硬桿/柔曲嵌段共聚高分子之陰離子合成，自組裝行為與超分子結構研究

Abstract

由於共軛高分子具有導電特性且可應用於製作低成本、大範圍塗佈及可撓曲的光學元件，因此近年來受到廣泛的研究。又當導電一端接上另一柔曲鏈段後，由於兩鏈段互不相容的結果，因此形成微觀相分離的奈米結構有助於元件效能的提升，且以柔曲高分子加以改質後對共軛型導電高分子而言在其機械及光電性質皆可有所提升。然而與傳統的柔曲型團聯共聚高分子相比，由於共軛高分子具有液晶特性以及π-π作用力的影響下，共軛硬桿-柔曲團聯共聚高分子在分析其微觀相行為時相較之下顯得複雜許多。因此，本論文希望藉由合成新潁的雙團聯共軛硬桿-柔曲型以及三團聯共軛硬桿-柔曲-柔曲型嵌段共聚高分子進行實驗分析進而與理論作相互的映證來探討含共軛硬桿的團聯高分子對相形態的影響。 首先，我以巨分子偶合法將導電共軛高分子PPV接上具有陰離子活性且不同分子量的柔曲型高分子P2VP來形成一系列不同體積分率之PPV-P2VP雙團聯共軛硬桿-柔曲型共聚高分子。接著，藉由電子顯微鏡、小角度及廣角度X光散射實驗來進行微觀相形態的分析。結果發現，隨著柔曲鏈段體積分率的增加，樣品中的奈米結構由大範圍的層板分佈破碎成小區塊的層板進而演變成長桿型、短桿型柱狀的六角堆疊，最後在含極大柔曲鏈段體積分率的樣品中可發現如小立方體般聚集的PPV區塊。接著，將具有層板結構之樣品的小角度散射數據進行摺合積分發現除了含極小柔曲鏈段體積分率的樣品外，PPV鏈段排列在層板中所形成的厚度隨著柔曲鏈段體積分率增加時仍然保持不變，且小於PPV自身長度，因此研判PPV鏈段排列在層狀區域時具有傾斜角。再進一步藉由簡單的幾何分析，我發現當PPV鏈段排列為單層時所造成的傾斜角為32度相當於主鏈間一個重複單元的位移，因此與雙層排列時所造成非整數個重複單元位移相比整體能量較為穩定，所以研判PPV-P2VP在柔曲鏈段體積分率為0.3~0.7時的層狀結構為具傾斜角的硬桿單層堆疊層板。最後，由於硬桿-柔曲分子鏈間的互斥力及硬桿間的π-π作用力皆為溫度相關函數，因此我將樣品加熱進行小角度及廣角度X光同步散設實驗來觀察這兩個作用力間的競爭，並由實驗結果製作PPV-P2VP體積分率對溫度變化的相圖。 接著，我將PPV-P2VP與界面活性劑十二烷基苯磺酸(dodecylbenzesulfonic acid，DBSA)形成錯合物，藉由P2VP與DBSA自我組裝形成硬桿型-梳狀(rod-comb)結構，進而產生兩種不同尺度的微觀相分離，其中較大尺寸的結構是由於PPV-P2VP(DBSA)不互容而形成，而較小尺寸的微結構則為P2VP鏈段與DBSA所形成之梳狀超分子結構，由於此兩種不同尺寸的結構的共存進而形成了階級性結構(hierarchical structure)。 接著，我再以巨分子偶合法將導電共軛高分子PPV接上具有陰離子活性且不同體積分率組成的雙柔曲型高分子PS-P2VP來合成分別以PPV、P2VP及PS作為主要組成之PPV-P2VP-PS三團聯共軛硬桿-柔曲-柔曲型共聚高分子。我發現以PPV為主要組成的三團聯共軛硬桿-柔曲-柔曲型共聚高分子其前驅物PS-P2VP由於其聚合度過小，因此無法形成微觀相分離。然而將其接上共軛硬桿型PPV形成三團聯共聚高分子後，藉由小角度X光散射實驗發現其在空間中形成層板結構，並透過染色技術再由電子顯微鏡下觀察此層板結構由PPV、P2VP及PS三相分離所形成，再由其小角度散射數據進行一維電子分佈圖的轉換可發現PPV分子鏈在空間中的堆疊與其在PPV-P2VP時的形形相仿，皆呈現一個單層排列且具約32度傾斜角之層板堆疊。而在以P2VP及PS為主要組成的三團聯共軛硬桿-柔曲-柔曲型共聚高分子中我發現雖然共軛硬桿型PPV只佔整體體積分率約百分之18，但整體結構卻可明顯觀察到仍為一三相分離之破碎層板結構。由此三種樣品看來，共軛硬桿型PPV的π-π作用力對為層板微結構的形成有絕對性的影響力，研判是由於PPV堆疊限制了PS-P2VP鏈段的活動能力，因而造成其亂度的減少，為了達到整體能量穩定，因而PS-P2VP也形成層板這種接觸面積最小的結構來達成此效果。同時我也對所有種品加熱進行小角度及廣角度X光同步散射實驗，發現當PPV的π-π作用力消失後樣品中的層板結構也隨之崩解，更證實了PPV的π-π作用力在形成微結構的過程中所具有的主導性。且在以PPV為主要組成的三團聯共軛硬桿-柔曲-柔曲型共聚高分子的加熱實驗中還發現在接近其有序-無序相轉換溫度時，由於PS與P2VP分子鏈有互容的趨勢，因此可觀察到原本三層相分離的層板結構轉換成雙層相分離層板結構。 最後，有別於上述兩個章節對含共軛硬桿型共聚高分子的相型態探討，我進行了一個以混四氯金酸及雙柔曲團聯共聚高分子PS-P2VP的實驗，並可發現隨著四氯金酸添加量的增加，P2VP分子鏈的型態也由柔曲型態進而演變成類似於一硬桿型高分子。本實驗所設計的雙柔曲團聯共聚高分子PS-P2VP具有極不對稱的體積分率組成，其中，可吸附四氯金酸的P2VP鏈段之體積分率為0.1。由電子顯微鏡及小角度X光散射可發現，隨著四氯金酸的增加，分子鏈在空間形成的微結構由球體體心堆積演變成六角柱狀排列，接著再形成極不對稱的層板結構，最後再形成六角蜂巢狀排列。我發現這些相轉換皆可在微量的四氯金酸添加下而進行，由小角度及廣角度X光散射實驗研判，當P2VP鏈段吸附上四氯金酸後，有別於對P4VP分子間交聯的效果，四氯金酸對P2VP分子鏈則是具有單一分子鏈內交聯的作用，因此隨著添加量的增加，P2VP有一鏈延展的趨勢。同時，PS與P2VP兩鏈段間分子鏈的型態由原本的柔曲-柔曲型趨向於柔曲-硬桿型共聚物的形式，進而使得有序-有序相轉換的體積分率往硬桿型高分子端靠近造成此實驗提早相轉換的因素。

Rcently, π-conjugated rigid-rod polymers with semiconducting properties have gained great interests since they possess unique optoelectronic properties with potential for use as an active component in large-area, flexible, and low-cost optoelectric devices. Over the last decade, diblock copolymers with one block consisting of the π-conjugated polymer chain and the other block of a flexible random coil-like chain have received a great deal of attention since they offer a new strategy to create nanometer-scale morphology for the organization of many conjugated polymers, thus providing synergistic improvements in their mechanical and optoelectronic properties. Compared with coil-coil diblock copolymer systems, the self-assembly behavior of a rod-coil system is further complicated due to the presence of the anisotropic interaction between the rod blocks. First, in Chapter 2, a series of PPV-P2VP rod-coil block copolymers with different block ratios was synthesized by using an end-coupling reaction between an aldehyde-terminated PPV of a fixed contour length with different molecular weigh P2VP living anions. The microphase-separated morphology of these block copolymers varies from lamellar, to broken lamellar, to strip-like, and to puck-like phase as the coil volume fraction, f, increases. Through the evolution of SAXS and WAXS patterns as a function of temperature, the detailed phase diagram of the system was then established. In Chapter 3, I studied the supramolecular rod-comb block copolymers formed by complexation of an amphiiphlic surfactant, dodecylbenzesulfonic acid (DBSA), with the P2VP blocks in PPV-P2VP rod-coil block copolymers. Hierarchical structure was exhibited in rod-comb complexes, where PPV blocks are microphase-separated from the P2VP(DBSA)X blocks and the small-scale mesophase organized by the P2VP(DBSA)X comb blocks In Chapter 4, a series of novel π-conjugated rod-coil-coil triblock copolymers of PPV-PVP-PSs was synthesized and their self-assembly behavior was explored. Three different triblock copolymers of PPV-PVP-PS1, PPV-PVP-PS2, and PPV-PVP-PS3, each with PPV, PS, and PVP, respectively in the copolymers as the major species, were used to study the effects of copolymer composition and the rod-rod interaction between PPV blocks on their morphology. Simultaneous SAXS and WAXS measurements show that all three triblock copolymers undergo the ordered lamella-to-disorder transition and the smectic/isotropic transition at the same temperature, indicating that the rod-rod interaction between PPV rods plays a critical role in forming and stabilizing these lamellar structures. The observation of the phase transformations is in good agreement with a recent mean-field prediction of a rod-coil-coil triblock copolymer system. In Chapter 5, I study the self-assembly of a hybrid system by the stoichiometric complexation of hydrogen tetrachloroaurate trihydrate (HAuCl4) with a compositinally coil-coil PS-P2VP block copolymer. A series of morphological transformations were observed from an originally body-centered cubic spherical structure of neat PS-P2VP to hexagonally packed cylinders, to the lamella, to inverted honeycomb-like cylinders, and eventually to disordered phase with increasing amount of HAuCl4 incorporated with P2VP chains. The intrachain-to-interchain intercalation of HAuCl4 to the P2VP domain was observed below and above the saturation Au/N loading ratio of 0.83/1, as evidenced by SAXS, WAXS, and the analysis of 1-D correlation function. In addition, the increasing amount of HAuCl4 would cause a rod-like chain conformation for P2VP chains. Consequently, the conformational asymmetry between PS and HAuCl4-incorporated P2VP chain leaded the order-order transitions (OOTs) to move towards a lower total P2VP/HAuCl4 volume fraction, elucidating the interesting phase behavior in this hybrid system that all phase transformations occurred when only a small amount of HAuCl4 was needed for phase transformation compared with the volume fraction.