Tunable Self-Assembled Elastomers Using Triply Hydrogen-Bonded Arrays

Dynamic Non-Covalent Exchange Intrinsic Self-Healing at 20 °C Mechanism of Polyurethane Induced by Interactions among Polycarbonate Soft Segments

Two polyurethanes (PUs) were similarly synthesized by reacting a cycloaliphatic isocyanate with 1,4-butanediol and two polyols of different nature (polyester, polycarbonate diol) with molecular weights of 1000 Da. Only the PU synthesized with polycarbonate diol polyol (YCD) showed intrinsic self-healing at 20 °C. For assessing the mechanism of intrinsic self-healing of YCD, a structural characterization by molecular weights determination, infrared and X-ray photoelectronic spectroscopies, differential scanning calorimetry, X-ray diffraction, thermal gravimetric analysis, and dynamic mechanical thermal analysis was carried out. The experimental evidence concluded that the self-healing at 20 °C of YCD was due to dynamic non-covalent exchange interactions among the polycarbonate soft segments. Therefore, the chemical nature of the polyol played a key role in developing PUs with intrinsic self-healing at 20 °C.

Phase Separation, Reaction Equilibrium, and Self-Assembly in Binary Telechelic Homopolymer Blends

We study a binary blend of telechelic homopolymers that can form reversible AB-type bonds at the chain ends. Reversibly bonding polymers display novel material properties, including thermal tunability and self-healing, that are not found in conventional covalently bonded polymers. Previous studies of reversibly bonding polymer systems have been limited by the computational demand of accounting for an infinite number of possible reaction products in a spatially inhomogeneous, self-assembled structure. We demonstrate that newly developed theoretical models and numerical methods enable the simultaneous computation of phase equilibrium, reaction equilibrium, and self-assembly via self-consistent field theory. Phase diagrams are computed at a variety of physically relevant conditions and are compared with nonreactive analogues as well as previous experimental studies of telechelic polymer blends.

Construction of a thermoreversible chemical crosslinking network – a new exploration for the efficient reusability of commercial rubber

A thermoreversible rubber DSBR was prepared via a reaction between a nitroxide-based crosslinker and commercial styrene–butadiene rubber. Impressive recoveries of mechanical properties of DSBR were achieved for the alkoxyamine crosslinking network.

Assembly of miscible supramolecular network blends using DDA·AAD hydrogen-bonding interactions of pendent side-chains

Miscible blends of poly(methyl methacrylate) and polystyrene polymers are assembled through triple hydrogen bonding between complementary ureidoimidazole and amidoisocytosine heterodimers.

Thermally healable polyurethane with tailored mechanical performance using dynamic crosslinking motifs

A tunable dynamic cross-linked polyurethane that makes a tradeoff between superior mechanical performance and excellent self-healing ability.

Readily functionalized AAA-DDD triply hydrogen-bonded motifs

Herein we present a new, readily functionalized AAA-DDD hydrogen bond array. A novel AAA monomeric unit (3a-b) was obtained from a two-step synthetic procedure starting with 2-aminonicotinaldehyde via microwave radiation (overall yield of 52-66%). 1H NMR and fluorescence spectroscopy confirmed the complexation event with a calculated association constant of 1.57 × 107 M-1. Likewise, the usefulness of this triple hydrogen bond motif in supramolecular polymerization was demonstrated through viscosity measurements in a crosslinked supramolecular alternating copolymer.

Enhancement of microphase ordering and mechanical properties of supramolecular hydrogen-bonded polyurethane networks

Enhanced thermoreversible and mechanical properties in supramolecular polyurethanes have been realised by the incorporation of flexible DBDI derived hard segments.

Rheology of nitrile rubber with hybrid crosslinked network composed of covalent bonding and hydrogen bonding

A hybrid crosslinked network composed of covalent bonding and non-covalent bonding was constructed in nitrile rubber (NBR) by using a compound crosslinking agents dicumyl peroxide (DCP) and N,N-methylenebis acrylamide (MBA).

An adhesive elastomeric supramolecular polyurethane healable at body temperature

In this paper, we report the synthesis and healing ability of a non-cytotoxic supramolecular polyurethane network whose mechanical properties can be recovered efficiently (>99%) at the temperature of the human body (37 °C). Rheological analysis revealed an acceleration in the drop of the storage modulus above 37 °C, on account of the dissociation of the supramolecular polyurethane network, and this decrease in viscosity enables the efficient recovery of the mechanical properties. Microscopic and mechanical characterisation has shown that this material is able to recover mechanical properties across a damage site with minimal contact required between the interfaces and also demonstrated that the mechanical properties improved when compared to other low temperature healing elastomers or gel-like materials. The supramolecular polyurethane was found to be non-toxic in a cytotoxicity assay carried out in human skin fibroblasts (cell viability > 94% and non-significantly different compared to the untreated control). This supramolecular network material also exhibited excellent adhesion to pig skin and could be healed completely in situ post damage indicating that biomedical applications could be targeted, such as artificial skin or wound dressings with supramolecular materials of this type.

Periodic introduction of a Hamilton receptor into a polystyrene backbone for a supramolecular graft copolymer with regular intervals

The Hamilton receptor group (–DADDAD–; D = hydrogen donor; A = hydrogen acceptor) was periodically introduced into a polystyrene backbone, starting from the ruthenium-catalyzed living radical polymerization of styrene with the Hamilton receptor-based bifunctional initiator.

Microphase separation induced in the melt of Pluronic copolymers by blending with a hydrogen bonding urea-urethane end-capped supramolecular polymer

Blending with a hydrogen-bonding supramolecular polymer is shown to be a successful novel strategy to induce microphase-separation in the melt of a Pluronic polyether block copolymer. The supramolecular polymer is a polybutadiene derivative with urea-urethane end caps. Microphase separation is analysed using small-angle X-ray scattering and its influence on the macroscopic rheological properties is analysed. FTIR spectroscopy provides a detailed picture of the inter-molecular interactions between the polymer chains that induces conformational changes leading to microphase separation.

Theoretical design and simulation of supramolecular polymer unit based on multiple hydrogen bonds

The heterocyclic urea of deazapterin (DeAPa) and its protomeric conformers (b, c) with different substituents are selected as the building block for a series of dimers in different configurations. The stabilities of all dimers in various conditions have been investigated by density functional theory. Homodimer of b has more stability than other dimers. Topological analyses certify the coexistence of intermolecular with intramolecular H-bonds. Investigations into frequency demonstrate that all H-bonds show an evident red shift in their stretching vibrational frequencies. Electron donating substituents can provide favorable free energies of the dimer. Solvent effect computations suggest that the dimerization can be favored in weakly polar solvents, such as toluene and chloroform. UV-visible spectra exhibit obvious difference of maximum absorption wavelengths between monomers and dimers, thus may have potential applications for identifying intermolecular H-bonds and calculating association constant of DeAP equilibrium systems in experiments.

Development of solvent-free synthesis of hydrogen-bonded supramolecular polyurethanes

A solvent free ball-milling method for the synthesis of small molecule and oligomeric carbamates is described that is applicable to supramolecular polymer synthesis.

In this work we describe the solvent free synthesis of supramolecular polyurethanes held together by heterocomplementary triple hydrogen bonding. We perform a systematic evaluation on the base catalyzed synthesis of small molecule ureas and carbamates from a range of isocyanates, amines and alcohols in solution and in the solid state using ball milling. These optimized procedures are then shown to be applicable to the synthesis of supramolecular polyurethanes using solvent-free methods.

DYNAMERS: dynamic polymers as self-healing materials

An overview of recent advances made in the field of constitutional dynamic materials, in particular dynamic polymers, dynamers, displaying self-healing features.

Isophthalic Acid-Pyridine H-Bonding: Simplicity in the Design of Mechanically Robust Phase-Segregated Supramolecular Polymers

We report a new series of supramolecular polymeric networks based on the isophthalic acid-pyridine (IPA-Py) H-bonding motif. The IPA units were attached as end-groups to telechelic poly(ethylene-co-butylene) to create a tetrafunctional macromonomer, which was cross-linked by the addition of various bispyridines. Some of the supramolecular polymer networks thus made display surprisingly good mechanical characteristics. We show that their structure and properties are strongly influenced by the nature of the bispyridine motif and by the fact that some of the IPA-Py motifs aggregate into particularly well-defined hard phases.

Supramolecular chemistry with ureido-benzoic acids

A novel, complementary quadruple hydrogen-bonding motif is presented that shows very strong dimerization and is switchable with pH.

Side-Chain Supramolecular Polymers Employing Conformer Independent Triple Hydrogen Bonding Arrays

Derivatives of thymine have been extensively used to promote supramolecular materials assembly. Such derivatives can be synthetically challenging to access and may be susceptible to degradation. The current article uses a conformer-independent acceptor-donor-acceptor array (ureidopyrimidine) which forms moderate affinity interactions with diamidopyridine derivatives to effect supramolecular blend formation between polystyrene and poly(methyl methacrylate) polymers obtained by RAFT which have been functionalized with the hydrogen bonding motifs.