📚 Polymers: IGCSE OCR Chemistry Revision Guide | 聚合物：IGCSE OCR 化学考点精讲
Polymers are giant molecules made from many small repeating units called monomers. In IGCSE OCR Chemistry, you need to understand the two main types of polymerisation – addition and condensation – and be able to draw polymer structures, identify monomers, and link properties to real-world uses. This article covers every key point with paired English and Chinese explanations to help you master the topic.
聚合物是由许多称为单体的小重复单元组成的大分子。在 IGCSE OCR 化学中，你需要理解两种主要的聚合类型——加成聚合和缩合聚合，并能够画出聚合物结构、识别单体以及将性质与实际用途联系起来。本文用配对的中英文讲解涵盖每一个关键点，帮助你掌握这个主题。
1. What Are Polymers? | 什么是聚合物？
Polymers are long-chain molecules formed by linking together thousands of small identical units called monomers. The process of forming a polymer from monomers is called polymerisation. The monomer must have a functional group or double bond that allows it to join with other monomers. Polymers can be synthetic, such as polythene and nylon, or natural, such as proteins and starch.
聚合物是通过将成千上万个称为单体的小相同单元连接在一起而形成的长链分子。由单体形成聚合物的过程称为聚合。单体必须具有能够使其与其他单体连接的官能团或双键。聚合物可以是合成的，例如聚乙烯和尼龙，也可以是天然的，例如蛋白质和淀粉。
2. Addition Polymerisation | 加成聚合
Addition polymerisation occurs when unsaturated monomers (usually alkenes) join together without losing any atoms. The double bond in the alkene monomer opens up, and monomers add to each other to form a saturated polymer backbone. All the atoms from the monomers end up in the polymer, so the repeating unit has exactly the same atoms as the monomer.
加成聚合发生在不饱和单体（通常是烯烃）互相连接而不丢失任何原子的情况下。烯烃单体中的双键打开，单体彼此加成形成饱和的聚合物主链。来自单体的所有原子最终都进入聚合物中，因此重复单元具有与单体完全相同的原子。
3. Drawing Addition Polymers | 绘制加成聚合物
To draw an addition polymer, draw the monomer with its double bond, then remove the double bond and show the carbon atoms connected by single bonds to the next repeating units. Use brackets and a subscript ‘n’ to show the repetition. For example, poly(ethene) from ethene monomer CH₂=CH₂: the repeating unit is –CH₂–CH₂–, and the polymer is [–CH₂–CH₂–]ₙ.
要绘制加成聚合物，先画出带双键的单体，然后去掉双键，用单键将碳原子与下一个重复单元连接起来。用括号和下标 ‘n’ 表示重复。例如，由乙烯单体 CH₂=CH₂ 制成的聚乙烯：重复单元是 –CH₂–CH₂–，聚合物是 [–CH₂–CH₂–]ₙ。
- Example monomer: CH₂=CHCl (chloroethene). Repeating unit: –CH₂–CHCl–. Polymer: poly(chloroethene), commonly PVC.
- 单体示例：CH₂=CHCl（氯乙烯）。重复单元：–CH₂–CHCl–。聚合物：聚氯乙烯，即 PVC。
4. Monomers and Repeating Units in Addition Polymers | 加成聚合物的单体和重复单元
To identify the monomer from an addition polymer, look at the repeating unit between brackets. Add a double bond between the two carbon atoms that were originally connected in the monomer. Make sure each carbon atom has the correct number of hydrogen or other atoms. The monomer is the small molecule that was polymerised, and the repeating unit is the part that repeats along the chain.
要从加成聚合物中识别单体，观察括号之间的重复单元。在原本相连的两个碳原子之间加上双键。确保每个碳原子具有正确数量的氢或其他原子。单体是被聚合的小分子，重复单元是沿链重复的部分。
Monomer: CH₂=CH₂ → Repeating unit: –CH₂–CH₂–
5. Condensation Polymerisation | 缩合聚合
Condensation polymerisation involves monomers with two functional groups at each end. When these monomers react, a small molecule such as water or hydrogen chloride is eliminated. The polymer chain forms by linking monomers through ester or amide bonds. Unlike addition polymerisation, the repeating unit contains fewer atoms than the monomers because of the lost small molecule.
缩合聚合涉及两端各有两个官能团的单体。当这些单体反应时，会消去一个小分子，如水或氯化氢。聚合物链通过酯键或酰胺键连接单体而形成。与加成聚合不同，由于失去小分子，重复单元所含的原子数少于单体。
6. Polyesters | 聚酯
Polyesters are condensation polymers formed from a diol (a molecule with two –OH groups) and a dicarboxylic acid (a molecule with two –COOH groups). Each ester link is formed by the reaction between an –OH group and a –COOH group, eliminating a water molecule. The polymer chain has alternating diol and diacid units joined by ester groups.
聚酯是由二元醇（带有两个 –OH 基团的分子）和二元羧酸（带有两个 –COOH 基团的分子）形成的缩合聚合物。每个酯键由 –OH 基团和 –COOH 基团之间的反应形成，并消除一个水分子。聚合物链具有通过酯基连接起来的交替二醇和二酸单元。
Example: ethane-1,2-diol and benzene-1,4-dicarboxylic acid form the polyester Terylene (PET). The repeating unit contains an ester linkage –COO–.
示例：乙二醇和对苯二甲酸形成聚酯涤纶（PET）。重复单元含有酯键 –COO–。
7. Polyamides | 聚酰胺
Polyamides are condensation polymers made from a diamine (a molecule with two –NH₂ groups) and a dicarboxylic acid. The amine group reacts with the carboxylic acid group to form an amide (or peptide) link –CONH–, with water eliminated. Proteins are natural polyamides where amino acid monomers are linked by peptide bonds. Synthetic polyamides include nylon-6,6.
聚酰胺是由二元胺（带有两个 –NH₂ 基团的分子）和二元羧酸制成的缩合聚合物。胺基与羧酸基团反应形成酰胺键（或肽键）–CONH–，同时消去水。蛋白质是天然的聚酰胺，其中氨基酸单体通过肽键连接。合成聚酰胺包括尼龙-6,6。
Nylon-6,6 is formed from hexane-1,6-diamine and hexane-1,6-dioic acid. Each repeat unit has an amide linkage, and the name indicates the number of carbon atoms in each monomer.
尼龙-6,6 由 1,6-己二胺和 1,6-己二酸形成。每个重复单元有一个酰胺键，名称表示每个单体中的碳原子数。
8. Drawing Condensation Polymers | 绘制缩合聚合物
When drawing a condensation polymer, show the two monomers alternating, with the link functional group (ester or amide) formed between them. Draw brackets around the repeating unit and place an ‘n’ subscript outside. The ends are often shown with a line indicating continuation. Remember to remove the atoms lost in the condensation (e.g., H from –NH₂ and –OH from –COOH to form water).
绘制缩合聚合物时，要显示两种单体交替排列，并在其间形成连接官能团（酯或酰胺）。在重复单元周围画括号，并在括号外标下标 ‘n’。末端通常用线表示延续。记得去掉缩合中失去的原子（例如，从 –NH₂ 去掉 H，从 –COOH 去掉 –OH 以形成水）。
Repeating unit for polyester: –[O–R–OOC–R’–CO]–ₙ
9. Identifying Monomers from Condensation Polymers | 从缩合聚合物识别单体
To find the monomers, break the ester or amide links by adding back the atoms of the eliminated small molecule. For a polyester, add H to the O atom and OH to the C=O carbon to regenerate the diol and dicarboxylic acid. For a polyamide, add H to the N atom and OH to the C=O carbon to regenerate the diamine and dicarboxylic acid. This reverse thinking is often tested.
为了找到单体，通过加回被消去的小分子的原子来断开酯键或酰胺键。对于聚酯，将 H 加到 O 原子上，将 OH 加到 C=O 碳上，重新生成二元醇和二元羧酸。对于聚酰胺，将 H 加到 N 原子上，将 OH 加到 C=O 碳上，重新生成二元胺和二元羧酸。这种逆向思维经常被考查。
10. Natural Polymers | 天然聚合物
Natural polymers are formed in living organisms. Proteins are condensation polymers of amino acids, held together by peptide (amide) bonds. Polysaccharides like starch and cellulose are condensation polymers of glucose units, with glycosidic bonds forming and water being eliminated. DNA is also a condensation polymer of nucleotides. The IGCSE OCR syllabus expects you to recognise these as polymers and understand their monomer units.
天然聚合物是在生物体内形成的。蛋白质是氨基酸的缩合聚合物，通过肽（酰胺）键连接。淀粉和纤维素等多糖是葡萄糖单元的缩合聚合物，形成糖苷键并消去水。DNA 也是核苷酸的缩合聚合物。IGCSE OCR 考纲希望你识别这些物质为聚合物，并理解它们的单体单元。
11. Properties and Uses of Polymers | 聚合物的性质与用途
The properties of polymers depend on their structure and bonding. Addition polymers like polythene are typically thermoplastic, meaning they soften when heated and can be remoulded. Condensation polymers often have stronger intermolecular forces due to polar groups (e.g., ester or amide links), making them stronger and suitable for fibres and engineering plastics. Uses include polythene for plastic bags, PVC for pipes, PET for bottles, and nylon for clothing.
聚合物的性质取决于其结构和键合。像聚乙烯这样的加成聚合物通常是热塑性的，意味着加热时软化并能重新塑形。缩合聚合物由于极性基团（如酯基或酰胺键）往往具有更强的分子间作用力，使其更坚固，适合用作纤维和工程塑料。用途包括：聚乙烯用于塑料袋，PVC 用于管道，PET 用于瓶子，尼龙用于服装。
| Polymer | Type | Key Use |
| Polythene | Addition | Plastic bags, bottles |
| PVC | Addition | Window frames, pipes |
| PET (Terylene) | Condensation (polyester) | Drinks bottles, clothing fibres |
| Nylon-6,6 | Condensation (polyamide) | Ropes, carpets, clothing |
12. Environmental Impact and Recycling | 环境影响与回收
Many synthetic polymers are non-biodegradable, leading to waste accumulation in the environment. Recycling polymers conserves resources and reduces landfill. Addition polymers can be melted and remoulded, so they are easier to recycle. Condensation polymers like PET can be chemically recycled by breaking the ester links. Biodegradable polymers, such as those made from starch, decompose naturally and are a focus for sustainable development. Combustion of polymers can release toxic gases if not controlled.
许多合成聚合物不可生物降解，导致废物在环境中积累。回收聚合物可以节约资源并减少填埋。加成聚合物可以熔化和重塑，因此更容易回收。像 PET 这样的缩合聚合物可以通过断裂酯键进行化学回收。可生物降解聚合物（例如由淀粉制成的聚合物）自然分解，是可持续发展的重点。聚合物的燃烧如果不加控制，会释放有毒气体。
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