Nonisocyanate Polyurethane Segmented Copolymers from Bis-Carbonylimidazolides.

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 80 wt. %. Dynamic mechanical analysis and differential scanning calorimetry reveal thermal transitions for soft, hard, and mixed phases. Hard segment incorporations between 40 and 60 wt. % 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.

Fast Response and Visual Transparency Switching Hydrochromic Film Based on the Rational Structure of Cellulose/Poloxamer Copolymers Design for Smart Window.

The authors are motivated to develop a series of hydrochromic copolymers with fast response, reversibility, repeatability, and visual transparency transition. The hydrochromic block copolymers are based on the rational ratio of hydrophilic segments of poloxamer block and hydrophobic segments of ethyl cellulose according to the preparation method of polyurethane. By tuning the ratio of hydrophilic segments or adding hygroscopic salts, the hydrochromic polymer is endowed with the ability to visualize the transparency in response to the relative humidity. Especially, the response time of the polymer is extremely shortened, up to 1 s for the optimized sample. Within the moisture stimulation, the hygroscopic swelling increases the film thickness, leading to a reversible transparency switching from a highly transparent state (82%) to an opaque white state (20.5%).

Synthesis of Sucrose-HDI Cooligomers: New Polyols for Novel Polyurethane Networks.

Sucrose-1,6-hexamethylene diisocyanate (HDI) cooligomers were synthesized and used as new polyols for poly(ε-caprolactone) (PCL)-based polyurethanes. The polyaddition reaction of sucrose and HDI was monitored by MALDI-TOF MS. It was found that by selecting appropriate reaction conditions, mostly linear oligomer chains containing 16 sucrose units could be obtained. For the synthesis of polyurethane networks, prepolymers were prepared by the reaction of poly(ε-caprolactone) (PCL, 10 kg/mol) with HDI or 4,4'-methylene diphenyl diisocyanate (MDI) and were reacted with sucrose-HDI cooligomers. The so-obtained sucrose-containing polyurethanes were characterized by means of attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FT IR), swelling, mechanical (uniaxial tensile tests) and differential scanning calorimetry (DSC).

Effect of New Eco-Polyols Based on PLA Waste on the Basic Properties of Rigid Polyurethane and Polyurethane/Polyisocyanurate Foams.

The aim of the presented research was to obtain two new eco-polyols based on waste polylactide (PLA) and to check the effect on the properties of rigid polyurethane (RPU) foams and, based on these, rigid polyurethane/polyisocyanurate (RPU/PIR) foams. The synthesis of eco-polyols was based on the transesterification reaction of melted PLA with diethylene glycol in the presence of an organometallic catalyst. Properties of the obtained eco-polyols were examined for their potential as raw materials for synthesis of rigid polyurethane and polyisocyanurate foams, i.e., hydroxyl value, acid value, density, viscosity, pH, water content. Spectroscopic studies (FTIR, 1H NMR and 13C NMR) were also carried out. Results of these tests confirmed the assumed chemical structure of the new polyols. RPU and RPU/PIR foam formulations were developed based on the obtained analytical results. Partial replacement of petrochemical polyol by eco-polyols in RPU and RPU/PIR foams decreased the value of apparent density, compressive strength, brittleness and water absorption. Moreover, all foams modified by eco-polyols showed higher resistance to aging. All RPU/PIR foams and most PRU foams modified by eco-polyols from waste PLA had better functional properties than the reference foams based on petrochemical polyol.

Eco-Friendly Ether and Ester-Urethane Prepolymer: Structure, Processing and Properties.

This study concerns bio-based urethane prepolymers. The relationship between the chemical structure and the thermal and processing parameters of bio-based isocyanate-terminated ether and ester-urethane prepolymers was investigated. Bio-based prepolymers were obtained with the use of bio-monomers such as bio-based diisocyanate, bio-based polyether polyol or polyester polyols. In addition to their composition, the bio-based prepolymers were different in the content of iso-cyanate groups content (ca. 6 and 8%). The process of pre-polymerization and the obtained bio-based prepolymers were analyzed by determining the content of unreacted NCO groups, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, thermogravimetry, and rheological measurements. The research conducted facilitated the evaluation of the properties and processability of urethane prepolymers based on natural components. The results indicate that a significant impact on the processability has the origin the polyol ingredient as well as the NCO content. The thermal stability of all of the prepolymers is similar. A prepolymer based on a poly-ether polyol is characterized by a lower viscosity at a lower temperature than the prepolymer based on a polyester polyol. The viscosity value depends on the NCO content.

Biobased Polyurethane Composite Foams Reinforced with Plum Stones and Silanized Plum Stones.

In the following study, ground plum stones and silanized ground plum stones were used as natural fillers for novel polyurethane (PUR) composite foams. The impact of 1, 2, and 5 wt.% of fillers on the cellular structure, foaming parameters, and mechanical, thermomechanical, and thermal properties of produced foams were assessed. The results showed that the silanization process leads to acquiring fillers with a smoother surface compared to unmodified filler. The results also showed that the morphology of the obtained materials is affected by the type and content of filler. Moreover, the modified PUR foams showed improved properties. For example, compared with the reference foam (PUR_REF), the foam with the addition of 1 wt.% of unmodified plum filler showed better mechanical properties, such as higher compressive strength (~8% improvement) and better flexural strength (~6% improvement). The addition of silanized plum filler improved the thermal stability and hydrophobic character of PUR foams. This work shows the relationship between the mechanical, thermal, and application properties of the obtained PUR composites depending on the modification of the filler used during synthesis.

Vascular Polyurethane Prostheses Modified with a Bioactive Coating-Physicochemical, Mechanical and Biological Properties.

This study describes a method for the modification of polyurethane small-diameter (5 mm) vascular prostheses obtained with the phase inversion method. The modification process involves two steps: the introduction of a linker (acrylic acid) and a peptide (REDV and YIGSR). FTIR and XPS analysis confirmed the process of chemical modification. The obtained prostheses had a porosity of approx. 60%, Young's Modulus in the range of 9-11 MPa, and a water contact angle around 40°. Endothelial (EC) and smooth muscle (SMC) cell co-culture showed that the surfaces modified with peptides increase the adhesion of ECs. At the same time, SMCs adhesion was low both on unmodified and peptide-modified surfaces. Analysis of blood-materials interaction showed high hemocompatibility of obtained materials. The whole blood clotting time assay showed differences in the amount of free hemoglobin present in blood contacted with different materials. It can be concluded that the peptide coating increased the hemocompatibility of the surface by increasing ECs adhesion and, at the same time, decreasing platelet adhesion. When comparing both types of peptide coatings, more promising results were obtained for the surfaces coated with the YISGR than REDV-coated prostheses.

Chemical and Mechanical Characterization of Licorice Root and Palm Leaf Waste Incorporated into Poly(urethane-acrylate) (PUA).

A poly(urethane-acrylate) polymer (PUA) was synthesized, and a sufficiently high molecular weight starting from urethane-acrylate oligomer (UAO) was obtained. PUA was then loaded with two types of powdered ligno-cellulosic waste, namely from licorice root and palm leaf, in amounts of 1, 5 and 10%, and the obtained composites were chemically and mechanically characterized. FTIR analysis of final PUA synthesized used for the composite production confirmed the new bonds formed during the polymerization process. The degradation temperatures of the two types of waste used were in line with what observed in most common natural fibers with an onset at 270 °C for licorice waste, and at 290 °C for palm leaf one. The former was more abundant in cellulose (44% vs. 12% lignin), whilst the latter was richer in lignin (30% vs. 26% cellulose). In the composites, only a limited reduction of degradation temperature was observed for palm leaf waste addition and some dispersion issues are observed for licorice root, leading to fluctuating results. Tensile performance of the composites indicates some reduction with respect to the pure polymer in terms of tensile strength, though stabilizing between data with 5 and 10% filler. In contrast, Shore A hardness of both composites slightly increases with higher filler content, while in stiffness-driven applications licorice-based composites showed potential due to an increase up to 50% compared to neat PUA. In general terms, the fracture surfaces tend to become rougher with filler introduction, which indicates the need for optimizing interfacial adhesion.

Recent Advances in Polyurethane/POSS Hybrids for Biomedical Applications.

Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented.

Design, Synthesis, Antibacterial, and Antitumor Activity of Linear Polyisocyanide Quaternary Ammonium Salts with Different Structures and Chain Lengths.

The development of organic polymer materials for disinfection and sterilization is thought of as one of the most promising avenues to solve the growth and spread of harmful microorganisms. Here, a series of linear polyisocyanide quaternary ammonium salts (L-PQASs) with different structures and chain lengths were designed and synthesized by polymerization of phenyl isocyanide monomer containing a 4-chloro-1-butyl side chain followed by quaternary amination salinization. The resultant compounds were characterized by 1H NMR and FT-IR. The antibacterial activity of L-PQASs with different structures and chain lengths against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was evaluated by determining the minimum inhibitory concentrations (MICs). The L-POcQAS-M50 has the strongest antimicrobial activity with MICs of 27 µg/mL against E. coli and 32 µg/mL against S. aureus. When the L-PQASs had the same polymerization degree, the order of the antibacterial activity of the L-PQASs was L-POcQAS-Mn > L-PBuQAS-Mn > L-PBnQAS-Mn > L-PDBQAS-Mn (linear, polyisocyanide quaternary ammonium salt, monomer, n = 50,100). However, when L-PQASs had the same side chain, the antibacterial activity reduced with the increase of the molecular weight of the main chain. These results demonstrated that the antibacterial activity of L-PQASs was dependent on the structure of the main chain and the length of the side chain. In addition, we also found that the L-POcQAS-M50 had a significant killing effect on MK-28 gastric cancer cells.

Sustainable Process for the Depolymerization/Oxidation of Softwood and Hardwood Kraft Lignins Using Hydrogen Peroxide under Ambient Conditions.

The present study demonstrated a sustainable and cost-effective approach to depolymerize/oxidize softwood (SW) and hardwood (HW) kraft lignins using concentrated hydrogen peroxide at temperatures ranging from 25 to 35 °C, in the absence of catalysts or organic solvents. The degree of lignin depolymerization could be simply controlled by reaction time, and no further separation process was needed at the completion of the treatment. The obtained depolymerized lignin products were comprehensively characterized by GPC-UV, FTIR, 31P-NMR, TGA, Py-GC/MS and elemental analysis. The weight-average molecular weights (Mw) of the depolymerized lignins obtained from SW or HW lignin at a lignin/H2O2 mass ratio of 1:1 after treatment for 120 h at room temperature (≈25 °C) were approximately 1420 Da. The contents of carboxylic acid groups in the obtained depolymerized lignins were found to significantly increase compared with those of the untreated raw lignins. Moreover, the depolymerized lignin products had lower thermal decomposition temperatures than those of the raw lignins, as expected, owing to the greatly reduced Mw. These findings represent a novel solution to lignin depolymerization for the production of chemicals that can be utilized as a bio-substitute for petroleum-based polyols in polyurethane production.

Non-isocyanate urethane linkage formation using l-lysine residues as amine sources.

Bio-based polyurethane materials are broadly applied in medicine as drug delivery systems. Nevertheless, their synthesis comprises the use of petroleum-based toxic amines, isocyanates and polyols, and their biocompatibility or functionalization is limited. Therefore, the use of lysine residues as amine sources to create non-isocyanate urethane (NIU) linkages was investigated. Therefore, a five-membered biscyclic carbonate (BCC) was firstly synthetized and reacted with a protected lysine, a tripeptide and a heptapeptide to confirm the urethane linkage formation with lysine moiety and to optimize reaction conditions. Afterwards, the reactions between BCC and a model protein, elastin-like protein (ELP), and ß-Lactoglobulin (BLG) obtained from whey protein, respectively, were performed. The synthesized protein materials were structural, thermally and morphologically characterized to confirm the urethane linkage formation. The results demonstrate that using both simple and more complex source of amines (lysine), urethane linkages were effectively achieved. This pioneering approach opens the possibility of using proteins to develop non-isocyanate polyurethanes (NIPUs) with tailored properties.

Structure-Activity Study of Antibacterial Poly(ester urethane)s with Uniform Distribution of Hydrophobic and Cationic Groups.

Infections associated with antibiotic-resistant bacteria have become a threat to the global public health. Antimicrobial polymers, which are synthetic mimics of antimicrobial peptides, have gained increasing attention, as they may have a lower chance of inducing resistance. The cationic-hydrophobic balance and distribution of cationic and hydrophobic moieties of these polymers is known to have a major effect on antimicrobial activity. We studied the properties of a series of facially amphiphilic antimicrobial surfactant-like poly(ester urethane)s with different hydrophobic pendant groups (P1, P2, and P3) and cationic groups distributed uniformly along the polymer chain. These polymers exhibited bactericidal activity against Gram-negative Escherichia coli and Pseudomonas aeruginosa, as well as Gram-positive Staphylococcus aureus and Staphylococcus epidermidis. Microscopy and dye release assays demonstrated that these polymers cause membrane disruption, which is dependent on the cationic-hydrophobic ratio in the polymer. Membrane permeability assays revealed that these polymers can permeabilize the outer membrane of E. coli and damage the cytoplasmic membrane of both E. coli and S. aureus. In addition, our results indicate that the three polymers exhibit a different extent of membrane disruption against E. coli. P1 caused minor damage to the cytoplasmic membrane integrity, but it was able to dissipate the cytoplasmic membrane potential, leading to cell death. P2 and P3 depolarized the cytoplasmic membrane and also caused significant damage to the cytoplasmic membrane. Overall, we showed a new class of broad-spectrum bactericidal polymers whose membrane disrupting ability against E. coli correlates with the structural differences of the hydrophobic pendant groups.

Polyurethane Coatings Based on Renewable White Dextrins and Isocyanate Trimers.

The polyurethane industry is strongly dependent on fossil-based polyols and polyisocyanates. Developing novel sustainable polyols from valuable biobased building blocks is a first step toward strong and durable development. The synthesis and properties of PU films based on pristine and acylated white dextrins (AVEDEX W80) as polyol and an aliphatic, low-viscosity, solvent-free triisocyanate based on hexamethylene diisocyanate (trimer-Desmodur N3300) as crosslinker is reported. After optimizing several conditions, such as the reaction time, reaction temperature, amount of solvent, isocyanate index, and amount per surface area, it is possible to obtain smooth PU films with good thermal properties.

Synthesis and application of triclosan methacrylate monomer in resin composites.

OBJECTIVES: To evaluate the antibacterial activity, bacterial viability, cytotoxicity, and mechanical/physical properties of a novel methacrylate triclosan-derivative monomer (TM) incorporated in dental resin composite. METHODS: TM was synthesized by esterification and, after characterization by FT-IR, was added to an experimental composite. Samples were divided into two groups according to TM presence, i.e., C1 (control) and C2 (C1 + 14.4% TM). Microbiological properties: Specimens (C1 and C2) were prepared and placed on bacterial suspensions of Streptococcus mutans. Antibacterial activity, MTT, and live/dead bacterial viability were used to test the resin composites. All assays were performed in triplicates. Mechanical properties: Specimens underwent compression (CS) and flexural strength (FS) tests conducted in an Instron universal testing machine at a crosshead speed of 0.5 mm/min. Physical properties: Specimens were assessed for Knoop hardness (KHN) and crosslink density (CD). Fourier transform infrared spectroscopy allowed the degree of conversion (DC) to be evaluated. Data were subjected to appropriate statistical tests according to data distribution and assay (p < 0.05). RESULTS: Microbiological properties: C2 showed the lowest biofilm accumulation and the highest membrane-compromised bacteria in the biofilm. Mechanical/physical properties: For CS, FS, KHN, and DC, there was no significant difference between groups C1 and C2; however, significant difference was observed for the CD assay. CONCLUSIONS: The triclosan methacrylate reduces bacterial adhesion of S. mutans and decreased the formation of bacterial biofilm without affecting important polymer properties. The triclosan methacrylate incorporated in resin composite could greatly reduce the live bacterial adhesion of S. mutans and decrease the formation of bacterial biofilm without affecting important polymer properties. CLINICAL SIGNIFICANCE: The resin composites containing triclosan methacrylate could greatly reduce the bacterial adhesion and biofilm formation. That might prevent the secondary caries round the margins of the restorations.

Synthesis of a green polyurethane foam from a biopolyol obtained by enzymatic glycerolysis and its use for immobilization of lipase NS-40116.

The use of green sources for materials synthesis has gained popularity in recent years. This work investigated the immobilization of lipase NS-40116 (Thermomyces lanuginosus lipase) in polyurethane foam (PUF) using a biopolyol obtained through the enzymatic glycerolysis between castor oil and glycerol, catalyzed by the commercial lipase Novozym 435 for the PUF formation. The reaction was performed to obtain biopolyol resulting in the conversion of 64% in mono- and diacylglycerol, promoting the efficient use of the reaction product as biopolyol to obtain polyurethane foam. The enzymatic derivative with immobilized lipase NS-40116 presented apparent density of 0.19 ± 0.03 g/cm3 and an immobilization yield was 94 ± 4%. Free and immobilized lipase NS-40116 were characterized in different solvents (methanol, ethanol, and propanol), temperatures (20, 40, 60 and 80 °C), pH (3, 5, 7, 9 and 11) and presence of ions Na+, Mg++, and Ca++. The support provided higher stability to the enzyme, mainly when subjected to acid pH (free lipase lost 80% of relative activity after 360 h of contact, when the enzymatic derivative lost around 22%) and high-temperature free lipase lost 50% of relative activity, while the immobilized remained 95%. The enzymatic derivative was also used for esterification reactions and conversions around 66% in fatty acid methyl esters, using abdominal chicken fat as feedstock, were obtained in the first use, maintaining this high conversion until the fourth reuse, proving that the support obtained using environmentally friendly techniques is applicable.

Synthesis, Characterization, and Bacterial Fouling-Resistance Properties of Polyethylene Glycol-Grafted Polyurethane Elastomers.

Despite advances in material sciences and clinical procedures for surgical hygiene, medical device implantation still exposes patients to the risk of developing local or systemic infections. The development of efficacious antimicrobial/antifouling materials may help with addressing such an issue. In this framework, polyethylene glycol (PEG)-grafted segmented polyurethanes were synthesized, physico-chemically characterized, and evaluated with respect to their bacterial fouling-resistance properties. PEG grafting significantly altered the polymer bulk and surface properties. Specifically, the PEG-grafted polyurethanes possessed a more pronounced hard/soft phase segregated microstructure, which contributed to improving the mechanical resistance of the polymers. The better flexibility of the soft phase in the PEG-functionalized polyurethanes compared to the pristine polyurethane (PU) was presumably also responsible for the higher ability of the polymer to uptake water. Additionally, dynamic contact angle measurements evidenced phenomena of surface reorganization of the PEG-functionalized polyurethanes, presumably involving the exposition of the polar PEG chains towards water. As a consequence, Staphylococcus epidermidis initial adhesion onto the surface of the PEG-functionalized PU was essentially inhibited. That was not true for the pristine PU. Biofilm formation was also strongly reduced.

The Synthesis and Properties of Liquid Crystalline Polyurethanes, Chemically Modified by Polyhedral Oligomericsilsesquioxanes.

In this work, we report for the first time on the influence of polyhedral oligomericsilsesquioxanes (POSS) on the structure and properties of liquid crystalline polyurethane (LCPU). LCPU/POSS hybrids were synthesized via a two-step method. In the first step, 4,4'-methylenephenyl diisocyanate (MDI) and polytetramethylene ether glycol (PTMG) reacted with functionalized trisilanolphenyl POSS (TSP-POSS) bearing three hydroxyl groups. In the second step, the growing chain was extended with 4,4'-bis(hydroxyhexoxy)biphenyl (BHHBP). FTIR measurements confirmed the chemical bonding between the POSS and LCPU matrix and showed the influence of the silsesquioxane modification on the intensity of hydrogen bonds. The DSC and POM techniques confirmed the formation of liquid crystalline phases. The incorporation of silsesquixanes into the LC matrix leads to higher melting and isotropization temperatures along with the broadening phase transition effect. Scanning electron microscopy showed a good distribution of POSS moieties, both in the bulk and on the surface of the liquid crystalline PU matrix, whereby wide-angle X-ray diffraction (WAXD) patterns revealed halos from both the liquid crystalline and unmodified polyurethane matrix. The stress at the breaking points for LCPU/POSS hybrids containing 50% and 60% of elastic segments is greater than the stress at the breaking point of the reference material (LCPU), what is due to good dispersion of POSS in less elastic matrix. Thermal properties of the LCPU/POSS materials obtained, determined by TGA, revealed that the char residue increased with the amount of POSS for 40% of elastic segments materials.

In Situ Incorporation of Diamino Silane Group into Waterborne Polyurethane for Enhancing Surface Hydrophobicity of Coating.

A series of waterborne polyurethanes (WPU) with crosslinked siloxane were obtained through introducing 3-(2-aminoethylamino)propyldimethoxymethylsilane (APTS) into WPU by in situ polymerization. The properties of WPU modified by APTS were studied through a variety of experimental methods. The water contact angle of the WPU coating surface increased from 64° to 86°, and the water resistance reduced to 3.90% when 3 wt% APTS was added, which improved the coating surface hydrophobicity. Firstly, Fourier transform infrared (FT-IR) and 1H-NMR spectra demonstrated the successful incorporation of APTS to polyurethanes and completed the hydrolytic condensation reaction-generated Si-O-Si crosslinking structure. Furthermore, the surface energy of the membrane was reduced when the crosslinking structure migrated and enriched on the surface of film. Besides, the crosslinking structure was abundant, and the distribution of siloxane in WPU was more uniform.

Synthesis and Characterization of Healable Waterborne Polyurethanes with Cystamine Chain Extenders.

In this study, environmentally friendly, self-healing waterborne polyurethanes (WPUs) were prepared based on the disulfide metathesis reaction in cystamine. The cystamine acted as a chain extender in the WPU film, which showed a high mechanical strength of 19.1 MPa. The possibility of self-healing reaction was simultaneously modeled via liquid chromatography-mass spectrometry (LC-MS). WPU was confirmed to self-heal a surface crack thermally after a scratch test, and the efficiency was measured by comparing the mechanical properties before and after a cut-and-healing test. In addition, the disulfide-thiol exchange reaction was confirmed to occur in WPU with cystamine as a chain extender and 2-mercaptoethanol. Hot press tests confirmed the possibility of reprocessing the WPU. The WPU incorporating disulfide groups showed great potential as a smart self-healing material.