📚 GCSE CCEA Chemistry: Polymers Revision Notes | GCSE CCEA 化学：聚合物考点精讲
Polymers are a key topic in GCSE CCEA Chemistry. They are giant covalent or supramolecular structures made from repeating monomer units. Understanding their formation, structure, properties, and environmental impact is essential for the exam.
聚合物是 GCSE CCEA 化学的重要主题。它们是由重复单体单元构成的巨型共价或超分子结构。理解它们的形成、结构、性质及环境影响对考试至关重要。
1. What Are Polymers? | 什么是聚合物？
A polymer is a very large molecule (macromolecule) built up from many small, repeating units called monomers. The term ‘polymer’ comes from Greek: ‘poly’ meaning many and ‘mer’ meaning part.
聚合物是由许多称为单体的小重复单元构成的大分子（高分子）。“聚合物”一词源自希腊语：“poly”意为“多”，“mer”意为“部分”。
Polymers can be natural, such as proteins, starch, cellulose, and DNA, or synthetic (man‑made), such as polyethylene and nylon. In GCSE CCEA Chemistry we focus mainly on synthetic organic polymers.
聚合物可以是天然的，如蛋白质、淀粉、纤维素和DNA，也可以是合成（人造）的，如聚乙烯和尼龙。在GCSE CCEA化学中，我们主要学习合成有机聚合物。
The process of joining monomers together is called polymerisation. There are two main types: addition polymerisation and condensation polymerisation.
将单体连接在一起的过程称为聚合。主要有两种类型：加成聚合和缩合聚合。
2. Monomers and Repeating Units | 单体和重复单元
A monomer is a small molecule that can be linked to many others to form a polymer. In addition polymerisation the monomer must contain a carbon‑carbon double bond (C=C).
单体是可以与许多其他分子连接形成聚合物的小分子。在加成聚合中，单体必须含有碳碳双键（C=C）。
The repeat unit is the smallest group of atoms that, when repeated many times, makes up the polymer chain. It is shown in brackets with bonds extending outwards and a subscript ‘n’ to indicate a large number of repeats.
重复单元是重复多次构成聚合物链的最小原子基团。通常用向外延伸键的方括号表示，并带有下标“n”表示大量重复。
For example, the repeat unit of poly(ethene) is –(CH₂–CH₂)–ₙ, derived from the monomer ethene, CH₂=CH₂.
例如，聚乙烯的重复单元是 –(CH₂–CH₂)–ₙ，衍生自单体乙烯 CH₂=CH₂。
3. Addition Polymerisation | 加成聚合
Addition polymerisation occurs when many alkene monomers (or monomers with a C=C bond) open up their double bond and join together to form a long chain. No other products are formed – the repeating unit has the same atoms as the monomer.
当许多烯烃单体（或含有C=C键的单体）打开双键并连接在一起形成长链时，就发生加成聚合。不生成其他产物——重复单元与单体具有相同的原子。
The general equation for addition polymerisation of an alkene is:
烯烃加成聚合的通式为：
n (monomer) → –[–repeat unit–]–ₙ
The double bond in each monomer changes to a single bond, allowing carbon atoms to form two new single bonds with neighbouring monomer units.
每个单体中的双键变为单键，使碳原子能够与相邻单体单元形成两个新的单键。
Addition polymers are named by placing the monomer name in brackets and adding the prefix ‘poly’, e.g. poly(ethene), poly(propene), poly(chloroethene).
加成聚合物的命名方法是将单体名称放在括号中并加上前缀“聚”，例如聚乙烯、聚丙烯、聚氯乙烯。
4. Drawing Addition Polymers | 绘制加成聚合物
To draw the repeat unit of an addition polymer, start with two carbon atoms singly bonded together (from the original C=C). Remove the double bond and attach the side groups as they appeared in the monomer, then show the open bonds that connect to the rest of the chain.
绘制加成聚合物的重复单元时，先从两个单键相连的碳原子开始（源自原来的C=C）。去掉双键，按单体中出现的侧基连接，然后画出连接链其余部分的开放键。
The repeat unit must be enclosed in square brackets, with the bonds extending through the brackets. The subscript ‘n’ is written outside the bracket on the right.
重复单元必须用方括号括起来，键延伸穿过括号。下标“n”写在括号外右侧。
For example, poly(chloroethene) (PVC) has the monomer CH₂=CHCl and its repeat unit is:
例如，聚氯乙烯（PVC）的单体为 CH₂=CHCl，其重复单元为：
–[–CH₂–CHCl–]–ₙ
5. Common Addition Polymers | 常见加成聚合物
The table below summarises some important addition polymers, their monomers and typical uses.
下表总结了一些重要的加成聚合物、它们的单体和典型用途。
| Monomer (单体) | Polymer (聚合物) | Common Uses (常见用途) |
|---|---|---|
| Ethene (CH₂=CH₂) | Poly(ethene) / PE | Plastic bags, bottles, packaging |
| Propene (CH₂=CHCH₃) | Poly(propene) / PP | Ropes, carpets, food containers |
| Chloroethene (CH₂=CHCl) | Poly(chloroethene) / PVC | Window frames, pipes, insulation |
| Styrene (CH₂=CHC₆H₅) | Poly(styrene) / PS | Packaging, insulation, disposable cups |
The side groups influence the properties. For instance, the large phenyl group (C₆H₅) in polystyrene makes it rigid, while the chlorine atoms in PVC make it strong and flame‑resistant.
侧基影响性能。例如，聚苯乙烯中的大苯基（C₆H₅）使其坚硬，而PVC中的氯原子使其坚固且阻燃。
6. Condensation Polymerisation | 缩合聚合
Condensation polymerisation involves monomers with at least two functional groups. When they react, a small molecule (usually water, or sometimes HCl) is eliminated as a by‑product.
缩合聚合涉及至少具有两个官能团的单体。当它们反应时，会脱去一个小分子（通常是水，有时是HCl）作为副产物。
Two important types of condensation polymers are polyesters and polyamides. These are often referred to by their common names, such as PET or nylon.
两种重要的缩合聚合物是聚酯和聚酰胺。它们通常使用通用名称，如PET或尼龙。
For example, polyethylene terephthalate (PET) is formed from ethane‑1,2‑diol and terephthalic acid:
例如，聚对苯二甲酸乙二酯（PET）由乙二醇和对苯二甲酸形成：
n HO–CH₂CH₂–OH + n HOOC–C₆H₄–COOH → –[–O–CH₂CH₂–O–CO–C₆H₄–CO–]–ₙ + 2n H₂O
Nylon‑6,6 is a polyamide made from hexane‑1,6‑diamine and hexanedioic acid:
尼龙‑6,6是一种聚酰胺，由己二胺和己二酸制成：
n H₂N–(CH₂)₆–NH₂ + n HOOC–(CH₂)₄–COOH → –[–NH–(CH₂)₆–NH–CO–(CH₂)₄–CO–]–ₙ + 2n H₂O
Condensation polymers can be designed with ester or amide links in the backbone, giving them different properties from addition polymers.
缩合聚合物的主链上可设计有酯键或酰胺键，使它们具有与加成聚合物不同的性质。
7. Thermoplastics and Thermosets | 热塑性塑料和热固性塑料
Polymers can be classified according to their behaviour when heated. Thermoplastics soften when heated and harden again when cooled. This process can be repeated many times because the polymer chains are held together by weak intermolecular forces, not cross‑links.
聚合物可根据受热时的行为进行分类。热塑性塑料加热时软化，冷却后又硬化。这个过程可以重复多次，因为聚合物链由较弱的分子间作用力聚集，没有交联。
Thermosetting polymers (thermosets) do not soften when reheated. During their initial shaping, strong covalent cross‑links form between chains, creating a rigid 3D network that cannot be remoulded.
热固性聚合物（热固性塑料）再次加热时不会软化。在最初成型过程中，链之间形成牢固的共价交联，产生一个坚硬的三维网络，无法重新塑形。
Examples of thermoplastics include poly(ethene), poly(propene), and PVC. Common thermosets are melamine‑formaldehyde (used for plates) and urea‑formaldehyde (used for adhesives).
热塑性塑料的例子包括聚乙烯、聚丙烯和PVC。常见的热固性塑料有三聚氰胺‑甲醛（用于制造碟子）和脲醛（用于胶粘剂）。
8. Properties and Uses Related to Structure | 与结构相关的性质与用途
The properties of a polymer depend on the monomer, the chain length, the presence of branched chains, and the degree of cross‑linking. These properties determine how the polymer is used.
聚合物的性质取决于单体、链长、支链的存在以及交联度。这些性质决定了聚合物的用途。
Low‑density poly(ethene) (LDPE) has branched chains, which make it flexible and suitable for plastic bags. High‑density poly(ethene) (HDPE) has straighter chains, giving it greater strength for bottles and pipes.
低密度聚乙烯（LDPE）具有支链，使其柔韧，适合制作塑料袋。高密度聚乙烯（HDPE）链更直，强度更大，适合制作瓶子和管道。
Poly(propene) is strong and tough, so it is used for ropes and car bumpers. PVC is durable and weather‑resistant, making it ideal for window frames.
聚丙烯坚固且坚韧，因此用于绳索和汽车保险杠。PVC耐用且耐候，非常适合用于窗框。
Thermosets are hard and heat‑resistant, so they are used for saucepan handles, electrical plugs and sockets, and kitchen worktops.
热固性塑料坚硬且耐热，因此用于锅柄、电插头插座和厨房台面。
9. Environmental Impact of Polymers | 聚合物的环境影响
Most synthetic polymers are not biodegradable because bacteria and fungi do not have the enzymes to break down the strong carbon‑carbon bonds in their backbone. This leads to long‑term pollution if they are discarded irresponsibly.
大多数合成聚合物是不可生物降解的，因为细菌和真菌没有分解其主链中坚固碳‑碳键的酶。如果随意丢弃，会导致长期污染。
When polymers are burned, they can release carbon dioxide (a greenhouse gas) and, if they contain chlorine (as in PVC), toxic hydrogen chloride (HCl) gas. Incomplete combustion can produce carbon monoxide.
聚合物燃烧时会释放二氧化碳（温室气体），如果含有氯（如PVC），还会释放有毒的氯化氢（HCl）气体。不完全燃烧会产生一氧化碳。
Addition polymers are made from monomers derived from crude oil, a non‑renewable resource. Their production therefore consumes fossil fuels and contributes to resource depletion.
加成聚合物的单体来自原油，这是一种不可再生资源。因此其生产消耗化石燃料并导致资源枯竭。
10. Recycling and Biodegradable Polymers | 回收与可生物降解聚合物
Recycling polymers reduces the need for new raw materials, saves energy, and decreases landfill waste. Thermoplastics can be melted and remoulded into new products, but thermosets cannot be recycled in this way because of their cross‑links.
回收聚合物减少了对新原材料的需求，节约能源，并减少了垃圾填埋量。热塑性塑料可以熔化和重塑制成新产品，但热固性塑料因交联无法以这种方式回收。
Biodegradable polymers are designed to be broken down by microorganisms into water, carbon dioxide, and biomass. Common examples include polylactic acid (PLA) derived from corn starch, and polyhydroxyalkanoates (PHAs) produced by bacteria.
可生物降解聚合物旨在被微生物分解成水、二氧化碳和生物质。常见例子包括由玉米淀粉制成的聚乳酸（PLA）和由细菌产生的聚羟基脂肪酸酯（PHA）。
Another approach is to use photodegradable polymers, which break down when exposed to sunlight. Incorporating starch granules into traditional polymers can also help fragments to degrade more readily.
另一种方法是使用光降解聚合物，它们在暴露于阳光下时分解。在传统聚合物中掺入淀粉颗粒也有助于碎片更容易降解。
In CCEA exams, you may be asked to evaluate the advantages and disadvantages of biodegradable polymers compared with recycling, considering both environmental and economic factors.
在 CCEA 考试中，你可能需要评估可生物降解聚合物与回收相比的优缺点，同时考虑环境和经济因素。
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