含DEH-PPV結構之剛-柔團聯共聚高分子的合成與自組裝之研究

Abstract

具有導電鏈段的剛-柔團聯共聚物受到廣泛的研究是由於他們具有極大的潛力可用於光電元件應用。例如，有機發光二極體，薄膜電晶體和光伏打電池。為了將這些元件的效率最佳化，將材料形態控制在10奈米的尺度下就變得極為重要。此論文中，我利用速配接合反應來合成製備DEH-PPV-b-PMMA和DEH-PPV-b-PLLA。由於此反應的高轉化率，此方法也被利用於合成具有尾端官能基的PMMA。DEH-PPV-b-PMMA和DEH-PPV-b-PLLA的自組裝行為在此論文中也被詳細的研究。 我們已合成出一系列不同組成且分子量分布(PDI)皆小於1.1的DEH-PPV-b-PMMA團聯共聚物。首先，利用Siegrist 聚縮合反應製備DEH-PPV，再將其尾端官能基轉換成炔屬烴，然後利用陰離子聚合法製備PMMA，再將其尾端官能基轉成疊氮。最後進行速配接合反應，將兩段DEH-PPV及PMMA聚合物連接起來形成剛-柔團聯共聚物。核磁共振光譜儀和凝膠滲透層析儀的測定結果顯示，製備這些高分子的尾端官能基和團聯共聚物，都具有高達98%的產率。我們利用電子顯微鏡和小解度X光散射儀詳細的研究此團聯共聚物的結構和相轉換。比較於之前剛-軟團聯共聚物的研究，DEH-PPV-b-PMMA具有較強的相分離強度，但是在可研究的溫度範圍內，我們還是能夠進行相轉換的研究。因此，此團聯共聚物提供了一個新的見解，有關於硬鏈段之間作用力和硬-柔鏈段之間作用力的競爭性。當此團聯共聚物的PMMA軟鏈段體積分率小於54%，DEH-PPV硬鏈段會以單層方式且傾斜於層狀法向量的方式(smectic C)排列於層狀奈米結構中。然而，當軟鏈段的體積分率增加後，DEH-PPV硬鏈段會形成條狀，然後排列成六角柱狀堆積。相較於之前的研究，當相分離的強度增加時，可逆的液晶和相分離的相轉換順序改變。將低柔軟鏈段分率的團聯共聚物加熱，可觀察到一系列明顯的相轉換，從smectic-層狀到非晶-層狀再到無規則結構。加熱高柔軟鏈段體積分率的團聯共聚物，則無法明顯地分辦相轉換是從smectic-六角柱狀到非晶-六角柱狀或者是smectic-六角柱狀到無規則結構。此外，規則與不規則轉換溫度(ODT)隨著PMMA含量的增加而緩慢的下降，smectic-to-isotropic (SI)相轉換溫度則保持不變。穩定的SI溫度顯示出硬鏈段之間的作用力很強，使得硬鏈段的液晶態能夠保持在奈米尺度的結構中，不受團聯共聚物中軟鏈段含量的影響。 我們合成出軟鏈段具有生物可分解和結晶性質且分子量分布小於1.2的DEH-PPV-b-PLLA剛-柔團聯共聚物，此共聚物具有大範圍的規則奈米結構。首先，利用Siegrist 聚縮合反應製備DEH-PPV和開環聚合法製備PLLA。最後進行速配接合反應，將兩段炔屬烴基尾端官能基的DEH-PPV及疊氮尾端官能基的PLLA聚合物連接起來形成剛-柔團聯共聚物。核磁共振光譜儀和凝膠滲透層析儀的測定結果顯示，製備這些高分子的尾端官能基和團聯共聚物，都具有高達98%的產率。我們利用電子顯微鏡和X光散射儀詳細的研究此團聯共聚物的結構。比較於DEH-PPV-b-PMMA的系統，DEH-PPV-b-PLLA在未受熱處理時，呈現較不規則的層狀結構，可能是PLLA的結晶行為造成DEH-PPV-b-PLLA這樣的自組裝行為。但是當DEH-PPV-b-PLLA和DEH-PPV-b-PMMA受完熱處後，兩種共聚物呈現相似的規則層裝結構。這樣的差異是由於PLLA的結晶行為對奈米結構的影響變小。 我們利用陰離子聚合法製備準確分子量，分子量分布小以及尾端接有溴官能基的PMMA，並且利用速配接合反應成功的轉換成各種不同的官能基，如羧基，氫氧基，甲基乙烯基，三甲基矽烷基和乙醚縮水甘油基。首先，利用疊氮官能基取代PMMA的溴尾端官能基，然後與各種具有炴屬烴的不同官能基(propiolic acid, propargyl alcohol, 2-methyl-1-buten-3-yne, propargyl trimethylsilane, and propargyl glycidylether)進行反應。利用核磁共振光譜儀，傅利葉變換紅外光譜儀和凝膠滲透層析儀在定性和定量的測定結果顯示，所有的反應都有得到需要的官能基，而且轉換率高達99%。 速配接合化學是一種非常有用的反應，而且我們可利用它來製備分子量準確和低分子量分佈的異量共聚物以及具有官能基的共聚物。由於軟鏈段結晶性質的影響，造成DEH-PPV-b-PMMA和DEH-PPV-b-PLLA其自組裝行為顯示不同的現象。

Rod-coil block copolymers consisted of semiconducting polymers have been extensively studied due to their great potential in optoelectronic applications such as organic light-emitting diodes, thin-film transistors, and photovoltaic cells. Control of the morphology in 10-nm length scale is extremely important for optimizing the efficiency of these devices. In this dissertation, the synthesis of DEH-PPV-b&not;-PMMA and DEH-PPV-b-PLLA by “click” chemistry is explored. The method has been expanded to the synthesis of high yield of end-functionalized PMMA. The self-assembly behaviors of DEH-PPV-b&not;-PMMA and DEH-PPV-b-PLLA are thoroughly investigated. A series of DEH-PPV-b-PMMA polymers with narrow polydispersity (PDI < 1.1) were synthesized using Siegrist polycondensation and anionic polymerizations followed by “click” chemistry. Alkyne-terminated DEH-PPV and azido-terminated PMMA were synthesized first, and then the two functionalized polymers underwent 1, 3-cycloaddition reaction to obtain copolymers. Both the conversion of the end-functionalization of the homopolymers and the yield of the “click” reaction were higher than 98% as determined by 1H NMR and GPC. TEM and SAXS studies reveal the details of copolymer morphology. The DEH-PPV-b-PMMA system presented here has higher block segregation strength than many previously studied rod-coil block copolymers yet still shows experimentally accessible phase transitions with respect to temperature. As a result, this molecule offers new insight into the competition between rod-rod and rod-coil interactions that occurs in the system. The DEH-PPV rods are organized as a monolayer that is inclined with the lamellar normal (smectic C) for the copolymers containing low volume fraction of PMMA coil (<54%). However, as the coil fraction increases, the strips containing DEH-PPV pack into hexagonal lattice. In contrast to previous work which demonstrated similar morphologies, the sequence of reversible liquid crystalline and microphase phase transitions is altered as a result of the increased block segregation. Upon heating the low coil fraction copolymers exhibit a series of clear transitions of smectic-lamellar to amorphous-lamellar to disordered structures. In high coil fraction copolymers, the transitions between smectic-hexagonal to amorphous-hexagonal and smectic-hexagonal to disorder structures could not be clearly differentiated. The order-to-disorder temperature (ODT) decreases slowly with increasing coil fraction while the smectic-to-isotropic transition (SI) temperature stays relatively unchanged. The steady SI temperature suggests that the strong rod-rod interaction keeps the liquid crystalline rod in the nanodomain structure regardless of the amount of coil segment in the copolymers. A rod-coil block copolymer, DEH-PPV-b-PLLA (PDI < 1.2) with biodegradable and crystalline coil segment, was synthesized using Siegrist polycondensation and ring-opening polymerization followed by “click” chemistry and exhibits the long-range ordered nanostructure. Alkyne-terminated DEH-PPV and azide-terminated PLLA were synthesized first, and then the two functionalized polymers underwent 1, 3-cycloaddition reaction to obtain copolymers. Both the conversion of the end-functionalization of the homopolymers and the yield of the “click” reaction were higher than 98% as determined by 1H NMR and GPC. TEM, SAXS, and WAXS studies reveal the details of the copolymer morphologies. Without annealing, DEH-PPV-b-PLLA exhibits less ordered lamellar nanostructure as compared with DEH-PPV-b-PMMA due to the crystalline characteristic of PLLA influences the self-assembled behavior of the DEH-PPV-b-PLLA. With annealing, DEH-PPV&not;-b-PLLA and DEH-PPV-b-PMMA exhibit similar ordered lamellar structure because the extent of the influence of PLLA crystalline characteristic is less. Well-defined poly(methyl methacrylate) (Mn = 3630 g mol-1, PDI = 1.06) with a primary benzylic bromide prepared using anionic polymerization was successfully transformed into diverse end-functionalities (ω-carboxyl, ω-hydroxy, ω-methyl-vinyl, ω-trimethylsilane, and ω-glycidyl-ether) via “click” reaction. The bromine end-terminated poly(methyl methacrylate) first was substituted by an azide function and sequentially was reacted with various functional alkynes (propiolic acid, propargyl alcohol, 2-methyl-1-buten-3-yne, propargyl trimethylsilane, and propargyl glycidylether). In all cases, 1H NMR, 13C NMR, FT-IR, and GPC measurements shows qualitative and quantitative transformation of the chain-end poly(methyl methacrylate) into the desired functionalities with high conversion (above 99%). The “click” chemistry is a very useful method to obtain well-defined copolymers and functionalized polymers. The differences of self-assembled behaviors between DEH-PPV-b-PMMA and DEH-PPV-b-PLLA are due to the crystalline characteristic of PLLA.