聚亞醯胺/苯取代矽石混成奈米材料的製備和特性研究

Abstract

本論文主要研究分為三部份: (1)低介電聚亞醯胺/苯取代矽石混成奈米材料製備及特性；(2)聚亞醯胺/苯取代矽石混成材料之動態機械性質；(3)聚亞醯胺/苯取代矽石混成材料之高溫生命期。本文研究利用溶膠-凝膠技術之自催化水解/縮合反應，製備聚亞醯胺/苯取代矽石奈米混成材料。混合二胺4,4′-Diaminodiphenyl ether (ODA) 與二酸酐3,3′-Oxydiphtalic anhydride (ODPA)，同時利用單官能胺基結構之p-Aminophenyltrimethoxysilane (APTS) 為末端官能基，控制聚亞醯胺ODA-ODPA分子鏈長為3000〜20000 g/mole之APTS-PAA寡聚合體溶液。並且導入phenyltrimethoxysilane (PTS) 至APTS-PAA溶液中形成PAA-PTS寡聚合體。兩寡聚合體經自催化水解/縮合反應後，獲得以線性網目PI及節點苯取代矽石(PSSQ-like)交聯之三度網狀空間結構的X-PIS和X-PIS-y-PTS (PI/PSSQ-like) 混成材料。本文將著重於苯取代矽石的組成及含量、網目PI分子鏈長、網狀交聯密度等對PI/PSSQ-like混成材料之組織形態、介電性、吸濕性、光學透明度、熱膨脹係數、耐熱性、動態機械性質與其高溫生命期 (可靠度) 做一系列完整的探討。 首先研究低介電聚亞醯胺/苯取代矽石奈米混成材料，在不額外添加水及酸或鹼催化劑之下可合成奈米級混成材料。在80 ℃下純PI可溶於有機溶劑而PI/PSSQ-like則不可溶。利用穿透式電子顯微鏡及掃描式電子顯微鏡可觀看PSSQ-like相域，微小且均勻的分散於混成膜中，並且在PTS含量相當高的混成薄膜中依然維持優異的光學透明度。熱重分析儀和微差掃描熱分析儀得知系列的PI/PSSQ-like混成薄膜皆比純ODA-ODPA有較高的熱分解溫度及玻璃轉移溫度。一系列的X-PIS混成薄膜，在低於玻璃轉移溫度之下，其熱膨脹係數隨APTS含量增加 (網目PI分子鏈縮短) 而減小；然而在X-PIS-y-PTS系列混成膜則隨PTS含量的增加而輕微增加。值得注意的是，在高於玻璃轉移溫度時，X-PIS和X-PIS-24-PTS之高溫熱膨脹係數比純PI低很多。在介電常數、密度和吸水率方面， X-PIS-y-PTS系列隨PTS含量增加而下降，在系列研究中，5000-PIS-140-PTS和10000-PIS-100-PTS有最低的介電常數，分別為2.79及2.85，歸因於混成膜的自由體積上升和吸水率下降之故。 本文第二部份主要研究PI/PSSQ-like混成薄膜之動態機械性質。在X-PIS系列混成薄膜中，縮短網目PI分子鏈長，則增加儲存模數、拉伸模數、和玻璃轉移溫度，而減低α-relaxation 的波峰強度和延伸率。當分子鏈長為10000 g/mole時具最大的α-transition 活化能。在X-PIS-y-PTS 系列混成薄膜中，當網目PI分子鏈長固定時，則儲存模數、拉伸模數、玻璃轉移溫度、α-relaxation波峰強度和α-transition 活化能隨PTS添加量的增加而減少。 論文的第三部份重點為PI/PSSQ-like混成薄膜高溫時之生命期其性能可靠度的研究。由熱重量分析之分解動力及動態機械分析之動態機械緩和顯示PI/PSSQ-like混成薄膜在熱性質及機械特性方面皆比純ODA-ODPA聚亞醯胺有更長的生命期。換言之，也就是具有更高的可靠性。在TGA熱分解動力方面，PI/PSSQ-like混成薄膜僅僅添加2 % APTS，而使用生命期就比純PI高出四倍之多。在動態機械緩和研究方面，依據時間-溫度重疊理論，其所得Tg附近之數據皆可最適化而得單一且平滑的主曲線，並且可導出WLF (Williams-Landel-Ferry) 方程式。在X-PIS混成薄膜系列中，縮短網目PI分子鏈長，則增加分解活化能、使用生命期 (TGA和DMA) 和緩和模數。有趣的是當參考溫度為 280 ℃、頻率 > 102 rad/sec時，10000-PIS-100-PTS混成薄膜其動態機械緩和模數將低於10000-PIS混成薄膜；但是當頻率 < 102 rad/sec時，則10000-PIS-100-PTS混成薄膜之緩和模數則大於10000-PIS混成薄膜。同理，對於緩和時間(相當於使用生命期)方面，若兩系列薄膜皆響應至5 ×10 8 Pa (接近玻璃態)緩和模數時，則前者低於後者；然而響應至5 ×10 7 Pa (接近橡膠態) 則後者的緩和時間將高於前者。

Synthesis of low dielectric polyimide/poly(silsesquioxane)-like (PI/PSSQ-like) hybrid nanocomposite material and their dynamic mechanical properties and high temperature lifetime were described in this thesis. The APTS-PAA oligomers were prepared by the reaction of 4,4′-Diaminodiphenyl ether (ODA) and the 3,3′-Oxydiphthalic anhydride (ODPA) in the presence of p-Aminophenyltrimethoxysilane (APTS). APTS controls the polyimide block chain length (X) ranging from 3000 to 20000 g mole-1 and end-group functionality. The PAA-PTS oligomers were prepared by phenyltrialkoxysilane (PTS) and APTS-PAA. The X-PIS and X-PIS-y-PTS (PI/PSSQ-like) hybrid films were obtained by self-catalyzed hydrosis/condensation the APTS-PAA and PAA-PTS, which are designed to form three-dimensional structure with linear polyimide block and crosslinked PSSQ-like structure. In this article, we intend to correlate the properties with the silica component, the PSSQ-like content, the polyimide block chain length and the crosslinking density. The influence of composition of the PI/PSSQ-like on their morphology, thermal stability, phase transitions, dielectric constants, thermal expansion coefficient, moisture absorption, optical transparency in visible, dynamic mechanical properties and high temperature lifetime. In the first part of this thesis, the PSSQ-like nanocomposite domain sizes with uniform size are fairly well separated in the hybrid films by transmission electron microscope (TEM) and scanning electron microscope (SEM). Moreover, the PI/PSSQ-like hybrid films have excellent transparency even under high PTS content. The lowest dielectric constants of the nanocomposite in the series of 5000-PIS-140-PTS and 10000-PIS-100-PTS are 2.79 and 2.85 respectively. The PI/PSSQ-like hybrid films have higher onset decomposition temperature and char yield in thermogravimetric analysis (TGA) and higher Tg in differential scanning calorimeter (DSC) than the pure PI. In the series of X-PIS hybrid films, the coefficient of thermal expansion below Tg decreases with the APTS content, and in the series of X-PIS-y-PTS films, it slightly increases with the PTS content. However, above Tg the coefficient of thermal expansion of X-PIS and X-PIS-24-PTS is much lower than that of the pure PI. The dielectric constant, density and water absorption of X-PIS-y-PTS films decrease with the PTS content because of the higher free volume and hydrophobicity. The second part of this thesis describes dynamic mechanical properties of PI/PSSQ-like hybrid films. In the series of X-PIS hybrid films, decreasing the PI block chain length enhances the storage modulus, tensile modulus and Tg, but reduces the α-relaxation damping peak intensity and elongation. The activation energy of the α-transition depends on the chain length of the PI block. A maximum value is shown at the chain length of 10000 g/mole. In the series of X-PIS-y-PTS films with a constant PI block length, the storage modulus, tensile modulus, Tg, α-relaxation damping peak intensity and activation energy decreases with the PTS content. The third parts of this thesis focus on high temperature lifetime of PI/PSSQ-like hybrid films. Decomposition kinetics in thermogravimetric analysis (TGA) and dynamic mechanical relaxation in dynamic mechanical analysis (DMA) reveal that the PI/PSSQ-like hybrid films have longer lifetime (more reliable) in the thermal and mechanical characteristics than the pure PI. Even just 2 wt % of APTS in the PI/PSSQ-like hybrid film can significantly promote the service lifetime as much as at least four times in TGA decomposition kinetic study. The dynamical relaxation data are well fitted to the calculated WLF (Williams-Landel-Ferry) master curves. In the series of X-PIS hybrid films, decreasing the PI block chain length increases the decomposition activation energy, service lifetime (in both TGA and DMA), and relaxation modulus. In the series of X-PIS-y-PTS hybrid films, the decomposition activation energy and lifetime (in TGA) increase with the PTS content. Interestingly, the dynamic mechanical relaxation modulus of 10000-PIS-100-PTS film is lower than that of the corresponding 10000-PIS film at frequency > 102 rad/sec, but higher at frequency < 102 rad/sec. The former has a lower relaxation time than the latter at the modulus 5 ×108 Pa, but the relaxation time of the former becomes higher at 5 ×107 Pa.