N-methyl-3-ethynylcarbazole(NMEC) was synthesized by the reaction of n-BuLi with N-methyl-3-(2,2-dibromovinyl)carbazole which was obtained from the Wittig reaction of N-methyl-3-formylcarbazole.
The polymerization of N-methyl-3-ethynylcarbazole was attempted by $WCl_6$ and $MoCl_5$-based catalysts under various reaction conditions. It was also attempted by Ziegler-Natta catalysts. The polymer yield and inherent viscosity were found to be dependent on the polymerization time. The catalytic activity of $WCl_6$ was greater than that of $MoCl_5$. In the polymerization of N-methyl-3-ethynylcarbazoel by Ziegler-Natta catalysts, it was found that the activity of catalysts containing $Ti(OBu)_4$ was very low.
The structure of obtained polymer was identified by IR, $^1H$-NMR spectroscopy. The infrared spectrum of poly(NMEC) showed characteristic absorption bands at $3080cm^{-1}(\nu=C-H)$ and $1620cm^{-1}(\nuC=C)$. In the $^1H$-NMR spectrum, an aliphatic proton peak of N-$CH_3$ appeared at around 3.8ppm, and the proton on conjugated chain and aromatic proton of carbazole at 5.8-8.2ppm. And also, this polymer showed a broad, weak π→$\phi^＊$ absorption appeared in the range of 300-500nm, the feature of conjugated polymer.
From these results, it is concluded that the polymer involves a linear conjugated polyene structure containing carbazolyl substituent. TGA exhibited that poly(NMEC) retained 90% of its original weight at 375-395℃.
단량체인 N-메틸-3-에티닐카르바졸은 N-메틸-3-포오밀카르바졸의 Wittig 반응에 의해 생성된 N-메틸-3-(2,2-디브로모비닐 )카르바졸과 n-부틸리튬의 반응에 의해서 합성되었다.
N-메틸-3-에티닐카르바졸의 중합은 $WCl_6$와 $MoCl_5$-계 촉매를 사용하여 여러가지 중합조건하에서 시도되었고 또한 Ziegler - Natta 촉매를 사용하여 시도되었다. 고분자 수율과 고유점도는 중합시간에 강한 의존성을 보였다. $WCl_6$-계 촉매의 활성도는 $MoCl_5$-계 촉매의 그것보다 더 좋은 것으로 나타냈다.
Ziegler-Natta촉매를 사용한 중합에 있어서 $Ti(OBu)_4$를 포함하는 촉매의 활성도는 매우 낮은 것으로 나타났다.
합성한 고분자의 구조는 $^1H$-NMR, IR스펙트럼에 의해 확인하였다.
IR스펙트럼에서 $3080cm^{-1}$ 에서 비닐 =C-H신축흡수띠가 $1620cm^{-1}$에서 C=C 신축흡수띠가 관측되었고, $^1H$-NMR스펙트럼에서 3.8 ppm 근처에서 $N-CH_3$의 proton피크와 5.8∼8.2 ppm 사이에서 공액구조를 갖는 주사슬의 proton피크와 카르바졸의 proton피크가 관측되었다. 또한 이 고분자는 공액구조를 갖는 고분자의 특징인 300∼ 500nm 범위에서 넓고 약한 π→$\pi^＊$ 에 해당하는 스펙트럼이 관찰되었다.
열중량분석에서 이 고분자는 10% 무게감소가 375∼395℃에서 일어남을 볼 수 있었다.
