📚 Polymers | 聚合物
Polymers are giant molecules (macromolecules) formed by joining thousands of smaller units called monomers through covalent bonds. The process is called polymerisation, and the number of monomer units in the chain is known as the degree of polymerisation (n).
聚合物是由成千上万个称为单体的较小单元通过共价键连接而成的巨大分子（高分子）。这一过程称为聚合反应，链中单体单元的数目称为聚合度（n）。
In AQA A-Level Chemistry, polymers are divided into two main classes: addition polymers, formed from alkenes, and condensation polymers, formed from monomers with functional groups at both ends. Understanding the mechanisms and the ability to draw repeating units are essential exam skills.
在 AQA A-Level 化学中，聚合物分为两大类：由烯烃形成的加成聚合物，以及由两端带有官能团的单体形成的缩合聚合物。理解反应机理并能够画出重复单元是至关重要的考试技能。
1. Addition Polymerisation | 加成聚合反应
kene monomers. Many alkene molecules add together to form a saturated polymer chain, and no other product is formed. The atom economy is therefore 100%.
加成聚合涉及烯烃单体中 C=C 双键的打开。大量烯烃分子加合在一起形成饱和的聚合物链，没有其他产物生成，因此原子经济性为 100%。
For example, ethene polymerises to form poly(ethene):
例如，乙烯聚合生成聚乙烯：
n CH₂=CH₂ → [−CH₂−CH₂−]ₙ
The polymer chain is built by breaking the π bond of each monomer and forming two new σ bonds between adjacent monomer units. For ethene, the industrial conditions are about 200 °C,
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