Polypeptide 유도체의 비선형 광학 성질

박영욱; 우정원

Polymer(Korea), Vol.21, No.2, 186-192, March, 1997

Export Citation

Polypeptide 유도체의 비선형 광학 성질

Nonlinear Optical Properties of Polypeptide Derivative

박영욱, 우정원

초록

Poly-L-glutamate 측쇄에 비선형 광학 성질이 우수한 NPP (4-nitro-phenyl prolinol)을 부착시킨 고분자 PNPPLG (poly(4-nitrophenylprolin)-L-glutamate)를 합성하고 자기장 속에서 수평으로 주쇄를 배열시킨 film의 수직방향의 비선형 광학 성질을 측정하였다. 측정된 비선형 광학성질 (χ⁽²⁾)은 같은 주쇄구조(α-helix)를 갖는 PBLG (poly-γ-benzyl-L-glutamate)와 비교하면 PBLG는 비선형 광학 성질이 거의 나타나지 않지만 PNPPLG의 χ⁽²⁾₁₁, χ⁽²⁾₂₂ quartz의 1/10 정도(2×10^-10esu)로 나타났다. 이것은 측쇄인 NPP가 주쇄의 배열로 인해 상당한 유도 배열성을 가지며 부분적으로 noncentrosymmetry를 갖게 됨을 의미한다. 또 PNPPLG와 PNPPLG+ 30wt% NPP를 자기장 속에서 수평으로 배열시킨 시료의 수직방향의 비선형 광학 특성을 비교한 결과 유리 NPP를 함유한 시료가 2배나 높게 나타났다. 이것은 측쇄에 달린 NPP의 경우 주쇄 배열에 의한 유도 배열이 주쇄에 의해 많은 제약을 받지만 유리 NPP의 경우 이와 같은 제약이 없으므로 배열성이 높다는 것을 의미한다.

PNPPLG (poly(4-nitrophenylprolin)-L-glutamate) with nonlinear optical (NLO) chromophores in the side-chain, was synthesized by transesterification of PBLG (poly-γ-benzyl-L-glutamate) with NPP (4-nitrophenylprolinol). PNPPLG was oriented parallel to the surface in the magnetic field. The NLO coefficients were measured by second harmonic generation (SHG) direction normal to the film surface. Measured SHG coefficient of PNPPLG film was one tenth of that of quartz, which is much higher than of PBLG. This result suggests that NPPs attached in the side-chain are inductively oriented by the orientation of main chain (α-helix), which renders them partially non-centrosymmetric. Comparing the PNPPLG film with PNPPLG + 30 wt% NPP, the SHG coefficient of the latter was found to be twice of that of the former. This result suggests that free NPP can be oriented more easily than the side-chain NPP whose motion is limited by the bulky main-chain.

Keywords:polypeptide derivative;PNPPLG;nonlinear optical properties;NPP

[References]

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[1] Laser Forcus World, p. 77, January (1990)

[2] Tsutsumi N, Davis GT, DeReggi AS, Macromolecules, 24, 6392 (1991)

[3] Francis CV, White KM, Newmark RA, Stephens MG, Macromolecules, 26, 4379 (1993)

[4] Wright ME, Mullick S, Macromolecules, 25, 6045 (1992)

[5] Levine BF, Bethea CG, J. Chem. Phys., 65(5), 1989 (1976)

[6] Zyss J, Nicound JF, Coguillay M, J. Chem. Phys., 81(9), 4160 (1984)

[7] Watanabe J, Ono H, Uematsu I, Abe A, Macromolecules, 18, 2141 (1985)

[8] Watanabe J, Takashina Y, Macromolecules, 24, 3423 (1991)

[9] Lee YM, Prog. Chem. Chem. Ind., V31(1), 11 (1991)

[10] Block H, "Poly(γ-benzyl-L-glutamate) and Other Glutamic Acid Containing Polymers," Gordon and Breach Sci. Publishers, New York (1983)

[11] Miyazawa T, "Poly-α-amino Acid," G.D. Fasman Ed., p. 69, Marcel Dekker, New York (1957)

[12] Park YW, Samulski ET, unpublished results