JP3607937B2 - Acrylamide copolymer, method for producing the same, and second-order nonlinear optical material - Google Patents

Description

で表わされる繰り返し単位、（Ｂ）式
【化８】

（式中のＲ^１は水素原子又はメチル基、Ｒ^２は水素原子又はｏ位若しくはｍ位に結合したメチル基である）
で表わされる繰り返し単位及び（Ｃ）式
【化９】

（式中のＲ^１及びＲ^２は前記と同じ意味をもつ）
で表わされる繰り返し単位からなり、重量平均分子量５０，０００〜３００，０００を有するアクリルアミド系共重合体及びこの共重合体から成る二次非線形光学材料を提供するものである。
【０００９】
前記アクリルアミド系共重合体は、本発明に従えば、Ｎ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルアクリル（又はメタクリル）アミドとをラジカル共重合させ、次いでこのようにして得られた共重合体に、ニトロアニリンをジアゾカップリングさせることにより、製造することができる。
【００１０】
【発明の実施の形態】
本発明のアクリルアミド系共重合体は、次の反応式に従って、Ｎ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルアクリル（又はメタクリル）アミドとをラジカル共重合させて、共重合体（ＩＶ）を製造する第一工程と、この共重合体にニトロアニリンをジアゾカップリングさせて、前記繰り返し単位（Ｉ）、（ＩＩ）及び（ＩＩＩ）からなるアクリルアミド系共重合体（Ｖ）を製造する第二工程から成っている。
【００１１】
【化１０】

（式中のｘ、ｙ及びｎは１以上の整数であり、Ｒ^１とＲ^２は前記と同じ意味をもつ）
【００１２】
【化１１】

（式中のｘ、ｎ及びＲ^１とＲ^２は前記と同じ意味をもち、ｙ_１＋ｙ_２＝ｙである）
【００１３】
この第一工程の共重合反応は、Ｎ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルアクリル（又はメタクリル）アミドとの混合物を、重合溶媒中、ラジカル重合開始剤の存在下で加熱することにより行われる。
この際のＮ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルアクリル（又はメタクリル）アミドとの使用割合は、モル比で２：１ないし１：２、好ましくは１．２：１ないし１：１．２の範囲内で選ばれる。これよりもＮ‐フェニルマレイミドの量が少ないと高温における配向構造の緩和を防止することができないし、またこれよりもＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルアクリル（又はメタクリル）アミドの量が少ないと、後続工程における色素の導入量が低くなり、所望の二次非線形光学活性が得られない。
【００１４】
この共重合反応は、溶液重合、乳化重合、懸濁重合のいずれでもよいが、第二工程を連続して行いうるという点で溶液重合が好ましい。この場合、重合溶媒を使用しないで行うこともできるが、重合溶媒を用いる場合には、テトラヒドロフラン、ジメチルホルムアミド、ジメチルアセトアミド、ジメチルスルホキシド、ジエチルスルホキシドなどが好適である。そのほか、ベンゼン、ニトロベンゼンなどの炭化水素類、第三ブチルアルコールのようなアルコール類も用いられる。
【００１５】
また、ラジカル重合開始剤としては、過酸化アセチル、過酸化ベンゾイル、過酸化ラウロイル、過酸化ｔ‐ジブチルのような過酸化物系重合開始剤や、アゾビスイソブチロニトリル、アゾビスシアノ吉草酸、アゾビスシクロヘキサンカルボニトリル、アゾビスイソブチルアミジン塩酸塩のようなアゾ系重合開始剤が用いられる。このラジカル重合開始剤の使用量は、通常、単量体全重量に基づき０．０５〜５．０重量％の範囲内で選ばれる。
【００１６】
次に、この共重合反応の温度としては、５０〜１００℃、好ましくは６０〜８０℃の範囲が有利である。これよりも低い温度では、反応速度が遅く実用的でないし、またこれよりも高い温度では、副反応を生じ、最終的に得られる共重合体の品質低下の原因になる。この温度における重合時間は通常１０〜５０時間である。
このようにして、数平均分子量３６，０００〜２５０，０００のＮ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルアクリル（メタクリル）アミドとの共重合体（ＩＶ）が白色固体として得られる。このもののＭｗ／Ｍｎ比は、１．５〜３．０の範囲であり、狭い分子量分布を示す。
【００１７】
次に、第二工程においては、このようにして得られた共重合体に、ニトロアニリン例えばニトロアニリンをジアゾカップリングさせる。このジアゾカップリング法については特に制限はなく、常法に従って行うことができる。例えばニトロアニリンを塩酸水溶液中に溶解又は懸濁させたのち、これに亜硝酸ナトリウムを、ニトロアニリンに対して実質上当モルの割合で添加し、さらに適当な溶媒に溶解させた前記共重合体を添加すればよい。
【００１８】
このジアゾカップリング率は、生成するアクリルアミド系共重合体（Ｖ）の二次非線形光学特性に応じて選択される。このジアゾカップリング率は、ニトロアニリンの使用量、反応時間により左右されるが、通常５０〜９５モル％、好ましくは７０〜９０モル％の範囲である。例えば共重合体（ＩＶ）中の繰り返し単位（ＩＩ）に対する化学量論的量により、やや過剰に使用し、２０〜１００時間程度反応させるのがよい。これにより、繰り返し単位（ＩＩ）の約７０モル％以上が、アゾ染料に変換される。
このようにして、一般式（Ｖ）で表わされる構造をもつ重量平均分子量５０，０００〜３００，０００の本発明のアクリルアミド系共重合体が赤色固体として得られる。
このようにして得られたアクリルアミド系共重合体は、文献未載の二次非線形光学特性を示す新規化合物で、その最適ポーリング温度は１６０〜１９０℃の範囲に存在し、また高温における二次非線形光学特性の緩和に対して、優れた抑制効果を示す。
【００１９】
【実施例】
次に、本発明を実施例によりさらに詳細に説明する。
【００２０】
実施例
Ｎ‐フェニルマレイミド１．４７ｇ（１０ミリモル）と、Ｎ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルメタクリルアミド２．１８ｇ（１０ミリモル）と、２，２′‐アゾビスイソブチロニトリル０．０３３ｇ（０．２ミリモル）と、テトラヒドロフラン５０ミリリットルとを１００ミリリットル容アンプル管に入れ、液体窒素を用いて脱気したのち、溶封し、２４時間ラジカル共重合を行った。
次いで生成物を取り出し、エーテルを用いて再沈殿して精製した。このようにしてＮ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルメタクリルアミドとの共重合体２．５ｇを白色固体として得た。
このものの分子量をゲルパーミエーションクロマトグラフィーにより測定したところ、重量平均分子量（Ｍｗ）は１５０，０００であり、またＭｗ／Ｍｎは２であった。
このものの^１Ｈ−ＮＭＲチャートを図１に示す。このチャートから、Ｎ‐フェニルマレイミド単位と、Ｎ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルメタクリルアミド単位とのモル比は０．５２８：０．４７１であることが分った。
【００２１】
次に、ｐ‐ニトロアニリン４．８３ｇ（３５ミリモル）を３０重量％濃度の塩酸水溶液１０ミリリットルに湯浴にて懸濁させ、これに亜硝酸ナトリウム２２．４２ｇ（３５ミリモル）を含む水溶液を滴下したのち、さらにジメチルホルムアミド４０ミリリットルに溶解させた前記共重合体２ｇを、反応液温５℃前後に保持しながら５時間要して滴下した。次いで、水酸化ナトリウム及び酢酸ナトリウムを用いてｐＨを３．５に調整し、０〜１０℃の温度を保持しながら、６０時間かきまぜ、ジアゾカップリング反応を行った。反応終了後、酢酸エチルを用い再沈殿して精製を行い、赤色固体２．５ｇを得た。この赤色固体について、^１Ｈ−ＮＭＲ測定を行った結果、ジアゾカップリング率（色素導入率）は、Ｎ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルメタクリルアミド単位に対して７４．５モル％であった。また、ゲルパーミエーションクロマトグラフィー法により測定した重量平均分子量（Ｍｗ）は２５０，０００であった。
このものの^１Ｈ−ＮＭＲチャートを図２に示す。
【００２２】
参考例
実施例で得られた共重合体をジメチルホルムアミドに溶解して３重量％濃度の溶液を調製した。この溶液を、親水化処理を施したガラス基板上に、３０００ｒｐｍ、１０秒間の条件下でスピンコートしたのち、１ｍｍＨｇの真空下で１５０℃にて２４時間加熱乾燥して、厚さ６２９Åの均一な薄膜を作製した。なお、スピンコート時に、溶液を温めるとともに、赤外線ランプにて基板を加熱した。
次に、このようにして作製した試料５個を、それぞれ１６０℃、１７０℃、１８０℃、１９０℃又は２００℃の温度において、コロナポーリング法に従い５ｋＶ／ｃｍ^２の強さで２０分間電場印加したのち、二次非線形光学定数（ｄ_３３）の値を求めた。
このｄ_３３値は、回転式メーカーフリンジ法に従い、Ｎｂ：ＹＡＧレーザ（λ＝１０６４ｎｍ）を励起光として用いた試料のＳＨＧ測定で得られるフリンジと、リファレンス（ＳｉＯ_２）のフリンジから求めた。この結果をグラフとして図３に示す。
このグラフより、この共重合体の最適ポーリング温度は１８０℃付近であることが分る。
次に、前記試料に、温度１８０℃において、前記と同様にしてポーリング処理を施したのち、この試料を空気中、８０℃において、３５０時間保持して、経時緩和を調べた。この結果をグラフとして図４に示す。
このグラフより、本発明の共重合体は優れた経時安定性を有することが分る。
【００２３】
【発明の効果】
本発明の共重合体は、二次非線形光学特性を有する新規化合物であって、しかも長時間にわたって、高温における二次非線形光学特性の緩和に対して、優れた抑制効果を示す。
【図面の簡単な説明】
【図１】Ｎ‐フェニルマレイミドとＮ‐（Ｎ‐フェニル‐Ｎ‐メチル）‐アミノエチルメタクリルアミドとの共重合体の１例の^１Ｈ−ＮＭＲチャート。
【図２】本発明共重合体の１例の^１Ｈ−ＮＭＲチャート。
【図３】本発明共重合体における温度とｄ_３３との関係の１例を示すグラフ。
【図４】本発明共重合体の二次非線形光学特性の経時緩和の１例を示すグラフ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel acrylamide copolymer exhibiting second-order nonlinear optical characteristics, a method for producing the same, and an organic second-order nonlinear optical material using the same.
[0002]
[Prior art]
In the future advanced information society, it will be necessary to transmit large volumes of precise information at high speed, high density, and high efficiency. Light is expected to play an important role in this field because it has characteristics such as parallelism, spatial processability, mass operability, and high density. Incidentally, organic nonlinear optical materials have recently attracted attention as one of the materials necessary for utilizing this light.
[0003]
The nonlinear effect of inorganic materials known so far is manifested by the absorption of lattice vibration, whereas the nonlinear effect of organic materials is due to the dipole moment generated by the non-local π-electron system being distorted by substituents. Since it is basically not accompanied by lattice vibration, a faster response is possible.
[0004]
By the way, in order to generate the second-order nonlinear effect, it is necessary to orient the induced dipole moment in the same direction, and this can be achieved by an organic crystal approach, an LB film or liquid crystal approach, or electric field orientation, that is, poling. Approach is known, but Pauling's approach can obtain an oriented structure with a simple process compared to other methods, and there are relatively few restrictions in molecular design. There is an advantage that a nonlinear effect can be generated.
[0005]
However, the second-order nonlinear optical effect obtained in this way tends to decrease over time because the active group in the molecule that generates it is relaxed by the thermal motion and electrical repulsion of the molecule.
As a method of suppressing such a time-dependent decrease of the second-order nonlinear optical effect, in the case of a polymer up to now, poling while sufficiently heat-treating near the glass transition temperature, and using a material having a high glass transition temperature However, satisfactory results have not been obtained.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a novel polymer material having secondary nonlinear optical properties with good thermal stability, in which relaxation of the alignment structure at high temperatures is suppressed.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to develop a polymer material having second-order nonlinear optical properties, the present inventors have introduced phenylmaleimide, which produces a polymer having a high glass transition point, into the main chain and is rigid. By forming a polymer skeleton and pendating a nonlinear optically active group as a side chain thereto, it is found that a polymer material having a second-order nonlinear optical property in which relaxation of the alignment structure at high temperature is suppressed can be obtained. The present invention has been made based on this finding.
[0008]
That is, the present invention relates to the formula (A)

A repeating unit represented by formula (B):

(Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a hydrogen atom or a methyl group bonded to the o-position or the m-position)
A repeating unit represented by formula (C):

(Wherein R ¹ and R ² have the same meaning as above)
An acrylamide copolymer having a weight average molecular weight of 50,000 to 300,000 and a second-order nonlinear optical material comprising the copolymer are provided.
[0009]
According to the present invention, the acrylamide copolymer is a radical copolymer of N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethylacrylic (or methacrylic) amide, and is thus treated in this manner. It can be produced by diazo coupling nitroaniline to the copolymer thus obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The acrylamide copolymer of the present invention is obtained by radically copolymerizing N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethylacrylic (or methacrylic) amide according to the following reaction formula. A first step of producing a polymer (IV), and a nitroaniline is diazo coupled to the copolymer to prepare an acrylamide copolymer (V) comprising the repeating units (I), (II) and (III). ) Consists of a second step.
[0011]
[Chemical Formula 10]

(Wherein x, y and n are integers of 1 or more, and R ¹ and R ² have the same meaning as described above)
[0012]
Embedded image

(Wherein x, n and R ¹ and R ² have the same meaning as described above, and y ₁ + y ₂ = y)
[0013]
In this first step, the copolymerization reaction involves the reaction of a mixture of N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethylacrylic (or methacrylic) amide in the polymerization solvent in the presence of a radical polymerization initiator. This is done by heating under.
In this case, the use ratio of N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethylacrylic (or methacrylic) amide is 2: 1 to 1: 2, preferably 1.2. It is selected within the range of 1 to 1: 1.2. If the amount of N-phenylmaleimide is less than this, relaxation of the orientation structure at high temperature cannot be prevented, and more than this, N- (N-phenyl-N-methyl) -aminoethylacrylic (or methacryl) amide If the amount is small, the amount of dye introduced in the subsequent step is low, and the desired second-order nonlinear optical activity cannot be obtained.
[0014]
This copolymerization reaction may be any of solution polymerization, emulsion polymerization, and suspension polymerization, but solution polymerization is preferred in that the second step can be performed continuously. In this case, the polymerization may be carried out without using a polymerization solvent. However, when a polymerization solvent is used, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, diethyl sulfoxide and the like are preferable. In addition, hydrocarbons such as benzene and nitrobenzene, and alcohols such as tertiary butyl alcohol are also used.
[0015]
In addition, as radical polymerization initiators, peroxide polymerization initiators such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, t-dibutyl peroxide, azobisisobutyronitrile, azobiscyanovaleric acid, azo An azo polymerization initiator such as biscyclohexanecarbonitrile or azobisisobutylamidine hydrochloride is used. The amount of the radical polymerization initiator used is usually selected within the range of 0.05 to 5.0% by weight based on the total weight of the monomers.
[0016]
Next, the temperature of this copolymerization reaction is advantageously in the range of 50 to 100 ° C, preferably 60 to 80 ° C. If the temperature is lower than this, the reaction rate is slow and impractical, and if the temperature is higher than this, a side reaction occurs, resulting in deterioration of the quality of the finally obtained copolymer. The polymerization time at this temperature is usually 10 to 50 hours.
Thus, the copolymer (IV) of N-phenylmaleimide having a number average molecular weight of 36,000 to 250,000 and N- (N-phenyl-N-methyl) -aminoethylacrylic (methacrylic) amide is white. Obtained as a solid. The Mw / Mn ratio of this is in the range of 1.5 to 3.0 and shows a narrow molecular weight distribution.
[0017]
Next, in the second step, a nitroaniline such as nitroaniline is diazo-coupled to the copolymer thus obtained. There is no restriction | limiting in particular about this diazo coupling method, It can carry out in accordance with a conventional method. For example, after dissolving or suspending nitroaniline in an aqueous hydrochloric acid solution, sodium nitrite is added to the nitroaniline in a substantially equimolar ratio with respect to the nitroaniline, and the copolymer dissolved in an appropriate solvent is further added. What is necessary is just to add.
[0018]
This diazo coupling rate is selected according to the second-order nonlinear optical characteristics of the acrylamide copolymer (V) to be produced. The diazo coupling rate depends on the amount of nitroaniline used and the reaction time, but is usually in the range of 50 to 95 mol%, preferably 70 to 90 mol%. For example, it may be used in a somewhat excessive amount depending on the stoichiometric amount with respect to the repeating unit (II) in the copolymer (IV) and allowed to react for about 20 to 100 hours. Thereby, about 70 mol% or more of the repeating unit (II) is converted into an azo dye.
In this way, the acrylamide copolymer of the present invention having a structure represented by the general formula (V) and having a weight average molecular weight of 50,000 to 300,000 is obtained as a red solid.
The acrylamide copolymer thus obtained is a novel compound exhibiting second-order nonlinear optical properties not described in literature, and its optimal poling temperature is in the range of 160 to 190 ° C., and second-order nonlinear at high temperatures. Excellent suppression effect on optical property relaxation.
[0019]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0020]
EXAMPLE 1.47 g (10 mmol) of N-phenylmaleimide, 2.18 g (10 mmol) of N- (N-phenyl-N-methyl) -aminoethylmethacrylamide, 2,2′-azobisisobutyro 0.033 g (0.2 mmol) of nitrile and 50 ml of tetrahydrofuran were placed in a 100 ml ampule tube, degassed with liquid nitrogen, sealed, and subjected to radical copolymerization for 24 hours.
The product was then removed and purified by reprecipitation with ether. Thus, 2.5 g of a copolymer of N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethylmethacrylamide was obtained as a white solid.
When the molecular weight of this product was measured by gel permeation chromatography, the weight average molecular weight (Mw) was 150,000 and Mw / Mn was 2.
A ¹ H-NMR chart of this product is shown in FIG. From this chart, it was found that the molar ratio of N-phenylmaleimide units to N- (N-phenyl-N-methyl) -aminoethylmethacrylamide units was 0.528: 0.471.
[0021]
Next, 4.83 g (35 mmol) of p-nitroaniline is suspended in 10 ml of a 30 wt% hydrochloric acid aqueous solution in a hot water bath, and an aqueous solution containing 22.42 g (35 mmol) of sodium nitrite is added dropwise thereto. Thereafter, 2 g of the copolymer dissolved in 40 ml of dimethylformamide was added dropwise over 5 hours while maintaining the reaction solution temperature at around 5 ° C. Next, the pH was adjusted to 3.5 using sodium hydroxide and sodium acetate, and the mixture was stirred for 60 hours while maintaining a temperature of 0 to 10 ° C. to carry out a diazo coupling reaction. After completion of the reaction, purification was performed by reprecipitation using ethyl acetate to obtain 2.5 g of a red solid. As a result of ¹ H-NMR measurement of this red solid, the diazo coupling rate (dye introduction rate) was 74.5 mol with respect to the N- (N-phenyl-N-methyl) -aminoethylmethacrylamide unit. %Met. Moreover, the weight average molecular weight (Mw) measured by the gel permeation chromatography method was 250,000.
A ¹ H-NMR chart of this product is shown in FIG.
[0022]
Reference Example The copolymer obtained in Example was dissolved in dimethylformamide to prepare a 3% strength by weight solution. This solution was spin-coated on a glass substrate subjected to hydrophilization treatment at 3000 rpm for 10 seconds, and then heat-dried at 150 ° C. for 24 hours under a vacuum of 1 mmHg to obtain a uniform thickness of 629 mm. A thin film was prepared. During spin coating, the solution was warmed and the substrate was heated with an infrared lamp.
Next, an electric field was applied to the five samples thus prepared at a temperature of 160 ° C., 170 ° C., 180 ° C., 190 ° C. or 200 ° C. for 20 minutes at a strength of 5 kV / cm ² according to the corona poling method. After that, the value of the second-order nonlinear optical constant (d ₃₃ ) was obtained.
This d ₃₃ value was determined from the fringe obtained by SHG measurement of a sample using an Nb: YAG laser (λ = 1064 nm) as excitation light and the reference (SiO ₂ ) fringe according to the rotary maker fringe method. The results are shown as a graph in FIG.
From this graph, it can be seen that the optimal poling temperature of this copolymer is around 180 ° C.
Next, the sample was subjected to a poling treatment in the same manner as described above at a temperature of 180 ° C., and then the sample was held in air at 80 ° C. for 350 hours to examine relaxation over time. The results are shown as a graph in FIG.
From this graph, it can be seen that the copolymer of the present invention has excellent temporal stability.
[0023]
【The invention's effect】
The copolymer of the present invention is a novel compound having second-order nonlinear optical characteristics, and exhibits an excellent inhibitory effect on relaxation of second-order nonlinear optical characteristics at high temperatures over a long period of time.
[Brief description of the drawings]
FIG. 1 is a ¹ H-NMR chart of an example of a copolymer of N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethyl methacrylamide.
FIG. 2 is a ¹ H-NMR chart of an example of the copolymer of the present invention.
FIG. 3 is a graph showing an example of the relationship between temperature and d ₃₃ in the copolymer of the present invention.
FIG. 4 is a graph showing an example of relaxation over time of the second-order nonlinear optical characteristics of the copolymer of the present invention.

Claims (3)

(A) Formula

A repeating unit represented by formula (B)

(Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a hydrogen atom or a methyl group bonded to the o-position or m-position)
A repeating unit represented by formula (C):

(Wherein R ¹ has the same meaning as described above, and R ² is a hydrogen atom or a methyl group)
An acrylamide copolymer having a weight average molecular weight of 50,000 to 300,000. Radical copolymerization of N-phenylmaleimide and N- (N-phenyl-N-methyl) -aminoethylacrylic (or methacrylic) amide, and then N-nitroaniline is added to the copolymer thus obtained. The method for producing an acrylamide copolymer according to claim 1, wherein diazo coupling is performed. (A) Formula

A repeating unit represented by formula (B)

(Wherein R ¹ is a hydrogen atom or a methyl group, R ² is a hydrogen atom or a methyl group bonded to the o-position or the m-position)
A repeating unit represented by formula (C):

(Wherein R ¹ has the same meaning as described above, and R ² is a hydrogen atom or a methyl group)
A second-order nonlinear optical material comprising an acrylamide copolymer having a weight average molecular weight of 50,000 to 300,000.

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