New Synthesis and Functionalization of Photosensitive Poly(silyl ether

Chapter 36

New Synthesis and Functionalization of Photosensitive Poly(silyl ether) by Addition Reaction of Bisepoxide with Dichlorosilane 1

Downloaded by NATL UNIV OF SINGAPORE on March 29, 2017 | http://pubs.acs.org Publication Date: May 5, 1995 | doi: 10.1021/bk-1994-0579.ch036

Atsushi Kameyama, Nobuyuki Hayashi, and Tadatomi Nishikubo Faculty of Engineering, Kanagawa University, Rokkakubashi, Kanagawa-ku, Yokohama 221, Japan

A poly(silyl ether)P-1containing silicon-silicon bond as a new class of silicon-containing polymer was successfully synthesized by polyaddition of1,2-dichloro-tetramethyldisilane with bisphenol A diglycidyl ether using quaternary onium salts. The polymer was further modified readily with photo-crosslinkable compounds by the substitution reaction using 1,8-diazabicyclo-[5.4.0]-undecene-7 under mild conditions to give multifunctional photopolymers P-2 having both a positive-working moiety in the main chain and a negative-working moiety in the side chain. Photochemical properties of P-1 and P-2 were investigated. P-1 was decomposed smoothly in a solution by irradiation with UV light. It was, furthermore, found that the photochemical reaction of P-2 was controlled easily by selecting the wavelength of the irradiation. Silicon-containing polymers have attracted considerable attention in the field of microlithography, since they have characteristic advantages such as resistance to oxygen-reactive ion etching and adhesion to variety of materials. Poly(siloxane)s or poly(silane)s have been investigated as useful materials for photolithography. Particularly, polymers containing silicon-silicon bonds undergo photochemical reactions upon UV irradiation (2-5). Poly(siloxane)s are usually synthesized (4) by the catalytic ring opening polymerization of cyclic siloxanes, and poly(silane)s have been obtained (5) by the reaction of dichlorosilanes with sodium metal. Poly(silyl 1

Corresponding author 0097-6156/94/0579-0443$08.00/0 © 1994 American Chemical Society

Ito et al.; Polymeric Materials for Microelectronic Applications ACS Symposium Series; American Chemical Society: Washington, DC, 1995.


444

POLYMERIC MATERIALS FOR MICROELECTRONIC APPLICATIONS

ether)s are categorized as a new class of silicon-containing polymers with various structures in the main chains and poly(silyl ether)s have different characteristics from poly(siloxane)s. Concerning the synthesis of poly(silyl ether)s, Imai et al. reported (6) the synthesis and characterization of poly(silyl ether)s containing disilane moieties by the reaction of l,2-bis(diethylamino)-tetramethyldisilane with various bisphenols. Although it is known that the addition reaction (7) of silyl chlorides with cyclic ethers give the corresponding silyl ethers, there were no reports on the synthesis of poly(silyl ether)s based on the silyl-ether formation reaction. We recently reported (8) in a communication the new synthesis of poly(silyl ether)s containing a disilane unit by the reaction of dichlorosilanes with bisepoxides, which was catalyzed efficiently by quaternary onium salts similar to the polyaddition (9) of diacyl chlorides with bis(cyclic ether)s giving the polyesters carrying reactive pendant chloromethyl groups. These polymers having pendant chloromethyl groups are very interesting materialsfromthe viewpoint of designing new type of functional polymers, since the pendant chloromethyl groups can be modified readily by conventional reactions. Meanwhile photosensitive polymers having both negative-working and positiveworking moieties in the side chains or in the main chains are interesting multifunctional photopolymers. We recently reported (10) for the first time the synthesis of new multifunctional copolyamides containing both cyclobutaneringsand conjugated double bonds in the main chain by the polycondensation of various diamines with bis(p-nitrophenyl) j3-truxinate and bis(p-nitrophenyl) esters of the unsaturated dicarboxylic acids. It was also found that the photochemistry of these copolyamides can be controlled by the selection of the exposing wavelength. From this background, we designed new type of multifunctional poly (silyl ether) with silicon-silicon bond in the main chain and photo-crosslinkable moieties in the side chains. In this paper, we wish to report the successful synthesis of a new poly(silyl ether) containing silicon-silicon bond by the polyaddition of bisepoxides with dichlorosilane compounds. Functionalizations of the resulting poly(silyl ether) were performed by the substitution reaction with photo-crosslinkable compounds using l,8-Diazabicyclo-[5.4.0]-undecene-7 (DBU). Photochemical properties of the multifunctional poly(silyl ether)s thus obtained were also investigated.


36. KAMEYAMA ET AL.

New Synthesis of Photosensitive Poly (silyl ether)

EXPERIMENTAL


l

Measurements. H NMR spectra were obtained on a JEOL EX-90 or FX-200 operating in the pulsed Fourier-transform (FT) modes, using tetramethylsilane (TMS) as an internal standard in chloroform-d. IR spectra were recorded on a JASCOIR700. UV spectra were recorded on a Shimadzu model UV-2100 spectrophotometer. The Mn and Mw/Mn of polymers were measured with a TOSOH HLC-8020 GPC unit using TSK-Gel columns (eluent: Ν,Ν-dimethyl-formamide (DMF), calibration: polystyrene standards). Materials. 1,2-Dichlorotetramethyldisilane (CMDS) was synthesized starting from hexamethyldisilane according to the reported procedure (11). 4Dimethylamino-cinnamic acid (MAC), 4-dimethylamino-a-cyanocinnamic acid (MACC), cinnamylidenecyanoacetic acid (CCA), and 4-dimethylamino-4'hydroxychalcone (MAHC) were prepared by the Knoevenagel condensation according to the literature (12). Bisphenol A diglycidyl ether (BPGE) was recrystallized from methanol /ethyl methyl ketone (4/1, v/v). Triphenylphosphine (TPP) was purified by recrystallization from methanol. Tetrabutylammonium bromide (TBAB) wasrecrystallizedfrom ethyl acetate. Other quaternary ammonium halides and cesium fluoride, and 18-crown-6 were used as received. Phenyl glycidyl ether (PGE) and DBU were purified by distillation. Solvents such as toluene, nitrobenzene, tetrahydrofurane (THF), DMF, Ν,Ν-dimethylacetamide (DMAc), Nmethyl-2-pyrolidone (NMP), and hexamethylphosphoroamide (HMPA) were dried and distilled before use. Synthesis of model compound by the addition reaction of CMDS with PGE. To a solution of PGE (1.502 g, 10 mmol) and TBAC (0.014 g, 0.05 mmol) in CHCI3 (1 mL) was added dropwise a solution of CMDS (0.936 g, 5 mmol) in 2 mL of CHCI3 at 0 °C, and then the reaction mixture was stirred at ambient temperature for 7 h. The reaction mixture was evaporated and the reaction product isolated by column chromatography with silica gel using chloroform/carbon tetrachloride (1/2, v/v) as the eluent. Yield; 85 %. IR (neat, cm* ): 1247 ( C-0-C), 1093,1049 (vSi-O-C), and 770 ( C-C1). H NMR (CDCI3, TMS): δ 0.27 (s, 12 H, CH ), 3.42-3.85 (m, 4 H, CH C1), 3.90-4.05 (m, 4 H, CH ), 4.10-4.35 (m, 2 H, CH), 6.80-7.40 (m, 10 H, Ar). 1

v

l

V

3

2

2


44


446


Synthesis of po!y(siIyI ether) by the polyaddition of CMDS with BPGE. To BPGE (0.8511 g, 2.5 mmol) in a 5 mL round-bottom flask was added dropwise the solution of CMDS (0.4680 g, 2.5 mmol) and 1 mol% of tetrabutylammonium chloride (TBAC, 0.025 mmol) in 2 mL of toluene at 0 °C. The reaction mixture was stirred at 0 °C for 1 h and at ambient temperature for 23 h. The reaction mixture was washed three times with water, and then poured into n-hexane. The polymer isolated was reprecipitated twice from chloroform in n-hexane and dried in vacuo at 60 °C to obtain the targeted polymer (P-l). Yield; 91 %. Mn; 24,000. IR (neat, cm' ): 1247 ( C-0-C), 1093, 1046 (ySi-O-C), and 769 ( C-C1). H NMR ( C D C I 3 , TMS): δ 0.31 (s, 12 H, S1-CH3), 1.61 (s, 6 H, C H 3 ) , 3.52-3.80 (m, 4 H, CH C1), 3.82-4.00 (m, 4 H, CH ), 4.05-4.35 (m, 2 H, CH), 6.76-7.12 (m, 8 H, Ar). 1

!

v

2

V

2

Typical procedure for reaction of the poly(silyl ether) with photocrosslinkable compounds. P - l (1.055 g, 2 mmol), MACC (0.714 g, 4.4 mmol), and DBU (0.670 g, 4.4 mmol) were dissolved in 5 mL of DMSO, which was stirred at 60 °C for 48 h. The reaction mixture was poured into methanol. The polymer isolated was purified by reprecipitation from chloroform in methanol to give the corresponding polymer (P-2b, 0.343 g). The degree of substitution of the resulting polymer was estimated by U NMR to be 39 %. IR (film, cm" ) 2210 ( CN), 1803, 1714 ( C=0), 1609 ( C=C), and 1246 ( C-0-C). H NMR (CDCI3, TMS) δ 0.15-0.31 (m, S1-CH3), 1.61 (s, C H 3 of BPGE unit), 3.09 (s, N - C H 3 ) , 3.50-4.55 (m, C H , CH), 6.55-6.90 (m, Ar), 7.12 (d, J = 8.57, Ar of BPGE), 7.92 (d, J = 9.01, Ar of MACC), and 8.62(s, CH =C). l

1

l

V

V

V

v

2

Photochemical reaction of P - l in THF solution. P - l (0.132 g, 0.25 mL) was dissolved in 100 mL of THF in a quartz cell reactor. The solution was bubbled with nitrogen for 1 h and then irradiated using a 500-W high-pressure mercury lamp (Ushio Electric Co,: USH 500D) under nitrogen. The change of the molecular weight was measured by GPC. Photochemical reaction of P-2 in the film state. A THF solution of P-2 (0.5 g/10 mL) was cast on the inside wall of a quartz cell and dried. The absorbance at 230 nm was 0.35-0.4. The polymer film on the quartz cell was irradiated by a 500-W high-pressure mercury lamp (USH-500D) through a monochromator (JASCO


36. KAMEYAMA ET AL.


Model CT-10). Appearance or disappearance of absorption peaks was measured using a UV spectrophotometer.


RESULTS AND DISCUSSION The additionreactionof CMDS with PGE was examined as a modelreactionfor the polyaddition of CMDS with BPGE. Thereactionwas carried out using TBAC as the catalyst at 0 °C for lh and at ambient temperature for 7 h to give the corresponding silyl ether 1 as addition product in 85 % yield. The structure of 1 was ascertained by means of IR, *H NMR spectroscopy, and elemental analysis. The *H NMR proved that /J-cleavage of the epoxyringof PGE occurred selectively in the reaction to afford 1. Thus it was found that the reaction of CMDS with epoxides proceeded very smoothly andregioselectivelyunder mild conditions. CH3CH3

CI-SI-SI-CI

+

TBAC

2 CH ^CHCH 0^ 2

2

CH3CH3

^

Ο

CMDS

PGE ÇH3ÇH3

Ç^OCH CHO—Sl-SI-OÇHCH 0-^~^ CH CI CH CH CH CI 2

2

2

3

3

2

Scheme 1 Based on the result of the model reaction, the polyadditionreactionof CMDS with BPGE was carried out using 1 mol% of TBAC in various solvents at 0 °C for 1 h and at ambient temperature for 23 h. Theresultsare summarised in Table I. The

H

CI-SI—Si-C! CH CH 3

3

/ = \ ? %=\ CH ^CHCH 0\^Ç-^^0CHPH-CH 2

2

Ο

CH

CMDS

TBAC 2

3

BPGE /CH3CH3

_

Ç 3_ H

\

J-SI-SI —0CHCH 0-^Ç-Ç)-0CH CH04-\CH3CH3 CH C! CH CH Cl/„ 2

2

2

Scheme 2

3

2

P-1


•

447

448


polymerization proceeded very efficiently in THF, toluene, and DMAc to afford the corresponding poly(silyl ether) P-l with number-average molecular weight (Mn) of Table I Solvent Effect on the Polyaddition of CMDS with BPGE* Solvent


Run 1 2 3 4 5 6 7

THF Toluene Benzene PhN0 DMAc NMP HMPA 2

Yield/%

MnxlO*

88 91 80 80 88 89 79

28.7 25.4 7.4 19.2 24.3 19.5 5.1

Mw/Mn 1.59 1.54 1.35 1.38 1.54 1.45 1.18

a)The reaction was carried out with 2.5 mmol of CMDS and BPGE using 1 moI% of TBAC in 2 ml of solvent at 0 °C for 1 h and at r.t. for 23 h.

Table II Polyaddition of BPGE with CMDS Using Various Catalysts Run

Catalyst

1 2 3 4 5 6 7 8 9

TPP TPP/KI DMAP 18-C-6/CsF TMBAC TBAB TBAC TBPB TBPC

MnxlO

Yield (%)

9.3 9.1 6.7 3.8 10.3 29.0 25.4 27.7 26.4

90 79 82 66 81 88 91 85 87

3

8

Mw/Mn 1.49 1.47 1.31 1.00 1.24 1.62 1.54 1.60 1.54

a)The reaction was carried out with 2.5 mmol of CMDS and BPGE using 1 mol% of various catalysts in 2 ml of toluene at 0 °C for lh and at r.t. for 23 h.

24,000-29,000 in high yield. The molecular weight of the polymer obtained was relatively low, when the reaction was conducted in chloroform or benzene. The IR spectrum of P-l obtained showed characteristic absorptions at 2954 cm" due to yCH, 1247 cm- due to C-0-C, 1093 and 1046 cm" due to Si-0-C, 769 cm" due to vC-Cl, respectively. H NMR spectral data supported the structure of P - l as shown in Scheme 2, and the methine protons were observed at 4.05-4.35 ppm with the expected intensity ratio. This result means that the polyaddition of CMDS with BPGE proceeded regioselectively in the presence of TBAC. In the UV absorption spectrum of P - l measured in THF, an absorption maximum was observed at 230 1

1

1

v

1

v

l



36. KAMEYAMA ET AL.


nm, which was assigned to the silicon-silicon bond. It was proved that the reaction using quaternary onium salts as catalysts took place smoothly in various solvents including cyclic ether, aromatic solvents, and aprotic polar solvents, particularly, THF, toluene, and DMAc were suitable solvent to obtain P-l with high molecular weight. The polyaddition of CMDS with BPGE was conducted using various catalysts in toluene (Table Π). In the case of the reaction using TPP as the catalyst, the molecular weight of the polymer obtained was low. Ν,Ν-Dimethylaminopyridine (DMAP) and 18-crown-6/CsF complex also gave the relatively low molecular weight polymer. On the other hand, the corresponding polymer with high molecular weight was obtained when the reaction was conducted using quaternary onium salts such as TBAB, TBAC, and tetrabutylphosphonium bromide and chloride. It was, therefore, found that quaternary onium salts have higher catalytic activity than TPP or DMAP, although it is reported (13) that TPP and quaternary onium salts catalyzed efficiently thereactionof silyl chlorides with cyclic ethers. Table ΠΙ shows the effect of TBAB concentration on the polyaddition of CMDS with BPGE. Thereactionwas catalyzed effectively by even 0.5 mol% of TBAB to produce P-l with Mn of 27,000. In the case of the reaction using 1 or 2 mol% of TBAB, the molecular weight of P-l obtained was about 30,000. However, increasing TBAB concentration further to 4 mol% tended to decrease the molecular weight (Mn; 25,000). In the reaction using 4 mol% of TBAB side reactions seem to occur slightly owing to a small amount of water contained in TBAB catalyst Table III Effect of TBAB Concentration TBAB/mol% Yeild/% MhxlO' _ _ _ _ 80

Run 2 3

4

4

1 2

88 87 84

29.0 31.0 25.0

3

Mw/Mn 1

6

6

1.62 1.54 1.48

a)The reaction was carried out with 2.5 mol of CMDS and BPGE in 2 ml of toluene and using TBAB as a catalyst at 0 °C for lh and at r.t. for 23 h.

P-l is insoluble in methanol and acetonitrile, but soluble in various organic solvents including ketones, halogenated hydrocarbons, aromatic solvents, and aprotic polar solvents.


449

450



As shown in Figure 1, the molecular weight of P - l decreased immediately when the irradiation was conducted in THF solution using a 500-W high pressure mercury lamp, particularly in the initial stage of the irradiation. On the contrary, the decrease in the molecular weight was not observed without irradiation. This result can be explained by the cleavage of the silicon-silicon bond in the polymer backbone upon UV light irradiation. It was thus demonstrated that P - l has a function as a positive type photopolymer. Further chemical modification of P - l was studied with photo-crosslinkable compounds such as MAC and MACC, which have absorption bands in the visible region. The reaction was carried out using DBU as a base in DMSO at 60 °C for 48 h, and the results are shown in Table IV. The reaction of P - l with MAC proceeded readily under the reaction conditions to afford the targeted polymer P-2a with 73 % of degree of substitution, which was estimated by the *H NMR spectrum. In the case of the reaction with MACC, the expected polymer P-2b was also obtained with /CH CH 3

3

—L s i - S i — O C H C H 0 "CH"C)~ 0CH 2f H0 \ ι ι I CH CH CI/ η \CH3CH3 CH CI

ROH/DBU

2

3

2

2

P-1

MAC

(P-2a)

MACC

O ÇN C-C=CH-CH=CH

(P-2b)

Ο II C-CHZCH

,CH ΝI *CH

3

3

CCA

(P-2C)

MAHC

(P-2d)

Scheme 3


36. KAMEYAMA ET AL.


39 % of degree of substitution. On the other hand, the modified polymers were not obtained when the reaction was conducted with CCA and MAHC under similar reaction condition. Table IV Chemical Modification of P - l with Photo-crosslinkable Compounds^


Run Polym. Compound Yield /g 1 2 3 4

P-2a P-2b P-2C> P-2d

MAC MACC CCA MAHC

D.SÏ> /%

0.525 0.343 0.896 0.154

73 39 —

Μη xlO 5.7 7.0 7.2 4.3

3

Mw/Mn Xmax /nm 365.0 1.24 1.16 420.0 — 1.20 — 1.04

a) The reaction was carried out with 2.0 mmol of poIy(siIyI ether) and 4.4 mmol of photo-crosslinkable compound and 4.4 mmol of DBU in 5 ml of DMSO at 60 °C for 48 h. l

b) Degree of substitution estimated by H - N M R . c) Reaction time:96 h.

The photochemical reaction of P-2a containing pendant MAC moiety was performed in the film state by irradiation with 365 nm light through a monochromator. Figure 2 shows the change of the UV spectrum of P-2a film which was formed from THF solution. The absorption due to the MAC moiety at 365 nm decreased rapidly and two isosbestic points were observed at 245 nm and 300 nm. This result means that the photo-crosslinking reaction of P-2a proceeded selectively upon 365 nm light irradiation. Figure 3 shows the time-course of the conversion of the C = C bond of the pendant MAC moiety upon 365 nm light irradiation. The conversion was 71 % for 5 min and 83 % for 15 min. It was thus demonstrated that the photo-crosslinking reaction proceeded very rapidly in the initial stage of the irradiation. After the photoreaction the polymer film became insoluble in THF. It was, therefore, proved that P-2a has a function as a negative type photoresist. When the P-2a film was irradiated with 230 nm light, the absorption at 230 nm based on silicon-silicon bond decreased immediately. This result suggested that the photo-decomposition of P-2a occurred selectively in the initial stage as shown in Figure 4. However, a prolonged irradiation caused the decrease in intensity of the absorption at 365 nm due to the MAC moiety; that is, photo-crosslinking reaction as a side reaction seemed to occur by long irradiation with 230 nm light. The polymer film irradiated with 230 nm light for 10 min became soluble in methanol, although P2a film was insoluble in methanol before irradiation. It is clear from these results


451


452


5

I

0

1

1

200

1

400

600

Irradiation time (min) Figure 1. Effect of UV irradiation on the molecular weight change of P-l in THF. (A): with irradiation, (·): without irradiation.

fj

irradiated with 365 nm light

1 1 1

J

1 1 1 1 1

/o\

Time (min) 0 0.2 0.3 0.6 1 1.5 2.5 4 6 9 14 r

200

300 400 500 Wavelength (nm)

Figure 2. Change of UV spectrum of P-2a in the film state observed upon irradiation with 365 nm light.


36. KAMEYAMA ET AL.


that P-2a function as a positive-working resist. P-2b containing MACC moiety in the side chain exhibited a behavior similar to P-2a toward the irradiation with 420 and 230 nm light and it was found P-2b also has both negative and positive capabilities. 100


80

c ο

60

"53 S ο

Ό

40 20

0

20

40

60

80

100

120

Irradiation time (min) Figure 3. Photochemical reaction of MCA moiety in P-2a film by irradiation with 365 nm light. 1.0

Irradiated with 230 nm light Time (min)

200

300

400

500

Wavelength (nm) Figure 4. Change of UV spectrum of P-2a in the film state observed upon irradiation with 230 nm light.


45

454


CONCLUSION The new poly(silyl ether) P-l containing photo-decomposable silicon-silicon bond was successfully synthesized by polyaddition of CMDS with BPGE using quaternary onium salts.

The poly(silyl ether) was modified easily with photo-

crosslinkable compounds by the substitution reaction using DBU under mild conditions to give multifunctional photopolymers P-2 having both positive-working


moiety in the main chain and negative-working moiety in the side chain, respectively. It was demonstrated that the photochemical reaction of P-2 was controlled easily by selecting the wavelength of the irradiation. These multifunctional polymers are a new type of photopolymers. REFERENCES 1. X. H. Zhang and R. West, J. Polym. Chem., Polym. Chem. Ed., 22, 225 (1984). 2. P. Trefonas III and R. West, J. Am. Chem.Soc.,1985, 107, 2737. 3. M. Ishikawa, N. Hongzhi, K. Matsusaki, K. Nate, T. Inoue, and H. Yokono, J. Polym. Sci., Polym. Lett., 1984, 22, 669. 4. For example: P. V. Wright, "Ring Opening Polymerization", Vol. 2, K. J. Ivin and T. Saegusa, Ed., Elsevier, London, 1984, pp 1055-1133. 5. For example: R. West, J. Organo-metallic Chem., 1986, 300, 327. 6. M. Padmanaban, M. Kakimoto, and Y. Imai, J. Polym. Sci., Part A: Polym. Chem., 1990, 28, 2997. 7. For example: W.P. Weber, "Silicon Reagents for organic Synthesis"; Springer, Berlin, 1983, pp 21-39. 8. T. Nishikubo, A. Kameyama, and N. Hayashi, Polym. J., 1993, 25, 1003. 9. a) A. Kameyama, S. Watanabe, E. Kobayashi, and T. Nishikubo, Macromolecules, 1992, 25, 2307. b) A. Kameyama, Y. Yamamoto, and T. Nishikubo, J. Polym. Sci., Part A: Polym. Chem., 1993, 31, 1639. 10. T. Nishikubo, T. Iizawa, Y. Shiozaki, and T. Koito, J. Polym. Sci., Part A: Polym. Chem., 1992, 30, 449. 11. H. Sakurai, M. Tominaga, T. Watanabe, and M. Kumada, Tetrahedron Lett., 1966, 5493. 12. G. Jones, "Organic Reactions", Vol. 15, John Wiley and Sons, New York, 1967, pp 204. 13. G. C. Andrews, T. C. Crawford, and L. D. Contillo, Jr., Tetrahedron Lett., 1981, 22, 3803. RECEIVED September 13, 1994


New Synthesis and Functionalization of Photosensitive Poly(silyl ether

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