嵌段共聚合物之特殊相轉化現象研究

Special Phase Transition Behavior of Block Copolymers

葉昭麟(Yeh, Chao Lin)

指導教授 ： 陳信龍

國立清華大學/工學院/化學工程學系/博士(2016年)

摘要

摘要
本論文主要探討嵌段共聚合物的特殊相轉化現象，包括低臨界有序化(lower critical ordering transition，LCOT)及球形微相之晶格結構和有序-有序轉化(order-order transiton)。我們利用變溫小角度X-光散射揭露了可以呈現LCOT行為的新系統，此嵌段共聚合物是由poly(ethylene oxide) (PEO) 與poly(2-vinylpyridine) (P2VP)或P4VP鏈段所組成，本研究深入探討共聚物組成及分子量對於該相轉化溫度的影響，另外利用高分子摻合體之熱力學理論計算相圖，證實這些共聚物系統的LCOT特性。透過PEO-b-P2VP及PEO-b-P4VP系統的比較，我們進一步解析了pyridine基團些微的化學構造差異性對於LCOT相圖的巨大影響。
我們亦將具有LCOT相行為的嵌段共聚合物PEO-b-P2VP跟界面活性劑DBSA錯合，形成超分子comb-coil嵌段共聚合物，我們利用SAXS解析該共聚物之階層性奈米結構，並揭露結構對於PEO鏈段結晶動力學的影響。本研究亦從變溫SAXS實驗中發現，PEO-b-P2VP的相轉化行為受到DBSA的錯合而產生改變，在錯合DBSA之後，從LCOT轉變為UCOT相行為。
最後，我們深入研討PEO-b-PB/PB均聚物摻合體球形微相的熱力學的平衡態結構，我們將摻合體加溫至無序態，以去除樣品所有的履歷，再降溫偵測共聚物從無序態中自組裝的結構。我們利用小角度X光散射圖譜揭露，在TODT以下的溫度，PEO鏈段確實會形成CPS相，然而，不同於之前所觀察的FCC排列，我們發現從無序態形成的PEO球形微相是以hcp晶格排列，此結果暗示hcp相的自由能比FCC相低，是嵌段共聚物CPS相中的平衡晶格結構。

關鍵字

低臨界有序化 ； 小角度散射 ； 嵌狀共聚合物 ； 相轉化現象 ； 相行為 ； 相圖 ； 界面活性劑 ； 結晶動力學 ； 熱力學

並列摘要

Abstract
This dissertation investigates the special phase transition behavior of block copolymers, including the unusual lower critical ordering transition (LCOT) and the order-order transition of the macrolattice of the spherical microdomains. Temperaure-dependent small angle X-ray scattering (SAXS) was employed to reveal the LCOT behavior of a new block copolymer system composed of poly(ethylene oxide) (PEO) and poly(vinyl pyridine) (P2VP and P4VP) blocks. We have studied the effects of copolymer composoiton and molecular weight on the phase transition temperature; moreover, a thermodynamic theory considering the compressibility of the constituents was adopted to calauclate the phase diagrams of PEO/P2VP and PEO/P4VP blends. Through comparing the phase diagrams and experimentally measured disorder-to-order transition (DOT) temperatures of the two system, the drastic effect of the structure of the pyridine moiety in PVP has been revealed.
We further studied the hierarchical structure and phase behavior of the supramolecular comb-coil block copolymer formed by the complexation of the P2VP block in PEO-b-P2VP with an amphiphilic surfactant dodecylbenzene sulfonic acid (DBSA). It was found that the crystallization kinetics of PEO blocks in the system exhibited a distinct correlation with the hierarchical structure of the comb-coil copolymer. The phase transition behavior of PEO-b-P2VP was also modified by the complexation with DBSA, where the original LCOT behavior transformed to UCOT type when the binding frcaton was sufficiently high.
Finally, we investigated the packing lattice of the PEO spherical microdomains formed in the blend of poly(ethylene oxide)-block-poly(1,4-butadiene) (PEO-b-PB) and PB homopolymer (h-PB). The sphere-forming blend was first heated to the disordered micelle state followed by cooling below TODT. It was found that PEO spherical microdomains packed in the closely-packed lattice. In contrast to the previously observed face-centered cubic (FCC) packing, the spherical domains packed into the hexagonal closely-packed (hcp) lattice. The result implies that the free energy of hcp phase is lower than that of FCC phase and may henve represent the stable CPS structure for block copolymer blends.

並列關鍵字

lower critical ordering transition ； LCOT ； Small angle X-ray scattering ； SAXS ； CPS ； hcp ； FCC ； PEO ； P2VP ； P4VP ； DBSA ； PB ； block copolymer ； surfactant

參考文獻

1. Hamley, I. W. The Physics of Block Copolymers; Oxford University Press: New York, 1998.

3. Matsen, M. W.; Bates, F. S. Macromolecules 1996, 29, 1091.

4. Ruzette, A.-V. G.; Mayes, A. M. Macromolecules 2001, 34, 1894-1907

15. Fox, T. G. Bulletin of the American Physical Society 1956, 1, 123.

1. Kim, J.-K. et al. Macromolecules 2007, 40, 2109.