本研究合成一具有光異構化特性之偶氮苯單體，再經由原子轉移自由基聚合法製備一系列分子量不同之雙團聯共聚物poly(tert-butyl acrylate)-block-poly(6-[4-(4'-methoxyphenylazo)phenoxy]hexylmethacrylate) (PtBA-b-Pazobenzene)，以FTIR、1H-NMR、EA鑑定分子結構，DSC觀察相變化溫度，並利用小角度X光散射與穿透式電子顯微鏡觀察雙團聯共聚物自組裝微相結構的變化。當偶氮苯所占體積分率(fazo)為0.3-0.78，高分子呈現層狀結構；當偶氮苯之體積分率為0.28時，則出現柱狀結構。
偶氮苯的光異構化特性使高分子經UV光誘導，構形由穩定的trans態轉變為cis態，反之cis態在可見光下會回復至trans態。我們利用紫外-可見光光譜探討PtBA-b-Pazobenzene在不同性質溶劑與薄膜系統中，偶氮苯基團異構化之光應答行為。研究發現在溶劑與薄膜狀態下，偶氮苯共聚物均可進行光異構化反應。
當PtBA-b-Pazobenzene在選擇性溶劑環境下，高分子產生H-aggregate的聚集，而在中性溶劑中則呈現無聚集。此H-aggregate的聚集使最大吸收波長發生藍位移現象，並且造成高分子光異構化的速率減慢以及順式異構物含量降低。
依照不同比例混合中性溶劑與選擇性溶劑，觀察此高分子在混合溶劑中的吸收光譜，實驗結果顯示，隨著雙團聯共聚物兩鏈段體積分率的不同，在溶液中自組裝的行為也不同。隨著選擇性溶劑比例增加，偶氮苯分子產生H-aggregate的聚集。將高分子濃度提高，可以觀察到微胞結構的形成。在THF/ethanol混合比例為50/50，高分子形成粒徑最大的large compound micelles。此微胞結構的變化受到高分子鏈段比例與溶劑的選擇性影響。
在聚合物薄膜系統中，偶氮苯分子緊密堆積排列在基材上，聚集行為以H-aggregate為主。經過熱處理後，會使偶氮苯垂直排列於基板上，改變聚集的行為。

A series of rod-coil diblock copolymer of poly(tert-butyl acrylate)-block-poly(6-[4-(4'-methoxyphenylazo)phenoxy]hexylmethacrylate) (PtBA-b-Pazobenzene) was synthesized using atom transfer radical polymerization to investigate the self-assembly and photo-induced behavior of the diblock copolymers. The chemical structures of synthesized compounds were characterized using FTIR, 1H-NMR, and EA analyzer. The phase transfer temperatures of monomer and polymers were determined by different scanning calorimetry (DSC). The phase behavior of these diblock copolymers were investigated using both small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). When the volume fraction of azobenzenes in PtBA-b-Pazobenzene is between 0.3 and 0.78, PtBA-b-Pazobenzene formed a lamellar structure. In contrast, when the volume fraction of azobenzene reduced to 0.28, the copolymer formed a cylindrical structure.
The rodlike block containing the azobenzene moiety exhibited the characteristics of photoisomerization. After the UV irradiation, the morphology of PtBA-b-Pazobenzene changed from the trans to the cis isomer and the reversible process could be initiated by visible light. We utilized the UV-visible spectrometer to investigate the aggregation state of azobenzene segment in both solvents and thin films. The diblock copolymers in both solutions and thin film state exhibited the reversible photoisomerization behavior.
The azobenzenes formed H-aggregates in both a selective solvent and a thin film, whereas they were randomly distributed in a neutral solvent. In a selective solvent, the absorption peak of UV spectra showed a blue shift, which was attributed to the formation of the H-aggregation in the azobenzenes. The occurrence of the H-aggregation of the azo chromophores resulted in a significant reduction of both the trans-to-cis isomerization rate and the cis isomer content at photo-stationary state.
When PtBA-b-Pazobenzene was dissolved in a mixed solvent (THF/ethanol), diblock copolymers with different volume fractions exhibited the different self-assembled behavior. As the amount of the selective solvent (ethanol) increased, it induced H-aggregate of azobenzenes. Additionally, the increasing polymer concentration promoted the formation of the micelle structures. As the THF / ethanol mixture ratio was 50/50, it exhibited coexisted structures of spherical and large compound micelles with a diameter ranged from 90 to 360 nm. This indicated that the micelle structure changed with the volume fraction of diblock copolymers and the solvent selectivity.
In the thin film, the azobenzene molecules were closely packed on the substrate. The aggregation behavior was H-aggregate. After thermal treatment, azobenzenes were homotropically aligned on the substrate, resulting in the change in aggregation behavior.

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