Synthesis and properties of new crosslinked polyurethane elastomers based on isosorbide

Synthesis and Characteristic Valuation of a Thermoplastic Polyurethane Electrode Binder for In-Mold Coating

A polyurethane series (PHEI-PU) was prepared via a one-shot bulk polymerization method using hexamethylene diisocyanate (HDI), polycarbonate diol (PCD), and isosorbide derivatives (ISBD) as chain extenders. The mechanical properties were evaluated using a universal testing machine (UTM), and the thermal properties were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PHEI-PU series exhibited excellent mechanical properties with an average tensile strength of 44.71 MPa and an elongation at break of 190%. To verify the applicability of different proportions of PU as an electrode binder, PU and Ag flakes were mixed (30/70 wt%) and coated on PCT substrates, the electrodes were evaluated by four-point probe before and after 50% elongation, and the dispersion was evaluated by scanning electron microscopy (SEM). The electrical resistance change rate of PHEI-PU series was less than 20%, and a coating layer with well-dispersed silver flakes was confirmed even after stretching. Therefore, it exhibited excellent physical properties, heat resistance, and electrical resistance change rate, confirming its applicability as an electrode binder for in-mold coating.

Controlled Degradation of Polycaprolactone Polymers through Ultrasound Stimulation

This study describes the development of an ultrasound-responsive polymer system that provides on-demand degradation when exposed to high-intensity focused ultrasound (HIFU). Diels-Alder cycloadducts were used to crosslink polycaprolactone (PCL) polymers and underwent a retro Diels-Alder reaction when stimulated with HIFU. Two Diels-Alder polymer compositions were explored to evaluate the link between reverse reaction energy barriers and polymer degradation rates. PCL crosslinked with isosorbide was also used as a non-Diels-Alder-based control polymer. An increase of HIFU exposure time and amplitude correlated with an increase of PCL degradation for Diels-Alder-based polymers. Ultrasound imaging during HIFU allowed for real-time visualization of the on-demand degradation through cavitation-based mechanisms. The temperature surrounding the sample was monitored with a thermocouple during HIFU stimulation; a minimal increase in temperature was observed. PCL polymers were characterized using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), optical profilometry, and mechanical testing. PCL degradation byproducts were identified by mass spectrometry, and their cytocompatibility was evaluated in vitro. Overall, this study demonstrated that HIFU is an effective image-guided, external stimulus to control the degradation of Diels-Alder-based PCL polymers on-demand.

Sustainable cycloaliphatic polyurethanes: from synthesis to applications

Polyurethanes (PUs) are a versatile and major polymer family, mainly produced via polyaddition between polyols and polyisocyanates. A large variety of fossil-based building blocks is commonly used to develop a wide range of macromolecular architectures with specific properties. Due to environmental concerns, legislation, rarefaction of some petrol fractions and price fluctuation, sustainable feedstocks are attracting significant attention, e.g., plastic waste and biobased resources from biomass. Consequently, various sustainable building blocks are available to develop new renewable macromolecular architectures such as aromatics, linear aliphatics and cycloaliphatics. Meanwhile, the relationship between the chemical structures of these building blocks and properties of the final PUs can be determined. For instance, aromatic building blocks are remarkable to endow materials with rigidity, hydrophobicity, fire resistance, chemical and thermal stability, whereas acyclic aliphatics endow them with oxidation and UV light resistance, flexibility and transparency. Cycloaliphatics are very interesting as they combine most of the advantages of linear aliphatic and aromatic compounds. This original and unique review presents a comprehensive overview of the synthesis of sustainable cycloaliphatic PUs using various renewable products such as biobased terpenes, carbohydrates, fatty acids and cholesterol and/or plastic waste. Herein, we summarize the chemical modification of the main sustainable cycloaliphatic feedstocks, synthesis of PUs using these building blocks and their corresponding properties and subsequently present their major applications in hot-topic fields, including building, transportation, packaging and biomedicine.

Effects of preparation routes on the physical and rheological properties of isosorbide-based thermoplastic polyurethanes

Biomass-derived isosorbide (ISB) is a promising alternative to petroleum-based monomers in industrial plastics. In this study, ISB-based thermoplastic polyurethanes (ISB-TPUs) were prepared using ISB as a biomass chain extender, and the effects of the preparation route on the structural and physical properties of the resultant polymers were investigated. Prepolymer methods were more suitable for obtaining the desired molecular weights (MWs) and physical properties of ISB-TPUs than the one-shot method. The presence of the solvent and catalyst in the prepolymer step had significant effects on the structural and physical properties of the resultant polymer. Among several prepolymer conditions, the solvent- and catalyst-free methods were the most suitable for preparing commercial-level ISB-TPUs, with number- and weight-average MWs (M _n and M _w ) of 32,881 and 90,929 g mol^-1, respectively, and a tensile modulus (E) and ultimate tensile strength (UTS) of 12.0 and 40.2 MPa, respectively. In comparison, the presence of a catalyst in the prepolymer step resulted in lower MWs and mechanical properties (81,033 g mol^-1 and 18.3 MPa of M _w and UTS, respectively). The co-existence of the catalyst/solvent led to a further decline in the properties of ISB-TPUs (26,506 and 10.0 MPa of M _w and UTS, respectively). ISB-TPU prepared via the solvent- and catalyst-free methods exhibited remarkable elastic recovery when subjected to up to 1000% strain in mechanical cycling tests. Rheological characterization confirmed the thermo-reversible phase change (thermoplasticity) of the polymer.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13233-023-00125-w.

Hyperelastic, shape‐memorable, and ultra‐cell‐adhesive degradable polycaprolactone‐polyurethane copolymer for tissue regeneration

Novel polycaprolactone‐based polyurethane (PCL‐PU) copolymers with hyperelasticity, shape‐memory, and ultra‐cell‐adhesion properties are reported as clinically applicable tissue‐regenerative biomaterials. New isosorbide derivatives (propoxylated or ethoxylated ones) were developed to improve mechanical properties by enhanced reactivity in copolymer synthesis compared to the original isosorbide. Optimized PCL‐PU with propoxylated isosorbide exhibited notable mechanical performance (50 MPa tensile strength and 1150% elongation with hyperelasticity under cyclic load). The shape‐memory effect was also revealed in different forms (film, thread, and 3D scaffold) with 40%–80% recovery in tension or compression mode after plastic deformation. The ultra‐cell‐adhesive property was proven in various cell types which were reasoned to involve the heat shock protein‐mediated integrin (α5 and αV) activation, as analyzed by RNA sequencing and inhibition tests. After the tissue regenerative potential (muscle and bone) was confirmed by the myogenic and osteogenic responses in vitro, biodegradability, compatible in vivo tissue response, and healing capacity were investigated with in vivo shape‐memorable behavior. The currently exploited PCL‐PU, with its multifunctional (hyperelastic, shape‐memorable, ultra‐cell‐adhesive, and degradable) nature and biocompatibility, is considered a potential tissue‐regenerative biomaterial, especially for minimally invasive surgery that requires small incisions to approach large defects with excellent regeneration capacity.

Ultra-Tough Elastomers from Stereochemistry-Directed Hydrogen Bonding in Isosorbide-Based Polymers

The remarkable elasticity and tensile strength found in natural elastomers are challenging to mimic. Synthetic elastomers typically feature covalently cross-linked networks (rubbers), but this hinders their reprocessability. Physical cross-linking via hydrogen bonding or ordered crystallite domains can afford reprocessable elastomers, but often at the cost of performance. Herein, we report the synthesis of ultra-tough, reprocessable elastomers based on linear alternating polymers. The incorporation of a rigid isohexide adjacent to urethane moieties affords elastomers with exceptional strain hardening, strain rate dependent behavior, and high optical clarity. Distinct differences were observed between isomannide and isosorbide-based elastomers where the latter displays superior tensile strength and strain recovery. These phenomena are attributed to the regiochemical irregularities in the polymers arising from their distinct stereochemistry and respective inter-chain hydrogen bonding.

Polyurethane elastomers with amphiphilic ABA tri-block co-polymers as the soft segments showing record-high tensile strength and simultaneously increased ductility

Polyurethane elastomers with amphiphilic ABA tri-block co-polymers as the soft segments robustly show record-high tensile strength and simultaneously increased ductility via producing small and uniform hard domains.

The effects of the inclusion of 1,2,4-triazole derivatives into the main chains of the polyurethane urea exposed to UV radiation

Linear polyurethane urea containing 1,2,4-triazole segments was obtained by polyaddition of the 3,5-diamino-1,2,4-triazole (DATA) to urethane prepolymer. Also, three crosslinked polymers with different crosslinkers (2,4,6-triaminopyrimidine (TAP), glycerin (Gly), castor oil (CO)) were synthesized. Thermogravimetric analysis, of the obtained polymers, indicated good thermal stability up to 310°C. The polyurethane urea chemical structure was confirmed by FTIR analysis. The glass transition temperatures (Tg) of these polymers, measured by differential scanning calorimetry (DSC), were found in the range of −52°C to −56°C. These values were not significantly influenced by the structure of the hard domain and the intermolecular interactions. The tensile testing showed that the inclusion of 1,2,4-triazole in polyurethane structure substantially improves the tensile strength up to 58 MPa. The obtained polyurethane urea presents surface slight hydrophobic and low interfacial tension. The positive effect of the 1,2,4-triazole segment from the polymer main chain in the UV aging process of these polymer materials has been studied. After exposure to UV radiation, few changes were observed in the molecular structure, in the surface morphology and the mechanical properties.

Structure–properties relationship of the polyurethanes that contain Schiff base in the main chain

This article studies the diversification of useful properties of polyurethane (PU) structures by the inclusion of new components. PUs containing a Schiff base in the main chain were synthesized by using N, N′-bis(salicylidene)-1,3-propanediamine as a chain extender. Novel Schiff base PUs were synthesized via a two-step polymerization starting from a Schiff base derivative diol chain extender with different molar ratios or by cross-linking with various natural raw materials. The sought after structures was confirmed by Fourier transform infrared spectra that showed the disappearance of the signals of both the hydroxyl and isocyanate groups. The thermal properties of these PUs were investigated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The initial degradation temperatures of the obtained PUs were found to be in the range of 300–350°C. Based on the results from DMA, the rigid structure of the Schiff base from the backbone of the PUs presented a higher storage modulus, results which may be connected to the physical cross-linking process of the macromolecules. Their optical properties were determined by fluorescence spectroscopy. The incorporation of Schiff base structures into the main PU chain generates new PU structures with improved thermomechanical properties, which includes possible bioactive Schiff base moieties, widening the range of practical applications for such polymers.

Conductive polyurethane elastomer electrolyte (PUEE) materials for anodic bonding

Polyurethane elastomer electrolyte (PUEE) represents a promising class of polymer solid electrolytes for the preparation and packaging of flexible devices by anodic bonding. In this work, PUEEs were designed and prepared via a pre-polymerization method and cured at room temperature using polypropylene glycol (PPG), toluene-2,4-diisocyanate (TDI) and 1,4-butanediol (BDO) in the presence of varying amounts of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI). All PUEEs exhibited high thermal stability and conductivity, with the highest ionic conductivity of 9.6 × 10⁻⁵ S cm⁻¹ for PUEE6 (n_{[NHCOO]/Li⁺} = 1) at 55 °C. The results showed that LiTFSI was dissolved completely in the polyurethane matrix, and the complexing reactions occurred between the lithium ions and the polar groups of polyurethane. After that, the prepared PUEE and the Al sheet were successfully joined by the anodic bonding process. The microstructures of the bonded interface between PUEE and the Al sheet with a clear intermediate bonding layer could be observed in the cross-section scanning electron microscopy (SEM) images, and the elements in each layer were also detected by energy dispersive spectroscopy (EDS), which indicated that the PUEE and the Al sheet were bonded together. The maximum tensile strength for bonded PUEE6/Al was up to 0.45 MPa. All these results demonstrated that the prepared PUEE material would be a promising candidate for the preparation and packaging of flexible devices by anodic bonding.

Polyurethane elastomer electrolytes (PUEE) were prepared as flexible substrates to be joined with Al sheets by anodic bonding for the preparation and packaging of flexible devices.

Microwave-assisted synthesis of isosorbide-derived diols for the preparation of thermally stable thermoplastic polyurethane

In order to prepare thermally stable isosorbide-derived thermoplastic polyurethane, the synthesis of two new chiral exo-exo configured diols, prepared from isosorbide, and two types of diphenols (bisphenol A and thiodiphenol) was described. The synthesis conditions were optimized under conventional heating and microwave irradiations. To prove their suitability in polymerization, these monomers were successfully polymerized using 4,4'-diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). Both monomers and polymers have been studied by NMR, FT-IR, TGA, DSC; intrinsic viscosity of polymers has also been determined. The results showed the effectiveness of the synthetic strategy proposed; moreover, a dramatic reduction of the reaction time and an important improvement of the monomers yield using microwave irradiation have been demonstrated. The monomers, as well as the polymers, showed excellent thermal stability both in air and nitrogen. It was also shown that the introduction of sulphur in the polyurethane backbone was effective in delaying the onset of degradation as well as the degradation rate.