Explain the terms of "mono-disperse" and "polydispersity index".( answer in English)
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列出测定聚合物分子量及其分布的三种主要方法。并阐述基本原理，基本过程。
Based on "ball-and-stick"model, list the main factors that determin the possible shapes and sizes of polymer molecules. (answer in English)
以正丁烷为例，分析何为“trans bonds”?何为“gauche bonds”? 二者有何区别？
简答Hydrogen bonding的概念，类型，特征？
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