高分子导电的奥秘

For most of us, a modern lifestyle without polymers is unthinkable…if only we knew what they were. The ordinary hardware-store terms we use for them include "plastics, polyethylene（聚乙烯）, epoxy resins¹（环氧树脂）, paints, adhesives², rubber" -- without ever recognizing the physical and chemical structures shared by this highly varied³ -- and talented -- family of engineering materials. Polymers increasingly form key components⁵ of electronic devices, too -- and with its ever-escalating pursuit of high efficiency and low cost, the electronics industry prizes understanding specific behaviors of polymers. The ability of polymers to conduct charge and transport energy is especially appealing.   Now there's help in appreciating the polymer mystique related to the emerging field of molecular⁶ conduction in which films of charge-transporting large molecules⁷ and polymers are used within electronic devices. These include small-scale applications such as light emitting diodes (LED). At the other end of the scale, in cities and across oceans, the polymer polyethylene is the vital insulating component⁴ in the reliable and safe transport of electrical energy by high voltage underground cables.   In work appearing in the current edition of the Journal of Applied⁸ Physics, researchers at the United Kingdom's Bangor University describes how electrical charges may leak away to the ground through its labyrinth⁹ of molecules.   Researchers Thomas J. Lewis and John P. Llewellyn pay particular attention to the nano-scale structure of polyethylene in which crystalline regions are separated by areas known as "amorphous¹⁰ zones." Their novel employment of superexchange and quantum mechanical tunneling of electrons through the amorphous（无定形的） parts of the polymer helps improve understanding of electrical charge conduction.   "These findings could lead not only to improved properties of high voltage cables but also to a wider understanding of polymer semiconductors¹¹ in device applications," said Lewis.   Their investigation¹² shows that the tunneling feature accounts for the majority of the reported high-field charge transport effects in polyethylene.