雙性團聯共聚高分子DEH-PPV-b-PNIPAM之合成、物理性質鑑定玉型態學研究

Synthesis, Characterization and Physical Properties of Amphiphilic Rod-Coil DEH-PPV-b-PNIPAM Block Copolymers

蔡欣潔(Hsin-Chieh Tsai)

指導教授 ： 林唯芳

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02491

摘要

我們成功地製備一系列不同組成且分子量分布(PDI)均小於1.2的DEH-PPV-b-PNIPAM雙性團聯共聚高分子。首先，利用Siegrist聚縮合反應製備DEH-PPV，再利用格林那試劑將其末端官能基轉換成炔屬烴，然後藉由具末端疊氮官能基的起始劑經由ATRP聚合法製備PNIPAM。最後進行速配接合反應，將DEH-PPV及PNIPAM聚合物接合起來形成剛-柔團聯共聚高分子。合成具末端官能基的高分子和團聯共聚物，由核磁共振光譜儀鑑定其化學結構和凝膠滲透層析儀測定分子量。因PNIPAM的雙親屬性，使得團聯共聚高分子容易地溶解在極性溶劑中。在甲醇中，不同軟鏈段體積分率皆能全溶解；在水中，則是軟鏈段體積分率要大於0.55才能夠全溶解。在這些溶液中，團聯共聚高分子發生H-型聚集現象使吸收光譜呈現藍移現象以及螢光光譜有淬息現象。根據TEM的結果，在極性溶劑中，不同軟鏈段組成的團聯共聚高分子自組裝成層狀結構，且具有相同寬度(6-8nm)，隨著軟鏈段體積分率從0.72下降到0.48，其層狀結構的長寬比隨之從6.5增加到13.8，該結果顯示團聯共聚高分子在溶液中的奈米結構主要由PPV所控制的。此外，團聯共聚高分子的最低臨界溶液溫度(LCST)值隨著親油性DEH-PPV鏈段組成增加而上升，由於DEH-PPV與PNIPAM間的不相容性低，故降低了PNIPAM能對溫度感應鏈段的真實長度。隨著溫度的變化微胞結構的大小與形態，可以藉由穿透式電子顯微鏡(TEM)與動態光散射(DLS)來研討。
雙親性剛-柔團聯共聚高分子DEH-PPV-b-PNIPAM在固態中的奈米結構以及相轉移現象，可以藉由小角度X光散射(SAXS), 穿透式電子顯微鏡(TEM),偏光顯微鏡(POM)與示差掃描量熱分析(DSC)等實驗來進行研究探討，並且建立起該系統之相圖(phase diagram)。當團聯共聚高分子的PNIPAM軟鏈段體積分率小於0.48，為層狀結構，DEH-PPV會以smectic方式排列。然而，當軟鏈段體積分率增加後，DEH-PPV會形成六角柱狀堆積。將低軟鏈段體積分率的團聯共聚高分子加熱後，可以觀察到一系列明顯的轉換，從smectic-層狀到nematic再到無規則結構。加熱高軟鏈段體積分率的團聯共聚高分子，同樣地，也能觀察到明顯的轉換，從smectic-六角柱狀到nematic再到無規則結構。此外，規則到不規則轉換溫度(ODT)與nematic-to-isotropic(NI)相轉移溫度，皆會隨著軟鏈段增加而有降低的趨勢。這些結果表現出雙親性剛-柔團聯共聚高分子的相轉移呈現了“低的相分離強度”行為。

關鍵字

雙親性 ； 剛-柔 ； 自組裝 ； 團聯共聚高分子 ； PNIPAM ； DEH-PPV

並列摘要

A series of poly(diethylhexyloxy-p-phenylenevinylene)-b-poly(N-isopropylacylamide) (DEH-PPV-b-PNIPAM) amphiphilic block copolymers were synthesized using Siegrist polycondensation and atom transfer radical polymerization (ATRP) followed by “click” chemistry. Theses copolymers are well-defined with PNIPAM block volume fraction from 0.40-0.72 and low polydispersity (< 1.2), as determined by 1H NMR and GPC. Due to the amphiphilic property of PNIPAM, these copolymers can be easily dissolved in polar solvent. The copolymers with all volume fractions of fPNIPAM are completely soluble in methanl and in water with fPNIPAM > 0.55. In both solutions, the copolymers show slightly blue shift of absorption (UV-Vis) and strong quenching of emission (PL), indicating H-aggregations occurred. These copolymers in polar solution were self-organized into lamellar structures with same width (6-8 nm) regardless the fPNIPAM according to the TEM studies. The average aspect ratio of these lamellae is increased from 6.5 to 13.8 when the fPNIPAM is decreasing from 0.72 to 0.48. These results suggest that the nanostructure of these copolymers is mainly dominated by the PPV block. The lower critical solution temperature (LCST) of block copolymers is increased with increasing hydrophobic DEH-PPV block ratio, since χ value between DEH-PPV and PNIPAM segment is weak to reduce the real thermo-responsive length of PNIPAM. The variation of the micelle size with temperature was judged to be similar from both TEM and DLS measurement. In bulk state, nanostructure and phase transition of the DEH-PPV-b-PNIPAM amphiphilic rod-coil block copolymers were experimentally investigated via SAXS, TEM, POM, and DSC to map the phase diagram. At low coil fraction (fPNIPAM<0.48), the DEH-PPV rods are organized smectic-lamellar structure. However, as coil fraction increases, DEH-PPV pack into hexagonal structure. Upon heating the low coil fraction copolymer exhibit a series of clear transition of smectic-lamellar to nematic to isotropic phase. Similarly, in high coil fraction copolymer, the transitions from smectic-hexagonal to nematic to disorder could be observed clearly. In addition, the order to microphase disorder transition (ODT) and nematic-to-isotropic (NI) transition temperature are decreased with increasing coil fraction. These results suggest that the phase transition of DEH-PPV-b-PNIPAM amphiphilic rod-coil block copolymer shows the weak segregation strength behavior.

並列關鍵字

amphiphilic ； rod-coil ； self-assembly ； block copolymer ； PNIPAM ； DEH-PPV

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