團聯式共聚高分子在溶液相中自組裝之行為研究

Abstract

近年來,奈米材料被運用在許多領域之中，其中團聯式共聚高分子(diblock copolymer) 在固體與液體下具有相當良好的奈米階級性的自組裝行為之研究更受到許多矚目與探討。在液態的環境中，團聯式共聚高分子處於一選擇性溶劑，由於鏈段喜好溶劑的程度不同，自我組裝形成一微胞型態，此微胞的核心由不溶鏈段聚集形成並被可溶鏈段所圍繞著。從過去幾年來，已有許多AB型態的團聯是共聚高分子所自組成的微胞型態已被深入研究與探討。 本研究中，我們利用陰離子的方式合成出一系列具有狹窄的高分子分部特性的AB型態團聯式共聚高分子並加以研究此些高分子在液態中自組裝的型態與結構： (1) 在丙酮的環境中 本研究中，成功的合成出多種鏈段比的poly(vinyl phenol-b- styrene)團聯式共聚高分子，並探討濃度與高分子組成比例對高分子微胞型態的影響。在不同的濃度與高分子組成中，我們可以觀察到球型、柱狀以及泡囊狀型態的高分子微球結構。微球的結構變化除了深受高分子本身的鏈段比例、濃度以外之影響，更深受PVPh 鏈段自身氫鍵的影響。我們另以poly(4-tert-butoxystyrene-b-styrene)以及添加poly (4-vinyl pyridine)來探討氫鍵對結構的影響。 (2) 在共溶劑/選擇性溶劑的系統中 在四氫呋喃/甲苯(THF/toluene)的系統中， 隨著添加選擇性溶劑(甲苯)含量的增加，高分子微球型態會隨之由球型轉變為柱狀、泡囊狀，甚至轉變為洋蔥狀結構。當高分子初始溶液大幅提高到20 mg/mL時，隨這添加甲苯的比例不同，更出現許多令人驚奇的型態產生，如蜂窩狀高分子薄膜、針狀高分子微球等結構。然而此針狀高分子微球所形成的表面具有與水為158°的接觸角表現。 (3) 利用非共價健(氫鍵)錯合方式形成高分子微球 本篇利用PS(OH)與P4VP之間強大的氫鍵作用力與PS與PMMA之間的不相容的特性來進行團聯式共聚高分子液態自組裝的研究。首先，在四氫呋喃的環境中，PS-b-PS(OH)與PMMA-b-P4VP形成泡囊狀結構，其殼層為PS(OH)與P4VP鏈段錯合所組成。在二甲基甲醯胺(DMF)的環境中，形成 “patched”狀的微球結構，球的核心為PS(OH)與P4VP鏈段所組成，周圍則被PS與PMMA分區包圍著。 (4) Poly (vinyl phenol-b-4-vinyl pyridine) 本篇探討共聚高分子與聚摻高分子之間的差異。首先利用陰離子方式合成一系列的poly(vinyl phenol-b-4-vinyl pyridine) (PVPh-b-P4VP) 共聚高分子。利用IR得知PVPh與P4VP之間具有很強的氫鍵作用力。DSC得知團聯式共聚高分子的玻璃轉化溫度(Tg)皆比聚摻高分子系統來的高。並且團聯式共聚高分子的Tg皆與聚摻系統在甲醇中錯合的特性雷同。我們以固態NMR來證明其現象乃為在二甲基甲醯胺(DMF)環境中的團聯式共聚高分子有較小的 值，其代表的團聯式共聚高分子在DMF環境中所具有的分散鏈段較聚摻系統中高分子分散鏈來的少所故。

Block copolymers are the focus of intense research due to their ability to self-assemble into nanostructures with well-defined morphology and size. The self-assembly can either occur in the solid state (thin films, bulk) or in solution (micelles, lyotropic systems). Indeed, when a block copolymer is dissolved in a selective solvent, the insoluble (or less soluble) segments aggregate into dense micellar cores which are surrounded by coronas formed by the soluble blocks. The vast majority of block copolymer micelles has been constructed from AB diblock copolymers. In this thesis, we synthesized a series of AB diblock copolymers through anionic polymerization and investigated their self-assembled in the solution state: (1) In Aectone Solution We describe the synthesis and solution morphologies of poly(vinyl phenol-b- styrene) (PVPh-b-PS) micelles and the effects that changing the copolymer composition and concentration have on self-assembly structures of PVPh-b-PS in acetone (a good solvent for PVPh). These PVPh-b-PS copolymers aggregated into spherical, rod-like, and vesicular morphologies. The transformations of the PVPh-b-PS block copolymer micelles in acetone depended on a number of parameters, including the relative block lengths, their concentrations, and the degree of self-association through hydrogen bonding of the coronal PVPh chains. We also investigated the morphologies of the micelles formed from acetone solutions of poly(4-tert-butoxystyrene-b-styrene) (PtBOS-b-PS) copolymers having the same degree of polymerization as the precursor of PVPh-b-PS copolymer before hydrolysis reaction. Our results indicate that the micelles formed from PVPh-b-PS copolymers in acetone were more complicated than those prepared from PtBOS-b-PS copolymers in acetone because hydrogen bonding occurs in the micelle corona of the PVPh block (2) In the Mixture (Common Solvent/Selective Solvent) Solvent System In common/selective (THF/toluene) solutions, the PVPh-b-PS morphologies of resulting aggregates are greatly influenced by changing the selective toluene solvent content from core-shell spheres, rodlike micelles, large compound rod micelles, vesicles, to onion-like aggregates in 2 mg/mL THF solution. When the initial block copolymer concentration increases to 20 mg/mL, it also has various fascinated morphologies such as honeycomb-architectured film, large porous sphere aggregates surface and pincushion-like sphere with protruding tubular vesicles aggregates by changing toluene contents. We further demonstrate that these surface-patterned films have significantly enhanced hydrophobicity, owing to the existence of the surface morphologies and roughness. Here, we propose that the superhydrophobic behavior can be achieved, with the maximum contact angle, 158°, by using the pincushion-like micellar structure. (3) Complex formation in PS-b-PS(OH) and PMMA-b-P4VP Diblock Copolymer We describe a new approach to self-assembly by hydrogen bonding complexation leading to a vesicle and a patched spherical structure from two species of block copolymers in nonselective solvents. Firstly, we discussed the intermolecular complex vesicle by mixing PS-b-PS(OH) with PMMA-b-P4VP in THF solution, which is driven by strong hydrogen-bonded complexation between the complementary binding sites on PS(OH) and P4VP. However, we found the well-defined patched spherical micelles by blending PS-b-PS(OH) with PMMA-b-P4VP in DMF solution. The relative weaker hydrogen bonding strength between PS(OH) and P4VP blocks in DMF solution than in THF solution results in the formation of a dense inner micellar core and a compartmentalized corona consisting of PS and PMMA blocks. (4) Poly(vinyl phenol-b-4-vinyl pyridine) A series of poly(vinyl phenol-b-4-vinyl pyridine) (PVPh-b-P4VP) block copolymers were prepared through anionic polymerizations. Infrared spectrum analysis suggests that this block copolymer possesses strong hydrogen-bonding interaction between the hydroxyl group of PVPh and the pyridine group of P4VP. DSC analyses indicate that these PVPh-b-P4VP copolymers always have higher glass transition temperatures than the corresponding PVPh/P4VP miscible blends obtained from DMF solution. However, the thermal behavior of PVPh-b-P4VP diblock copolymer shows similar Tg value with PVPh/P4VP blend complex obtained from methanol solution at a 1:1 (PVPh:P4VP) molar ratio. We proposed that the polymer chain behavior of PVPh/P4VP blend from DMF solution is separated coils. Spin–lattice relaxation time in the rotating frame ( ) based on solid state NMR analysis is able to provide positive evidence that the polymer complex aggregate in the diblock copolymer has a shorter value than the separated coils in the miscible blend.