活性聚合Living polymerization

所有链几乎同时引发、以相同速率增长，且不终止，因此数均聚合度 Xₙ = 转化率 × [M]₀/[I]₀，Mₙ 随转化率线性增长，分子量分布接近泊松分布（Đ ≈ 1 + 1/Xₙ）。判断依据包括：ln([M]₀/[M]) 对时间呈直线；Mₙ 与转化率呈直线；再次加入单体链可继续增长。

All chains start almost together, grow at the same rate and never terminate, so Xₙ = conversion × [M]₀/[I]₀, Mₙ rises linearly with conversion and the distribution approaches Poisson (Đ ≈ 1 + 1/Xₙ). Diagnostic tests are a linear plot of ln([M]₀/[M]) against time, a linear plot of Mₙ against conversion, and continued growth when more monomer is added.

1956 年施瓦克用萘钠引发苯乙烯阴离子聚合，发现反应液保持红色（活性链端），加入新单体可继续聚合，提出“活性聚合物”概念。1980 年代发展了活性阳离子聚合（东村敏延、肯尼迪）和基团转移聚合。1990 年代的 ATRP、RAFT、NMP 实现了“可控/活性自由基聚合”，适用单体范围大大扩展。开环易位聚合和配位聚合中也有活性体系。

In 1956 Szwarc initiated anionic polymerisation of styrene with sodium naphthalenide and found the solution stayed red, from active chain ends, and resumed polymerising when more monomer was added; he coined 'living polymers'. Living cationic polymerisation (Higashimura, Kennedy) and group-transfer polymerisation followed in the 1980s, and ATRP, RAFT and NMP brought 'controlled/living radical polymerisation' in the 1990s, greatly widening the range of monomers. Living systems also exist in ring-opening metathesis and coordination polymerisation.

苯乙烯-丁二烯-苯乙烯（SBS）三嵌段共聚物在常温下聚苯乙烯段聚集成物理交联点，表现为橡胶，加热又可熔融加工，是热塑性弹性体的代表，用于鞋底和沥青改性。两亲嵌段共聚物在溶液中自组装成胶束和囊泡，用于药物递送；嵌段共聚物薄膜的微相分离可用于纳米图案化光刻。

In styrene–butadiene–styrene (SBS) triblock copolymers the polystyrene ends cluster into physical crosslinks at room temperature, so the material behaves as rubber yet melts for processing; it is the classic thermoplastic elastomer, used in shoe soles and asphalt modification. Amphiphilic block copolymers self-assemble in solution into micelles and vesicles for drug delivery, and microphase separation in block-copolymer films is used for nanoscale lithographic patterning.