Condensation Polymerisation | 缩合聚合反应

📚 Condensation Polymerisation | 缩合聚合反应

Condensation polymerisation is a type of polymerisation in which monomers with two or more functional groups join together, releasing small molecules such as water, hydrogen chloride or ammonia in the process.

缩合聚合是一类聚合反应，其中含有两个或更多官能团的单体相互连接，同时释放出水、氯化氢或氨等小分子。

1. What is Condensation Polymerisation? | 什么是缩合聚合？

Condensation polymerisation involves the reaction between bifunctional or polyfunctional monomers, resulting in the formation of polymer chains along with the elimination of small molecules. The monomers must possess at least two reactive functional groups per molecule to allow chain extension.

缩合聚合涉及双官能团或多官能团单体之间的反应，形成聚合物链的同时消除小分子。每个单体分子必须至少含有两个反应性官能团，才能实现链的增长。

For example, when a dicarboxylic acid reacts with a diol, the -COOH group of one monomer reacts with the -OH group of another, forming an ester linkage (-COO-) and releasing a molecule of water.

例如，当二羧酸与二醇反应时，一个单体的-COOH基团与另一个单体的-OH基团反应，形成酯键（-COO-）并释放一分子水。

HOOC-R-COOH + HO-R'-OH → [-CO-R-COO-R'-O-]ₙ + nH₂O

Each condensation step creates a covalent bond between monomers while a small by-product (usually water) is lost. The process repeats to form a long-chain polymer.

每一步缩合都在单体之间形成共价键，同时失去一个小分子副产物（通常是水）。该过程重复进行，形成长链聚合物。

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2. Key Features of Condensation Polymerisation | 缩合聚合的主要特征

Several distinguishing features define condensation polymerisation:

以下几个特征定义了缩合聚合反应：

• Monomers contain two functional groups per molecule (e.g., -COOH, -OH, -NH₂).

  每个单体分子含有两个官能团（如-COOH、-OH、-NH₂）。

• A small molecule is eliminated at each step of chain growth.

  链增长的每一步都会消除一个小分子。

• The polymer repeat unit does not have the same molecular formula as the monomer (unlike addition polymers).

  聚合物的重复单元与单体的分子式不同（与加成聚合物不同）。

• Monomers can be the same or different compounds — condensation polymerisation often involves two different monomers.

  单体可以是相同或不同的化合物——缩合聚合通常涉及两种不同的单体。

• The reaction proceeds by a step-growth mechanism, meaning polymer chains grow gradually over time.

  反应通过逐步增长机理进行，意味着聚合物链随时间逐渐增长。

In A-Level Chemistry, the two main classes of condensation polymers you must know are polyesters and polyamides.

在A-Level化学中，你必须掌握的两种主要缩合聚合物类别是聚酯和聚酰胺。

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3. Polyesters | 聚酯

Polyesters are formed by the condensation polymerisation of a dicarboxylic acid and a diol. The ester linkage (-COO-) joins the monomer units together.

聚酯由二羧酸和二醇通过缩合聚合反应形成。酯键（-COO-）将单体单元连接在一起。

Consider the reaction between ethane-1,2-diol (ethylene glycol) and benzene-1,4-dicarboxylic acid (terephthalic acid):

考虑乙烷-1,2-二醇（乙二醇）与苯-1,4-二甲酸（对苯二甲酸）之间的反应：

n HOCH₂CH₂OH + n HOOC-C₆H₄-COOH → [-OCH₂CH₂OCO-C₆H₄-CO-]ₙ + 2n H₂O

The polymer produced is poly(ethylene terephthalate), commonly known as PET, which is widely used in plastic bottles and textile fibres (polyester).

生成的聚合物是聚对苯二甲酸乙二醇酯（PET），广泛用于塑料瓶和纺织纤维（涤纶）。

To draw the repeat unit of a polyester:

要绘制聚酯的重复单元：

• Identify the two monomers: a diol (HO-R-OH) and a dicarboxylic acid (HOOC-R'-COOH).

  识别两种单体：二醇（HO-R-OH）和二羧酸（HOOC-R'-COOH）。

• Remove one H from each -OH group of the diol and the -OH from each -COOH group of the acid.

  从二醇的每个-OH基团上移除一个H，从酸的每个-COOH基团上移除-OH。

• Join the remaining fragments via ester linkages: -O-CO-R'-CO-O-R-.

  通过酯键连接剩余片段：-O-CO-R'-CO-O-R-。

• Add n to indicate the polymer chain length.

  添加n以表示聚合物链长。

For exam purposes, you should be able to deduce the monomers from a given polyester structure and vice versa.

在考试中，你应该能够从给定的聚酯结构推导出单体，反之亦然。

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4. Polyamides | 聚酰胺

Polyamides are formed when a dicarboxylic acid reacts with a diamine. The amide linkage (-CONH-) joins the monomer units. Nylon and Kevlar are the most notable examples.

当二羧酸与二胺反应时形成聚酰胺。酰胺键（-CONH-）连接单体单元。尼龙和凯夫拉是最著名的例子。

Nylon-6,6 is produced from hexane-1,6-diamine and hexanedioic acid (adipic acid):

尼龙-6,6由己-1,6-二胺和己二酸（肥酸）生产：

n H₂N(CH₂)₆NH₂ + n HOOC(CH₂)₄COOH → [-NH(CH₂)₆NHCO(CH₂)₄CO-]ₙ + 2n H₂O

The name "Nylon-6,6" reflects the number of carbon atoms in each diamine (6) and each dicarboxylic acid (6).

"尼龙-6,6"的名称反映了每个二胺（6）和每个二羧酸（6）中的碳原子数。

Polyamides can also be formed from amino acids, which contain both an amine group and a carboxylic acid group in the same molecule. For example, 6-aminohexanoic acid polymerises to form nylon-6:

聚酰胺也可以由氨基酸形成，氨基酸在同一分子

Published by TutorHao | A-Level Chemistry Revision Series | aleveler.com

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