Polyethylenes functionalized with ureidopyrimidone: synthesis, thermomechanical properties and shape memory behavior

A well-defined quadruple hydrogen bonding strategy involving dimerization of 2-ureido-4[1H]-pyrimidone (UPy) units is innovatively designed to prepare polyureas with high overall mechanical properties. Three polyureas containing different amounts of UPy units were synthesized by replacing a portion of isophorone diisocyanate (IPDI) with a UPy-derived diisocyanate. The formation of quadruple hydrogen bonds in hard segments via UPy dimers was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the polyureas were evaluated by uniaxial tensile testing. Compared to the polyurea without UPy units, remarkable improvements in Young’s modulus, tensile strength, and toughness were simultaneously achieved when UPy units were incorporated. The mechanism behind the strong strengthening effect rooted in the stronger intermolecular forces among hard segments brought by the quadruple hydrogen bonds, which were stronger than the inherent bidentate and monodentate hydrogen bonds among urea groups, and the slower soft segmental dynamics reaveled by both increased Tg and relaxation time of the soft segments. The mechanism behind the strong toughening effect was ascribed to more effective energy dissipation brought by the quadruple hydrogen bonds that served as stronger sacrificial bonds upon deformation. This work may offer new insight into the design of polyurea elastomers with comprehensively improved mechanical properties.

A facile method for preparing supramolecular waterborne polyurethane (WPU) based on quadruple hydrogen bonds (4H‐WPU) is reported. Herein, 4H‐WPU with quadruple hydrogen bonds in main chain were synthesized by poly (1,4‐buthylene‐neopentylene adipate glycol) as soft segment, 2‐ureido‐4[1H]‐pyrimidinone (UPy) functionalized monomer, isophorone diisocyanate, 2,2‐Bis(hydroxymethyl)propionic acid (hydrophilic monomer), isophorondiamine, triethylamine (neutralizer), and monoethanolamine (blocking agent) as hard segment. The molecular weight of 4H‐WPU was controlled around 18,000 consistently. The properties of 4H‐WPU with different content of hydrophilic group, hard segment, and UPy units were characterized and the results could provide the reference for preparing supramolecular WPU with high mechanical and self‐healing performance while maintaining dispersion stability. The tensile strength of 4H‐WPU was 10 times of the blank sample. The healing time of scratched 4H‐WPU film was inversely proportional to the content of UPy‐ functionalized monomer and the shortest healing time is 2.5 hr at 80°C. Mechanical performance of healed films can be restored to more than 90%.

It is still challenging and attractive to prepare polyurethane (PU) materials with excellent self-healing ability while improving their mechanical properties and high ductility. Here, a multifunctional linear PU supramolecular elastomer was successfully prepared by introducing a cross-linking network of quadruple hydrogen bonds and thermo-reversible Diels–Alder bonds and rigid ring structure to the linear backbone. The results exhibited that the obtained PU elastomer displayed a high tensile strength (6.30 MPa), elongation (1957.84%), toughness (84.48 MJ/m3), and excellent repair efficiency (93.33%). The quadruple hydrogen bonds from 5-(2-hydroxyethyl)-6-methyl-2-aminouracil and thermo-reversible Diels–Alder bonds from the conjugated reaction of 4,4′-bismaleimide diphenylmethane with furfuryl alcohol, due to its synergetic dual reversible bonds, formed the PU elastomer that possessed excellent mechanical, self-healing, shape recovery, and reprocessing properties. The prepared multifunctional PU can be used as a substrate for flexible conductive materials or as conductive composite material with conductive materials, which can self-repair many times when the surface is damaged, can be recycled, and greatly improve the service life of the material. Therefore, the prepared multifunctional high-performance self-healing PU materials have potential applications in several fields.

Toughening diene elastomers by strong hydrogen bond interactions

Shape memory and self-healing properties of polymer-grafted Fe3O4 nanocomposites implemented with supramolecular quadruple hydrogen bonds

Balancing the mechanical strength and self-healing performance of polyurethane (PU) remains a significant challenge in achieving excellent self-repairing PU materials. In this study, a self-healing waterborne PU elastomer was designed from a bionic concept by incorporating 2'-deoxythymidine (2'-dT) and isophorone diamine (IPDA) into the polymer chain. The loose stacking of IPDA's irregular cycloaliphatic structure resulted in the irregular arrangement of urethane bonds in the hard domain. The formation of sextuple hydrogen bonds between 2'-dT and urethane bonds, as well as quadruple hydrogen bonds between urethane bonds themselves, enhanced the mechanical properties of the material. The multiple hydrogen bonds can dissociate, recombine, and dissipate energy, thereby improving the material's repair capability. The hierarchical self-assembly of hydrogen bonds enabled the PU to achieve a tensile strength of 15.3 MPa and toughness of 100.75 MJ/m3. The prepared PU film is highly transparent and has a transmittance of more than 90%. Additionally, it can undergo rapid repair under high temperatures or under trace solvent conditions. When used as a flexible conductive substrate, it quickly restored the conductivity and enhanced the material's lifespan after surface damage. This environmentally friendly and self-healing waterborne PU elastomer will hold broad application prospects in the field of flexible electronic devices.

A set of fluorene oligomers has been synthesized by stepwise palladium-catalyzed (Suzuki) couplings of fluorene monomers. Ureidopyrimidinones (UPy), functional groups that can dimerize via quadruple hydrogen bonds, were attached to both ends of the oligofluorenes. The resulting bis-UPy-terminated oligomers self-assemble into supramolecular chain polymers. For comparison, oligofluorenes of the same oligomer lengths but without terminal hydrogen-bonding groups were synthesized. Chains of hydrogen-bonded fluorenes can be simply endcapped by a variety of chain stoppers, molecules that have one UPy group. In this manner, we have endcapped the hydrogen-bonded fluorene chains with either oligo(p-phenylenevinylene) or perylene bisimide. Energy-transfer experiments in solution and the solid state demonstrate that oligofluorenes can donate energy to a variety of energy acceptors, but that this energy transfer occurs most effectively when the donor fluorene is hydrogen-bonded to the acceptor.

This paper presents the course of synthesis and the properties of biodegradable terpolymers obtained by ROP of L-lactide with glycolide, catalysed with zirconium(IV) acetylacetonate and conducted in the presence of a macroinitiator – trimethylene carbonate oligomers terminated with hydroxyl groups. The oligomers were also prepared by ROP reaction of TMC catalysed by zinc(II) acetylacetonate monohydrate in the presence of polyols as initiators. Depending on the type of initiator used, the oligomers had a linear or branched structure of the chain with different hydroxyl end-groups. Some of the obtained oligomers formed a network. The effect of the terpolymer chain structure on mechanical and thermomechanical properties as well as shape-memory behaviour was shown. The ability to control the speed of return from a temporary to a permanent shape, the value of stress of return triggered by this phenomenon, and the magnitude of the temperature range in which the phenomenon took place through appropriate selection of conditions for programming the temporary shape or/and terpolymer chain microstructure has been shown. The possibility of adjusting these parameters as presented in this paper is vital in the process of designing a bioresorbable material, which can be used for forming self-expanding stents or self-clamping surgical staples.

Sequential and selective shape memory by remote electrical control

Breaking point: The unbinding behavior of single supramolecular polymers formed through quadruple hydrogen bonds between 2-ureido-4(1H)-pyrimidinone (UPy) units was studied by AFM-based single-molecule force spectroscopy. The interactions between individual UPy moieties and the stretching of polyethylene glycol (PEG) spacers in reversible supramolecular polymer chains were unveiled by AFM force-displacement measurements.

A solid plasticizer UPU in PEO-based SPEs: facilitating Li+ transport through semi-interpenetrating networks (SIPN) based on quadruple hydrogen bonds.

A new method of supramolecular emulsion interfacial polymerization is developed, which can be used to fabricate supramolecular polymeric nanospheres. We designed a water-soluble monomer containing two maleimide end groups, acting as both building block and surfactant, and an oil-soluble supramonomer bearing two thiol groups connected by quadruple hydrogen bonds. With the assist of ultrasonication, hollow nanospheres can be controllably prepared by thiol-maleimide reaction of two monomers at the emulsion interface, which exhibit good stability and dynamic property. In addition, the encapsulated guest molecules could be controllably released from the supramolecular polymeric nanospheres, owing to their stimuli-responsiveness. It is anticipated that this approach will enrich the methodology of supramolecular polymerization and can be applied to constructing supramolecular materials with controllable structures and functions.

Arms bearing ureido-pyrimidinone functional groups with self-association capability (through quadruple hydrogen bonds) were successfully grafted onto hydroxyapatite nanoparticles. The supramolecularly modified nanoparticles (nHApUPy) exhibited enhanced colloidal stability compared to the original hydroxyapatite nanoparticles and were uniformly dispersed in supramolecular polycaprolactone in PCL(UPy)2/HApUPy nanocomposites at different filler loadings. The combined atomic force microscopy, mechanical, and rheological analyses confirmed a high degree of compatibility of HApUPy nanoparticles with the polymer matrix. The temperature dependence of the supramolecular structure in PCL(UPy)2/HApUPy nanocomposites was determined from dynamic rheological measurements at two different temperatures, 60°C and 85°C. The osteocompatibility of the nanocomposite containing HApUPy nanoparticles was compared to the pure polymer. The preliminary cell results clearly confirm that the supramolecular nanocomposites are nontoxic and biocompatible. Therefore, it is postulated that supramolecular nanocomposites provide a new way of tuning the mechanical properties of the supramolecular polymers, particularly supramolecular polycaprolactones.

A series of poly(lactide) (PLA)‐based supramolecular polymers based on linear PLLA‐b‐PCL‐b‐PLLA triblock copolymers (PLLA, poly(l‐lactide); PCL, poly(ε‐caprolactone)) or/and three‐arm star (PCL‐b‐PDLA)3 block copolymers (PDLA, poly(d‐lactide)) were synthesized. The effects of the structure and composition on crystal structure, crystallization behavior, spherulite morphology and mechanical properties of the synthesized supramolecular polymers were investigated. The results of DSC and polarized optical microscopy indicated that the supramolecular polymer exhibited poor crystallization ability with respect to PCL/PLA block copolymer, and the crystallinity of the supramolecular polymer with alternating PCL/PLA multiblock structure was stronger than that with similar crosslinked network structure. The presence of molten PCL blocks disturbed the orientation of lamellae, forming spherulites with feather‐like dendrites, and ring‐banded spherulites were observed as the molecular weight of the PLA blocks increased. The results of tensile tests demonstrated that supramolecular polymers with larger molecular weight of PLA blocks showed the pronounced ductile fracture. On this basis, stereocomplexed supramolecular polymers were also synthesized, and it was found that the stereocomplex crystals had a significant impact on the crystallization and mechanical properties of the supramolecular polymers. Therefore, in this work a novel technique for manufacturing toughened PLA‐based material and tuning its performances is proposed, which may promote the application of PLA‐based materials in more fields. © 2022 Society of Industrial Chemistry.

A three-dimensional (3D) printing method has been suggested as a manufacturing tool for complex structures. However, 3D printed parts have poor mechanical properties compared to those fabricated by traditional methods such as injection and compression molding. To overcome the disadvantage, the 3D printing system of continuous carbon fiber reinforced shape memory polymer composites (SMPC) was constructed using a material extrusion type-3D printer. The two types of matrices were used; thermoplastics and thermosets. With regard to the matrix type, the different method was adjusted to each printer. In order to set the proper condition of 3D printing, the thermal and rheological properties of various SMP matrices were characterized. The process parameters, such as temperature and printing speed, were varied for optimizing the printing system. Then, the tensile specimens of SMPC were printed and their mechanical and shape memory properties were evaluated. The printed SMPC showed good mechanical properties compared to those of conventionally 3D printed polymer in the fiber direction. Their shape memory behavior and thermomechanical properties were characterized. Then, a complex 3D shapes composed of basic unit cells was designed considering the fiber orientation. The possibility of developing morphing structures using 3D printing of continuous carbon fiber reinforced SMPC was investigated.