Traditionally the dispersion of particles in polymeric materials has proven difficult and frequently results phase separation agglomeration. We show that thermodynamically stable nanoparticles into a liquid is enhanced for systems where radius gyration linear polymer greater than nanoparticle. Dispersed swell chains, resulting grows with nanoparticle volume fraction. It proposed this entropically unfavorable process offset by an enthalpy gain due to increase molecular contacts at dispersed...

Despite numerous strategies involving dynamic covalent bond exchange for and self-healing materials, it remains a challenge to be able tune the malleability properties of bulk materials through simple small molecule perturbations. Here we describe use tunable rates boronic ester transesterification efficiencies materials. Specifically, used two telechelic diboronic molecules with variable kinetics dynamically cross-link 1,2-diol-containing polymer backbones. The sample cross-linked...

Ethylene pressure has been used to control the competition between isomerization (chain walking) and monomer insertion processes for ethylene coordination polymerization catalyzed by a palladium-alpha-diimine catalyst. The topology of polyethylene varies from linear with moderate branching "hyperbranched" structures. Although overall number distribution short-chain change very slightly, architecture or changes branches at high pressures hyperbranched low pressures.

A new self-healing multiphase polymer is developed in which a pervasive network of dynamic metal-ligand (zinc-imidazole) interactions are programmed the soft matrix hard/soft two-phase brush copolymer system. The mechanical and properties materials can be tuned by varying number molecular parameters (e.g., backbone/brush degree polymerization density) as well ligand/metal ratio. Following damage, these thermoplastic elastomers show excellent ability under ambient conditions without any intervention.

Covalently cross-linked polymers have many technological applications for their excellent properties, but they suffer from the lack of processability and adaptive properties. We report a simple, efficient method generating via olefin metathesis. By introducing very low level Grubbs' second-generation Ru metathesis catalyst, chemically polybutadiene network becomes malleable at room temperature while retaining its insolubility. The stress relaxation capability increases with increasing...

In this article, we demonstrate transition-metal-catalyzed olefin metathesis as a simple, effective method for healing polymers via dynamic exchange of strong carbon–carbon double bonds. Upon introducing very low level the Grubbs’ second-generation Ru catalyst into cross-linked polybutadiene (PBD) network, material self-heals effectively at various conditions under moderate pressures. sharp contrast, catalyst-free control samples with identical network topology and cross-linking density show...

Here we introduce silyl ether linkage as a novel dynamic covalent motif for material design. Through introduction of neighboring amino moiety, show that the exchange rate can be accelerated by almost three orders magnitude. By incorporating such linkages into covalently cross-linked polymer networks, demonstrate network polymers displaying both malleability and reprocessability. The networks is studied monitoring stress relaxation at varying temperature, their topology freezing temperatures...

A catalytic alkane metathesis provides a mild and selective degradation of polyethylene wastes into valuable fuels waxes.

Polymers that repair themselves after mechanical damage can significantly improve their durability and safety. A major goal in the field of self-healing materials is to combine robust efficient healing properties. Here, we show incorporation sacrificial bonds into a self-repairable network dramatically improves overall Specifically, use simple secondary amide side chains create dynamic energy dissipative hydrogen covalently cross-linked polymer network, which self-heal via olefin...

Traditional thermoset materials have favorable material properties but are unable to reprocess and difficult recycle. Small molecule boroxines been shown undergo a reversible exchange reaction. Herein we employ boroxine as dynamic cross-links construct novel type of that is strong, highly malleable, recyclable. The synthesis mechanical networks described. Upon heating in water the can be recycled back its monomer. With multitude tunable variables, anticipate this system platform for...

Polymer, heal thyself! Supramolecular ABA triblock copolymers formed by dimerization of 2-ureido-4-pyrimidinone (UPy) end-functionalized polystyrene-b-poly(n-butyl acrylate) (PS-b-PBA) AB diblock have been synthesized, resulting in a self-healing material that combines the advantageous mechanical properties thermoplastic elastomers and dynamic features supramolecular materials.

Vitrimers are a new class of polymeric materials that simultaneously offer the desired physical properties thermosets and malleability/reprocessability thermoplastics. Despite significant progress being made in field vitrimers, there exists critical need for development robust dynamic covalent chemistries production strong thermally stable vitrimers. In this work, we discovered silyl ether metathesis reaction used it preparation vitrimers with exceptional thermal stability. small-molecule...

The innovation of polyolefin with unique architecture, composition and topology continues to inspire polymer chemists. An exciting recent direction in the field is design new catalysts based on late-transition metals. In this review, we highlight developments rationally designing metal for olefin polymerization. examples described review showcase power well-defined late-metal tailored synthesis, which may usher a era industry.

Better by design: Exploitation of the macrocyclic architecture a cyclophane-based ligand provides new highly active catalysts with improved thermal stability for ethylene polymerization. The strategic positioning metal center at core is key to observed high activity and stability, molecular weight polyethylene (see picture; red: Pd, green: Cl, blue: N, gray: C).

Natural materials employ many elegant strategies to achieve mechanical properties required for survival under varying environmental conditions. Thus these remarkable biopolymers and nanocomposites often not only have a combination of such as high modulus, toughness, elasticity, but also exhibit adaptive stimuli-responsive properties. Inspired by skeletal muscle protein titin, we synthesized biomimetic modular polymer that closely mimics the multidomain structure manifests an exciting...

A group of polyethylenes synthesized using palladium α-diimine catalysts were studied 13C NMR spectroscopy, intensity light scattering, dynamic and viscometry. These are known to produce branched without α-olefin comonomers. The series polymers under conditions varying ethylene pressure. highly completely amorphous thus soluble in common organic solvents at ambient temperatures. Light scattering determinations the root-mean-square radius gyration (Rg) molecular weight M fractions eluting...

A series of bis-(aryl)-α-diimine ligands were synthesized bearing a range electron-donating and -withdrawing substituents to systematically investigate the ligand electronic effects on late transition metal olefin polymerization catalysts. Their palladium(II) complexes prepared characterized. Electronic perturbations verified by analysis 1H 13C NMR chemical shifts corresponding methyl chloride CO stretching frequencies cationic carbonyl complexes, which found correlate strongly with Hammet...

We report a direct synthesis of polyamides via catalytic dehydrogenation diols and diamines. A PNN pincer ruthenium complex, the Milstein catalyst, was used for this reaction with number average molecular weight from ∼10 to 30 kDa could be obtained wide variety diamines bearing aliphatic or aromatic, linear cyclic spacers. Because high selectivity primary amine over secondary amine, polyamines conveniently incorporated into without tedious protection/deprotection steps. Compared conventional...

Polar olefins were copolymerized with ethylene using a cyclophane-based palladium(II) α-diimine catalyst. The incorporation levels of both methyl acrylate and tert-butyl are unusually high compared to what is obtained the corresponding acyclic Mechanistic studies by low-temperature NMR spectroscopy revealed that differences between insertion barriers for MA (ΔΔG⧧) similar cyclophane catalysts. equilibration comonomers, fast on experimental time scales catalyst, was too slow be measured These...

Triblock copolymers having glassy PMMA blocks and dynamic hydrogen bonding were synthesized by sequential atom transfer radical polymerization (ATRP). The triblock self-assemble into nanocomposite materials exhibiting a combination of mechanical strength, toughness, self-healing capability.

In this study, we designed and synthesized a biodegradable dendronized polypeptide (denpol) platform for delivery of small interfering RNA (siRNA). The novel denpol architecture combines the multivalency dendrimers conformational flexibility linear polymers optimal siRNA binding. Multifunctional amino acids were incorporated onto dendrons structure was tuned both systematically combinatorially to select vectors. By screening focused library, identified several denpols that can effectively...

The synthesis and characterization of Ni(II) Pd(II) α-diimine olefin polymerization catalysts bearing a fluorinated cyclophane-based ligand were performed. Fluorine was placed in such manner as to interact with the metal center from axial direction. active ethylene, showing substantial differences both catalytic behavior polymer size structure compared their nonfluorinated analogues. Both afforded comparatively low branching density high molecular weight. catalysts, precursor...