超疏水/超親油表面製備及聚(N-異丙基丙烯胺)於固態或液態溶液中之相行為研究

Abstract

在表面化學的領域當中，液體於固體表面的潤濕現象是個非常重要的課題，它對於各方面的應用有很大的潛能。在近年來的研究當中，科學家們熱衷於製備有特別潤濕現象的固體表面，例如超疏水、超親油甚至於一個固體表面具有超疏水/超親油等現象。對於製備這種具有特別潤濕現象的固體表面，控制其表面的微米/奈米級結構及化學組成通常是最關鍵的一個步驟。在這篇論文當中，我們發展出一個全新的方法直接製備帶有微米級球狀與奈米級纖維狀結構的粗糙混成聚苯乙烯(polystyrene)薄膜，並且沒有做任何後續的表面化學改質。這個粗糙混成聚苯乙烯結構表面具有超疏水/超親油現象，且可以利用在油水分離的系統或是當做一個吸油材質。 在現代高分子工程與基因傳導送系統中，生物相容性高分子的發展也是一個很重要的課題。聚(N-異丙基丙烯胺) [poly(N-isopropylacrylamide)]是一個最具代表性的一個生物相容性高分子，在水溶液它是個熱敏性的高分子，其低臨界溶液溫度(lower critical solution temperature)大約是在32 °C。因為它轉變的溫度低於體溫，這對對於生物醫學的應用，是一個方便於學術研究的溫度範圍。 我們利用原子轉移自由基聚合法設計合成了聚（環氧乙烷⋅ N-異丙基丙烯胺）[poly(ethylene oxide-block-N-isopropylacrylamide)]嵌段共聚物。α-環糊精（α-CD）可選擇性與其聚（環氧乙烷）鏈段形成內包錯合物 (inclusion complex)。利用廣角X 射線衍射（WAXD）可發現其α-環糊精與聚（環氧乙烷）鏈段產生的內包錯合物為長條型的棒狀結構，彼此堆疊形成一個六角狀結晶型態。小角X 射線 散射（SAXS）的數據進一步發現，α-環糊精/聚（環氧乙烷⋅N-異丙基丙烯胺）之內包錯合物自組裝成一個遠程有序交替的層狀結構，其層間為交替的未錯合之非晶相聚（環氧乙烷⋅N-異丙基丙烯胺）部分和α-環糊精與聚（環氧乙烷）鏈段產生的內包錯合物的晶相區域。 側鏈上的官能基、摩爾分率、共溶劑、鹽類和表面活性劑對聚(N-異丙基丙烯胺)的最低臨界溶解溫度會產生重大的變化。我們採用傅里葉變換紅外光譜（FTIR）光譜儀於25 °C 下，研究聚(N-異丙基丙烯胺)於重水與氘代四氢呋喃共溶劑的相行為變化。可發現到聚(N-異丙基丙烯胺)從線狀延展之溶解形態到球狀聚集的不可溶形態的轉變原因是非常複雜的，與聚(N-異丙基丙烯胺)、重水與氘代四氢呋喃三者之間的內部相互作用力變化有關。我們推論水合作用和疏水基團的聚集是形態轉變的主要驅動力，聚(N-異丙基丙烯胺)自身的分子內與分子間氫鍵作用力和聚(N-異丙基丙烯胺)與重水氫鍵作用力為形態轉變的次要因素。

The wetting behavior of solid surfaces by a liquid is a very important aspect of surface chemistry, which may have a variety of practical applications. Recent achievements in the construction of surfaces with special wettabilities, such as superhydrophobicity, superoleophilicity, superhydrophobicity/superoleophilicity, and others are presented. The control of the surface micro-/nanostructure and the chemical composition is critical for these special properties. In this thesis, we have developed a directly method to prepare a rough polystyrene surface consisting of micro-beads and nano-fibers mixed structure without any chemical modification. The mixed structure shows superhydrophobic and superoleophilic properties, and then it can be used to separate oil/water or used as an oil-sorbent. The development of biocompatible polymer is an important problem in the modern macromolecular engineering and gene delivery systems. Poly(N-isopropylacrylamide) (PNIPAM) is one of the best known biocompatible polymer which reveals thermo-responsive property with lower critical solution temperature (LCST) about 32 °C. This is a convenient temperature form the context of biomedical applications because it is below body temperature. We have synthesized poly(ethylene oxide-block-N-isopropylacrylamide) diblock copolymer (PEO-b-PNIPAM) by atom transfer radical polymerization. The α-cyclodextrin (α-CD) can form the inclusion complexes (ICs) with PEO-b-PNIPAM after selective threading of the PEO segment. The α-CD/PEO IC shows a long rod-like structure and stacks each other to form a hexagonally packed plate as evidenced by wide-angle X-ray diffraction (WAXD). Small-angle X-ray scattering (SAXS) data further reveals that the α-CD/PEO-b-PNIPAM IC self-assembled to long range ordered lamellar structure exhibiting alternating layers of the amorphous phase of unincluded PEO/PNIPAM and crystal phase of α-CD/PEO IC. The LCST for PNIPAM is affected by the nature of substituent groups, molar mass, co-solvent, salts and surfactants. We focus on the phase behavior of PNIPAM in the mixed solvent of D2O and tetrahydrofuran-d8 by Fourier transform infrared (FTIR) spectroscopy. The evolution of the coil-to-globule-to-coil transition at 25 °C was caused by complicated interactions in the PNIPAM THF-d8/D2O and PNIPAM. We believe that dehydration and aggregation of the hydrophobic groups are the major driving force, while the inter- and intra-chain hydrogen bond of PNIPAM and hydrogen bond between D2O and PNIPAM are the minor factor for the subsequent aggregation and the coil-to-globule transition.