聚合反应 Polymerization — 定义、原理与由来

定义Definition

聚合反应是小分子单体通过化学键相互连接，形成高分子（聚合物）的反应。按机理分为链式聚合（自由基、离子、配位聚合）和逐步聚合（缩聚、加成型逐步聚合）。

Polymerisation links small monomers by chemical bonds into macromolecules. By mechanism it divides into chain-growth (radical, ionic, coordination) and step-growth (condensation and polyaddition) polymerisation.

链式聚合Chain-growth polymerisation

活性中心（自由基、碳正离子、碳负离子或金属–碳键）一旦生成，就迅速加上大量单体；任何时刻体系中主要是单体和高分子，分子量很快达到最大。包括引发、增长、终止（和链转移）。活性聚合（无终止）可得窄分布和嵌段共聚物。

Once an active centre (radical, cation, anion or metal–carbon bond) forms it adds many monomers rapidly; the mixture contains mainly monomer and high polymer, and molar mass is reached early. Steps: initiation, propagation, termination (and transfer). Living polymerisations without termination give narrow distributions and block copolymers.

逐步聚合Step-growth polymerisation

任何两个带官能团的分子（单体、低聚物）都能相互反应，分子量随反应程度缓慢增长，只有在转化率接近 100% 时才得到高分子（卡罗瑟斯方程）。尼龙、聚酯、聚氨酯、环氧树脂都属此类。

Any two functional molecules (monomers or oligomers) can react, so molar mass grows slowly and becomes high only near full conversion (Carothers equation). Nylons, polyesters, polyurethanes and epoxies are made this way.

历史History

施陶丁格（1920）提出大分子是共价连接的长链（1953 年诺贝尔化学奖）；卡罗瑟斯（1930 年代）在杜邦发明尼龙-66 与氯丁橡胶；齐格勒与纳塔（1950 年代）发展配位聚合。

Staudinger (1920) proposed that macromolecules are covalent long chains (Nobel 1953); Carothers at DuPont invented nylon-6,6 and neoprene in the 1930s; Ziegler and Natta developed coordination polymerisation in the 1950s.

反应Reactions

n CH₂=CHR ⟶ –[CH₂–CHR]ₙ–链式n HOOC–R–COOH + n H₂N–R′–NH₂ ⟶ –[CO–R–CO–NH–R′–NH]ₙ– + 2n H₂O逐步n CH₂=CHR ⟶ –[CH₂–CHR]ₙ–; n HOOC–R–COOH + n H₂N–R′–NH₂ ⟶ –[CO–R–CO–NH–R′–NH]ₙ– + 2n H₂O

视聚合类型而定

Depends on the polymerisation type

链式：引发 → 增长 → 终止 / 链转移。
Chain: initiation → propagation → termination/transfer.
逐步：官能团间逐步反应，分子量随转化率缓慢升高。
Step: stepwise reaction of functional groups, molar mass rising slowly with conversion.

n CH₂=CHCl ⟶ PVC

氯乙烯自由基聚合。

Radical polymerisation of vinyl chloride.

年表Timeline

1920
施陶丁格提出大分子概念
Staudinger proposes the macromolecule concept
1935
卡罗瑟斯合成尼龙-66
Carothers synthesises nylon-6,6
1953
齐格勒催化剂低压聚乙烯
Ziegler’s low-pressure polyethylene
1956
施瓦茨报道活性阴离子聚合
Szwarc reports living anionic polymerisation

聚合反应Polymerization