利用層接層及點擊反應製備共價穩定之雙刺激響應高分子囊球與其性質探討

Abstract

本研究利用點擊反應及層接層方式將具有溫度及酸鹼應答性質之共聚高分子批覆於二氧化矽微球模板上，經氫氟酸侵蝕後，製備出一雙應答性中空囊狀微球。將具溫度及酸鹼應答性高分子，Poly(N-isopropylacrylamide) (PNIPAm) 及Poly(N-acryloylalanine) (PAAL) 利用原子轉移自由基聚合法 (ATRP) 或可逆加成斷裂鏈轉移聚合法 (RAFT) 聚合出帶有可進行點擊反應之炔丙基及疊氮官能基之環境應答型共聚高分子。接著利用點擊反應及層接層方式批覆三層之雙層結構於二氧化矽微球模板上，分別為PNIPAm/PAAL/PNIPAm。將所需層數批覆完畢後，以氫氟酸侵蝕內層二氧化矽微球，形成具溫度及酸鹼應答功能性中空微球。利用核磁共振光譜儀 (NMR) 鑑定各項化合物及高分子；傅立葉轉換紅外線光譜儀 (FT-IR) 鑑定共聚高分子中可使用於點擊反應之官能基；利用差分掃瞄式熱卡計 (DSC) 找出共聚後之溫度應答型高分子在層接層時最適合溫度；利用共軛焦顯微鏡 (CLSM) 研究酸鹼應答功能性中空微球於酸鹼值改變時於水溶液中大小的立即變化；利用原子力顯微鏡 (AFM) 及穿透式電子顯微鏡 (TEM) 研究溫度及酸鹼應答功能性中空微球於溫度或酸鹼值改變時之大小及厚度變化。以酸鹼度改變來說，從CLSM、TEM及AFM圖中結果顯示出環境為酸性時，PAAL之羧酸基以 (-COOH) 狀態存在，於PAAL與PAAL及PAAL及PNIPAm之間產生氫鍵作用力，造成此層部分較為緊縮，但加上PNIPAAm 低於LCST時之澎潤現象，使其為輕微澎潤；環境為鹼性時，PAAL之羧酸基以 (-COO-) 狀態存在，PAAL與PAAL間產生靜電排斥力(負電)，使結構更為鬆散，加上PNIPAAm 在低於LCST之澎潤現象，使其結構更為澎潤。以溫度改變來說，升溫時，質子化之PAAL傾向與PAAL及PNIPAm產生氫鍵，屬於〝疏水〞狀態，使PNIPAm共聚物本身之LCST下降，將其升溫後，結構型態更為緊縮。由實驗結果得知，結合層接層方式及銅觸媒1, 3-偶極環加成反應可將不同官能基之共聚高分子以共價穩定之接合方式存在，並可設計出先進及具有環境刺激響應之中空囊狀微球。

We report a click chemistry approach for the consecutive layer-by-layer (LbL) assembly of thermo and pH-sensitive clickable copolymers on silica particles and the subsequent formation of a vesicle-like dual-responsive click capsules. We synthesized azido- and acetylene-functionalized thermo-sensitive Poly(N-isopropylacrylamide) (PNIPAm) and pH-sensitive Poly(N-acryloylalanine) (PAAL) clickable random copolymers via atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Such LbL assembled polymer click capsules, a sequence of three bilayers PNIPAm/PAAL/PNIPAm stabilization by aromatic 1,2,3-triazoles linkages, not only have robust covalent-stabilized nanostructure but also exhibit reversible swelling/deswelling behaviors by elevating the solution temperature and incubating in acidic or basic solutions respectively. The physical properties of the synthesized compound and click capsule were analyzed by DSC, NMR and FT-IR. The morphologies and responsive behaviors of the solutions condition or air-dried capsules in acidic, basic, and thermo conditions were examined by using confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) and. From the image of CLSM, the shape-change of immersing in acidic or basic solutions shows slightly swelling in acidic condition and swelling in basic condition. The morphologies of the air-dried capsules from the images of TEM and AFM that show spherical structures with features of folds and creases because of prepared by LbL assembly on particle templates. TEM and AFM images also provide responsive evidences from size variation of the dried click capsules when surrounding condition change. This approach exhibits great interests in preparing well-defined vesicle-like capsules, because of the flexibility in introducing a range of new materials including different functional polymers, resulting in covalently stabilized.