Dai Xiying, Niu Jiali, Ren Zhongjie, Sun Xiaoli, Yan Shouke
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology , Beijing 100029, China.
Beijing National Laboratory for Molecular Sciences, Department of Polymer Science and Engineering & The Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, China.
J Phys Chem B. 2016 Feb 4;120(4):843-50. doi: 10.1021/acs.jpcb.5b11178. Epub 2016 Jan 25.
Poly(vinylidene fluoride) (PVDF) nanotubes were fabricated by melt-wetting into porous anodic aluminum oxide (AAO) templates with two different interfacial properties: one is pristine AAO, and the other is modified by FOTS (AAO-F). Their crystallization and melting behaviors are compared with those of a bulk sample. For the PVDF in AAO-F, the nonisothermal crystallization temperature is slightly lower than that of bulk, and the melting temperature is similar to that of bulk. For the PVDF in pristine AAO, when the pore diameter is 200 nm, the crystallization is induced by two kinds of nucleation: heterogeneous nucleation and interface-induced nucleation. On the contrary, in the AAO template with pore diameter smaller than 200 nm, only interface-induced nucleation occurs. The melting temperature of PVDF crystals in the pristine AAO is much higher than that of bulk which can be attributed to the presence of an interfacial layer of PVDF on the template inner surface. The interaction between PVDF and AAO template produces the interfacial layer. Such an interfacial layer plays an important role in enhancing the melting temperature of PVDF crystals. The higher melting peak is always observed when the PVDF is nonisothermally crystallized in the AAO template irrespective of the thermal erasing temperature suggesting the interfacial layer is very stable on the AAO template surface. If the PVDF nanostructures are released from AAO template, the higher melting peak disappears with the enhancement of thermal erasing temperature.
通过熔体浸润法将聚偏氟乙烯（PVDF）制备成纳米管，所用的多孔阳极氧化铝（AAO）模板具有两种不同的界面性质：一种是原始AAO，另一种是经氟代十八烷基三甲氧基硅烷（FOTS）改性的AAO（AAO-F）。将它们的结晶和熔融行为与本体样品的进行比较。对于AAO-F中的PVDF，非等温结晶温度略低于本体，熔融温度与本体相似。对于原始AAO中的PVDF，当孔径为200 nm时，结晶由两种成核方式诱导：异相成核和界面诱导成核。相反，在孔径小于200 nm的AAO模板中，仅发生界面诱导成核。原始AAO中PVDF晶体的熔融温度远高于本体，这可归因于模板内表面上存在PVDF界面层。PVDF与AAO模板之间的相互作用产生了界面层。这样的界面层在提高PVDF晶体的熔融温度方面起着重要作用。当PVDF在AAO模板中进行非等温结晶时，无论热擦除温度如何，总是观察到较高的熔融峰，这表明界面层在AAO模板表面非常稳定。如果将PVDF纳米结构从AAO模板中释放出来，随着热擦除温度的升高，较高的熔融峰消失。
