1-Hexene was polymerized with a commercial MgCl₂-supported Ziegler-Natta catalyst using triethylaluminum as cocatalyst at different monomer/catalyst mass ratio (m_hexene/m_cat = 5, 15, 30), and the number of active centers ([C^*]/[Ti]) was determined by quench-labeling the catalyst with 2-thiophenecarbonyl chloride and monitoring sulfur content of the polymer. Changes of polymerization rate (R_p) and propagation rate constant (k_p) with time were also determined. [C^*]/[Ti] was found to increase with time for 3 − 5 folds in the first 10 min of polymerization, but the maximum [C^*]/[Ti] value reached after the induction period markedly enhanced with increase of monomer/catalyst mass ratio. Gradual fragmentation of the catalyst particles in parallel with the [C^*]/[Ti] increase was observed by SEM analysis. It means that a large proportion of active center precursors are inaccessible to cocatalyst and monomer at the beginning of reaction, and fragmentation of the particles by hydraulic force of the growing polymer chains leads to exposure and activation of these precursors. Raising the monomer concentration can provide larger hydraulic force to expose those active site precursors that are more tightly buried inside the catalyst particle. The polymer molecular weight distribution and related active center distribution was found to shift with increase of the monomer/catalyst ratio, meaning that there are different types of buried active center precursors, and their exposure requires different extent of particle fragmentation.

使用三乙基铝作为助催化剂，以市售MgCl ₂负载的Ziegler-Natta催化剂与_1-己烯在不同的单体/催化剂质量比（间_己烯/ m _cat  = 5、15、30）和活性中心数（[C通过用2-噻吩羰基氯对催化剂进行淬灭标记并监测聚合物的硫含量来确定^* ] / [Ti]）。还确定了聚合速率（R _p）和传播速率常数（k _p）随时间的变化。发现[C ^* ] / [Ti]在聚合的前10分钟内随时间增加3-5倍，但最大值[C ^* ] / [Ti]诱导期后达到的] / [Ti]值随着单体/催化剂质量比的增加而显着提高。与[C ^*通过SEM分析观察到] / [Ti]增加。这意味着在反应开始时助催化剂和单体无法获得大部分的活性中心前体，并且由于生长中的聚合物链的水力而导致的颗粒破碎会导致这些前体的暴露和活化。提高单体浓度可以提供更大的水力，以暴露出那些更紧密地埋在催化剂颗粒内部的活性位点前体。发现聚合物分子量分布和相关的活性中心分布随着单体/催化剂比的增加而移动，这意味着存在不同类型的掩埋的活性中心前体，并且它们的暴露需要不同程度的颗粒破碎。