“Side-chain-type” and crosslinkable quaternized polypropylene was prepared by heterogeneous Ziegler–Natta catalyst mediated polymerization for use in highly stable anion exchange membranes.

We report a kinetic model of chain-shuttling copolymerization using dual catalysts for solution α-olefin polymerization processes. This model focuses on predicting polymer properties such as the molecular weight and molecular weight distribution and the overall copolymer composition. We first validate the model through qualitative comparison between the model predictions and experimental observations reported in Arriola et al. (Science) in both a semibatch reactor and a continuous stirred-tank reactor (CSTR). Then, examples are given to illustrate how the model can be used to examine the effects of the chain-shuttling rate constant and the chain-shuttling-agent feed rate in a CSTR. Moreover, simulations using this model demonstrate how to prepare polymers with desired properties by manipulating catalyst compositions and monomer compositions in the feed.

This paper discusses the synthesis of a new family of well-controlled isotactic polypropylene ionomers (iPP-NH 3 + Cl − ) containing up to 5 mol % of NH 3 + Cl − ionic groups, with high molecular weight and narrow molecular weight and composition distributions, as well as good processability in melt and solution. A systematic study was conducted using various isospecific Ziegler−Natta and metallocene catalysts in the copolymerization of propylene and a high α-olefin comonomer containing a silane-protected amino group and the subsequent work-up procedures that can prevent undesirable side reactions in forming iPP-NH 3 + Cl − ionomers in a one-pot process. The resulting copolymers were carefully monitored by polymer solubility and a combination of NMR, GPC-triple detectors, DSC, and mechanical property measurements. Evidently, the most suitable reaction process requires a combination of the rac-Me 2 Si[2-Me-4-Ph(Ind)] 2 ZrCl 2 metallocene catalyst system with a purified d-MAO (TMA-free), 6bis(trimethylsilyl)amino-1-hexene comonomer during the copolymerization reaction and a work-up procedure to directly interconvert the silane-protected amino groups (−N(SiMe 3 ) 2 ) into −NH 3 + Cl − ionic groups before exposing to air. The attempt of isolating both iPP-N(SiMe 3 ) 2 and iPP-NH 2 intermediates resulted in the insoluble (cross-linked) products. On the other hand, the resulting iPP-NH 3 + Cl − ionomers were melt processed in air and showed a systematic increase of mechanical properties and high-temperature stability with the increase of NH 3 + Cl − content.

Mechanophores (mechanoresponsive molecules) offer great promises for the development of smart force-responsive materials. The activity of a mechano­phore can be tuned by altering its structure or the composition of the actuating polymer. Here we show that a [2]­catenane can act as a mechanical protecting group by diverting tensional forces away from a mechanically active functional group embedded in one of its rings. This property emerges from the mobility of the two rings of the catenane, which are able to rotate along each other until the tension equalizes over the entirety of the catenated framework. This approach provides a new way to control the mechanical activity of a mechanophore.

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Mechanical bonds are known to efficiently absorb mechanical energy at low forces, but their behavior at high forces is unknown. Here we investigate the impact of a mechanical bond on the rate of activation of a Diels–Alder mechanophore. Using a combination of experimental and computational techniques, we found that the rate of a retro-Diels–Alder reaction under tension is decreased when the mechanophore is embedded in the axle of a rotaxane due to the presence of a competing high-stress region at the junction between the macrocycle and the axle.

A series of tubular molecules with different lengths have been synthesized by attaching Trp-incorporated peptides to the pillar[5]arene backbone. The tubular molecules are able to insert into the lipid bilayer to form unimolecular transmembrane channels. One of the channels has been revealed to specifically insert into the bilayer of the Gram-positive bacteria. In contrast, this channel cannot insert into the membranes of the mammalian rat erythrocytes even at the high concentration of 100 μm. It was further demonstrated that, as a result of this high membrane selectivity, the channel exhibits efficient antimicrobial activity for the Gram-positive bacteria and very low hemolytic toxicity for mammalian erythrocytes.