本研究合成具有光異構化特性之偶氮苯單體，再以原子轉移自由基聚合法製備不同偶氮苯含量之雙團聯共聚物poly(ethylene glycol)methyl ether-block-poly(6-[4-(4’-methoxyphenylazo)phenoxy]hexylmethacrylate) (mPEG-b-PMMAzo)，並研究其在不同環境中之結構與光異構化行為的變化。
mPEG-b-PMMAzo具有偶氮苯光異構化之行為，經紫外光及可見光照射後可進行可逆trans-cis-trans光異構化反應，我們探討了mPEG-b-PMMAzo在中性、選擇性溶劑與薄膜中的光異構化速率。於中性溶劑中，偶氮苯基團以速率較快的translational mechansim進行光異構化；然而，在選擇性溶劑中，因PMMAzo鏈段溶解度較差，團聯共聚物自組裝形成微胞，偶氮苯光異構化空間受到壓縮，偏向以速率較慢的rotational mechanism反應；在薄膜中，由於固體中自由體積相較於溶液中更小，以及液晶分子之間有序排列造成的立體障礙，mPEG-b-PMMAzo薄膜光異構化速率為三者之中最慢。
mPEG-b-PMMAzo在中性溶劑中為random coil結構，以non-association型態為主；在選擇性溶劑中，低偶氮苯含量之mPEG-b-PMMAzo以球狀微胞存在，造導致偶氮苯以並排的H-aggregate為主，π-π* transition之最大吸收波長藍位移，隨著偶氮苯含量增加，微胞從球狀轉變為柱狀結構；在薄膜中，mPEG-b-PMMAzo形成層狀結構，由於此微相結構與液晶相之間的超分子合作運動，薄膜中偶氮苯以頭對頭的J-aggregate聚集為主，並有紅位移現象。此外，當mPEG-b-PMMAzo處於同一環境時，若PMMAzo含量增加，偶氮苯的H-aggreagte或J-aggregate聚集型態比例亦上升。
mPEG-b-PMMAzo之熱性質經由微差熱掃描卡計與偏光光學顯微鏡觀察。隨著PMMAzo鏈段長度增加，由於液晶有序結構的存在造成mPEG結晶的限制作用，使得mPEG結晶度減少、熔融溫度與結晶溫度下降；液晶相之間的合作運動亦隨著液晶鏈段含量上升而加強，這可以穩定液晶排列，因此液晶相轉移溫度亦上升。

A series of azobenezene-containing block copolymer poly(ethylene glycol)methyl ether-block-poly(6-[4-(4’-methoxyphenylazo)phenoxy]hexylmethacryalte) (mPEG-b-PMMAzo) with various contents of azobenzene was synthesized through atom transfer radical polymerization, and was investigated the morphology and photoisomerization behavior in different enviroments. mPEG-b-PMMAzo exhibited photoisomerization behavior and the photoisomerization rate was investigated in neutral solvents, selective solvents and thin films. When dissolved in selective solvents, mPEG-b-PMMAzo self-assembled into micelles because of the poor miscibility of PMMAzo. The photoisomerization rate was slower than that in neutral solvents. Moreover, the photoisomerization rate of mPEG-b-PMMAzo in thin films was much slower than that in solution due to the even smaller free volume for azobenzene isomerization in thin films. mPEG-b-PMMAzo exhibited a random coil conformation, and chromophores were not associated in neutral solvents. By contrast, mPEG-b-PMMAzo with the low contents of PMMAzo assembled into spherical micelles when dissolved in selective solvents. The confined geometry resulted in the H-aggregated mesogens causing a blue shift. When the fraction of PMMAzo was increased, the structure of mPEG-b-PMMAzo changed from spherical micelles to cylindrical micelles. In thin films, mPEG-b-PMMAzo formed a lamellar structure resulting in the formation of J-aggregated chromophores and a red shift. The thermal properties of mPEG-b-PMMAzo were characterized by differential scanning calorimetry and polarized optical microscopy. When the chain length of PMMAzo was increased, the degree of crystallinity, melting temperature, and crystallization temperature of mPEG decreased, while the phase transition temperature of liquid crystals increased.

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