x electrode; polysulfide electrolyte;I(CH)x gels; low density (CH), vapor phase doping; solution doping; electr,chemi- OV

ABSTRACT (Continue an reverse aide It niecessary and Idenify b7r blot: namibot)-"oth cis- and trans-forms of polyacetylene, (CH)., may be prepared as silvery,flexible polycrystalline, semic6nducting films. " he cis-fiIms -canbe stretchedto over three times their original length with partial alignment of the (CH)

fibrils. Through chemical or electrochemical doping, the electrical conduct-,i-ty of the films can be increaj6 d over twqlve orders of magnitude with propertiesrangiqg froi iniulator (caQ! - ohm,.-'e--4 to semiconductor to metal-(a>.i0 - . . By the use of donors or acceptors, n-type or R-type polymer,respectively, is produced. PhLOW!vJ r k1LCU cl--po vat Ca t-t3lsaVdbee 0

o-DD I #J' 7 3 1473 EDITION OF I NOV 65 S OBSOLETE UnclassifiedS/N 3102-014-6501 -A CrG

19. cal doping; donors and acceptors; polyacetylene interfaces

20Nfabricated using (CHk as the active photoelectrode.Wr example, using asodium polysulfide so'Ttion as an electrolyte, V -0.3 volts arndI sc-40p~ amps/cm2 were obtained under an illumina~on of ca. 1 sun.

t Vt

T istrl.-

L~ or 0

all.seC-

Special

(OFFICE ENVLRSAC

Contract 47-;

C7--Task No. 356-602

IECHNICAL REQ JI NQ. 9-8

rganic Metals and Semiconductors: .

'The Chemistry of Polyacetylene, (CH)x, and Its Derivatives/

by ~> :V7',Alan G. ~acDiarmid 40 Alan J Aeeger ,j1

Paper given at

Advanced Study Institute

on the

Physics and Chemistry of Low Dimensional Solids

Tomar, Portugal

Departments of Chemistry and PhysicsI.

University of Pennsylvania

Philadelphia, Pennsylvania 19104

October 21, 1979

Reproduction in whole or in part is permitted for

any purpose of the United States Government

Approved for public release; distribution unlimited

ADVANCED STUDY INSTITUTE ON THE PHYSICS AND CHEMISTRY OF LU4-DLIENSIONALSOLIDS - TCIAR, PORTUGAL, AUGUST 26-SEPTEMBER 7, 1979

ORGANIC METALS AND SEMICONDUCTORS: THE CHEMISTRY OF POLYACETY-LENE, (CH)x, AND ITS DERIVATIVES

Alan C. MacDiarnid and Alan 3. Heeger

Departments of Chemistry and PhysicsUniversity of PennsylvaniaPhiladelphia, Pa. 19104

ABSTRACT

Both cis- and trans-forms of polyacetylene, (CH)_, may be pre-pared as silvery, flexible, polycrystalline, semiconucting films.

-t The cis-films can be stretched to over three times their original* *' length with partial alignment of the (CH)x fibrils. Through chem-

ical or electrochemical doping, the electrical conductivity of thefilms can be increased over twelve orders of magnitude with pro-perties ranging from insulator (c<10 - 10 ohm-lcm- 1) to semiconduc-tor to metal (0>103 ohm-lcml- ). By the use of donors or acceptors,n-type or k-type polymer, respectively, is produced. Photoelectro-chemical photovoltaic cells have been fabricated using (CH) asthe active photoelectrode. For example, using a sodium polysulf~desolution as an electrolyte, V -0.3 volts and Isc -40 p amps/cmwere obtained under an illumination of ca. I sun.

Polyacetylene, (CH) x, is the simplest possible conjugated or-ganic polymer and is therefore of special fundamental interest.It can be prepared in the form of lustrous, silvery, flexible,polycrystalline films having any desired cis/trans content bycatalytic polymerization of gaseou* acetylene, C2H2 (1-4):

/

. ciS TRANS

mmmam4

The cis-rich films can be stretched easily at room temperature inexcess of three times their original length with concomitant par-tial alignment of the (CH), fibrils (5,6). Dark red gels of tol-uene In (CH)x may be prepared using a lower catalyst concentration(7). Highly porous, very low density, "foam-like" (CH) can be

obtained from these gels (7). Both" cis- and trans-(CH) are p-type semiconductors (8) which can be treated with a variety of p-or n-type dopants with concomitant Increase in conductivity to givea series of semiconductors and ultimately, "organic metals." Thisreport will be directed primarily towards a description of themore chemically oriented aspects of (CH) and its derivatives.

X

1. DOPING OF (CH)x FILMS

The various types of dopants and doping procedures, the natureof the (CH) chain, and the nature of the dopant in the films willbe describe below. The terms "cis" and "trans" used in conjunctionwith a doped film will refer to the principal isomeric compositionbefore doping and does not imply that the isomeric compositioneither remains constant or changes during the doping process.

1.1. P-type doping

1.1.1. Dopants and methods of doping. When either cis or transfilms are exposed to the vapor of electron-attracting substances(p-type dopants) such as Br2 , I, AsF_, H So., HClO., etc. (9,10)tfey become "doped" with the species and their electrical (11)(Table I) and optical (12) properties change markedly. Dopant

TABLE I

DOPANTS FOR (CH) a,bConductivity.(o-m-1)

.25°CCls-(CH) x 1.7 x 10 -

trans-(CH) 4.4 x 10A. p-type (electron-attracting) dopants

trans-[CH(B r)0.04]x C 7 x l0- 4

0.0lo02 x 1. trans-CUC 0O]x lx 1 "

trans-[CHBr0 .231 4 x 10 "1

t ciS-[C"(ICl) .14x 5 10

.-[Co.o . 5.5 x 102

(continued on next page)

t.n [R • .O. TABLE I (continued)"trans-[CHI 0.20] x "1.6 X 10 2

cis-[CH(IBr)0.15]x 4.0 x 102

trans- [CH(AsF) O 1 0 ] 4.0 x 102

cis-[C1(AsF5)0.101x c 1.2 x 10

cis-[C11.(AsF 6 )o.10 x ca. 7 x 102

cis-[CH(SbF 6)0 .05]x 4.0 x 102

cis-[CH(SbCl 6)O. 9 ] I x10

cis-[CH(SbCl 8)O 0 0 9 5 ] I x 101

.cis-[CH(SbCl5)0 .022'x 2L{--C(F).q z 10 o2

d~'0 dX X 2cis-Cli(S03F) "7 x 102

cis-[CH(C10)O 6 4 5]x 9.7 x 104~. 0.64 10cs-[CH(AsF4) 0 .077 2.0 x

2* cis-[CH1, 0 1 1 (AsF5 OH) 0 0 1 1 ] ca. 7 x 10

cis-[CH. 0 5 8 (PF5 OH)0. 0 5 8 ]6 ca. 3.x 101

Cis-[CH(H 2 So4 )oO.10 6 (H2 )O.07O1x 1.2 x 103

cis-[C1(RCO 4 )0. 1 2 7 (U 2 0) 0 . 2 9 7 x 1.2 x 103

B. n-type (electron-donating) dopants €

cs-[Li 0 . 30 (CH) ]x 2.0 x 102

_s-[Na 0 .21 (cR)3 2.5 x 101

___IO (C) 5.0 X 10cis- 0 . 6(CH) xtrans-[Na0. 2 8 (CH)]x 8.0 X 101

a) "cis" or "trans" refers to the principal isomeric compositionbefore doping

b) composition by elemental analysis except where stated otherwisec) composition by weight uptaked) dopant used: (SO 3 F) . No composition or analysis given. Anderson,

L.R., Pez, G.P., a3 Hsu, S.L.: 1978,J.C.S. Chem. Comm.,pp.1066.e) by electrochemical doping using [(n-C Ra).Nl [PF1]-. Nigrey,

P.J.. MacDiarmid, A.G.. and Reeger, A.J.: 1979, unpublished ob-servations.

pressures <1 tort are usually satisfactory. With many dopants theconductivity increases rapidly through the semiconducting regimeto the metallic •regime. The concentrations of the dopants given

- -. * --.. .-. . -

......

(in Table I are generally the maximum or close to the maximun valuereadily obtainable. Doping can be terminated at any degree oflower doping level desired, with corresponding lower conductivity.

+ +Salts containing the (NO) or (NO2) ions also act as good

dopants (10). For example, the SbF6 group can be introduced read-ily into (CH) simply by treating a (CH) film (ca. 85% cis isomer)with C NO -CH Cl solution of the appropriate salt. Thus,(NO ) (SbF 6) yields gol den, flexible, highly conducting films of[CHlSbF 6)0.05x), (Table I) with liberation of NO2 , viz.,

(C)M + 0.05x(NO2 )(SbF 6 - [CH(SbF6)0.0 50j x + 0.05xNO2 (1)

It has been found very recently that (CH) films may be dopedelectrochemically either to the semiconducting or metallic regime(13). This is a most important development since it opens up ageneral, very simple, readily controllable means of doping with awide variety of species which can not be introduced by any obviousconventional chemical means. For example, it was found that whena strip of (CH) film (ca. 82% cis-isomer) was used as the anodein the electrolysis of aqueous 0.5K KI solution with a potentialof 9 V. it was doped during ca. 0.5 hour to the metallic state, togive, by elemental analysis, (CHI 0n) . It is important to notethat the flexible, golden-silvery flIn contained no oxygen (total

* C, H. and I contenC=99.8Z) and hence had undergone no hydrolysisand/or oxidation during the electrolytic doping process. When the(CM)_ was usd as the anode in the electrolysis of 0.5M[(n-6dHo)4 N] [C1O] in CH2 Cl at 9 V., doping occurred during ca.1 hour o give highly conducting (Table I), flexible films which,by elemental analysis, had the composition [CH(CIO.) 064 1 (13).Lower doping levels obtained during shorter electrolysis iesgave material having conductivities in the semiconductor region.Similar results were obtained by tte electrolysis of methylenechloride solutions of [(n-C4 H9 ) N] [SOCF f and[(n-C H ) .KR[AsF6I- both of wlich gave Righly conducting golden-

silvery fdexible flms. The former is assumed to contain the

(S03CF3) and the latter, the (AsF4 ) species, since elemental analy-sis of the film gave a composition corresponding to [CH(AsF4)0 .077.The (AsF4) is probably formed by a reaction sequence involving pro-ton abstraction from [(n-C HR) hI] by fluorine atoms from AsF6during the electrolysis pr ces b (13).

1.1.2. Nature of the (CH)x chains and dopant species. Ramanstudies show thai the lodinated and broutnated films should be for-uulated as [(CH)' (X3)y]x where X-Br or I, at least a significantportion of the halogen being present as the X - ion (14). Thehalogen partly depopulates the pi bonding system and oxidizes the(CH) to a polycarbontum ion chain. This conclusion is suported

by carbon Is core shifts from ESCA studies (15). The (NO) ionsare also excellent species for oxidizing the pi system of (CH)x

and are capable Of concomitantly introducing anions which stabil-

* ize the polycarbonium ion chains (10). For example, the[CH(SbF6) 0o^] species given in equation 1 is more appropriate-ly formul [CH+O.OSO(SbF 6 )0. 0 50

The most simple and general method for simultaneously oxidiz-Ing the (CH)x pi system and introducing stabilizing anions appearsto be that involving electrochemical doping (13). Thus, speciessuch as [CH(CIO.4) ..... ]x, [CH(AsF4).... , etc. formed electro-

chemically as descri e in - .section 1.1.1. are be-lieved to contain the (CIO,) and (AsF4)- ions, respectively, al-• "" though the extent to hih charge transfer to the anionic species

occurs may be expected to vary according to the nature of the do-pant. It is interesting to note that AgCIO4 has also been foundto dope (CH) films with (CIO 4) ion, although to lower conducti-

vity levels f16) (ca. 3 ohm'1cm-I1 ) than that obtained withelectrochemical doping. The resulting+film is contaminated withmetallic silver. In this case, the Ag ion acts as the oxidizingagent, viz.,

(CH) + O.018xAgClO 4 [(Ca) 40"018 Clo + O.Oi8Ag (2)

Although most studies of (CH)_ have been carried out on AsF -(-or I -doped films. the actual chemical form in which the AsF 5

exiss in the film is still not completely clear. When (CH)film-is treated with very pure AsF 5 vapor in a vacuum line pre-treated with AsF5 , elemental analyses for C, H, As and F give anarsenic to fluorine ratio of 1:5 (Table I) (17, 18Y. The sum ofthe elemental analyses is 99.7% or better and hence the film con-tains no significant amounts of oxygen. Photoelectron spectrosco-py also shows the principal arsenic species contains arsenic andfluorine in the ratio of 1:5 (15). Since epr (19) and magneticsusceptibility studies (20) show the paramagnetic radical anion,AsF j is not present it seems that the AsF might be in the formof The previously unreported diamagnetic (Rs 2 F10 ) ion. If the[CH(AsF5) ] film is treated either with AsF5 vapor containing HFor Is i r rsed in 42% aqueous HF, then elemental analyses for C,E, As and F give an arsenic to fluorine ratio of 1:6 (Table I)(17).Again, the sum of the elemental analyses for all elements is great-er than 99.7%. If, on the other hand, the [CH(AsF ) I film ispumped for many hours ina vacuum system containing osible tracesof air, elemental-analyses corre'sponding to [CHi (AsF5 OH)V x,(Table I), are obtained. In this respect, it mig~ht be noted thatmany salts containing the [AsF 5(OR)]- ioh are known. The conduc-tivity of all three types of species is essentially identical.These experimental observations are consistent with the reactionsbelow:

. (CH) + yAsF5 [C(AsFy) x (3)

Liy .

(CEI(AsF 5) I3 +yHF (CH [C 4,y(AsF )_ (4)-5yxJ.+y 6y

-.- H+ yH2o [CH(AsF5 OH) 1 (5)

The weak protonic acids, RF and HOH can be regarded as combiningthe AsF. specles to give the strong protonic acids,

"h(AsF 6 ) and "H (AsF OH)-", respectively, which then dope the

(CH)_ portion of the maierial according to equations (4) and (5)(17).

Other investigators have shown on the basis of X-ray absorptionand infrared data that AsF5-doped film, of unknown elemental com-position, contains the AsF 6 ion (21). This is in no way incon-sistent with the above conclusions based on eleiental analyses;

* indeed, it supports the formulation of the [CH. (AsF6)-] speciesgiven above. However, these investigators suggest that tle(.sF 6)_ ion arises through the reaction below which involves dis-proportionation of the AsF:

(CH) X+ 3yAsF 5 IR F*2' + yAsF 3 (6

Since AsF is readily removed by pumping (21), the resulting ma-3terial should always contain arsenic to fluorine in the ratio of

1:6. This is in conflict with the elemental analytical data forthe [CH(AsF ) ] material. Since [CH(AsF ) ] decomposes ther-mally with l fiberation of gaseous HF a.dYAxF3 , it is also quite

possible that [CH(AsF ) I could be converted to JCR *.Y(AsF ) Iaccording to equation (Z)Xby the HF so formed under cettain c n-ditions of handling or storage of the AsF5-doped films.

1.2. N-type doping

Electron-donating, i.e. "n-type" dopants, may also be intro-duced into (CH) films (22) (-able I) simply by immersing the filmin a THF solution of e.g. sodium naphthalide, viz.,

(CH)x + 0.21xNa+Npth 34 [Nao. 2 1 (CH)] x + 0.21xNpth (7)

A very large increase in conductivity is noted but it is not asgreat as that observed with most p-type dopants. Alkali metalsmay also be introduced by, for example, allowing a liquid sodium'potassium alloy at room temperature, or Molten potassium to con-tact a (CH) film(23). A liquid sodium amalgam will also Na-dopethe film at room temperature (23). Preliminary experiments indi-cate that the (CH) pi system may also be reduced electrochemical-ly to give n-type 5oping by, for example, the electrolysis of a[sol-tion oC-LiI in THF using a (CH) film as the cathode, to give[L ir (CH) y] films (13).

7 -

a

The(C) X chain in these materials may be+considered as a poly-carbanion associated with the corresponding M metal ion. Theyare extremely sensitive to air and moisture. This appears to bea direct result of the anionic nature of the (CH) chain and is

not directly related to the presence of the metal'ion. Thus itseems likely that all n-doped (CH)x will be highly reactive re-gardless of the attendat metal ion, which of course is stable to-air and water. Treatment of Na-doped (CH) with D 0 results inpartial hydrogenation of the carbon-carbonXdouble ?onds (17).

2. PHOTOELECTROCHF!iICAL REACTIONS AT POLYACETYLENE INTERFACES

A chemical reaction involving a reduction process, e.g.,

S2-2 + 2e- - 2S- 2 . (8)

2

can take place with the concomitant production of an electric cur-rent when a p-type (C11) film, immersed in a solution containingthe oxidized-and reduceA forms of an appropriate couple, is irra-diated with light of appropriate wavelength (24). In the case ofthe polysulfide system, the reverse (oxidation) process,

( 2S- 2 P S2 - 2 + 2e- (9)will take place simultaneously at the counter electrode, e.g., Pt,

which is not irradiated. The ions produced at a given electrodethen diffuse to the other electrode and become available for re-use at that electrode as shown in Figure 1. The process is, there-fore, continuous as long as the (CH) electrode is irradiated withlight of appropriate wavelength (24,5). A definite photovoltaiceffect can be observed (V -0.3 volts under illumination of ca. 1sun) even with the simple°set-up shown in Figure 1 if a fairlythick film of trans-(CH) is used in order to reduce somewhat theotherwise high resistance of the (CH), electrode. By using a dif-ferent cell configuration, described In det2il elsewhere (24,25),an open circuit current of ca. 40 V amps/cm may be obtained.This will undoubtedly be increased by using partially doped (CH)xand thinner films. Since (CH) is a p-type semiconductor, photo-generated electron-hole pairs tecome Teparated at the (CH) -elec-trolyte interface and electrons are injected into the electrolyteas shown in Figure 2.

Prelina experiments have been carried out (24) usingaqueous solutions of the couple

SO 3 + 20H S0 4 "2 + H2 0 + 2e- (10)

with qualitatively similar results. It therefore seems highly..... likely that It should be possible to fabricate a variety of photo-

Pt WIRE

Trons-(CH), FILM

1w No2 Sy SOLN. IN WATER.ETC.

Figure 1. Simple (CH) /sodium polysulfide photoelectrochemicalphotovoltai cl.

P-(CH)X Pt METAL

E redox

\2S-2-0S-22e

Figure 2. Electrode processes fi a (CH) /sodium polysulfide photo-electrochemical photovoltaic cell.

voltaic cells using (CH)x electrodes immersed in aqueous or non-aqueous solutions of appropriate redox couples.

3. CONCLUSIONS

It can be seen clearly that (CH) is quite remarkable in thatits conductivity can be readily modilied to span an extraordinarilylarge range. Considering possible polyacetylene derivatives, re-placement of some or all of the hydrogen atoms in (CH) with or-0 xganic or inorganic groups, copolymerization of acetylene withother acetylenes or olefins, and the use of different dopantsshould lead to the development of a large new class of conductingorganic polymers with electrical properties that can be controlledover the full range from insulator to semiconductor to metal.Furthermore, there is considerable potential for the possibleapplication of parent or doped (CH) to the fabrication of variousxtypes of electronic devices, solar cells, etc.

4. ACKNOWLEDGHTENT

This work was supported principally by the Office of Naval Re-search.

5. REFERENCES

1. Shirakawa, H. and Ikeda, S.: 1971, Polym. J. 2, pp. 231-244.2. Shirakawa, H., Ito, T., and Ikeda, S.: 1973, Polym. J. 4, pp.

460-462.3. Ito, T., Shirakawa, H., and Ikeda, S.: 1974, J. Polym. Sci.

Polym. Chem. Ed. 12, pp. 11-20.4. Ito, T., Shirakawa, H., and Ikeda, S.: 1975, J. Polym. Sci.

Polym. Chem. Ed. 13, pp. 1943-1950.5. Druy, M.A., Tsang, C.-H.,Brown, N., Heeger, A.J., and MacDiar-

mid, A.G.: 1979, J. Polym. Sci. Polym. Phys. Ed. (in press);Shirakawa, H. and Ikeda, S.: 1979 (to be published).

6. Park, Y.W., Druy, M.A., Chiang, C.K., MacDiarmid, A.G., Heeger,A.J., Shirakawa, H., and Ikeda, S.: 1979, J. Polym. Sci. Polym.Lett. Ed. 17, pp. 195-201.Wnek, G.E., Chien, J.C.W., Karasz, F.E., Druy, M.A., Park, Y.W.,MacDiarmid, A.G., and Heeger, A.J.: 1979, J. Polym. Sci. Polym.Lett. Ed. (in press); Karasz, F.E., Chien, J.C.W., Galkiewicz,R., Wnek, G.E., Heeger, A.J., and MacDiarmid, A.G.: 1979, Na-ture, submitted.

8. Park, Y.W., Denenstein, A., Chiang, C.K., Heeger, A.i., andMacDiarmid, A.G.: 1979, Solid State Commun. 29, pp. 747-751.

9. Chiang, C.K., Druy, M.A., Gau, S.C., Heeger, A.J., Louis, E.J.,-MacDiarmid, A.G., Park, Y.W., and Shirakawa, H.: 1978, J. Amer.

.4..

Chem. Soc. 100, pp. 1013-1015.10. Gau, S.C., Milliken, J., Pron, A., MacDiarmid, A.G., and Hee-

ger, A.J.: 1979, Chem. Comm. (in press).,11. Chiang, C.K., Park, Y.W., Heeger, A.J., Shirakawa, H., Louis,

: vE.J., and MacDiarmid, A.G.: 1978, J. Chem. Phys, 69, pp. 5098-i " 5104.

12. Fincher, Jr., C.R., Ozaki, M., Tanaka, M., Peebles, D.L.,Lauchlan, L., Heeger, A.J., and MacDiarmid, A.G.: 1979, Phys.

'1.Rev. B (in press).13. Nigrey, P.3., MacDiarmid, A.G., and Heeger, A.J.: 1979, Chem.

Comm. (in press).14. Hsu, S.L., Signorelli, A.J., Pez, G.P., and Baughman, R.H.:

1978, J. Chem. Phys. 69, pp. 106-111; Lefrant, S., Lichtmann,L.S., Temkin, H., Fitchen, D.B., Miller, D.C., Whitwell, II,G.E., and Burlitch, J.M.: 1979, Solid State Commun. (in press);Harada, I., Tasumi, M., Shirakawa, H., and Ikeda, S.: 1978,Chem. Lett. 12, pp. X411-1414.

15. Salaneck, W.R., Thomas, R.R., Duke, C.B., Paton, A., Plummer,E.W., Heeger, A.J., and MacDiarmid, A.G.: 1979, J. Chem. Phys.(in press).

16. Clarke, T.C., Geiss, R.R., Kwak, J.F., and Street, G.B.: 1978,Chem. Comm., pp. 489-490.

1 17. Pron, A., MacDiarmid, A.G., and Heeger, A.J.: 1979, unpub-lished observations.

18. MacDiarmid, A.G. and Heeger, A.J.: 1979, "Molecular Metals,"Ed., W.E. Hatfield, Plenum Press, New York, N.Y., pp. 161-186.

19. Goldberg, I.B., Crowe, H.R., Newman, P.R., Heeger, A.J. andMacDiarmid, A.G.: 1979, J. Chem. Phys. 70, pp. 1132-1136.

20. Weinberger, B.R., Kaufer, J., Heeger, A.J., Pron, A. and Mac-Diarmid, A.G.: 1979, Phys. Rev. B 20, pp. 223-230.

21. Clarke, T.C., Geiss, R.H., Gill, W.D., Grant, P.M., Macklin,J.W., Morawitz, H., Rabolt, J.F., Sayers, D.E., and Street,G.B.: 1979, Chem. Comm., pp. 332-333.

22. Chiang, C.K., Gau, S.C., Fincher, Jr., C.R., Park, Y.W., Mac-Diarmid, A.G., and Reeger, A.3.: 1978, Appl. Phys. Lett. 33,pp. 18-20.

23. Gau, S.C., MacDiarmid, A.G., and Heeger, A.J.: 1979, unpub-lished observations.

24. Chen, S.N., Heeger, A.J., Kiss* Z., MacDiarmid, A.G., Gau,S.C., and Peebles, D.L.: 1979, Appl. Phys. Lett. (in press).

25. Heeger, A.J. and MacDiarmid, A.G.: 1979, Proceedings NATO ASIon Low Dimensional Solids, Tomar, Portugal, Aug. 1979.

* t

I • . C

I.B

UNIVERSITY of PENNSYLVANIAPHILADELPHIA 19174

Department of Chemistry

July 18, 1980

TO WHOM IT MAY CONCERN:

I wish to inform you that ONR report # 79-8 had an

incorrect manuscript attached to it. Enclosed is report

# 79-8 with the correct manuscript. We apologize for any

inconvenience that it may have caused.

Sincerel ours

-Joann Miliken

JM/grmenclosure

80 7 24 045