📚 Tackling questions on addition polymers | 攻克加成聚合物考题
Addition polymers appear in almost every Cambridge A-Level Chemistry exam, yet students often lose marks by confusing monomers with repeat units, misplacing side groups, or failing to explain properties at the molecular level. This article breaks down exactly what examiners look for, from drawing polymer chains and deducing monomers to explaining unreactivity and disposal problems. Whether you are tackling multiple‑choice or structured long‑answer questions, these strategies will sharpen your answers.
加成聚合物几乎出现在每一份剑桥A-Level化学试卷中，但学生常常因混淆单体与重复单元、错放侧基或未能从分子层面解释性质而失分。本文详细拆解了考官关注的要点，从绘制聚合物链、推断单体，到解释化学惰性与废弃处理问题。无论你面对的是选择题还是结构化长答题，这些策略都将让你答题更加精准。
1. Understanding Addition Polymerisation | 理解加成聚合反应
Addition polymerisation is a process in which many small unsaturated monomer molecules – each containing a C=C double bond – cules. Typical industrial conditions involve high pressure, elevated temperature and a free‑ the monomer given a polymer or to describe how reaction conditions influence the product.
加成聚合是许多含C=C双键的不饱和小分子单体连接形成长链饱和聚合物的过程。双键打开，单体相互加成而不消除任何小分子。典型的工业条件涉及高压、高温和自由基引发剂，如有机过氧化物。考题中，你可能需要根据聚合物推断单体，或描述反应条件如何影响产物。
2. Recognising Monomers and Repeat Units | 识别单体与重复单元
of atoms that repeats along the polymer backbone. To identify it, look for a repeating two‑ C of the monomer. Then, to deduce the monomer, reconnect the double bond between those carbons and attach the side groups as they appear. Remember that the polymer chain is usually represented as –(CH₂–CHX)–, where X is the side group. The table below summarises the most common addition polymers.
重复单元是沿聚合物主链重复的最小原子组合。要识别它，在主链中寻找重复的两个碳模式；这两个碳最初来自单体的C=C。接着，为推断单体，在这两个碳之间重新连接双键，并按出现的位置连接侧基。记住聚合物链通常表示为 –(CH₂–CHX)–ₙ，其中X为侧基。下表总结了最常见的加成聚合物。
| Monomer | Repeat Unit | Polymer Name |
|---|---|---|
| CH₂=CH₂ | –(CH₂–CH₂)–ₙ | Poly(ethene) |
| CH₂=CHCl | –(CH₂–CHCl)–ₙ | Poly(chloroethene) – PVC |
| CH₂=CHCH₃ | –(CH₂–CH(CH₃))–ₙ | Poly(propene) |
| CF₂=CF₂ | –(CF₂–CF₂)–ₙ | Poly(tetrafluoroethene) – PTFE |
3. Drawing Polymer Chains from Monomers | 从单体绘制聚合物链
When asked to draw a section of polymer from a given monomer, you must show at least one complete repeat unit enclosed in brackets, with bonds extending beyond the brackets at both ends to indicate chain continuation. The subscript 'n' outside the brackets denotes a large number of repeating units. For instance, poly(propene) from propene is drawn as –(CH(CH₃)–CH₂)–ₙ. With unsymmetrical alken
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