| 摘要: | 嵌段式聚氨基甲酸酯（Segment polyurethane）為一種多團聯共聚物，其物性除了受到團聯高分子本身化學結構之影響外，更受到其團聯分子鏈段自我組裝所形成之微相結構所影響。過去本實驗室針對第二吸熱熔融峰（T2）上之研究，認為非極性式PU因為軟硬兩相界面力強，導致硬質鏈段受到局限而無法更規則排列。因此本實驗室提出藉由兩相界面的鬆弛，使得硬質鏈段在微相域中更規則排列的想法，並期許如此的想法能改進非極性示PU的機械性質。近幾年來，本實驗室將非極性軟段poly-ip進行改質，末端接上不同數量lactone或不同長度的脂肪族diacid等極性單體，並以此為新polyol。接著以MDI二異氰酸鹽（4,4-diphenylmethane diisocyanate）及BD鏈延劑（1,4-butadiol extender）為硬質段，利用Two-step溶液聚合法，合成出一系列線性嵌段式共聚物PU。 本研究以FT-IR證實，末端接上脂肪族diacid極性單體的改質polyol與MDI會有兩種反應途徑，而無法形成我們所期待的嵌段式PU。前幾年，軟段末端以不同數量lactone改質所合成的嵌段式PU，其在熱分析、(動態)機械性質的測試中都已有相當正確的成果。本研究繼續藉由穿透式電子顯微鏡，直接觀察其形態。藉由大量影像鑑定與size分析，我們以最大可能性來判定各種形態。我們發現當形態皆為cylinder，其顯微像圖明暗交替條紋出現頻率越高，則第二吸熱熔融峰（T2）peak越往高溫位置移動或具越尖銳T2 peak。若形態為lamellar，我們發現未改質軟段的PU其domain呈現豌豆形，而改質軟段的PU其domain皆呈現扭轉或半月形的偏差變形。另外藉由T2溫度位置與tanδ高溫區peak的溫度位置與tanδ值相互佐證，界面鬆弛的確有助於硬鏈段規則排列。然而pu-4-yy系列藉由△Cp趨勢與domain邊界清晰度的應證下，我們認為pu-4-yy可能比較容易產生不理想的互溶界面，反而影響排列規則性或規則量。在機械性質方面，在考慮誤差下，末端改質並無明顯增強了極限強度，這或許是因為些微互溶程度的增加，造成pseudo crosslink density的下降，因此較小的domain其所能承受的應力較小。但是從起始模數來看，在相同硬段含量下，末端改質系列皆高於未改質系列，尤其以質段含量為55%下，最為明顯。 According to our research in the past years, in the systems of nonpolar-based polyurethane, we think that owing to strong force at interface, hardsegments are restrained.Therefore,we have an idea that if relaxation of interface occurs, hardsegments can pack more orderly.In 2004, Lai modified poly-ip(hydroxyl terminated polyisoprene),which end-caped with various amount of polar lactone, as new polyols.Lai further synthesized a series of nonpolar-based segment polyurethanes, which were made from the new polyols, MDI(4,4´-diphenylmethane diisocyanate) and BD(1,4-butadiol). In this study, we utilized TEM for direct observation of morphology of these segment polyurethanes.By analysizing a large number of micrographs, we found some changes from these nonpolar-based segment polyurethanes.For example, when hard content is 55%,the segment polyurethanes, whose soft segments are the modified poly-ip, show lamellar structure and the different departures.We combined the results of TEM with the results of DSC,DMA and tensile test,so that we could determine how the relaxation of interface affect the morphology and the properties.Finally, we also used succinic acid to modify poly-ip, as another new polyols,but that this new polyol reacted with MDI failed to form the prepolymer of segment polyurethane. |
