It is believed that polymer chains mainly terminate through bimolecular termination in free-radical polymerization, however, there is few convincing evidence to support it. In benzoyl peroxide (BPO) initiated styrene free-radical polymerization, our studies demonstrate that polymer chain terminates dominantly through primary radical termination rather than by bimolecular termination as described in polymer textbooks. Even at very high primary radical concentration or at very low monomer concentration, primary radical termination still dominates (F_PRT&CTI>70%) besides the occurrence of some bimolecular coupling terminations. Two kinds of model polymers were prepared, one for bimolecular coupling termination, and the other for primary radical termination. The ¹H-, ¹³C-, DEPT135-, and 2D HSQC NMR spectra of the polystyrene initiated by BPO are almost the same as those of the model polystyrene for primary radical termination, but they are quite different from those of the model polystyrene for bimolecular coupling termination, demonstrating directly that primary radical termination rather than bimolecular coupling termination dominates in BPO-initiated styrene free-radical polymerization.

据信在自由基聚合中聚合物链主要通过双分子终止而终止，但是，几乎没有令人信服的证据来支持它。在过氧化苯甲酰（BPO）引发的苯乙烯自由基聚合中，我们的研究表明，聚合物链主要通过伯自由基终止而不是如聚合物教科书中所述的双分子终止。即使在非常高的伯自由基浓度或在非常低的单体浓度下，除某些双分子偶联终止作用外，伯自由基终止作用仍然占主导地位（F _PRT＆CTI > 70％）。制备了两种模型聚合物，一种用于双分子偶联终止，另一种用于伯自由基终止。的¹ H-，由BPO引发的聚苯乙烯的¹³ C-，DEPT135-和2D HSQC NMR谱图与用于初级自由基终止的模型聚苯乙烯的光谱几乎相同，但与用于双分子偶联终止的模型聚苯乙烯的光谱完全不同，表明直接地，伯自由基终止而不是双分子偶联终止在BPO引发的苯乙烯自由基聚合中占主导地位。