Polymers that contain mechanical bonds have unique and useful properties. It is difficult to prepare linear polyrotaxanes that contain well-defined mechanical bonds, which has made it challenging to establish the influence of mechanical bonding on linear polyrotaxane properties. We disclose the synthesis of 1,9-decadiene-pseudorotaxane linear copolymers with variable densities of threaded macrocycles using acyclic diene metathesis (ADMET) polymerization. This enabled our investigation into how macrocyclic threading impacts the thermomechanical properties of linear polypseudorotaxanes. Specifically, we observe that the melting enthalpy decreased from 67 to 5 J g-1 as we increased the molar incorporation of a pseudorotaxane unit. Going forward, we expect ADMET to be a useful strategy to prepare linear mechanically interlocked macromolecules at scales relevant for characterizing their thermomechanical properties.

Pt-containing oligomers synthesized by ADMET oligomerization and polycondensation phosphoresced under N2, while did not under air. They served as sensitizers of triplet–triplet annihilation upconversion with 9,10-diphenylanthracene as an emitter.

Los elastómeros son macromoléculas cuya longitud puede incrementarse hasta un 400 % cuando son sometidos a una fuerza externa, pero que regresan a su longitud inicial una vez ésta cesa de actuar. En este artículo se describe la aplicación de una reacción de polimerización recientemente descubierta, metátesis, en la obtención de materiales elásticos. Efectivamente, el uso de los principios básicos que explican el fenómeno de la elasticidad, en la polimerización de α, ω- dienos acíclicos, mediante la reacción de metátesis, dio lugar a la transformación de materiales inicialmente frágiles al estiramiento, en materiales crecientemente elásticos.

The functionalization of the chain end of a polymer is gathering increasing attention in the field of synthetic polymer chemistry. The present study is the first example to demonstrate the incorporation of a platinum-acetylide complex at the terminal of a polynorbornene derivative. N-Benzyl-5-norbornene-2-exo,3exo-dicarboxyimide (1) was polymerized with Grubbs 3rd generation catalyst (G3). The polymerization was quenched with (Z)-1,4-bis(3-((trimethylsilyl)ethynyl)phenoxy)-2-butene (2) to obtain poly(1)', followed by the cleavage of trimethylsilyl group and dehydroiodination coupling with trans-bis(tributylphosphine)phenylethynyl iodo platinum (3a) to obtain poly(1a), which was functionalized with a platinum complex at the chain end. Poly(1)' exhibited no remarkable absorption around 330 nm, while poly(1a) exhibited an intense absorption based on ligand-to-metal charge transfer transition. Poly(1b) functionalized with a naphthylamide ethynyl platinum complex was synthesized in a similar fashion. The photoluminescene color of a poly(1b) solution in CH2Cl2 changed from green to red with Ar bubbling and rapidly returned to green by ceasing Ar bubbling. A poly(1b)-containing polymethyl methacrylate film exhibited a similar trend, as was observed for the polymer in solution. The weight residues of poly(1a) and poly(1b) at 800 degrees C were higher than that of poly(1).

Acyclic Diene Metathesis polycondensation produces materials with well-defined primary structures, perfection that is the consequence of symmetry imparted by monomer design. Diverse functionalities can be incorporated either in the polymer backbone or as pendant groups; chemical compatibility of the functional group with the catalyst is a requirement. Structural perfection led to structure/property investigations that would be difficult in imprecise systems. This comprehensive review summarizes the synthetic strategies for production of ADMET polymers. Further presented are the effects on secondary structure of controlling branch identity, in-chain functional groups, and frequency along the polymer chain. Results of spectroscopic, thermal and imaging techniques have been key for understanding the relationships between structure and properties.

The synthesis of hyperbranched aminobisphosphonic acid polymers via reversible addition-fragmentation chain transfer (RAFT) self-condensing vinyl polymerization is reported. A novel acrylamide-functional chain transfer monomer is synthesized and characterized by 1 H and 13 C NMR spectroscopy, elemental analysis, and mass spectrometry. The monomer is subsequently copolymerized with an acrylamide monomer bearing a pendent amine group to create hyperbranched amine-functional polymers with degrees of branching dictated by changing the reaction stoichiometry. The aminobisphosphonate functional group is introduced via a 3-component Kabachnik-Fields reaction. An alternate functionalization of the amine polymers to create acid-degradable imine hydrogels is also employed. This work demonstrates the application of multicomponent reactions to RAFT-derived hyperbranched polymers and provides a new route to previously inaccessible polymers.

Fully saturated, aliphatic polymers containing adamantane moieties evenly distributed along the polymer backbone are of great interest due to their exceptional thermal stability, yet more synthetic strategies toward these polymers would be desirable. Herein, we report for the first time the synthesis of poly(1,3-adamantylene alkylene)s based on α,ω-dienes containing bulky 1,3-adamantylene defects precisely located on every 11th, 17th, 19th, and 21st chain carbon via acyclic diene metathesis polycondensation. All saturated polymers revealed excellent thermal stabilities (452-456 °C) that were significantly higher compared to those of structurally similar polyolefins with aliphatic or aromatic ring systems in the backbone of polyethylene (PE). Their crystallinity increases successively from shorter to longer CH2 chains between the adamantane defects. The adamantanes were located in the PE crystals distorting the PE unit cell by the incorporation of the adamantane defect at the kinks of a terrace arrangement. Precise positioning of structural defects within the polymeric backbone provides various opportunities to customize material properties by "defect engineering" in soft polymeric materials.

Polyethylene and nanosilica represent the most ubiquitous commodity plastic and nanocomposite filler, respectively. Despite their potential utility, few examples exist in the literature of successfully combining these two materials to form polyethylene nanocomposites. Synthesizing well-defined polyethylene grafted to a surface is a significant challenge in the nanocomposites community. Presented here is a synthetic approach toward polyethylene grafted nanoparticles with controllable graft density and molecular weight of the grafted polymer. The variably grafted nanoparticles were then incorporated into a commercial high density polyethylene matrix. The synthesis, characterization, and challenges in making these materials are discussed.

Bulk acyclic diene metathesis (ADMET) polymerization performed in the melt at temperatures up to 175 degrees C is completed using a cyclic (alkyl)(amino) carbene (CAAC) ruthenium-based Grubbs catalyst. High temperature stability is investigated at temperatures well above conventional ADMET chemistry, leading to the highest weight-average molecular weights ever achieved for any ADMET polymer. A study of isomerization tendency (double bond migration) is done via self-metathesis of a small molecule model compound using CAAC catalysts. Minimal olefin isomerization is observed using appropriate catalyst ratios and temperatures.

Thermo-responsive micelles were prepared from brush-like block copolymers of proline-derived norbornene and macromonomers bearing oligo(lactide) groups. The brush-like polymers with moderate molecular weights were synthesized by the ring-opening metathesis block copolymerization of a proline-functionalized norbornene (1) with norbornene macromonomers bearing oligo(lactide) groups using Umicore M31 as a catalyst. The proline-functionalized polynorbornene [poly(1)] exhibited the lower critical solution temperature (LCST) at 18 degrees C. Phase separation was reversible on heating and cooling without hysteresis. Poly(1) featured amphiphilic character, it self-assembled to form micelles in water at temperatures below the LCST, and aggregation of micelles was observed above the LCST. The LCST of the block copolymers increased with increasing percentage of the branched oligo(lactide) component, suggesting that the phase transition temperatures are tunable with respect to the monomer composition. The block copolymers self-assembled into micelles below the LCST, and further aggregated into larger particles, presumably due to dehydration at the corona, at temperatures above the LCST. The block copolymers also showed the potential to self-assemble into a variety of shapes determined by the amphiphilic balance of the block components.

Journal Article High Resolution TEM Imaging of Polymer Crystals using Low Dose Techniques Get access Ingo Lieberwirth, Ingo Lieberwirth Max-Planck Institute for Polymer Research, Mainz, Germany Corresponding author: lieberw@mpip-mainz.mpg.de Search for other works by this author on: Oxford Academic Google Scholar Frederic Wurm, Frederic Wurm Max-Planck Institute for Polymer Research, Mainz, Germany Search for other works by this author on: Oxford Academic Google Scholar Kenneth Wagener, Kenneth Wagener University of Florida, Department of Chemistry, Gainsville FL, United States Search for other works by this author on: Oxford Academic Google Scholar Oksana Suraeva Oksana Suraeva Max-Planck Institute for Polymer Research, Mainz, Germany Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 1708–1709, https://doi.org/10.1017/S1431927619009279 Published: 01 August 2019

Recent advances in polymer synthesis have allowed remarkable control over chain microstructure and conformation. Capitalizing on such developments, here we create well-controlled chain folding in sulfonated polyethylene, leading to highly uniform hydrated acid layers of subnanometre thickness with high proton conductivity. The linear polyethylene contains sulfonic acid groups pendant to precisely every twenty-first carbon atom that induce tight chain folds to form the hydrated layers, while the methylene segments crystallize. The proton conductivity is on par with Nafion 117, the benchmark for fuel cell membranes. We demonstrate that well-controlled hairpin chain folding can be utilized for proton conductivity within a crystalline polymer structure, and we project that this structure could be adapted for ion transport. This layered polyethylene-based structure is an innovative and versatile design paradigm for functional polymer membranes, opening doors to efficient and selective transport of other ions and small molecules on appropriate selection of functional groups.

High molar mass polyethylenes with bromine atoms placed on each and every 21st, 19th, 15th, or 9th backbone carbon crystallize into two distinctive layered polymorphs by changing undercooling. Crystallization at low temperatures produces Form I, a planar all-trans conformation, while at higher temperatures gauche conformers set for backbone bonds adjacent to the methine due to a close intermolecular staggering of bromines resulting in a herringbone Form II structure. In this work, the sharp range of isothermal crystallization temperatures for the transition between Form I and Form II is first identified via WARD and melting behaviors for all members of the series. Furthermore, the temperature dependence of the isothermal linear spherulitic growth rates of Form II has been studied for a wide range of crystallization temperatures. The linear growth rates display a discrete minimum with decreasing temperature at a crystallization temperature near the melting point of Form I, a feature which is reminiscent of the minimum found in the crystallization rate of long-chain n-alkanes. Changes in spherulitic morphology and the growth rate minima are analyzed on the basis of self-poisoning at the growth front resulting from frequent but unstable Form I depositions on the growth surface of Form II. The similarity with the behavior observed in the growth of long-chain n-alkanes crystallites supports a polymer crystallization process controlled by events that take place at the crystal growth front.