(I) 低介電常數聚倍半矽氧烷材料及其奈米孔洞衍生物 (II) 新穎環境應答高分子及在檢測DNA及鋅金屬分子上的應用

Abstract

本論文的第一部份研究聚倍半矽氧烷材料的結構變化及其奈米孔洞衍生物的製備及性質分析。聚倍半矽氧烷材料及其奈米孔洞衍生物逐漸成為積體電路製程中新一代的低介電常數材料。然而在烘烤過程中﹐文獻並未對於其結構和性質的關係著墨許多﹐並且在以雙親性共聚高分子控制其奈米孔洞形態的研究上仍有許多值得探討的地方。在此﹐吾人針對攝氏 240 到 340 度聚氫基倍半矽氧烷之間的烘烤過程進行研究﹐並利用poly(styrene-b-2-vinylpyridine)共聚高分子作為模板材料來製備聚甲基倍半矽氧烷的奈米孔洞衍生物。利用活性陰離子聚合法製備可控制分子量、分子量散布及結構形態的共聚高分子。本研究試圖建立以共聚高分子控制奈米孔洞形態及衍生物薄膜性質的基礎方法。

針對聚氫倍半矽氧烷在攝氏240到340 度的熱處理製程下﹐其結構會從籠狀逐漸交聯成為網狀結構﹐此反應可用兩階段零級反應來描述之。實驗顯示出第一階段的反應常數遠大於第二階段﹐這是由於第二階段的熱交聯程度已經影響到分子結構的運動導致頻率因子大幅降低。研究顯示熱處理導致的結構變化會顯著影響聚倍半矽氧烷材料的性質。

在製備聚倍半矽氧烷材料奈米孔洞衍生物方面﹐以活性陰離子聚合法來製備雙親性嵌段共聚物poly(styrene-b-2-vinylpyridnine) (PS-b-P2VP)，並將此嵌段共聚物分散於聚甲基倍半矽氧烷材料中，作為孔洞的雛形，最後以熱裂解的方式將有機高分子裂解而生成多孔隙材料。由實驗和理論分析得知﹐聚倍半矽氧烷預聚物和PS-b-P2VP之間的氫鍵作用力促成良好的混成材料﹐其微相分離可形成適當的球形奈米孔洞。當孔洞生成劑所加入的量為0% ~ 60%時，折射率與介電常數的變化各1.38~1.17為2.36~1.51。線性和星狀的 PS-b-P2VP 都可以形成適當分佈的球形奈米孔洞﹐但是 PS-b-P4VP 比較容易形成蟲狀聚集。這是由於甲基倍半矽氧烷預聚物在熱處理時﹐其性質會逐漸從親水性變成親油性﹐原本與甲基倍半矽氧烷預聚物親和性較大的PS-b-P4VP反而會感受到比PS-b-P4VP大的排斥力。此一排斥力導致聚甲基倍半矽氧烷和PS-b-P4VP容易出現蟲狀的相分離結構而非球形孔洞。本研究指出控制共聚高分子的組成和形態﹐及其氫鍵作用力可在聚倍半矽氧烷材料中製備出適當的奈米球形孔洞﹐以作為良好的低介電常數材料。

本論文的第二部份製備了多種環境響應型高分子﹐並研究其對於pH值、溶劑極性、溫度及鋅金屬離子、質體DNA的交互作用。利用水溶性、生物可相容性的poly(N-isopropylacrylamide)高分子作為載體﹐將可發出螢光的fluorene或hydroxyphenyl benzoxazole官能基接在poly(N-isopropylacrylamide)高分子側鏈。接有fluorene官能基的poly(N-isopropylacrylamide)高分子﹐其水溶液螢光性質會隨著pH值及溫度改變。將fluorene官能基四級胺化後帶有正離子﹐其水溶液螢光可以被水溶液中的質體DNA所熄滅﹐可以作為質體DNA的檢測劑。接有hydroxyphenyl benzoxazole官能基的poly(N-isopropylacrylamide)高分子﹐其水溶液螢光在鹼性條件下﹐或是與金屬鋅離子錯合時﹐破壞了原有的激發態內質子交換（ESIPT）行為﹐使得螢光強度升高可作為pH或鋅金屬的檢測劑。

對於hydroxyphenyl benzoxazole官能基的進一步研究﹐為了應用在雙光子螢光上﹐設計了四種高分子和四種小分子的結構以研究其金屬檢測和環境響應的作用﹐針對其pi鍵共軛長度及取代基位置進行探討。實驗結果說明具備適當的pi鍵共軛長度及取代基位置的分子結構﹐可以與金屬錯合而增加其溶液螢光強度。具備較長的pi鍵共軛長度的分子﹐其雙光子螢光也具備比較高的強度。經由適當設計的取代基位置﹐使得hydroxyphenyl benzoxazole可以作為具備金屬檢測能力的新穎雙光子染劑。

In the first part of this thesis, the structural transformation of poly(silsesquioxanes) materials and the preparation of their nanoporous derivatives were investigated. Poly(silsesquioxanes) and their nanoporous derivatives with dielectric constant (k) less than 2.0 have become a new class of low k materials for advanced integrated circuits (IC). However, the structure and properties of poly(silsesquioxanes) during curing have not been addressed yet and the control of pore morphology of nanoporous poly(silsesquioxanes) through the composition or architecture of the amphiphilic block copolymers (ABCs) requires further exploration to obtain materials with medium porosity and closed-cell nanopores. To achieve the above goal, the structures and properties of poly(silsesquioxanes) films produced by curing were studied in the temperature range of 2400 to 3400C and the templating approach of ABCs was investigated for preparing low k nanoporous film. The methyl silsesquioxane (MSSQ) precursor and poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) or poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) were used as the matrix and templating agent, respectively. The ABCs with controllable molecular weight, distribution and architecture were prepared by living anionic polymerization. The effects of various architectures, molecular structures and compositions were investigated. A methodology on controlling the pore structure and properties of nanoporous films by ABCs as templates was proposed in this study.

The experimental results of the hydrogen silsesquioxane (HSQ) curing show that the transformation of the cage structure to the network structure is the major reaction in the temperature range of 240 to 3400C. The cage/network transformation can be explained by two-stage zero order kinetics. The rate constant of the first stage is 10-35 times more than that of the second stage. The difference is probably because the network structure of the second stage limits the structural transformation and results in a small frequency factor. The porosity of the cured HSQ films increases rapidly with curing times in the first 10 minutes and then reaches at a steady value. The evolution of porosity is probably due to the outgassing of the reaction side-product (SiH4), the trapped solvent (4-methyl-pentan-2-one) or the cage/network transformation.

Low dielectric constant nanoporous poly(methyl silsesquioxane) (PMSSQ) was prepared through the templating of ABCs. The experimental and theoretical studies suggest that the intermolecular hydrogen bonding interaction is existed between the PMSSQ precursor and PS-b-P2VP. The miscible hybrid and the narrow thermal decomposition of the PS-b-P2VP lead to nanopores in the prepared films from the results of transmission electronic microscopy (TEM), atomic force microscopy (AFM), and small angle X-ray scattering (SAXS). The effects of the loading ratio and the PS block volume ratio (fPS) were investigated. The AFM and TEM studies suggest that the uniform pore morphology should be prepared from a modest porogen loading level for the optimum intermolecular hydrogen bonding. The refractive index and dielectric constant of the prepared nanoporous films could be tuned by the loading ratio in the range of 1.361–1.139 and 2.359–1.509, respectively. The linear and star-shaped PS-b-P2VP all gave a well-dispersive pore structures while the repulsive interaction between cured hydrophobic PMSSQ and PS-b-P4VP led to a worm-like morphology. This study demonstrates the control of the morphology and properties of the nanoporous films through the polymer structure. In the second part of this thesis, several environment-stimuli polymers were prepared and the pH, solvent polarity, temperature and zinc or DNA responsive UV-Vis and fluorescence spectral were characterized. The fluorescence-based sensoring materials are of importance for the visualization of target molecules in biological environments. Though many organic compounds of the fluorene- or benzoxazole-derivatives have been reported, nearly no paper reports the study of the environmental stimuli using the polymers containing the fluorene or benzoxazole. To achieve the above goal, the poly(N-isopropylacrylamide) copolymers containing the fluorene or benzoxazole moieties and several novel two-photon dye materials including polymers and small molecules were prepared and characterized. The effect of the pi-conjugation length and substitution position were investigated through the molecular design. The experimental results disclosed the fluorescence intensity of the target molecules could be enhanced due to the coordination with metal cations or in the basic condition. The interrupted ESIPT character of the HBO gave the possibility of metal sensoring. The longer pi-conjugation length led to a larger two-photon fluorescence and well-designed substitution position gave the character of hydroxyphenyl benzoxazoles which could be the candidate of novel two-photon dyes with metal sensoring ability.