臺灣博碩士論文加值系統

本實驗針對對排聚苯乙烯(Syndiotactic Polystyrene, sPS)在不同溶劑中的凝膠化行為進行研究，所選用的溶劑分別為o-Xylene (oxy)與Cyclohexanone (cho)及兩者之混合溶劑，混合溶劑以體積比(oxy/cho)：3/7、5/5與7/3均勻混合。
首先針對sPS在兩種純溶劑中形成的凝膠為主，探討其基本性質，建構凝膠的相圖，包含不同濃度的凝膠熔點與凝膠化溫度，再藉由廣角X光繞射與傅立葉轉換紅外光譜儀確定凝膠架橋點的結構為δ form結晶，因此判斷不同厚度的δ form結晶是造成這兩種凝膠熔點的差異；同時利用光學顯微鏡以及電子顯微鏡 (SEM) 觀察兩種凝膠的結構，可以發現sPS/oxy凝膠為三維纖維網狀結構，而sPS/cho凝膠為球晶碰撞堆積的三維結構。δ form結晶由TTGG螺旋構象分子鏈段與鑲嵌在苯環間空位的溶劑分子所構成，當較大的溶劑分子o-Xylene鑲嵌在空位中，螺旋構象分子鏈段表現出較為剛直，而體積較小的溶劑Cyclohexanone鑲嵌在苯環間的空位中，螺旋構象的分子鏈段仍然可以摺疊形成片晶，進而形成球晶結構。
接著，藉由凝膠化動力學判別sPS在不同溶劑中的凝膠化機制，在sPS/oxy溶液中，n=0.44接近逾滲理論中的三維晶格理論指數值β=0.45，而在sPS/cho溶液中，n=2.54接近分子鏈聚集的指數值n=2，然而混合溶液的凝膠生成機制為percolation與分子鏈聚集行為競爭有關，隨著兩種溶劑的含量變化而改變。以極限黏度劃分sPS濃度區域，因為PS單體與o-Xylene的相互吸引力較大，因此sPS分子鏈呈現延展的狀態，sPS/oxy溶液在稀薄溶液中即可產生凝膠化行為，而混合溶劑因為o-Xylene的存在，雖然濃度尚未達到臨界交疊濃度，溶液仍然可以產生凝膠化。
最後以小角光散射討論混合溶液產生的凝膠，以Debye-Bueche理論分析凝膠結構中的相關長度，可以對應SEM圖片中網目結構大小，隨著o-Xylene的含量增加，網目結構較大，小角光散射所得到的相關長度也隨之增加。

In this study, the effects of altering different volume ratio of two solvents and sPS gel on the structure and gelation mechanisms are discussed. The solvent used in this work, prepared at the volume ration of 3/7, 5/5, and 7/3, are o-Xylene (oxy) and Cyclohexanone (cho), respectively. The phase diagrams of sPS/oxy and sPS/cho gels reveal the melting and gelation temperature and the junction points, however, were δ form crystals according to the results obtained via FTIR and WAXD. The melting temperatures appeared different due to the larger thickness of the crystals in sPS/oxy gel .The structures of three-dimensional fibril network in sPS/oxy gel and spherulites packing in sPS/cho gel were also observed from POM and SEM owing to the variant
volumes in the solvents.
The gelation rates of sPS gels were measured by test tube tilting in five solvents at different polymer concentrations at 30oC. The gelation rate is expressed as concentration-dependent function: tgel-1= [(c-c*)/c*]n. The value of exponent n depends on the mechanisms of gelation. Exponent n=0.44 in sPS/oxy gel is close to percolation exponent β=0.45, which indicates that three-dimensional percolation is a suitable model for gelation process of sPS/oxy solution. Exponent n=2.54 in sPS/cho gel is close to chain aggregation exponent n=2, indicating that the gelation process is chain aggregating in sPS/cho solution. The n values of the mixture solutions between 0.44 and 2.54 indicate the competition of percolation and aggregation. According to the physical meaning of the [η]c value, it can divide concentration into four regions by chain aggregation. In sPS/oxy solution gelation occurs in infinite dilution limit ([η]c<1) since the strong interaction between PS monomers and o-Xylene observed
from Huggins content (k).
X-type patterns were observed from Hv mode SALS in three mixture solutions at low concentration. The characteristic length (ξ) of gel was analyzed through Debye-Bueche theory. The characteristic length is close to the mesh size of gel network from SEM picture. Therefore, the intensity of Hv scattering contains the orientation fluctuation of forming gel structure.

論文提要內容
Abstract
目錄
圖表目錄
論文符號表

第一章 前言
1.1凝膠的定義與分類
1.2物理凝膠形成機制
1.2.1巨觀不均一性凝膠
1.2.2成核凝膠
1.3凝膠形成理論-逾滲理論(Percolation theory)
1.4對排聚苯乙烯(Syndiotactic Polystyrene)凝膠
1.5小角光散射在物理凝膠上的解析
1.6研究目的

第二章 實驗
2.1藥品與樣品製備
2.2實驗方法
2.2.1凝膠熔點(Tm)
2.2.2 sol-gel曲線(Tgel)
2.2.3凝膠化速率(tgel-1)
2.2.4極限黏度 ([η])的測定
2.2.5光學顯微鏡 (POM)
2.2.6掃描式電子顯微鏡 (SEM)
2.2.7傅立葉轉換紅外光譜儀(FTIR)
2.2.8廣角X光繞射(WAXD)
2.2.9小角光散射(SALS)

第三章 結果與討論
3.1 sPS/oxy與sPS/cho的凝膠性質與結構
3.1.1 sPS/o-Xylene 相圖
3.1.2 sPS/Cyclohexanone 相圖
3.1.3 sPS/oxy與sPS/cho凝膠結構的差異
3.2凝膠化動力學之探討
3.2.1 sPS溶液的極限黏度
3.2.2凝膠化動力學
3.3 sPS混合溶液凝膠之小角光散射之研究

第四章 總結
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