📚 IGCSE Edexcel Chemistry: Polymers – Key Points Mastery | IGCSE Edexcel 化学：聚合物考点精讲
Polymers are everywhere – from plastic bottles and nylon clothing to the DNA inside every living cell. In IGCSE Edexcel Chemistry, the topic of polymers bridges organic chemistry and real-world applications. This article will walk you through the essential concepts, reaction types, structures, and environmental considerations you need to master for your exam, with clear bilingual explanations to boost your understanding and confidence.
聚合物无处不在——从塑料瓶、尼龙衣物到每个活细胞内的 DNA。在 IGCSE Edexcel 化学中，聚合物这一主题连接了有机化学与现实应用。本文将带你系统梳理考试中需要掌握的核心概念、反应类型、结构以及环境因素，并以清晰的双语讲解提升你的理解与应考信心。
1. Monomers and Polymers | 单体与聚合物
A polymer is a long-chain molecule made up of many repeating units called monomers. The process of joining monomers together is polymerisation. Monomers are typically small alkene molecules for addition polymers, or molecules with two functional groups for condensation polymers.
聚合物是由许多称为单体的重复单元组成的长链分子。将单体连接起来的过程称为聚合反应。对于加成聚合物，单体通常是小的烯烃分子；对于缩合聚合物，单体则通常具有两个官能团。
Think of monomers as individual paperclips. When you link hundreds of them together, you form a long chain – that’s your polymer. The chemical bonds replace the mechanical links.
可以把单体想象成单个回形针。当你把成百上千个回形针连接起来，就形成了一条长链——这就是你的聚合物。化学键取代了物理连接。
2. Addition Polymerisation | 加成聚合反应
Addition polymerisation involves unsaturated monomers (alkenes) opening their carbon‑carbon double bond (C=C) to form a long saturated chain. No other products are formed – just the polymer. For example, ethene (C₂H₄) polymerises to poly(ethene), commonly known as polythene.
加成聚合反应涉及不饱和单体（烯烃）打开其碳碳双键（C=C）形成一条长的饱和链。反应过程中没有其他产物生成——只得到聚合物。例如，乙烯（C₂H₄）聚合成聚乙烯，俗称聚乙烯。
The general equation can be written as: n CH₂=CH₂ → –(CH₂–CH₂)–ₙ. The repeating unit is –CH₂–CH₂–, and n represents a large number.
通式可写为：n CH₂=CH₂ → –(CH₂–CH₂)–ₙ。重复单元为 –CH₂–CH₂–，n 代表一个很大的数目。
High pressure and a catalyst are often used to initiate the reaction. Poly(propene) is made from propene (CH₃CH=CH₂) in a similar way.
反应通常在高压和催化剂条件下引发。聚丙烯由丙烯（CH₃CH=CH₂）以类似方式制得。
3. Drawing Addition Polymers | 绘制加成聚合物
When drawing the repeating unit of an addition polymer, first identify the monomer. Remove the double bond and show the two carbon atoms with single bonds continuing to brackets on both sides. Attach any side groups exactly as they were on the monomer.
绘制加成聚合物的重复单元时，首先识别单体。去掉双键，画出两个碳原子，用单键向两侧括号延伸。侧基保持与单体上一致。
For example, poly(propene) from CH₃–CH=CH₂: the repeating unit is –[CH(CH₃)–CH₂]–. Always show the pendant methyl group on the second carbon, and draw the brackets with n outside.
例如，由 CH₃–CH=CH₂ 制得的聚丙烯：重复单元为 –[CH(CH₃)–CH₂]–。始终在第二个碳原子上画出悬挂的甲基，并在括号外标注 n。
Exam tip: Do not draw the double bond in the polymer backbone; it is a saturated chain after addition polymerisation.
考试提示：不要在聚合物主链中画双键；加成聚合后已是饱和链。
4. Properties and Uses of Addition Polymers | 加成聚合物的性质与用途
Addition polymers like poly(ethene), poly(propene), poly(chloroethene) (PVC) and poly(tetrafluoroethene) (PTFE) have different properties based on their side groups. Poly(ethene) is flexible and used for plastic bags; poly(propene) is tougher and used for crates and ropes; PVC is rigid and used for pipes; PTFE is non‑stick and used for coatings.
加成聚合物如聚乙烯、聚丙烯、聚氯乙烯（PVC）和聚四氟乙烯（PTFE）因侧基不同而具有不同的性质。聚乙烯柔韧，用于塑料袋；聚丙烯更坚韧，用于板条箱和绳索；聚氯乙烯坚硬，用于管道；聚四氟乙烯不粘，用于涂层。
These polymers are chemically unreactive due to the strong C–C and C–H bonds, which make them durable but also non‑biodegradable.
由于存在牢固的 C–C 和 C–H 键，这些聚合物化学性质不活泼，这使得它们经久耐用，但同时也难以生物降解。
5. Condensation Polymerisation | 缩合聚合反应
Condensation polymerisation involves monomers with two reactive functional groups joining together, with the elimination of a small molecule – usually water or hydrogen chloride. Two types of condensation polymers you need to know are polyesters and polyamides.
缩合聚合反应涉及带有两个反应性官能团的单体彼此连接，同时脱去一个小分子——通常是水或氯化氢。你需要了解的两种缩合聚合物是聚酯和聚酰胺。
For example, a dicarboxylic acid and a diol react to form a polyester, releasing water. A dicarboxylic acid and a diamine form a polyamide, also releasing water. The repeating units contain ester (–COO–) or amide (–CONH–) linkages.
例如，二元羧酸与二元醇反应生成聚酯，同时释放水。二元羧酸与二元胺生成聚酰胺，同样释放水。重复单元中含有酯基（–COO–）或酰胺基（–CONH–）连接。
Unlike addition polymerisation, the monomer and the polymer don’t have the same empirical formula because of the loss of small molecules.
与加成聚合不同，由于小分子的失去，单体和聚合物的经验式不相同。
6. Polyesters | 聚酯
A common polyester is Terylene (PET), made from ethane‑1,2‑diol and terephthalic acid (a dicarboxylic acid). Each monomer provides two functional groups: the diol gives two –OH groups, and the diacid gives two –COOH groups.
常见的聚酯是涤纶（PET），由乙二醇（1,2-乙二醇）和对苯二甲酸（一种二元羧酸）制成。每种单体提供两个官能团：二醇提供两个 –OH 基团，二元酸提供两个 –COOH 基团。
During polymerisation, the –OH of the diol and the –COOH of the diacid react, eliminating water and forming ester linkages: –O–CO–. The repeating unit in PET is –O–CH₂–CH₂–O–CO–C₆H₄–CO–.
在聚合过程中，二醇的 –OH 与二元酸的 –COOH 反应，脱去水并形成酯键：–O–CO–。PET 中的重复单元为 –O–CH₂–CH₂–O–CO–C₆H₄–CO–。
Polyesters are used in fabrics, plastic bottles, and films. They can be hydrolysed by acids or alkalis, breaking the ester links – a property useful for recycling.
聚酯用于织物、塑料瓶和薄膜。它们在酸或碱作用下可水解，断裂酯键——这一性质对回收利用很有帮助。
7. Polyamides | 聚酰胺
Nylon is a well‑known polyamide, typically made from a dicarboxylic acid and a diamine, such as hexanedioic acid and 1,6‑diaminohexane. The amide linkages (–CONH–) form between the monomers, with water eliminated each time.
尼龙是一种广为人知的聚酰胺，通常由二元羧酸和二元胺制成，如己二酸和 1,6-己二胺。酰胺键（–CONH–）在单体之间形成，每次均脱去一个水分子。
The repeating unit for Nylon‑6,6 is –NH–(CH₂)₆–NH–CO–(CH₂)₄–CO–. The numbers ‘6,6’ refer to the number of carbon atoms in each monomer.
尼龙‑6,6 的重复单元为 –NH–(CH₂)₆–NH–CO–(CH₂)₄–CO–。数字 “6,6” 指的是每种单体中的碳原子数。
Polyamides have high tensile strength and are used for ropes, parachutes, and clothing. Naturally occurring polyamides include proteins, where amino acids act as monomers.
聚酰胺具有高拉伸强度，用于绳索、降落伞和衣物。天然存在的聚酰胺包括蛋白质，其中氨基酸充当单体。
8. Natural Polymers: DNA and Proteins | 天然聚合物：DNA 与蛋白质
DNA is a natural condensation polymer made from nucleotide monomers. Each nucleotide consists of a phosphate group, a sugar (deoxyribose), and a nitrogenous base. The nucleotides join via phosphodiester bonds with the elimination of water.
DNA 是一种天然缩合聚合物，由核苷酸单体组成。每个核苷酸包含一个磷酸基团、一个糖（脱氧核糖）和一个含氮碱基。核苷酸通过磷酸二酯键连接，同时脱去水。
Proteins are polyamides formed from amino acid monomers. Each amino acid has an amine group (–NH₂) and a carboxyl group (–COOH). They link through peptide bonds (–CONH–), producing a polypeptide chain and releasing water.
蛋白质是由氨基酸单体形成的聚酰胺。每个氨基酸含有一个氨基（–NH₂）和一个羧基（–COOH）。氨基酸通过肽键（–CONH–）连接，形成多肽链并释放水。
Both DNA and proteins are essential biological molecules; their specific sequences determine genetic information and protein function.
DNA 和蛋白质都是关键的生物分子；它们的特定序列决定了遗传信息和蛋白质功能。
9. Starch and Cellulose | 淀粉与纤维素
Starch and cellulose are natural polymers made from glucose monomers. Glucose molecules (C₆H₁₂O₆) join by condensation reactions, eliminating water to form glycosidic linkages. Starch is a mixture of amylose (unbranched helix) and amylopectin (branched). Cellulose is a straight, unbranched polymer with strong hydrogen bonds between chains, making it rigid and ideal for plant cell walls.
淀粉和纤维素是由葡萄糖单体组成的天然聚合物。葡萄糖分子（C₆H₁₂O₆）通过缩合反应连接，脱去水形成糖苷键。淀粉是直链淀粉（无支链螺旋）和支链淀粉（有分支）的混合物。纤维素是直链无分支聚合物，链间有强大的氢键，使其坚硬，是植物细胞壁的理想材料。
While both are made of glucose, the difference in bonding (α‑1,4 in starch vs β‑1,4 in cellulose) leads to vastly different properties and functions. Humans can digest starch but cannot digest cellulose due to the lack of the cellulase enzyme.
虽然两者均由葡萄糖构成，但键的类型不同（淀粉为 α-1,4 糖苷键，纤维素为 β-1,4 糖苷键），导致性质和功能差异巨大。人类能消化淀粉，但因缺乏纤维素酶而无法消化纤维素。
10. Disposal and Environmental Issues | 废弃处理与环境问题
Addition polymers like polythene and PVC are non‑biodegradable due to the strength of their C–C backbones. They persist in landfill, causing long‑term waste problems. Incineration can generate energy but may release toxic gases – burning PVC produces hydrogen chloride, which leads to acid rain unless scrubbed.
加成聚合物如聚乙烯和聚氯乙烯由于 C–C 主链的强度而难以生物降解。它们长期存在于垃圾填埋场，造成持续的废物问题。焚烧可以产生能量，但可能释放有毒气体——焚烧 PVC 会产生氯化氢，若不处理会引发酸雨。
Recycling conserves resources and reduces waste. Thermoplastics (e.g., poly(ethene), PET) can be melted and remoulded, whereas thermosetting plastics cannot.
回收利用节约资源并减少废物。热塑性塑料（如聚乙烯、PET）可熔融重塑，而热固性塑料不能。
11. Biodegradable Polymers | 可生物降解聚合物
Biodegradable polymers can be broken down by microorganisms into water, carbon dioxide, and biological matter. Examples include poly(lactic acid) (PLA) derived from corn starch, and polyesters made from renewable sources. They contain ester or amide bonds that are susceptible to enzymatic hydrolysis.
可生物降解聚合物能被微生物分解为水、二氧化碳和生物质。例如源自玉米淀粉的聚乳酸（PLA），以及由可再生资源制成的聚酯。它们含有酯键或酰胺键，易受酶促水解的影响。
Biodegradable polymers are often used in packaging, medical sutures, and agricultural films. However, they must be disposed of under the right conditions (e.g., industrial composting) to degrade effectively.
可生物降解聚合物常用于包装、医用缝合线和农用薄膜。然而，它们必须在适当的条件（如工业堆肥）下处理，才能有效降解。
12. Comparing Addition and Condensation Polymers | 加成与缩合聚合物的对比
The main differences between the two types of polymerisation are summarised in the table below:
两种聚合方式的主要区别总结如下表：
| Feature 特征 | Addition Polymerisation 加成聚合 | Condensation Polymerisation 缩合聚合 |
|---|---|---|
| Monomers 单体 | Alkenes (C=C) 烯烃 | Two functional groups per monomer (e.g., diol + diacid, diamine + diacid) 每个单体有两个官能团 |
| Other Products 副产物 | None 无 | Small molecule (often H₂O or HCl) 小分子（常为水或 HCl） |
| Polymer Backbone 聚合物主链 | Carbon‑carbon chain only 仅碳碳链 | Contains ester or amide linkages 含酯键或酰胺键 |
| Empirical Formula 经验式 | Same as monomer 与单体相同 | Different from monomers due to small molecule loss 因小分子失去而与单体不同 |
| Biodegradability 生物可降解性 | Generally non‑biodegradable 通常不可生物降解 | Often biodegradable (hydrolysable linkages) 常可生物降解（可水解键） |
Remember: both types are important in your syllabus. You should be able to identify the type from the polymer structure and describe the polymerisation process.
记住：两种类型在你的考纲中都很重要。你应该能从聚合物结构中识别其类型，并能描述聚合过程。
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