Okuzaki Hidenori, Kobayashi Keiko, Hishiki Fumiya, Su Shi-Jian, Yan Hu
Laboratory of Organic Robotics, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-4-37 Takeda, Kofu 400-8511, Japan.
J Nanosci Nanotechnol. 2011 Jun;11(6):5193-8. doi: 10.1166/jnn.2011.4186.
Copolymers of N-isopropylacrylamide and stearyl acrylate (PNIPA-SAX) with various SA feed ratios (X = 1-10 mol%) were synthesized and electrospun into nanofiber mats. It was found that average diameter of nanofibers electrospun at concentration of 25% and voltage of 30 kV linearly increased from 165 nm (PNIPA) to 497 nm (PNIPA-SA10) with increasing the SA content. The PNIPA-SAX (X = 3-10 mol%) nanofiber mats were insoluble in water at 25 degrees C, in which inter-polymer and interfiber physical cross-links were formed through hydrophobic interaction of stearyl side-chains. With increasing the temperature from 25 to 40 degrees C the PNIPA-SA3 nanofiber mat exhibited significant volume contraction of 66%, while that of a single nanofiber estimated by AFM measurements was found to be 37%. The results allowed us to conclude that not only swelling-deswelling but also dissociation-association of the nanofibers via hydrophobic interactions were crucially important for the macroscopic volume changes of the nanofiber mats.
合成了具有不同硬脂酸丙烯酸酯（SA）进料比（X = 1 - 10 mol%）的N - 异丙基丙烯酰胺与硬脂酸丙烯酸酯共聚物（PNIPA - SAX），并将其静电纺丝成纳米纤维垫。研究发现，在浓度为25%、电压为30 kV的条件下静电纺丝得到的纳米纤维，其平均直径随着SA含量的增加从165 nm（PNIPA）线性增加到497 nm（PNIPA - SA10）。PNIPA - SAX（X = 3 - 10 mol%）纳米纤维垫在25℃下不溶于水，其中聚合物间和纤维间通过硬脂基侧链的疏水相互作用形成了物理交联。随着温度从25℃升高到40℃，PNIPA - SA3纳米纤维垫表现出66%的显著体积收缩，而通过原子力显微镜测量估计的单根纳米纤维的体积收缩率为37%。这些结果使我们得出结论，纳米纤维通过疏水相互作用的溶胀 - 去溶胀以及解离 - 缔合对于纳米纤维垫的宏观体积变化至关重要。
