Innovations in applications and prospects of non-isocyanate polyurethane bioplastics

Currently, conventional plastics are necessary for a variety of aspects of modern daily life, including applications in the fields of healthcare, technology, and construction. However, they could also contain potentially hazardous compounds like isocyanates, whose degradation has a negative impact on both the environment and human health. Therefore, researchers are exploring alternatives to plastic which is sustainable and environmentally friendly without compromising its mechanical and physical features. This review study highlights the production of highly eco-friendly bioplastic as an efficient alternative to non-biodegradable conventional plastic. Bioplastics are produced from various renewable biomass sources such as plant debris, fatty acids, and oils. Poly-addition of di-isocyanates and polyols is a technique employed over decades to produce polyurethanes (PUs) bioplastics from renewable biomass feedstock. The toxicity of isocyanates is a major concern with the above-mentioned approach. Novel green synthetic approaches for polyurethanes without using isocyanates have been attracting greater interest in recent years to overcome the toxicity of isocyanate-containing raw materials. The polyaddition of cyclic carbonates (CCs) and polyfunctional amines appears to be the most promising method to obtain non-isocyanate polyurethanes (NIPUs). This method results in the creation of polymeric materials with distinctive and adaptable features with the elimination of harmful compounds. Consequently, non-isocyanate polyurethanes represent a new class of green polymeric materials. In this review study, we have discussed the possibility of creating novel NIPUs from renewable feedstocks in the context of the growing demand for efficient and ecologically friendly plastic products.

A review on room-temperature self-healing polyurethane: synthesis, self-healing mechanism and application

Polyurethanes have been widely used in many fields due to their remarkable features such as excellent mechanical strength, good abrasion resistance, toughness, low temperature flexibility, etc. In recent years, room-temperature self-healing polyurethanes have been attracting broad and growing interest because under mild conditions, room-temperature self-healing polyurethanes can repair damages, thereby extending their lifetimes and reducing maintenance costs. In this paper, the recent advances of room-temperature self-healing polyurethanes based on dynamic covalent bonds, noncovalent bonds and combined dual or triple dynamic bonds are reviewed, focusing on their synthesis methods and self-healing mechanisms, and their mechanical properties, healing efficiency and healing time are also described in detial. In addition, the latest applications of room-temperature self-healing polyurethanes in the fields of leather coatings, photoluminescence materials, flexible electronics and biomaterials are summarized. Finally, the current challenges and future development directions of the room-temprature self-healing polyurethanes are highlighted. Overall, this review is expected to provide a valuable reference for the prosperous development of room-temperature self-healing polyurethanes.

Graphical abstract

Nanocomposites of Polyhydroxyurethane with POSS Microdomains: Synthesis via Non-Isocyanate Approach, Morphologies and Reprocessing Properties

In this contribution, we reported the synthesis of a novel trifunctional POSS cyclic carbonate [POSS-3(5CC)]. With a difunctional five-member cyclic carbonate and a trifunctional polyetheramine as the precursor, the nanocomposites of polyhydroxyurethane (PHU) with POSS were synthesized. Transmission electron microscopy (TEM) showed that the nanocomposites of PHUs with POSS were microphase-separated; the spherical POSS microdomains via POSS-POSS interactions were generated with the size of 20~40 nm in diameter. After the introduction of POSS microdomains, the nanocomposites displayed improved thermal and mechanical properties. More importantly, the nanocomposites still displayed the reprocessing properties of vitrimers.

Trends in non-isocyanate polyurethane (NIPU) development

The transition towards safer and more sustainable production of polymers has led to a growing body of academic research into non-isocyanate polyurethanes (NIPUs) as potential replacements for conventional, isocyanate-based polyurethane materials. This perspective article focuses on the opportunities and current limitations of NIPUs produced by the reaction between biobased cyclic carbonates with amines, which offers an interesting pathway to renewable NIPUs. While it was initially thought that due to the similarities in the chemical structure, NIPUs could be used to directly replace conventional polyurethanes (PU), this has proven to be more challenging to achieve in practice. As a result, and in spite of the vast amount of academic research into this topic, the market size of NIPUs remains negligible. In this perspective, we will emphasize the main limitations of NIPUs in comparison to conventional PUs and the most significant advances made by others and us to overcome these limitations. Finally, we provide our personal view of where research should be directed to promote the transition from the academic to the industrial sector.

Mechanically Strong, Autonomous Self-Healing, and Fully Recyclable Silicone Coordination Elastomers with Unique Photoluminescent Properties

The combination of excellent mechanical performances, high reprocess efficiency, and wide-range tunability for functional dynamic siloxane materials is a challenging subject. Herein, the fabrication of mechanically strong, autonomous self-healing, and fully recyclable silicone elastomers with unique photoluminescent properties by coordination of poly(dimethylsiloxane) (PDMS) containing coordination bonding motifs with Zn²⁺ ions is reported. Salicylaldimine groups, which are introduced into the polysiloxane backbone via mild Schiff-base reaction, coordinate with zinc ions to form elastomeric networks The obtained supramolecular elastomers have excellent mechanical properties, with the optimized tensile strength up to 10.0 MPa, which is unprecedented among the reported thermoplastic polysiloxane-based elastomers. Both mechanical properties and stress relaxation kinetics are tunable via adjusting the length of PDMS segments or the molar ratio of metal versus salicylaldimine. Furthermore, these elastomers can be conveniently healed and recycled to regain their original mechanical properties and integrity under mild conditions. In addition, this new kind of polysiloxane also exhibits coordination-enhanced fluorescence, showing great promise for preparing photoluminescent elastomers or coatings.

Ionic Inter-Particle Complexation Effect on the Performance of Waterborne Coatings

The performance of waterborne (meth)acrylic coatings is critically affected by the film formation process, in which the individual polymer particles must join to form a continuous film. Consequently, the waterborne polymers present lower performance than their solvent-borne counter-polymers. To decrease this effect, in this work, ionic complexation between oppositely charged polymer particles was introduced and its effect on the performance of waterborne polymer films was studied. The (meth)acrylic particles were charged by the addition of a small amount of ionic monomers, such as sodium styrene sulfonate and 2-(dimethylamino)ethyl methacrylate. Density functional theory calculations showed that the interaction between the selected main charges of the respective functional monomers (sulfonate-amine) is favored against the interactions with their counter ions (sulfonate-Na and amine-H). To induce ionic complexation, the oppositely charged latexes were blended, either based on the same number of charges or the same number of particles. The performance of the ionic complexed coatings was determined by means of tensile tests and water uptake measurements. The ionic complexed films were compared with reference films obtained at pH at which the cationic charges were in neutral form. The mechanical resistance was raised slightly by ionic bonding between particles, producing much more flexible films, whereas the water penetration within the polymeric films was considerably hindered. By exploring the process of polymer chains interdiffusion using Fluorescence Resonance Energy Transfer (FRET) analysis, it was found that the ionic complexation was established between the particles, which reduced significantly the interdiffusion process of polymer chains. The presented ionic complexes of sulfonate-amine functionalized particles open a promising approach for reinforcing waterborne coatings.

Cationic polyurethane from CO2-polyol as an effective barrier binder for polyaniline-based metal anti-corrosion materials

An internal crosslinked waterborne cationic polyurethane from CO₂-polyol featuring neutral characterization was designed and prepared for the development of a sustainable polyaniline-based metal anti-corrosion material.

Study of Moisture-Curable Hybrid NIPUs Based on Glycerol with Various Diamines: Emergent Advantages of PDMS Diamines

A sol/gel curing method is used in this work to synthesize hybrid partially bio-based polyhydroxyurethanes (PHUs) from dicarbonates derived from glycerol and various diamines. The method consists of end-capping the PHU prepolymers with moisture-sensitive groups, so sealants and adhesives can be produced from partially sustainable hybrid PHUs (HPHUs), similar to their preparation from end-capped conventional polyurethanes. Diglycerol dicarbonate (DGC) is synthesized and polymerized with different diamines of various chain lengths, and the resulting structural and thermal properties of the PHUs are qualitatively and quantitively characterized. This characterization led to two potential candidates: PHU 4, made of DGC and a poly(propylene glycol) diamine, and PHU 10, prepared from DGC and a poly(dimethylsiloxane) diamine. These polymers, with respective relative number-average molecular weights of 3200 and 7400 g/mol, are end-capped and left to cure under ambient lab conditions (22 °C and 40-50% humidity), and the curing processes are monitored rheologically. Notably, moisture curing does not require any catalyst. The chemical stability of the resulting hybrid PHUs (HPHUs) 4 and 10 in pure water is investigated to check the viability of applying them under outdoor conditions. Only HPHU 10 is found to be resistant to water and shows hydrophobicity with a contact angle of 109°. Tensile tests are conducted on HPHU 10 samples cured under lab conditions for a week and others cured for another week while being immersed in water. The mechanical properties, tensile strength and elongation at break, improve with the samples cured in water, indicating the high-water repellency of HPHU 10.

Water-based non-isocyanate polyurethane-ureas (NIPUUs)

This review aims at discussing the achievements and the remaining challenges in the development of water-soluble NIPUUs, NIPUUs-based hydrogels and water-borne NIPUU dispersions.

Effects of surfactant and ionic concentration on properties of dual physical crosslinking self-healing hydrogels by hydrophobic association and ionic interactions

Two kinds of dual crosslinking hydrogels have adjustable mechanical properties, self-healing and self-recovery performances.