We have kinetically elucidated the origins of activity enhancement because of the addition of comonomer in Ziegler‐Natta propylene polymerization, using stopped‐flow and continuously purged polymerization. Stopped‐flow polymerization (with the polymerization time of 0.1–0.2 s) enabled us to neglect contributions of physical phenomena to the activity, such as catalyst fragmentation and reagent diffusion through produced polymer. The propagation rate constant kp and active‐site concentration [C*] were compared between homopolymerization and copolymerization in the absence of physical effects. kp for propylene was increased by 30% because of the addition of a small amount of ethylene, whereas [C*] was constant. On the contrary, both kp (for propylene) and [C*] remained unchanged by the addition of 1‐hexene. Thus, only ethylene could chemically activate propylene polymerization. However, continuously purged polymerization for 30 s resulted in much more significant activation by the addition of comonomer, clearly indicating that the activation phenomenon mainly arises from the physical effects. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Solubilization of single-walled carbon nanotubes (SWNTs) by physical adsorption of cyclodextrins (CDs), guest molecules, and host-guest complexes was investigated. As guest compounds, sodium adamantanecarboxylate (AdCNa), sodium dodecylbenzenesulfonate (SDBS), sodium ursodeoxycholate (UdCNa), sodium ferrocenecarboxylate (FeCNa), and TritonX-405 were employed. As host compounds, R-, β-, and γ-cyclodextrins (R-, β-, and γ-CDs) were used. By using CDs as a solubilizing agent, SWNTs were insoluble in aqueous media. In the presence of AdCNa and FeCNa, solubility of SWNTs was dramatically increased by formation of host-guest complex with βor γ-CDs. By using SDBS-CD complexes, solubility of SWNTs was also enhanced compared to only guest molecules. On the other hand, solubility of SWNTs was decreased by formation of host-guest complexes of UdCNa and TritonX-405 with CDs. Formation of host-guest complex mostly resulted in enhancement of water solubility of SWNTs.

Stopped‐flow (SF) polymerization is a powerful tool to investigate the nature of the active site of heterogeneous Ziegler‐Natta catalysts, but poor polymer yields due to short polymerization times limit detailed structural analyses of the obtained polymer. A new large‐scale SF polymerization system is described in which an arbitrary volume of slurry can be transferred to obtain a polymer yield sufficient for a variety of analytic purposes. The developed LSF system is proven to be highly scalable and stable, leading to reproducible polymerization in an expanded time range from 0.03 s to a few seconds. The accurate polymerization below 0.1 s is promising for future studies to evaluate accurate kinetics as well as dormant processes in Ziegler‐Natta olefin polymerization.

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