Poly(GMA-co-St)을 이용한 감광성 고분자의 합성과 광화학 반응성 고찰

박희영, 박성영, 우항수, 박대원

부산대학교 화학공학과

Synthesis of Poly(CNMA-co-St) and Its Photochemical Reaction

H. Y. Park, S. Y. Park, H. S. Woo, D. W. Park

Dept. of Chem. Eng., Pusan National University

INTRODUCTION

Synthesis of polymers carrying reactive functional groups has been an active field of research in polymer science in recent years. Polymers containing an □,□-unsaturated carbonyl group undergo crosslinking upon irradiation with UV light and are used as photoresists to make large-scale integrated circuits, printing plates, photocurable coatings, photorecorders and photoconductors etc.1 Several negative photo-resists which can be used in various applications because of the structural variety of their photofunctional groups as well as their polymer backbones2 have been reported in the literature. Polymers with pendant cinnamic ester groups,3 pendant chalcone, □-cyano-cinnamic ester and □-phenylmaleimide systems have been reported.

Polyglycidylmethacrylate and its copolymer were known as useful functional polymers. The syntheses of polyesters by the addition reactions of epoxides with dicarboxylic acid chlorides have been reported recently.3 It was considered that this method could be adapted to the synthesis of photosensitive polymers and the modification of the resulting polymers.

We propose the syntheses of polymers with pendant cinnamic ester and chloromethyl groups by the addition reaction of poly(GMA-co-St) with cinnamoyl chloride, and then study the photochemical reactions of the obtained polymers.

EXPERIMENTAL

1. Materials

Glycidyl methacrylate(GMA) and styrene(St) monomers were washed with an aqueous sodium hydroxide solution, rinsed with distilled water, then dried over calcium chloride. Tetrabutyl ammonium chloride(TBAC), cinnamoyl chloride(CNC) were all reagent grades and were used as purchased without purification.

2. Polymer Synthesis

A radical copolymer of glycidyl methacrylate[28.43g (0.2mol)] with styrene[10.42g(0.1mol)](poly(GMA-co-St)) was prepared in DMSO(360ml) using AIBN(0.39g) as an initiator at 70℃ for 24h under nitrogen atmosphere, then the solution was poured into distilled water to give a precipitate. Polymers were recovered using an excess of methanol, and dried in vacuum at 30℃ for 12h.

3. Addition Reaction of Poly(GMA-co-St) with Cinnamoyl Chloride

Poly(GMA-co-St)[5.43g (28mmol)] was dissolved in 70ml of sulfolane, and 4.69g (28mmol) of cinnamoyl chloride and 0.28g(1mmol) of TBAC were added to the solution. The mixture was stirred at 100℃ for 10h, and then was poured into 700ml of methanol, and dried in vacuum oven at 50℃.

The objected polymer, poly(3-chloro-2-cinnamoyloxypropyl methacrylate-co-Styrene) (Poly(CNMA-co-St)), is represented to schme 1.

Schme 1. Synthesis of Poly(CNMA-co-St) via Incoporation of Cinnamoyl Chloride into Poly(GMA-co-St).

4. Measurement of Polymer Photochemical Reaction

The polymer solution in tetrahydrofuran(THF) was cast on a grass plate and dried. The film on the plate was irradiated by a high pressure mercury lamp(Q-PANEL Co., UVC-313) without a filter at a distance of 20cm. The rates of disappearance of the absorptions of the C=C group at 1640cm-1 was measured by IR spectroscopy (ASI REACT IRTM 1000).

The rate of disappearance of absorption due to the C=C of the cinnamic ester of the polymer was followed using the expression.

Conversion of -C=C- (%) = [eqn: { { { A}_{O,-C=C-} } over { { A}_{O,-CO-} } - { { A}_{-C=C-} } over {{ A}_{-CO-} } } over {{ { A}_{O,-C=C-} } over { { A}_{O,-CO-} } }] × 100

Where, AO,-C=C- and A-C=C- are absorption peak area (after baseline correction) due to C=C of the cinnamic ester (1640cm-1) after irradiation times t=0 and t=T, respectively. AO,-CO- and A-CO- are absorption peak area due to C=O (1730cm-1) after irradiation times t=0 and t=T, respectively.

RESULTS AND DISCUSSION

1. Addition Reaction of Poly(GMA-co-St) with Cinnamoyl Chloride

The synthesis of poly(CNMA-co-St) was carried out by the reaction of poly(GMA-co-St) with Cinnamoyl Chloride using Tetrabutyl Ammonium Chloride(TBAC). The IR spectrum of the polymer obtained from the reaction of poly(GMA-co-St) with CNC showed absorptions at 1730cm-1, due to C=O stretching; at 1640cm-1, due to C=C stretching; and at 680cm-1, due to C-Cl stretching; no absoption due to O-H stretching near 3500cm-1; and showed the disappearance of the absorption due to epoxide ring at 910cm-1. This result is shown in Fig. 1. The 1H-NMR analysis also confirmed the synthesis of poly(CNMA-co-St).

Figure 1. FT-IR Spectra of Poly(GMA-co-St) and Poly(CNMA-co-St).

2. Photochemical Reaction of the Obtained Polymer.

The photocrosslinking reaction of poly(CNMA-co-St) was studied on thin films in tetrahydrofuran solution (0.02%; 3×3cm2 grass plate) in the absence of a photosensitizer. Samples were irradiated with a high pressure mercury lamp in the presence of air. The changes in the IR spectral pattern of the polymer are presented in Fig. 2. Initially, the polymer shows a IR absorption band at 1640cm-1 due to C=C stretching of cinnamic ester. The irradiation resulted in a fast decrease of the absorption at 1640cm-1, and the absorption almost completely disappeared within 24h of irradiation. This behaviour clearly indicates crosslinking of the polymer chains through 2□ + 2□ cycloaddition of the C=C group of the pendant cinnamoyl units. Because the  2□ + 2□ cycloaddition destroys conjugation in the entire □-electron system, the IR absorption intensity decreases with irradiation time.4,5 Figure 3 shows the rate of disappearance of C=C of the polymer. In the polymer film, photoconversion values of about 66.9% and 100% were reached after 6hr and 24hr of irradiation.

From these results, it is concluded that poly(CNMA-co-St) prepared by the addition reaction of poly(GMA-co-St) with cinnamoyl chloride has high photosensitivity, even in the absence of sensitizer.

Figure 2. The Changes in the IR Spectral Patterns of the Poly(CNMA-co-St) by UV Irradiation.

Figure 3. The Rate of Disappearance of C=C of the Cinnamic Ester

REFERENCE

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4. T. Nishikubo, T. Iizawa, and M. Yamada, J. Polymer Sci., Polym. Lett. Ed.,    19, 177 (1981).

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