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 the formation mechanism of entanglements when the ethylene polymerization is conducted by the heterogeneous catalysts. In this study, a series of weakly entangled UHMWPE was synthesized by the polyhedral oligomeric silsesquioxane/MgCl2 nanoaggregates modified Ziegler–Natta catalysts. The structure of nanoaggregates was evaluated by X-ray photoelectron spectroscopy, density functional theory simulations, and scanning probe microscope experiments, where the coordination strategy of MgCl2 and hydroxyl of POSS was investigated. These nanoaggregates presented extremely low activity on ethylene polymerization and were proved to serve as isolators for separating the active sites and growing chains. The entanglement density of nascent UHMWPE (reflected by the value of initial storage modulus G′(t=0)) was exponentially decayed with the polymerization activity of increased numbers of nanoaggregates. Importantly, this exponentially decayed effect contributed by increased numbers of POSS/MgCl2 isolators offset the rapid power function increment of entanglements upon rising the temperature, which was the essential reason for the successful synthesis of weakly entangled UHMWPE even at 85 °C. Finally, we have proposed the dependence and sensitivity of G′(t=0) (i.e., indicating the initial entanglement density of nascent polymers) on the polymerization activity, which was able to trace the formation of entanglements during polymerization through the POSS modified heterogeneous catalyst.

Alzheimer's disease (AD) and type 2 diabetes (T2D) are two common protein misfolding diseases. Increasing evidence suggests that these two diseases may be correlated with each other via cross-sequence interactions between β-amyloid peptide (Aβ) associated with AD and human islet amyloid polypeptide (hIAPP) associated with T2D. However, little is known about how these two peptides work and how they interact with each other to induce amyloidogenesis. In this work, we study the effect of cross-sequence interactions between Aβ and hIAPP peptides on hybrid amyloid structures, conformational changes, and aggregation kinetics using combined experimental and simulation approaches. Experimental results confirm that Aβ and hIAPP can interact with each other to aggregate into hybrid amyloid fibrils containing β-sheet-rich structures morphologically similar to pure Aβ and hIAPP. The cross-seeding of Aβ and hIAPP leads to the coexistence of both a retarded process at the initial nucleation stage and an accelerated process at the fibrillization stage, in conjunction with a conformational transition from random structures to α-helix to β-sheet. Further molecular dynamics simulations reveal that Aβ and hIAPP oligomers can efficiently cross-seed each other via the association of two highly similar U-shaped β-sheet structures; thus, conformational compatibility between Aβ and hIAPP aggregates appears to play a key role in determining barriers to cross-seeding. The cross-seeding effects in this work may provide new insights into the molecular mechanisms of interactions between AD and T2D.

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