致第三届中国国际毛纺织会议组织者和参加者

祝贺大会召开 !这次不能如邀访问西安 ,我感到遗憾。祝第三届中国国际毛纺织会议圆满成功。着手研究羊毛及产品的性能与结构之间关系 ,正值此时。大约在 1 92 0到 1 970年这段时期 ,有一批扎实的实验研究项目 ,为研究羊毛结构和机械性能提供了大量资料信息。同时 ,开始了理论模拟研究。这些研究结果请参见由 W.S.Simpson和 G.H.Crawshaw主编、Woodhead Publishing出版社的书 :《Wool:Science and Technology》。尽管这些研究为发展羊毛技术提供了有用的基本信息 ,但是对工业界的直接影响甚小。相比之下 ,羊毛化学的知识为羊毛化学处理…     

Relaxation in polymer electrolytes on the nanosecond timescale

The relation between mechanical and electrical relaxation in polymer/lithium-salt complexes is a fascinating and still unresolved problem in condensed-matter physics, yet has an important bearing on the viability of such materials for use as electrolytes in lithium batteries. At room temperature, these materials are biphasic: they consist of both fluid amorphous regions and salt-enriched crystalline regions. Ionic conduction is known to occur predominantly in the amorphous fluid regions. Although the conduction mechanisms are not yet fully understood, it is widely accepted that lithium ions, coordinated with groups of ether oxygen atoms on single or perhaps double polymer chains, move through re-coordination with other oxygen-bearing groups. The formation and disruption of these coordination bonds must be accompanied by strong relaxation of the local chain structure. Here we probe the relaxation on a nanosecond timescale using quasielastic neutron scattering, and we show that at least two processes are involved: a slow process with a translational character and one or two fast processes with a rotational character. Whereas the former reflects the slowing-down of the translational relaxation commonly observed in polyethylene oxide and other polymer melts, the latter appears to be unique to the polymer electrolytes and has not (to our knowledge) been observed before. A clear picture emerges of the lithium cations forming crosslinks between chain segments and thereby profoundly altering the dynamics of the polymer network.