含聚(3-己烷基噻吩)及聚羥基苯乙烯之嵌段共聚高分子的合成、自組裝微結構及光學性質之研究

Abstract

我們利用耦合法耦合末端改質為醛基之P3HT與PHS的陰離子前驅物，以及後續的化學反應合成出一系列不同組成且具有兩親性的poly(3-hexylthiophene-b-hydroxystyrene) (P3HT-PHS)雙嵌段共聚高分子以及poly(hydroxystyrene-b-3-hexylthiophene-b-hydroxystyrene) (PHS-P3HT-PHS)三嵌段共聚高分子，並分析這些高分子之塊材及薄膜在不同熱處理條件下的微結構、結晶性及光學性質。 由於PHS鏈段之hydroxystyrene重複單元間因氫鍵而有強的作用力，並具有高於P3HT的Tg，對於嵌段共聚高分子在微相分離行為與P3HT之結晶性有很強的影響，使含有P3HT及PHS的嵌段共聚高分子與一般含有P3HT的剛-柔嵌段共聚高分子有非常不同的自組裝特性。 在許多常見的含有P3HT的剛-柔嵌段共聚高分子中，當柔鏈段的比例較小時，通常會自組裝形成纖維或層狀結構。但在P3HT-PHS雙嵌段共聚高分子中，由於PHS鏈段之間很強的氫鍵作用力，除了纖維與層狀結構之外，我們也觀察到圓柱結構。 將雙嵌段共聚高分子以旋轉塗佈法在玻璃基板上形成的薄膜在熱處理前具有整齊的纖維結構且對長波長的光有較強的吸收。然而可能由於PHS鏈段間有較強的作用力與物理交聯的效應而抑制了P3HT的堆疊，以致於不論在三嵌段共聚高分子的塊材或薄膜中，皆無法觀察到有序的微相分離。 在塊材當中，P3HT在(100)面的結晶性在熱處理後上升，但仍較純P3HT來的差。在薄膜當中，當熱處理溫度低於PHS的Tg時，P3HT的結晶性上升，但當處理溫度高於PHS的Tg時，P3HT的結晶性下降。可能是由於PHS之間強烈的作用力抑制了P3HT分子鏈間形成整齊的堆疊。 不論在塊材或薄膜中，由於PHS鏈段間的氫鍵作用力對微結構及P3HT結晶性有強烈的影響，因此比起三嵌段共聚高分子，雙嵌段共聚高分子可以形成較整齊的微結構，且其中之P3HT在(100)面有較好的結晶。

A series of amphiphilic poly(3-hexylthiophene-b-hydroxystyrene) (P3HT-PHS) diblock and poly(hydroxystyrene-b-3-hexylthiophene-b-hydroxystyrene) (PHS-P3HT-PHS) triblock copolymers with various compositions were synthesized via coupling reaction between aldehyde end-functionalized P3HT and precursor polymer anion of PHS as well as the following analogous chemistry. The morphologies, the crystallinity of P3HT and the optical properties of bulk samples and thin films of these copolymers under various thermal treatments were investigated. The strong interaction between polyhydroxystyrene repeat units through hydrogen bonding and high glass transition temperature of PHS were shown to significantly affect the microphase separation behaviors and crystallinity of P3HT of these block copolymers, making the self-assembly behavior very different from most P3HT based rod-coil block copolymers. For P3HT-PHS diblock copolymers, different form most other P3HT based rod-coil block copolymers that formed fibrillar or lamellar structure with low coil volume fraction, bulk samples formed not only fibers and lamellar structures but also cylindrical structure due to the strong hydrogen bonding between PHS. Well ordered fibers were observed for spin coated thin films of diblock copolymers on glass substrate before annealing and showed enhanced absorption at long wavelength. However, no organized microphase separated morphologies were observed for both bulk samples and thin films of triblock copolymers, probably due to the strong interaction between PHS segments and physical crosslink effect to prevent the packing of P3HT. For bulk samples, Crystallinity of (100) plane of P3HT increased after thermal annealing, but still weaker than pristine P3HT. In thin films, annealing improved the crystallinity of P3HT with the annealing temperatures below Tg of PHS, but worsened the crystallinity when the annealing temperature was above Tg of PHS. These effects might due to the strong interaction of hydrogen bonding between PHS segments that prevented ordered packing of P3HT chains. In both bulk samples and thin films, diblock copolymers showed more well ordered microstructures than triblock copolymers, and the crystallinity of diblock copolymers were better than triblock copolymers, as a result that the strong interaction of hydrogen bonding of PHS significantly affect the morphology and crystallinity of block copolymers.