以聚醯亞胺及聚苯胺為基材之高分子奈米複合材料之合成及性質研究

Abstract

本研究的主軸在於使用不同的奈米添加劑於聚醯亞胺及聚苯胺之中，使其形成奈米高分子複合材料，研究奈米添加劑對於整體高分子複合材料特性的影響。我們針對熱性質、結構、機械性、電性等進行探討。

本研究主要的實驗有三個部份；第一是奈米Silica添加於PI（Polyimide）的影響，以及Silica表面以不同的含氟單體改質後所產生的效應進行研究。第二部份是以多層奈米碳管（MWNTs）添加於PI的影響。第三部份是以不同粒徑的奈米TiO2添加於PANI（Polyaniline）的影響進行研究與探討。

對於PI中添加SiO2 奈米，一系列含氟的PI- SiO2 奈米複合材料已合成。藉由nano- SiO2及含氟單體6FBPA對於SiO2的表面改質，PI薄膜的介電常數明顯降低，可達2.55。含氟的6FBPA單體，可提供均勻分佈的PI- SiO2薄膜。但添加含氟BISAF單體並未有明顯改善。藉實驗證明，經氟化表面改質的SiO2若能均勻分佈於PI時，將會增加其不純度及接觸界面，因而造成自由體積增加，如此可使介電常數明顯下降。

PI中添加奈米碳管，PI/MWNTs 奈米複合材料成功地以簡單的聚合製程備製完成。經酸化處理的MWNTs 加入PI系統中，其熱性質、機械性質及電性都獲得改善。在室溫下，添加15wt%的MWNTs 其儲存模數（storage modulus）達28.457 GPa 約為純PI 9倍的儲存模數，而添加7wt% 的MWNTs其抗拉強度約為純PI兩倍的抗拉強度。當MWNTs添加到10 wt%時，將達到percolation threshold 使其由絕緣體變成導體。

一系列的PANI/TiO2 奈米高分子複合材料之合成及備製已完成。由XRD 及TEM的分析結果，TiO2已成功地混合於PANI之中。由SEM的照片中可以看出TiO2的粒徑大小對於合成的外觀有決定性的影響。在1~5wt%TiO2的添加量下，介電常數及介電損失都隨著TiO2 的增加而增加，導電度也隨著TiO2 （1~5wt%）的增加而增加。實驗證明P-25的奈米TiO2粒子有較均勻的分散，也因著P-25的奈米TiO2粒子均勻的分散，使其PANI/TiO2 奈米高分子複合材料在鹼化的條件下，增加其導電性、介電系數及介電損失。導電性的增加主要是因為TiO2粒子均勻的分散，形成一個有利於電荷移動的傳輸網絡。

The major study of this thesis is adding different nano particle in Polyimide and Polyaniline to be nanocomposites. The effect of the nano particle in Polymer was carried out. We study on the nanocomposites thermal property、mechanical property、electric property etc.

This study was divided into three parts, it includes （1）nano-silica adding into Polyimide and the silica modify with different fluorine-modified ,（2）MWNTs adding into Polyimide and （3）two type nano TiO2 adding into PANI.

A series of PI-silica nanocomposites was synthesized by mixing and polymerizing the novel fluorine-modified silica nano particles into the PI matrix. By using the silica or the 6FBPA-modified silica nano particles, dielectric constants of PI films are greatly reduced. The modifier 6FBPA provides dual functions in the formation of uniform PI-SiO2 nanocomposites. The modifier BISAF possesses higher content of fluorine than that of 6FBPA but does not significantly affect the dielectric constant due to the flocculation of silica. It is believed that the free volume originated from the imperfection of the interface between PI and silica, when distributes uniformly, has significant contribution to the reduction of dielectric constants.

Polyimide-MWNT nanocomposites were successfully prepared via a simple in-situ polymerization process. The addition of acid-modified MWNTs into a polyimide matrix led to obvious improvements in the thermal, mechanical and dielectric properties. For the nanocomposites containing 15 wt% MWNTs, the storage modulus reaches 28.457 GPa, about 9 times of pristine polyimide at room temperature. The tensile strength of the PI-7 wt% MWNT nanocomposite is almost double that of pristine PI. The PI polymer also gradually changes to a conductive system from an insulator at an identified percolation threshold at around 10 wt% MWNTs.

A series of polyaniline-TiO2 nanocomposite materials were prepared using an in-situ polymerization process. From the characterization of SEM, TEM and X-ray diffraction, it was identified that the fine TiO2 colloids (Hombikat) form a relatively non-uniform distribution in the PANI matrix, while P25 is more uniformly distributed. Dielectric characterization demonstrated that TiO2 nanoparticles exhibit a strong effect on the dielectric properties of resultant PANI-TiO2 nanocomposites. The uniform packing of P25 TiO2 results an enhanced conductivity of the base form of the polyaniline film and thus enhances dielectric constants and losses. The increased conductivity is attributed to the formation of a better charge transport network in the relatively insulating polyaniline matrix.