我们报告了固有的微孔性(network-PIMs)网络聚合物的合成和性质,该聚合物来自具有连接至其桥头位置的烷基的三茂基单体。可以通过烷基链的长度和支链来控制气体的吸附,从而使材料的表观BET表面积可以在618-1760 m 2 g -1的范围内进行调整。。较短的(例如甲基)或支链的(例如异丙基)烷基链提供了最大的微孔性,而较长的烷基链似乎阻止了由刚性有机骨架产生的微孔。与其他PIM相比,增强的微孔性源自骨架的大分子形状,这是由三萜烯单元决定的,这有助于减少刚性骨架的延伸平面支柱之间的分子间接触,从而降低了填充在骨架内的效率。坚硬的。对于具有低或中等压力(在1 bar / 77K下为1.83质量%;在18 bar / 77 K下为3.4质量%)的纯有机材料,具有甲基或异丙基取代基的三茂基PIM的氢吸附能力是最高的。 )。
我们报告了固有的微孔性(network-PIMs)网络聚合物的合成和性质,该聚合物来自具有连接至其桥头位置的烷基的三茂基单体。可以通过烷基链的长度和支链来控制气体的吸附,从而使材料的表观BET表面积可以在618-1760 m 2 g -1的范围内进行调整。。较短的(例如甲基)或支链的(例如异丙基)烷基链提供了最大的微孔性,而较长的烷基链似乎阻止了由刚性有机骨架产生的微孔。与其他PIM相比,增强的微孔性源自骨架的大分子形状,这是由三萜烯单元决定的,这有助于减少刚性骨架的延伸平面支柱之间的分子间接触,从而降低了填充在骨架内的效率。坚硬的。对于具有低或中等压力(在1 bar / 77K下为1.83质量%;在18 bar / 77 K下为3.4质量%)的纯有机材料,具有甲基或异丙基取代基的三茂基PIM的氢吸附能力是最高的。 )。
The synthesis of anthracene crown ethers derived from benzo-crown ethers
作者:Ryszard Ostaszewski
DOI:10.1016/s0040-4020(98)00370-6
日期:1998.6
The sulfuric acid-promoted reaction of benzo-15-crown-5 (3) and benzo-18-crown-6 (6) with aliphatic aldehydes, leading to the formation of anthracene crownethers, was studied. A substantial substituenteffect on the reaction course was found. For the isobutyl group the highest yield was obtained, while for longer and shorter alkyl groups the yield dropped down. Reaction of acetaldehyde and benzo-15-crown-5
Fishing and Farming at Lake Chad: Responses to Lake-level Fluctuations
作者:MARIE-THERESE SARCH、CHARON BIRKETT
DOI:10.1111/j.1475-4959.2000.tb00015.x
日期:2000.6
Lake Chad lies at the southern extreme of the Sahara Desert and is well known for large fluctuations in its surface area this century. Seasonal fluctuations, however, have received much less attention. This paper presents the results of two complimentary research efforts on the south‐west shore of the lake. These illustrate how important both inter and intra‐annual fluctuations in the level of the lake are, both in terms of their impact on the environment and in the response of the communities living on the lake shore. The paper compares a time series of the fluctuations in the level of Lake Chad as monitored by the TOPEX/POSEIDON satellite with findings from participatory research with the communities of the south‐west lake shore. It shows how the communities of the lake have responded to lake‐level fluctuations with their livelihood choices. These results are used to show that although vastly different in scope, a high degree of complimentarity exists between remotely‐sensed information and community‐based research and that they are of potentially great value to development initiatives on the shores of Lake Chad.
Ostaszewski; Kozbial, Polish Journal of Chemistry, 1999, vol. 73, # 9, p. 1489 - 1502