Bis-carbonylimidazolide (BCI) functionalization enables an efficient synthetic strategy to generate high molecular weight segmented nonisocyanate polyurethanes (NIPUs). Melt phase polymerization of ED-2003 Jeffamine, 4,4'-methylenebis(cyclohexylamine), and a BCI monomer that mimics a 1,4-butanediol chain extender enables polyether NIPUs that contain varying concentrations of hard segments ranging from 40 to 80wt. %. Dynamic mechanical analysis and differential scanning calorimetry reveal thermal transitions for soft, hard, and mixed phases. Hard segment incorporations between 40 and 60wt. % display up to three distinct phases pertaining to the poly(ethylene glycol) (PEG) soft segment Tg , melting transition, and hard segment Tg , while higher hard segment concentrations prohibit soft segment crystallization, presumably due to restricted molecular mobility from the hard segment. Atomic force microscopy allows for visualization and size determination of nanophase-separated regimes, revealing a nanoscale rod-like assembly of HS. Small-angle X-ray scattering confirms nanophase separation within the NIPU, characterizing both nanoscale amorphous domains and varying degrees of crystallinity. These NIPUs, which are synthesized with BCI monomers, display expected phase separation that is comparable to isocyanate-derived analogues. This work demonstrates nanophase separation in BCI-derived NIPUs and the feasibility of this nonisocyanate synthetic pathway for the preparation of segmented PU copolymers.

Conventional polyurethanes are typically obtained from polyisocyanates, polyols, and chain extenders. The main starting materials—isocyanates used in this process—raise severe health hazard concerns. Therefore, there is a growing demand for environment‐friendly processes and products. This review article summarizes progress that has been made in recent years in the development of alternative methods of polyurethane synthesis. In most of them, carbon dioxide is applied as a sustainable feedstock for polyurethane production directly or indirectly. The resulting non‐isocyanate polyurethanes are characterized by a solvent‐free synthesis, resistance to chemical degradation, 20% more wear resistance than conventional polyurethane, and can be applied on wet substrates and cured under cold conditions. Three general polymer synthetic methods, step‐growth polyaddition, polycondensation, and ring‐opening polymerization, are presented in the review. Much attention is given to the most popular and having potential industrial importance method of obtaining non‐isocyanate polyurethanes, poly(hydroxy‐urethane)s, based upon multicyclic carbonates and aliphatic amines. It is evident from the present review that considerable effort has been made during the last years to develop environmentally friendly methods of obtaining polyurethanes, especially those with the use of carbon dioxide or simple esters of carbonic acid. Copyright © 2015 John Wiley & Sons, Ltd.

This work reports on the thermal properties of non-isocyanate polyurethanes (NIPUs) obtained via the polyaddition reaction of polyether diamine with five membered tri(cyclic carbonate) by using a prepolymerization method. The non-isocyanate polyurethanes were further chemically modified by trifunctional polyhedral oligomeric silsesquioxane (POSS) - triglycidylisobutyl POSS (3epPOSS), resulting in hybrid composite materials containing 5 to 15 wt% POSS. Thermal properties of the obtained materials were studied by various methods, such as Thermogravimetric analysis (TGA), Pyrolysis with gas chromatography and mass spectrometry (Py-GC/MS), and Microscale Combustion Calorimetry (MCC), and were later discussed in dependence of their composition and structure assessed by Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) techniques. FTIR spectra confirm the successful synthesis of NIPUs and their hybrids with POSS. The results of XRD and SEM revealed homogeneous distribution of silsesquioxane in the bulk of the NIPU matrix. Depending on the POSS concentration in the PU hybrids, various self-assembling structures were formed. TGA analysis indicated a two- and three-step degradation process of NIPU materials in inert and oxidative atmospheres, respectively. Significantly higher degradation temperatures and a remarkably reduced degradation rate for composite materials compared to unmodified NIPU matrix were observed during the second degradation step under an oxidative atmosphere. Based on the overall stabilization effect (OSE), hybrids containing 10 and 15 wt% of 3epPOSS were more thermally stable than the unmodified NIPU matrix. Py-GC/MS demonstrated that the products of NIPU thermal decomposition originate from hydroxyurethane moieties, main substrate core structures, and others, such as catalysts. Incorporation of 3epPOSS into the NIPU matrix decreases its flammability, as evidenced by the results of the MCC, with a nearly 20 % reduction effect noted for the composite with of 15 wt% of POSS, compared to the unmodified NIPU matrix. Importantly, chemical modification of NIPU by POSS caused a reduction of the heat of combustion in the final stage of degradation by ca. 30 %.

AbstractA simple and green method was established to prepare self‐healing cross‐linked nonisocyanate polyurethanes (SH‐cNIPUs) from biobased diglycerol bis(cyclic carbonate) (DGDC). Two nonisocyanate polyurethane prepolymers with furan terminal groups (tFU‐NIPUs) were synthesized through a ring‐opening reaction of DGDC with furan methylamine and trimethylolpropane tris(poly[propylene glycol], amine terminated) ether, or tris(2‐aminoethyl) amine under mild conditions. The SH‐cNIPUs were prepared via a Diels–Alder reaction between tFU‐NIPUs and a bismaleimide. SH‐cNIPUs were characterized by ATI‐FTIR,1H NMR, differential scanning calorimetry, polarized optical microscope, and tensile strength after being damaged and healed. SH‐cNIPUs with glass transition temperature from 8 to 49°C, tensile strength up to 21 MPa, and self‐healing efficiency from 67 to 80% were successfully synthesized.

Non-isocyanate polyurethanes (NIPUs) constitute one of the most prospective groups of eco-friendly materials based on their phosgene-free synthesis pathway. Moreover, one of the steps of their obtaining includes the use of carbon dioxide (CO2), which allows for the promotion of the development of carbon dioxide capture and storage technologies. In this work, non-isocyanate polyurethanes were obtained via three-step synthesis pathway with the use of epichlorohydrin. In the I step, the addition reaction of epichlorohydrin with polyhydric alcohols was conducted for diglicydyl ethers obtaining. In the II step carbon dioxide reacted with diglicydyl ethers to obtain five-membered bis (cyclic carbonate)s in the cycloaddition reaction. Then, one-pot polyaddition reaction between bis (cyclic carbonate) and dimerized fatty acids-based diamine allowed for non-isocyanate polyurethanes (NIPU)s preparation. Three bio-based materials (two semi-products and one bio-NIPU) and three petrochemical-based materials (two semi-products and one NIPU) were obtained. The selected properties of the products of each step of NIPUs preparation were compared. Fourier transform infrared spectroscopy FTIR and proton nuclear magnetic resonance 1H NMR measurements allowed to verify the chemical structure of all obtained products. The average molecular masses of the semi-products were measured with the use of size exclusion chromatography SEC. Moreover, thermal stability and thermal degradation kinetics were determined based on thermogravimetric analysis TGA. The results confirmed that the activation energy of thermal decomposition was lower for semi-products and NIPUs prepared with the use of petrochemical-based epichlorohydrin than for their bio-based counterparts.

A series of environmentally friendly non-isocyanate polyurethanes (NIPUs) were successfully prepared via the polyaddition reaction of bio-based polyether polyol-based cyclic carbonate with diamine derivative of dimerized fatty acids. The syntheses of NIPUs were realized by the three-step method in the absence of toxic solvents and, importantly, the process of carbonation did not require the use of elevated pressure. The effect of using various types of bio-based amines, [amine]/[cyclic carbonate] molar ratio as well as different reaction temperatures on the chemical structure and thermal properties were widely investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA), respectively. The Gaussian deconvolution technique was used to decompose the carbonyl region (-CO) of three peaks in various samples. It was found that the molar ratio of substrates and curing temperature have an effect on the distribution of free and H-bonded carbonyl groups as well as carbonyl groups from cyclic carbonates in the chemical structure of the prepared compounds. On this basis, the role of hydrogen bonds in the chemical structure of NIPU on selected sample properties was determined. Moreover, the impact of water during 6 months of immersion on the polymer networks was examined.

AbstractDue to the utilization of the potentially hazardous monomer, isocyanate compound, polyurethanes (PUs) with good properties are restricted in several fields, such as bio‐engineering. Non‐isocyanate polyurethanes (NIPUs) with high overall performance and self‐healing properties were synthesized by dicarbamate, bio‐based isosorbide (IS) and polycarbonate diols (PCDLs) through a solvent‐free and ecologically friendly melt polycondensation route. Previously, few bio‐based monomers have been introduced into polycondensation reactions of PUs. Chemical structures of NIPUs were analyzed by Fourier transform‐infrared spectroscopy (FT‐IR), proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). With changing the IS content and the molecular weight of PCDL, the obtained NIPUs had linear structures and high molecular weights ranging from 3.3 × 104 to 5.9 × 104 g/mol. Results of tensile testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) suggested NIPUs had well thermal and mechanical properties, with Td,5% above 286.2°C and tensile strength between 8.0 and 16.7 MPa due to the crystallization and the hydrogen bonding interactions. Furthermore, the NIPUs exhibited self‐healing ability and recyclability, having great potential for industrialization.

Commercially available polyurethanes are synthesized by the polyaddition of diisocyanates with polyols and low molecular weight chain extenders. A new approach to polyurethanes synthesis is realized via non-isocyanate routes. Negative impacts of petroleum-based chemicals on the environment and human health as well as gradual reduction of fuel-based resources, which leads to an increase in their prices, are an incentive to looking for bio-based components derived from renewable resources for the polyurethanes synthesis. The purpose of the presented review is a critical summary of the possibilities of using renewable natural resources as green intermediates to obtain non-isocyanate polyurethanes by polyaddition of bis(cyclic carbonate)s and di- or polyamines. The possibility of using carbon dioxide, plant oils, fatty acids and biomass-derived platform chemicals in non-isocyanate polyurethane synthesis is exhaustively commented.

Conventional synthesis routes for thermoplastic polyurethanes (TPUs) still require the use of isocyanates and tin-based catalysts, which pose considerable safety and environmental hazards. To reduce both the ecological footprint and human health dangers for nonwoven TPU scaffolds, it is key to establish a green synthesis route, which eliminates the use of these toxic compounds and results in biocompatible TPUs with facile processability. In this study, we developed high-molecular-weight nonisocyanate polyurethanes (NIPUs) through transurethanization of 1,6-hexanedicarbamate with polycarbonate diols (PCDLs). Various molecular weights of PCDL were employed to maximize the molecular weight of NIPUs and consequently facilitate their electrospinnability. The synthesized NIPUs were characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The highest achieved molecular weight (M w) was 58,600 g/mol. The NIPUs were consecutively electrospun into fibrous scaffolds with fiber diameters in the submicron range, as shown by scanning electron microscopy (SEM). To assess the suitability of electrospun NIPU mats as a possible biomimetic load-bearing pericardial substitute in cardiac tissue engineering, their cytotoxicity was investigated in vitro using primary human fibroblasts and a human epithelial cell line. The bare NIPU mats did not need further biofunctionalization to enhance cell adhesion, as it was not outperformed by collagen-functionalized NIPU mats and hence showed that the NIPU mats possess a great potential for use in biomimetic scaffolds.

Commercially, polyurethanes are produced by the reaction of diisocyanates, polyols (polyester or polyether) and low molecular weight chain extender. Toxicity, moisture sensitivity and phosgene-based synthesis of diisocyanates resulted in investigations focused on obtaining the non-isocyanate polyurethanes (NIPUs). This work presents the review of synthesis and structure–properties relationship of non-isocyanate polyurethanes obtained by reacting cyclic carbonated intermediates with diamines or polyamines. Moreover, the presented methods of NIPU synthesis were analysed from the environmental point of view. Described five-membered ring cyclic carbonate intermediates were obtained by carbonation of glycidyl ethers or thiol-ene coupling of unsaturated cyclic carbonate monomers and thiols. The special interest was put on the bio-based non-isocyanate polyurethanes, obtained from chemically modified bio-based substances, e.g. carbonated vegetable oils. The mechanical and thermal properties of NIPUs are affected by functionality, structure and molecular weight of cyclic carbonate intermediates and diamines or polyamines.