Homopolymerization of ethylene and 1‐hexene and their copolymerizations were compared to investigate the influence of α‐olefin on the enhancement of ethylene polymerization rate (Rp), which is often referred to as the “comonomer” effect. With the two homogeneous Ziegler–Natta catalysts, Et[Ind]2ZrCl2/MAO and (π‐C5H5)2ZrCl2/MAO (MAO = methylaluminoxane), hexene causes reduction of Rp—in other words a negative “comonomer” effect. In the case of the high activity MgCl2 supported TiCl3 catalysts there is a slight positive “comonomer” effect; the Rp increases by 25 to 70% with the addition of 15 mol % of hexene. The “comonomer” effects in there catalyst systems are much smaller than that observed for the classical TiCl3 catalyst. © 1993 John Wiley & Sons, Inc.

Cycloaddition of carbon dioxide to oxiranes was excellently promoted by the complexes of organotin halides and tetraalkylonium halides, while either components of the complexes had no catalytic activity individually. Particularly, the complex composed of Bu3SnI–Bu4PI was the most favorable catalyst, yielding a variety of fivemembered cyclic carbonates under neutral and mild conditions.

N-Doped carbon dots (N-CDs) from tannic acids showed a capability to act as visible light active photosensitisers. The photosensitizing efficiency of N-CDs was enhanced by the conjugation with gold nanoparticles.

In this study, ultrahigh molecular weight polyethene homopolymer and copolymer were successfully produced with the metallocene and the Ziegler catalyst system. In case with the metallocene catalyst system, viscosity average molecular weight of the homopolymer was controlled from 2 million to 10 million. Also, the molecular weight of the copolymer was reached up to 6 million. In case with the Ziegler catalyst system, the molecular weight of the copolymer was reached up to 4 million. The transparency of the copolymer by the Ziegler catalyst, with which the copolymer with better uniformity was produced, could be comparable with that by the metallocene catalyst.

Hydrogen (pH2 = 72 torr) increases the rate of propylene polymerization by a MgCl2/ethyl benzoate/p‐cresol/AlEt3/TiCl4‐AlEt3/methyl‐p‐toluate catalyst (CW‐catalyst) by two‐to three‐fold which corresponds closely with the increase in the number of active sites as counted by radiolabeling with tritiated methanol. The oxidation states of titanium in decene polymerizations by the CW‐catalyst were determined as a function of time of polymerization (tp). In the absence of H2, all [Ti+n] for n = 2, 3, 4 remain constant during a batch polymerization. In the presence of H2 and within 5 min of tp, [Ti+2] decreases by an amount, corresponding to 15% of the total titanium and [Ti+3] increases by the same amount, while [Ti+4] is not changed. Therefore, three‐fourths of the H2 activation result from oxidative addition processes. The remaining one‐fourth of the H2 activation may be attributed to the activation of previously deactivated Ti+3 ions by hydrogenolysis. Monomer converts some of the EPR silent Ti+3 sites to EPR observable species resulting in their activation.