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A full elucidation of chemisorbed donor behavior is of fundamental importance for tailoring the active species but has not yet been achieved for Ziegler–Natta catalysts. Herein, by exploiting the s...

The polyhedral oligomeric silsesquioxane (POSS)-modified Ziegler–Natta catalysts with judicious immobilization of TiCl4 were synthesized for ethylene polymerization. The structure of active sites i...

An immobilization strategy of catalytic TiCl4 on polyhedral oligomeric silsesquioxanes (POSSs) is developed, which features both robustness and equivalence of active sites in ethylene polymerization thanks to the non-covalent O-Ti coordination. The symmetric structure of POSS homogenizes the coordination of the TiCl4 molecules, enabling considerable activity in the synthesis of narrowly distributed polyethylene.

Chain entanglement was very important for adjusting the processability and mechanical property of nascent ultrahigh molecular weight polyethylene (UHMWPE). So far, it is still a mystery to unravel ...

In the molecular doping of organic semiconductors(OSC), achieving efficient charge generationand managing the energetic cost for chargerelease from local molecular charge transfercomplexes (CTCs) to the host matrix is ofcentral importance. Experimentally tremendousprogress has been made in this direction.However, the relation between OSC filmstructure on a nanoscopic level including differentinter-molecular geometrical arrangementsand the macroscopic properties of doped OSCfilms is usually only established quite indirectly.Explicit microscopic insights into the underlyingdoping mechanisms and resulting electronicstructure are still scarce and mostly limitedto the study of the individual molecular constituentsor isolated bi-molecular dopant:hostcomplexes. In the present study we investigaten-type doping of the frequently investigatedOSC materials ZnPC and F8ZnPc andtheir mixtures which are n-doped with 2-Cyc-DMBI. We report significant electronic differencesfor complexes with nominally the samematerial composition but different geometricalstructures. One specific important finding inthis context is that complexes containing twoadjacent dopant molecules show much reducedionization energy values, leading to substantiallyreduced energy cost for charge release. Furthermore our results demonstrate that importanttrends towards macroscopic system behaviorcan already be obtained with increasingsize and varying composition of the relativelysmall molecular dopant-host complexes considered,including systematic shifts in the Fermilevel energies in the doped OSC.

A Polyhedral oligomeric silsesquioxane (POSS) modified Ziegler-Natta catalyst is reported to synthesize the weakly entangled ultra-high molecular weight polyethylene at a high temperature and with a high activity. Incorporation of POSS can form numbers of aggregates with a mean size of 48 nm adsorbing on the surface of SiO 2 . The structure of nanoaggregates is evidenced by the experiments and theoretical calculations where one POSS can coordinate with multiple MgCl 2 molecules serving as an electric donor to the further immobilized TiCl 4 . The catalyst is thus featured by two distinct active regions positioned in the POSS/MgCl 2 nanoaggregates and δ -MgCl 2 , respectively. The former regions present extremely low activity on ethylene polymerization, which function as horizontal separators for isolating the active TiCl 4 sites and the growing chains. This catalyst exhibits an exceptional activity ( i.e. 1.3 × 10 6 gPE mol Ti −1 h −1 bar −1 ) for the synthesis of weakly entangled polyethylene at 60 °C.

We report a selective immobilization strategy to control the catalytic performance of the target active species in hybrid multisite catalysts. The sterically bulky and electronically donated polyhedral oligomeric silsesquioxane (POSS) is introduced onto the support and offers extra immobilization sites for the target pre-catalyst. DFT and CO low-temperature adsorption facilitate to understand the distribution of active sites. The nickel pre-catalyst can interact with the POSS, endowing the scattered distribution of nickel sites. The large steric and electronic donated iron pre-catalyst exhibits the inertness to POSS, confining iron species on the POSS-free space. The selective dispersion of nickel species enhances its contribution in the synthesis of UHMWPE fraction with an exceptional activity, a much higher molecular weight and branching degree. This promoted contribution synchronously enhances the impact resistance (+27%), tensile strength (+53%), Young’s modulus (+111%) and elongation ratio (+37%) of the synthesized bimodal PE compared to those of commercial UHMWPE.