奈米碳管/聚(氮-異丙基丙烯醯胺)複合薄膜及纖維之製備，性質與形態分析

Abstract

本研究是利用旋轉塗佈及靜電紡絲方法製備奈米碳管/聚(氮-異丙基丙烯醯胺)之複合薄膜與纖維，並分析其形態與性質。藉由此複合材料中奈米碳管的導電性質與聚(氮-異丙基丙烯醯胺)對於溫度的感應性質，成功製備出在高溼度環境下具有溫度感應性質之導電複合材料。 首先利用硫酸與硝酸的混合溶液改質多層奈米碳管，使其表面接上羧基、羥基等基團，增加在水中的分散性，並利用拉曼光譜儀與化學分析影像能譜儀，選定適合的酸化條件。然後將改質後的多層奈米碳管與在室溫下合成之氮-異丙基丙烯醯胺與丙烯酸、氮-羥甲基丙烯醯胺的共聚物進行混摻，利用微分掃瞄熱分析儀量測溶液之體積相轉移溫度，討論分子間作用力對於溫感性質的影響。 接著將混摻溶液以靜電紡絲的方式製作複合奈米纖維，以掃瞄式電子顯微鏡探討靜電紡絲的溶液組成及操作條件對於纖維之形態影響。在穩定的操作條件下所製備出的奈米纖維直徑約為400~500奈米；利用穿透式電子顯微鏡觀察複合奈米纖維中之奈米碳管的分布情形。其結果顯示，多層奈米碳管會分佈在複合奈米纖維之中，並且沿著纖維之軸向排列。此外，藉由氮-羥甲基丙烯醯胺的熱可交聯特性，能夠使複合材料在交聯後的耐水性能與形態產生變化。 最後的部分是複合薄膜及纖維在不同溫溼度環境下的電學性質研究。將複合薄膜及纖維放置在以恆溫恆溼烘箱設定的平衡環境下，經由升溫或降溫過程進行材料表面電阻的動態測試，討論溫度感應性對電阻的影響。

In this research, multi-walled carbon nanotube/poly(N-isopropylacrylamide) (poly(NIPAAm)) composite films and fibers were prepared via spin coating and electrospinning, respectively. Because of the thermosensitivity of poly(NIPAAm), the electrical conductivity properties of the composites depend on temperature and humidity. First, sulfuric acid and nitric acid were used to modify multi-walled carbon nanotube (MWCNT) in order to disperse MWCNT better within the matrix. Dimension Raman system and electron spectroscopy for chemical analysis system (ESCA) were used to analyze modified MWCNT for choosing appropriate reaction condition. The effects of molecular interactions on volume phase transition temperature were discussed by differential scanning calorimeter (DSC). Second, the morphology of electrospun nanofibers with difference polymer concentration and electrospinning parameters were characterized by field-emission scanning electron microscope (SEM). It was found that MWCNTs were embedded in nanofibers and mostly aligned along the fiber axis observed by transmitting electron microscope (TEM). In addition, the thermal crosslinking of N-methylolacrylamide (NMA) segments provided the ability of confining the morphology of nanofibers, which prevented the composite from dissolving in water. Finally, electrical properties of the composite films and fibers were measured at different temperatures and relative humidity. The relationship between surface electrical resistance and temperature in dynamic process was studied.