pH-Responsive Shape Memory Poly(ethylene glycol)鈥揚oly(蔚-caprolactone)-based Polyurethane/Cellulose Nanocrystals Nanocomposite

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• 作者：Ying Li ; Hongmei Chen ; Dian Liu ; Wenxi Wang ; Ye Liu ; Shaobing Zhou
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：June 17, 2015
• 年：2015
• 卷：7
• 期：23
• 页码：12988-12999
• 全文大小：707K
• ISSN：1944-8252

文摘

In this study, we developed a pH-responsive shape-memory polymer nanocomposite by blending poly(ethylene glycol)鈥損oly(蔚-caprolactone)-based polyurethane (PECU) with functionalized cellulose nanocrystals (CNCs). CNCs were functionalized with pyridine moieties (CNC鈥揅₆H₄NO₂) through hydroxyl substitution of CNCs with pyridine-4-carbonyl chloride and with carboxyl groups (CNC鈥揅O₂H) via 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) mediated surface oxidation, respectively. At a high pH value, the CNC鈥揅₆H₄NO₂ had attractive interactions from the hydrogen bonding between pyridine groups and hydroxyl moieties; at a low pH value, the interactions reduced or disappeared due to the protonation of pyridine groups, which are a Lewis base. The CNC鈥揅O₂H responded to pH variation in an opposite manner. The hydrogen bonding interactions of both CNC鈥揅₆H₄NO₂ and CNC鈥揅O₂H can be readily disassociated by altering pH values, endowing the pH-responsiveness of CNCs. When these functionalized CNCs were added in PECU polymer matrix to form nanocomposite network which was confirmed with rheological measurements, the mechanical properties of PECU were not only obviously improved but also the pH-responsiveness of CNCs could be transferred to the nanocomposite network. The pH-sensitive CNC percolation network in polymer matrix served as the switch units of shape-memory polymers (SMPs). Furthermore, the modified CNC percolation network and polymer molecular chains also had strong hydrogen bonding interactions among hydroxyl, carboxyl, pyridine moieties, and isocyanate groups, which could be formed or destroyed through changing pH value. The shape memory function of the nanocomposite network was only dependent on the pH variation of the environment. Therefore, this pH-responsive shape-memory nancomposite could be potentially developed into a new smart polymer material.