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An approach to the preparation of polyacene by LB method
Synthetic Metals, 28 (1989) C801 C806
c801
AN APPROACHTO THE PREPARATIONOF POLYACENEBY LB METHOD
M. OZAKI, Y. IKEDA and I. NAGOYA The Research Association for Basic Polymer Technology 2-5-21, Toranomon, Minatoku, Tokyo 105 (JAPAN)
ABSTRACT ~e have studied the preparation of polyacene via its prepolymer (polyethynylacetylene PEA) by Langmuir-Blodgett (LB) method using 22,24-pentacosadiynoic acid (,~-PDY) as a LB monomer. The molecular structure of photopolymerized w-PDY t,B films was investigated by optical measurements. It was shown that 3,4-photopolymerization predominantly occurred to give conjugated sequences (CH=CH)20 in the LB films.
The preliminary study of C~C bonds cyelization in the photopolymerized LB
films by heat treatment was performed to prepare polyacene. INTRODUCTION Polyacene (PA) is an i n f i n i t e linear acene, namely one-dimensional graphite which is expected to have a high electrical conductivity without doping from the result of the band calculations [ I - 2 ] . ration of PA.
Thus far no one has succeeded in the prepa-
In our previous study [3-4] we investigated a method to prepare PA
via its prepolymer, polyethynylacetylene (PEA) by the catalyst polymerization. It was, however, proved to be d i f f i c u l t to prepare the pure and trans form PEA by the catalyst polymerization.
Recently thin conducting films have been made using the
Langmuir-Blodgett (LB) method that is known as a method for orienting organic molecules regularly [5-6].
Then we have studied the preparation of PA using the LB
method by which the pure and trans form PEA should be prepared by the process shown in Figure I. In this paper we report about the preparation of LB multilayers 2 of monosubstituted 1,3-butadiyne LB monomers, the molecular structure of the photopolymeriaed LB
Mailing address: Central Laboratory, Asahi Chemical Ind. Co. Ltd., 2-I, Samejima, Fuji-shi, Shizuoka-ken 416, Japan. 0379-6779/89/$3.50
© Elsevier Sequoia/Printed in The Netherlands
C802
,I P r e p a r a t i o n
III I, I, uI i I i
hV
/1111//11/1111111111 IIIIIIIIIIIIIIIIII substrate
A or i e-beam
Ill I
PA ~v
o
oI
IIII1~i
( ~H, )20
IIII
COOH Fig.1
The process f o r the preparation of polyacene by LB method
f i l m s 3 and the p r e l i m i n a r y r e s u l t of e l e c t r i c a l c o n d u c t i v i t i e s by heat-treated LB f i l m s ~.
RESULTS AND DISCUSSION PEe~aration of m u l t i l a y e r s of HC~C-C~C-(CH~)~-COOH Monosubstituted 1,3-butadiyne LB monomers,
HC~C-C~C-(CH2).-COOH (n=8,14,20),
were synthesized by the acetylene coupling reaction between p r o p a r g y l i c acid HC~C-COOH and iodoacetylenic long chain f a t t y acid IC~C-(CH2)n-COOH (n=8,14,20) previously reported by RuaudeI-Teixier et a l . E 7 ] .
The production y i e l d s were lO~
(n=8), 5~ (n=14,20), r e s p e c t i v e l y , and the s t r u c t u r e of these compounds was i d e n t i f i e d by IR and 'H-NMR spectra. The s o l u t i o n of each 1,3-butadiyne LB monomer (2 X 10-3 M in chloroform) was spread on a water subphase containing CdCI2 (5 X 10.4 M).
The force-area ( H - A )
curve f o r a monolayer of each LB monomer is shown in Figure 2.
The LB monomer of n
=20, namely 22,24-pentacosadiynoic acid (~-PDV) showed a sharp force-area curve in which H - v a l u e s a b r u p t l y increased at smaller area A in comparison with LB monomers of n=8,H.
A t o t a l number of 20 carbon atoms in a f a t t y acid is necessary to form
a condensed surface s t a t e on the subphase.
~-PDV monolayers were successively
transferred onto a CaF2 substrate as Y type u n t i l a m u l t i l a y e r of defined thickness was obtained.
X-ray d i f f r a c t i o n patterns ( F i g . 3 ) of the m u l t i l a y e r showed high
order signals ( 0 0 )
up to
=7 with d-spacing (002) = 28 ~ which corresponds to one
molecular length of ~-PDY.
I t means that the ~-PDY m u l t i l a y e r was uniformly
formed by the LB technique.
The molecular long axis in the m u l t i l a y e r was found to
be inclined spectra.
about 66 ° to the layer plane from the analysis of polarized FT-IR
C803
40
~l~n=2
0 n=14 = Fe3 + )
20
0
20
40
60
A(A2/molecule) Fi8.2 Force-~treacurves for monolayers of LB monomers (n=8, 14, 20) on CdCl2 (5 X lO-4 M) subphase at T=15~
4k (002)
2k
1(003) (005) A(O04)///(006)
I0
2e
20
Fig.3 X-ray diffraction patterns of ~-PDY multilayers (135 layers) transferred to CaF2 substrate at H=25 mN/m, T=15~
2.0
•
~
~
(4)
'. 0.0~-
i
200
3oo
4oo 5o0 ~(nm)
i
80o
~oo
Fig.4 UV-VIS spect#a of ~-PDY multilayers before (1) and after UV irradiation for (2)Smin, (3)lOmin, (4)20min.
C804 Characterization of photopolymerized ~-PDY multilayers -PDY multilayers vere readily polymerized by UV irradiation (lO0~ Iov-pressure Bg lamp) and their UV-VIS absorption spectra (Fig.~) shoved that the absorption edge only redshifted vithout any hey absorption band in the v i s i b l e region. Tieke et a l . [ 8 ] observed tvo kinds of nev absorption bands at arround 500 nm and 600 nm by the photopolymerization of disubstituted diacetylene multilayers, vhich resulted in linear polydiaeetylene by 1,4-polymeri2ation. Therefore, our results suggest that the other polymerization form such as 1,2- or 3,4-polymerization occurs in monosubstituted diaeetylene multilayer rather than 1,4-polymerization.
(a) 0.B0"81
V(C3=---i~k~ I ~ C I ~ - C 2 )
/ V(C=--C)
0.2
4000
3000
2500
2000 /
2000
400
1000
wave n u m b e r ( c m - 1) (b) 1.0 V(C1-C2) at 2225cm-1
(c)1.1 V(CI---C2) at 2225cm-1
II _
~
© V(C3-C4) at 2301cm-1
O 0.0
I 5 UV
I 10 irradiation
I 15
i 2O t i m e (rain)
~ 25
0.(
I
0
5 UV
I
I
I
i
10 15 2O 25 irradiation time (min)
Fig.5 The change of FT-IR spectra of ~-PDY multilayer by UV irradiation. (a)FTIR spectra before irradiation (135 layers), (b)OD(t)/OD(t=O) versus UV i r r a d i a t i o n time in the ~-PDY Y type multilayer (135 layers), (c)that in the alternating multilayer of ~-PDY and arachidic acid (each 50 layers).
The photopolymerization form of ¢o-PDY multi layers was examined by FT-IR measurement (Fig.5). With increasing UV i r r a d i a t i o n time, absorption intensities of acetylenic IR bands u(=C-H) at 3278 cm-1 and v(C--C) at 2225, 2301 cm-~ decreased, and those of o l e f i n i c IR bands v(=C-H) at 3070 cm-~ and v(C=C) at 1587 cm-1 increased. IR bands v(C--C) at 2225 cm-1 and 2301 cm-~ are assigned to stretching vibrations of B-C--C- and -C~C- t r i p l e bonds, respectively, since the
C805 v lh!'atlon ener~,w of monosl]hslitu[vd a(:etyiene is u s u a l l y .~Iklltled a~t'iyl~'ne ~9]. ir;adiation
*i'he opt. ira!
lime in Pi~,,Ire 5 ( b ) .
fasi.er tilan 1,2-poiym~'riza~1,')n. la~,er photonol~'meriz, a t i o n , a ( i d whi(:h ~.~ I m ; c n ~ l l i v e
lower ~.han i h a l of iIisHh-
,k,rl.,;i~y of bolh IR iland.~; ~,'as H]oil~'d w'r~us t3,'
ii snuwed that :3,4-polyiIff:ri:.:ation was r e l a t i v v l ~ ' im l.he oLher hand,
in order to ~-×~;lqde the i n l P r -
~he att, crnaLin, ~, t.t_~ m u l ~ i a y e r
of (,>-PD¥ and ~r~:h~,iiv
f.o i.~V irradiai-,ion was prepared on a l:aF. ~ub~Iral.e.
}:']'-
!l~ measuremellt~ of LII~ a l t e r n a t i n~; mul i i l a y v r wur'~" per-formvd and Lhe chan~e (,f b()~h IR hands at. 2225 rm ~ 230] (m ~ ~as l i k v w i s ( ' ploil.(.d in Pi?,ure .S((:).
!I also
xhowed t.ha~ :{,.1-pol3merixaf ion pF(~dominanLly oc(:ilvred arld 1,2-po] ymer12aJlon ~,:.I~ .xuppr,.s~(~d Ill l.hv al Lelnalin;~ lllUl | i layer ('ompar'ed wi Lh ill [h(-' Y-I~pe ImJlli ]~yer. The inLcnsli.y (:han?.~- of
IR band :.'(---(I-H) aL 327g ('m ~ was almost Lh,." same as that
of IR band ~((::~(;) aL 2225('m '
~n h,flh Y Lyp~: and a i L r r n a l i n ~ m u l l i l a y e r ~ .
Raman ~l,e(;Jl'a (Fi g.~;) of Y LyHe mill f.i layer were measur(Jd L o e s ] i nla~.~ H~e number (el) of conju?aLed sequences ((tt=('fl)~.
(,~-PDY inulLilayer' (¥-l, ype) was found t,.)
!.~e r e a d i l y pol3~merized h~ i r r a d i a t i o n
(~f ,\r e×(:iLal, ion la,~;er (3,=5]L}5 /.,) dllr~ng
lhe measurement of l~aman .~peetrum.
Thv p o l y m e r i z a t i o n ,
b~ i r r a d i a t , ion of Ik~-Ne excit.al, ion laser (,k:~;?;2g /~).
howe,.mr, did not take pla~;e kaman ~ignal at ['L')O rln
due Lo ~ ( C = ( ) band was ob.~erved in i r r a d i a f , ion of bot.h [iV ~nd .~r e × r i } a L i o n (Fi~.6(a)
and f i ( h ) ) .
las,'r"
The number n of (£1i=('H)~, was eslimaLed Lo be 20 by ~pldyin~',
}he' value of ]490 cm ] Io lhe r'elal, iurl between n and Raman s h i f t
val,,es in
(::onjiJxaLed Ilolyenc [lOn,.
k e x = 6328.~
C= C
(b)
.
~c-c 2500
2000 Raman
1500 shi~ (cm-1)
1000
2500
2000 1500 I000 Raman shift (cm-l)
500
Fig.6 Raman spectra of the ~-PDY multilayer (340 layers) on a Si wafer (a)measured with 6328~ excitation when increasing UV irradiation time, (1)0 min, (2)1 min, (3)5 min ; (b)measured with 5145A excitation.
X-ray d i f f r a c t i o n
speeLrum of phoLopolymerized oJ-PIIV mul Li layer shoved Lhat f.he
inLensiLy of (OOm) r e f l e ( ' L i o n s (re:even) increased whereas Lhat of (OOn) r e f l e c L i o n s (n=odd) decreased l:Jy U V - i r r a d i a L i o n .
IL implies LhaL [1 elecLron densiLy increases
heLween mono!a.vers, and then the ordered u n i t
lengLh ¢han4es from Lhe Lhiekrtess of
one b i l a y e r Lo LhaL of one monolayer in Lhe Y-Lype r n u l L i l a y e r . Prom Lhese c h a r a ( : L e r i z a t i o n by o p t i c a l measuremenLs we conclude Lhat Lhe pr~~polymer PEA w iLh conjugaLed sequences (CH:CH)~ was parll.~ formed in each monolayer hy predominanL 3,4-phoLopo]ymerizaLion of ~-P[)Y LB monomer'.
C806 Heat-treatment of 3boto~ol~merized ~)-PDY m u l t i ~ e r The preliminary examination of C~C bonds cyclization in the photopolymeri2ed -PDY multila~er was performed by heat-treatment at T=200°C, 300°C for 2 hr.
The
color of specimen changed to be more brownish, and UV-VIS spectra showed the increase in absorption intensity through UV and VIS regions.
The e l e c t r i c a l
conductivities after heat-treatment at 200~, 300~ increased from 5 X I0 -8 S/cm to 7 X 10-8 S/cm, 2 X lO ~ S/cm , respectively.
12-dopedspecimen showed the conduc-
t i v i t i e s of 5 X I0 -4 S/cm (before heat-treatment) and I X 10 3 S/cm (after heattreatment at 200°C).
These conductivities were not so large.
and long conjugated PEA have not been obtained yet.
This is because purP
On the other hand, the
d i s t o r t i o n parameter of ~-PDY multilayer was estimated to be a few percent by Microstrain Model analysis of X-ray d i f f r a c t i o n patterns of Fig.2(b).
The LB
molecular packing density in monolayer was lower by about 10 % than that of hexagonal closest packing by the result of transmission X-ray d i f f r a c t i o n patterns. Therefore, for the preparation of a metallic polyacene in the future, i t is necessary to increase the packing density of o-PDV in each monolayer, and to exclude the interlayer photopolymerization in the multilayer by using alternating L B method. ACKNOWLEDGEMENTS This work was performed as a part of the R&D project of basic technology for future industries sponsored by Agency of Industrial Science and Technology, Ministry of International Trade and Industry.
REFERENCES ] K. Tanaka, K. Ohzeki, S. Nankai and T. Yamabe, J. Ph~s:Chem. Solids, 44(I1) (1983)1069. 2 S. Kivelson and O. L. Chapman, Phys. Rev., B28(12)(1983)T236. 3 M. Ozaki, Y. Ikeda and I. Nagoya, 30th IUPAC-ISM meeting abstracts(1985)443. 4 M. 02aki, Y. Ikeda and I. Nagoya, S~nth. Met., 18(I987)485. 5 A. RuaudeI-Teixier, M. Vandevyver, A. Barraud, Mol. C~st. Liq. Cryst., 120 (1985)319. 6 T. Nakamura, F. Takei, M. Tanaka, M. Matsumoto, T. Sekiguchi, E. Manda, Y. Kauabata and G. Saito, Chem. Lett.(1986)323. A. RuaudeI-Teixier, MoI. C r ~ t ~ i q . Cr~st~L96(1983)365. B. Tieke, G. Lieser and G. Wegner, J~Polym. Sci., Polym. Chem. Ed.(]7)(1979) 1631. L. J. Bellamy, Advances in Infrared Group Frequencies, Methuen & Co. LTD., 1st edn., 1968. 10 I. Harada, M. Tasumi, H. Shirakawa, S. Ikeda, Chem. Lett.(1978)141].
c801
AN APPROACHTO THE PREPARATIONOF POLYACENEBY LB METHOD
M. OZAKI, Y. IKEDA and I. NAGOYA The Research Association for Basic Polymer Technology 2-5-21, Toranomon, Minatoku, Tokyo 105 (JAPAN)
ABSTRACT ~e have studied the preparation of polyacene via its prepolymer (polyethynylacetylene PEA) by Langmuir-Blodgett (LB) method using 22,24-pentacosadiynoic acid (,~-PDY) as a LB monomer. The molecular structure of photopolymerized w-PDY t,B films was investigated by optical measurements. It was shown that 3,4-photopolymerization predominantly occurred to give conjugated sequences (CH=CH)20 in the LB films.
The preliminary study of C~C bonds cyelization in the photopolymerized LB
films by heat treatment was performed to prepare polyacene. INTRODUCTION Polyacene (PA) is an i n f i n i t e linear acene, namely one-dimensional graphite which is expected to have a high electrical conductivity without doping from the result of the band calculations [ I - 2 ] . ration of PA.
Thus far no one has succeeded in the prepa-
In our previous study [3-4] we investigated a method to prepare PA
via its prepolymer, polyethynylacetylene (PEA) by the catalyst polymerization. It was, however, proved to be d i f f i c u l t to prepare the pure and trans form PEA by the catalyst polymerization.
Recently thin conducting films have been made using the
Langmuir-Blodgett (LB) method that is known as a method for orienting organic molecules regularly [5-6].
Then we have studied the preparation of PA using the LB
method by which the pure and trans form PEA should be prepared by the process shown in Figure I. In this paper we report about the preparation of LB multilayers 2 of monosubstituted 1,3-butadiyne LB monomers, the molecular structure of the photopolymeriaed LB
Mailing address: Central Laboratory, Asahi Chemical Ind. Co. Ltd., 2-I, Samejima, Fuji-shi, Shizuoka-ken 416, Japan. 0379-6779/89/$3.50
© Elsevier Sequoia/Printed in The Netherlands
C802
,I P r e p a r a t i o n
III I, I, uI i I i
hV
/1111//11/1111111111 IIIIIIIIIIIIIIIIII substrate
A or i e-beam
Ill I
PA ~v
o
oI
IIII1~i
( ~H, )20
IIII
COOH Fig.1
The process f o r the preparation of polyacene by LB method
f i l m s 3 and the p r e l i m i n a r y r e s u l t of e l e c t r i c a l c o n d u c t i v i t i e s by heat-treated LB f i l m s ~.
RESULTS AND DISCUSSION PEe~aration of m u l t i l a y e r s of HC~C-C~C-(CH~)~-COOH Monosubstituted 1,3-butadiyne LB monomers,
HC~C-C~C-(CH2).-COOH (n=8,14,20),
were synthesized by the acetylene coupling reaction between p r o p a r g y l i c acid HC~C-COOH and iodoacetylenic long chain f a t t y acid IC~C-(CH2)n-COOH (n=8,14,20) previously reported by RuaudeI-Teixier et a l . E 7 ] .
The production y i e l d s were lO~
(n=8), 5~ (n=14,20), r e s p e c t i v e l y , and the s t r u c t u r e of these compounds was i d e n t i f i e d by IR and 'H-NMR spectra. The s o l u t i o n of each 1,3-butadiyne LB monomer (2 X 10-3 M in chloroform) was spread on a water subphase containing CdCI2 (5 X 10.4 M).
The force-area ( H - A )
curve f o r a monolayer of each LB monomer is shown in Figure 2.
The LB monomer of n
=20, namely 22,24-pentacosadiynoic acid (~-PDV) showed a sharp force-area curve in which H - v a l u e s a b r u p t l y increased at smaller area A in comparison with LB monomers of n=8,H.
A t o t a l number of 20 carbon atoms in a f a t t y acid is necessary to form
a condensed surface s t a t e on the subphase.
~-PDV monolayers were successively
transferred onto a CaF2 substrate as Y type u n t i l a m u l t i l a y e r of defined thickness was obtained.
X-ray d i f f r a c t i o n patterns ( F i g . 3 ) of the m u l t i l a y e r showed high
order signals ( 0 0 )
up to
=7 with d-spacing (002) = 28 ~ which corresponds to one
molecular length of ~-PDY.
I t means that the ~-PDY m u l t i l a y e r was uniformly
formed by the LB technique.
The molecular long axis in the m u l t i l a y e r was found to
be inclined spectra.
about 66 ° to the layer plane from the analysis of polarized FT-IR
C803
40
~l~n=2
0 n=14 = Fe3 + )
20
0
20
40
60
A(A2/molecule) Fi8.2 Force-~treacurves for monolayers of LB monomers (n=8, 14, 20) on CdCl2 (5 X lO-4 M) subphase at T=15~
4k (002)
2k
1(003) (005) A(O04)///(006)
I0
2e
20
Fig.3 X-ray diffraction patterns of ~-PDY multilayers (135 layers) transferred to CaF2 substrate at H=25 mN/m, T=15~
2.0
•
~
~
(4)
'. 0.0~-
i
200
3oo
4oo 5o0 ~(nm)
i
80o
~oo
Fig.4 UV-VIS spect#a of ~-PDY multilayers before (1) and after UV irradiation for (2)Smin, (3)lOmin, (4)20min.
C804 Characterization of photopolymerized ~-PDY multilayers -PDY multilayers vere readily polymerized by UV irradiation (lO0~ Iov-pressure Bg lamp) and their UV-VIS absorption spectra (Fig.~) shoved that the absorption edge only redshifted vithout any hey absorption band in the v i s i b l e region. Tieke et a l . [ 8 ] observed tvo kinds of nev absorption bands at arround 500 nm and 600 nm by the photopolymerization of disubstituted diacetylene multilayers, vhich resulted in linear polydiaeetylene by 1,4-polymeri2ation. Therefore, our results suggest that the other polymerization form such as 1,2- or 3,4-polymerization occurs in monosubstituted diaeetylene multilayer rather than 1,4-polymerization.
(a) 0.B0"81
V(C3=---i~k~ I ~ C I ~ - C 2 )
/ V(C=--C)
0.2
4000
3000
2500
2000 /
2000
400
1000
wave n u m b e r ( c m - 1) (b) 1.0 V(C1-C2) at 2225cm-1
(c)1.1 V(CI---C2) at 2225cm-1
II _
~
© V(C3-C4) at 2301cm-1
O 0.0
I 5 UV
I 10 irradiation
I 15
i 2O t i m e (rain)
~ 25
0.(
I
0
5 UV
I
I
I
i
10 15 2O 25 irradiation time (min)
Fig.5 The change of FT-IR spectra of ~-PDY multilayer by UV irradiation. (a)FTIR spectra before irradiation (135 layers), (b)OD(t)/OD(t=O) versus UV i r r a d i a t i o n time in the ~-PDY Y type multilayer (135 layers), (c)that in the alternating multilayer of ~-PDY and arachidic acid (each 50 layers).
The photopolymerization form of ¢o-PDY multi layers was examined by FT-IR measurement (Fig.5). With increasing UV i r r a d i a t i o n time, absorption intensities of acetylenic IR bands u(=C-H) at 3278 cm-1 and v(C--C) at 2225, 2301 cm-~ decreased, and those of o l e f i n i c IR bands v(=C-H) at 3070 cm-~ and v(C=C) at 1587 cm-1 increased. IR bands v(C--C) at 2225 cm-1 and 2301 cm-~ are assigned to stretching vibrations of B-C--C- and -C~C- t r i p l e bonds, respectively, since the
C805 v lh!'atlon ener~,w of monosl]hslitu[vd a(:etyiene is u s u a l l y .~Iklltled a~t'iyl~'ne ~9]. ir;adiation
*i'he opt. ira!
lime in Pi~,,Ire 5 ( b ) .
fasi.er tilan 1,2-poiym~'riza~1,')n. la~,er photonol~'meriz, a t i o n , a ( i d whi(:h ~.~ I m ; c n ~ l l i v e
lower ~.han i h a l of iIisHh-
,k,rl.,;i~y of bolh IR iland.~; ~,'as H]oil~'d w'r~us t3,'
ii snuwed that :3,4-polyiIff:ri:.:ation was r e l a t i v v l ~ ' im l.he oLher hand,
in order to ~-×~;lqde the i n l P r -
~he att, crnaLin, ~, t.t_~ m u l ~ i a y e r
of (,>-PD¥ and ~r~:h~,iiv
f.o i.~V irradiai-,ion was prepared on a l:aF. ~ub~Iral.e.
}:']'-
!l~ measuremellt~ of LII~ a l t e r n a t i n~; mul i i l a y v r wur'~" per-formvd and Lhe chan~e (,f b()~h IR hands at. 2225 rm ~ 230] (m ~ ~as l i k v w i s ( ' ploil.(.d in Pi?,ure .S((:).
!I also
xhowed t.ha~ :{,.1-pol3merixaf ion pF(~dominanLly oc(:ilvred arld 1,2-po] ymer12aJlon ~,:.I~ .xuppr,.s~(~d Ill l.hv al Lelnalin;~ lllUl | i layer ('ompar'ed wi Lh ill [h(-' Y-I~pe ImJlli ]~yer. The inLcnsli.y (:han?.~- of
IR band :.'(---(I-H) aL 327g ('m ~ was almost Lh,." same as that
of IR band ~((::~(;) aL 2225('m '
~n h,flh Y Lyp~: and a i L r r n a l i n ~ m u l l i l a y e r ~ .
Raman ~l,e(;Jl'a (Fi g.~;) of Y LyHe mill f.i layer were measur(Jd L o e s ] i nla~.~ H~e number (el) of conju?aLed sequences ((tt=('fl)~.
(,~-PDY inulLilayer' (¥-l, ype) was found t,.)
!.~e r e a d i l y pol3~merized h~ i r r a d i a t i o n
(~f ,\r e×(:iLal, ion la,~;er (3,=5]L}5 /.,) dllr~ng
lhe measurement of l~aman .~peetrum.
Thv p o l y m e r i z a t i o n ,
b~ i r r a d i a t , ion of Ik~-Ne excit.al, ion laser (,k:~;?;2g /~).
howe,.mr, did not take pla~;e kaman ~ignal at ['L')O rln
due Lo ~ ( C = ( ) band was ob.~erved in i r r a d i a f , ion of bot.h [iV ~nd .~r e × r i } a L i o n (Fi~.6(a)
and f i ( h ) ) .
las,'r"
The number n of (£1i=('H)~, was eslimaLed Lo be 20 by ~pldyin~',
}he' value of ]490 cm ] Io lhe r'elal, iurl between n and Raman s h i f t
val,,es in
(::onjiJxaLed Ilolyenc [lOn,.
k e x = 6328.~
C= C
(b)
.
~c-c 2500
2000 Raman
1500 shi~ (cm-1)
1000
2500
2000 1500 I000 Raman shift (cm-l)
500
Fig.6 Raman spectra of the ~-PDY multilayer (340 layers) on a Si wafer (a)measured with 6328~ excitation when increasing UV irradiation time, (1)0 min, (2)1 min, (3)5 min ; (b)measured with 5145A excitation.
X-ray d i f f r a c t i o n
speeLrum of phoLopolymerized oJ-PIIV mul Li layer shoved Lhat f.he
inLensiLy of (OOm) r e f l e ( ' L i o n s (re:even) increased whereas Lhat of (OOn) r e f l e c L i o n s (n=odd) decreased l:Jy U V - i r r a d i a L i o n .
IL implies LhaL [1 elecLron densiLy increases
heLween mono!a.vers, and then the ordered u n i t
lengLh ¢han4es from Lhe Lhiekrtess of
one b i l a y e r Lo LhaL of one monolayer in Lhe Y-Lype r n u l L i l a y e r . Prom Lhese c h a r a ( : L e r i z a t i o n by o p t i c a l measuremenLs we conclude Lhat Lhe pr~~polymer PEA w iLh conjugaLed sequences (CH:CH)~ was parll.~ formed in each monolayer hy predominanL 3,4-phoLopo]ymerizaLion of ~-P[)Y LB monomer'.
C806 Heat-treatment of 3boto~ol~merized ~)-PDY m u l t i ~ e r The preliminary examination of C~C bonds cyclization in the photopolymeri2ed -PDY multila~er was performed by heat-treatment at T=200°C, 300°C for 2 hr.
The
color of specimen changed to be more brownish, and UV-VIS spectra showed the increase in absorption intensity through UV and VIS regions.
The e l e c t r i c a l
conductivities after heat-treatment at 200~, 300~ increased from 5 X I0 -8 S/cm to 7 X 10-8 S/cm, 2 X lO ~ S/cm , respectively.
12-dopedspecimen showed the conduc-
t i v i t i e s of 5 X I0 -4 S/cm (before heat-treatment) and I X 10 3 S/cm (after heattreatment at 200°C).
These conductivities were not so large.
and long conjugated PEA have not been obtained yet.
This is because purP
On the other hand, the
d i s t o r t i o n parameter of ~-PDY multilayer was estimated to be a few percent by Microstrain Model analysis of X-ray d i f f r a c t i o n patterns of Fig.2(b).
The LB
molecular packing density in monolayer was lower by about 10 % than that of hexagonal closest packing by the result of transmission X-ray d i f f r a c t i o n patterns. Therefore, for the preparation of a metallic polyacene in the future, i t is necessary to increase the packing density of o-PDV in each monolayer, and to exclude the interlayer photopolymerization in the multilayer by using alternating L B method. ACKNOWLEDGEMENTS This work was performed as a part of the R&D project of basic technology for future industries sponsored by Agency of Industrial Science and Technology, Ministry of International Trade and Industry.
REFERENCES ] K. Tanaka, K. Ohzeki, S. Nankai and T. Yamabe, J. Ph~s:Chem. Solids, 44(I1) (1983)1069. 2 S. Kivelson and O. L. Chapman, Phys. Rev., B28(12)(1983)T236. 3 M. Ozaki, Y. Ikeda and I. Nagoya, 30th IUPAC-ISM meeting abstracts(1985)443. 4 M. 02aki, Y. Ikeda and I. Nagoya, S~nth. Met., 18(I987)485. 5 A. RuaudeI-Teixier, M. Vandevyver, A. Barraud, Mol. C~st. Liq. Cryst., 120 (1985)319. 6 T. Nakamura, F. Takei, M. Tanaka, M. Matsumoto, T. Sekiguchi, E. Manda, Y. Kauabata and G. Saito, Chem. Lett.(1986)323. A. RuaudeI-Teixier, MoI. C r ~ t ~ i q . Cr~st~L96(1983)365. B. Tieke, G. Lieser and G. Wegner, J~Polym. Sci., Polym. Chem. Ed.(]7)(1979) 1631. L. J. Bellamy, Advances in Infrared Group Frequencies, Methuen & Co. LTD., 1st edn., 1968. 10 I. Harada, M. Tasumi, H. Shirakawa, S. Ikeda, Chem. Lett.(1978)141].