本論文是利用粒子追蹤之微流變技術來探討單一高分子鏈的溶脹緊縮轉變。此研究方法是透過經典Flory-deGennes理論的預測與奧士瓦黏度計的測量結果來驗證微流變技術(第三章)。此外還使用小角度X光散射探測高分子鏈的微觀結構來作為輔助之佐證(第四章)。
　　在第三章我們從巨觀角度測量聚2-乙烯基吡啶(P2VP)的稀薄溶液黏度如何隨pH值改變，並從中了解P2VP分子鏈如何在微觀上隨pH值改變其絨球半徑Rg。具體來說，我們藉由測量溶液的比黏度ηsp或本質黏度[η]來估算Rg。我們發現在調整pH值從3.7增加到4.3的過程中，Rg會在pH=4.1時會從原本的30nm劇烈縮小到12nm，此現象暗示P2VP可能發生從蓬鬆的溶脹狀態突然轉變成緊實狀態。為了判別這兩種不同的構象狀態，我們改變不同分子量Mp並測量個別對應的Rg大小，並分析其間關係得到Rg(pH<4.1)~Mp0.59與Rg(pH>4.1)~Mp0.36，此結果與Flory-deGennes理論預測Rg(coil)~Mp0.6與Rg(globule)~Mp1/3近乎一致。
　　我們還將研究範圍擴展至半稀薄溶液，此時單體濃度Cm已經高於重疊濃度 。而本論文的微流變技術在稀薄溶液與半稀薄溶液中二者所測量得到的結果，都和Ostwald黏度計所得到的結果非常相近。結果顯示ηsp大致上雖然隨著Cm而增加，而其增長的趨勢pH<4.1明顯的與pH>4.1不同。特別的是在半稀薄溶液中，我們發現後者增長的速率遠高於前者。
　　而為了補充本論文的微流變測量結果，我們進一步透過SAXS實驗，直接在奈米尺度來探測P2VP的微觀結構。我們發現在相同的體積分率下，在緊縮狀態(pH>4.1)的SAXS散射訊號比在溶脹狀態(pH<4.1)還強，此結果定性上與微流變技術結果相符，高分子鏈在前者中的確是較緊實的。我們也觀察到，雖然大部分測量到的SAXS訊號都來自於背景溶液中的鹽，但短鏈分子與長鏈分子所測得SAXS圖譜截然不同。這暗示所添加的著鹽離子對分子鏈的構象變化可能有重要的影響，故為了解讀所量測之SAXS圖譜，還需另外考慮鹽離子與P2VP分子鏈之間的耦合于形狀因子或(與)結構因子的影響。

This thesis is to explore the use of particle-tracking microrheology techniques in studying the coil-globule transition of single molecule polymer. This approach is validated by comparing the measured results with predictions by the classical Flory-deGennes theory and those using the Ostwald viscometer (Chapter 3). As a complementary study, small angle X-ray scattering (SAXS) is also employed to probe the microstructures of a polymer chain (Chapter 4).
In Chapter 3 we measure how the viscosity of a dilute poly-2-vinylpyridine (P2VP) solution changes with pH macroscopically to see how a P2VP chain changes its radius of gyration Rg microscopically under the influence of pH. Specifically, we measure Rg by relating it to the specific viscosity sp or the intrinsic viscosity [] of the solution. We find that when increasing pH from 3.7 to 4.3, there is a sharp decrease from Rg  30 nm to 12 nm at pH  4.1, indicating a possible transition from the swollen coil state to the compact globule state. These conformational states are identified by measuring how the respective values of Rg vary with the molecular weight Mp: Rg (pH<4.1)~ Mp0.59 and Rg (pH>4.1)~ Mp0.36 in excellent agreement with the scaling relationships predicted by the Flory-deGennes theory: Rg (coil) ~ Mp3/5 and Rg (globule)~ Mp1/3.
We also extend our study to the semi-dilute regime where the monomer concentration Cm is higher than the overlap concentration . For both the dilute and semi-dilute regimes, the measured data are found to be in good agreement with those using the Ostwald viscometer. The data also reveal that while sp generally grows with Cm, its growing behavior for pH < 4.1 appears quite distinct from that for pH > 4.1. In the semi-dilute regime, in particular, we find that the latter grows much faster than the former.
To complement the results using microrheology, we further carry out SAXS experiments for directly probing the microstructures of a P2VP chain at the nanoscale level. We find that at the same polymer volume fraction, the SAXS signals at the globule state (pH >4.1) are stronger than those at the coil state (pH <4.1), which qualitatively agrees with the observation using microrheology that a polymer chain in the former case is actually more compact. We also observe that although most of the observed SAXS signals come from added salts in the background solution, the SAXS spectrum for short chains is rather different from that for long chains. This implies that salt ion effects might play important roles in the chain’s conformational changes, thereby requiring additional coupling between salt ions and a P2VP chain in the form factor or/and the structure factor for deciphering the observed SAXS spectra.

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林聖翔 2010應用粒子追蹤之微流變技術探討單一聚電解質分子鏈的構象變化與膠體交互作用，國立成功大學，碩士論文.
陳信龍2011膠體粒子交互作用與單一高分子鏈構形變化之偵測與診斷，國立成功大學，碩士論文.
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