Synthesis and characterization of novel laccol based polyurethanes

Development of polyurethanes (PU) has come a long way from their origin in 1937 and has unique applications in a diverse set of fields. Recent PU developments are focusing more on the naturally-derived diols in the synthesis process in an effort to make them more environmentally friendly. In this study, three different diisocyanates (aliphatic, cycloaliphatic, and aromatic diisocyanates) were combined with laccol, which extracted from Vietnamese lacquer sap (Toxicodendron succedanea) to synthesize novel PUs. Influence of the different diisocyanates in novel PUs, hydrogen bonding capability, and crosslinking ability were investigated to provide a broader characteristic scope for future developments. Resulting materials illustrated good thermal stability after exposed to higher temperatures and the hydrogen bonding regions corresponding to N H (3326 cm⁻¹) and CO (1652 cm⁻¹) groups were shifted to higher wavenumber according to Fourier transform infra-red spectroscopy analysis. Further curing occurred with temperature treatment and improved the overall quality of novel PUs. Powder X-ray analysis, micro hardness, and swelling analysis were utilized to identify molecular packing and crosslinking effects. Higher crosslink density observed for cycloaliphatic and aromatic diisocyanate incorporated novel polyurethanes compared to aliphatic diisocyanate incorporated polyurethane.     

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure–property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.     

Properties of copolymer-type polyacetal/polyurethane blends

Mechanical and physical properties of the blends of copolymer-type polyacetals (POM) with polyurethane (PU) were investigated. The properties relationships of POM/PU blends are established by studying their morphology and compatibility. For the blends rich in POM, the morphology of the blends observed with a scanning electron microscopy (SEM) indicates that the blends containing lower than 50 wt % (46 vol %) PU are almost completely filled with spherical particles of the dispersed PU. As the concentration of PU increases, the spherulites of the POM observed by SEM become less perfect with coarse fine structure. Furthermore, when the concentration of PU was increased up to 50 wt %, the spherulties of POM in the blends are smaller than those of unblended POM. X-ray diffraction studies reveal that the degree of crystallinity of POM decreases with increasing PU content, which is nonmonotonic. This conclusion agrees with the observations made by differential scanning calorimetry (DSC) and density measurements. For the blends rich in POM, mechanical properties show that the impact strength of POM/PU blends increased with decreasing spherical size of the dispersed PU.     

One‐step formation of polyurea gel as a multifunctional approach for biological and environmental applications

This work presents a facile one‐pot fabrication of polyurea (PU) organogels based on polyetheramine (PEO, Jeffamine ED‐2003) and a crosslinker hexamethylene diisocyanate trimer (HDI) which were subsequently used as a drug carrier to incorporate a curcumin hydrophobic molecule in aqueous conditions and for removal of an anionic pollutant in water. PU can be obtained in different shapes with easy control of film thickness with high transparency, flexibility and homogeneous dispersion of curcumin in the matrix. Due to the hydrophilic nature of PEO a high swelling degree was demonstrated by the PU gel. The phase separated domains and the temperature's influence on the system's structural order/disorder were examined by small‐angle X‐ray scattering, showing a more PU ordered system (interface between hard and soft segments) after decreasing the temperature to ?90 °C. The presence of curcumin in the structure of PU was confirmed by Fourier transform infrared, photoluminescence and release studies. A highly efficient removal of Congo red dye from aqueous solution using PU as adsorbent was observed. Moreover, the effect of unloaded and curcumin‐loaded PU gels was evaluated on Schistosoma mansoni adult worms. Detailed in vitro cell viability experiments showed the biocompatibility of loaded and unloaded PU gels. The easy processability of the multifunctional PU shows that it has promising applications as transdermal and soft tissue implantable delivery devices for a large number of poorly water‐soluble drugs and as an efficient adsorbent for removal of organic dyes; it can also be used in the future in dermatological treatments against malignant melanoma. © 2020 Society of Chemical Industry     

Blends of polyurethane-polymethyl methacrylate/TiO2-based composites

Polyurethanes (PUs) prepolymer was prepared by the reaction of toluene-2,4-diisocyanate (TDI) and poly caprolactone diols and the chain was further extended with 1,4-butane diol (1,4-BDO) to get final polyurethane (PU). FTIR spectra of the monomers, PU prepolymer, chain extender and final PU confirmed the reaction progress. A series of blends were prepared by varying the percent compositions of prepared PU, procured polymethyl methacylates (PMMA) and titanium dioxide (TiO₂). Pellets were formed from the prepared blends (PU-PMMA/TiO₂) using a self-designed mechanical tool. Scanning electron microscope (SEM) images were also taken to confirm the incorporation of the TiO₂ contents into the prepared blends. Mechanical properties such as hardness and compressive strength were studied and discussed. The results of the study reveal that the blended sample having 80% PU, 20% PMMA content with 2.5 g TiO₂ in 100 g mixture of PU and PMMA is very suitable for suggesting dental materials.     

Synthesis of biodegradable polyurethanes chain‐extended with (2S)‐bis(2‐hydroxypropyl) 2‐aminopentane dioate

Polyurethanes (PUs) are the most widely used polymers because of their biocompatibility, tunable mechanical properties, and chemical versatility. In this study, a two‐step condensation polymerization of polycaprolactone diol and hexamethylene diisocyanate was carried out, and a glutamic acid ester derivative, (2S)‐bis(2‐hydroxypropyl) 2‐aminopentane dioate (HPAP), was used as a new chain extender to accelerate the biodegradation properties of PU. HPAP was synthesized by the Fischer esterification of l ‐glutamic acid. The chemical structure of HPAP was confirmed by high‐resolution mass spectroscopy and m/z (EI) was found to be 264.1447 [calculated value = 264.1443 for C₁₁H₂₁NO₆ (M⁺)]. The Berry plot of static light‐scattering measurements showed that PU–HPAP had a weight‐average molecular weight and radius of gyration of 33,100 g/mol and 1420 nm, respectively. The presence of HPAP in the PU structure facilitated hydrogen bonding between the polymer chains and increased the glass‐transition temperature from ?56 °C (PU) to ?50 °C (PU–HPAP). PU–HPAP showed the highest hydrophilicity and surface free energy among all of samples, and this accelerated the in vitro biodegradation period via surface erosion. In addition, PU–HPAP did not show any cytotoxic effects on the L929 cells. A new biodegradable and biocompatible PU–HPAP was obtained as candidate for tissue engineering applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45764.     

高性能CHDI型聚醚聚氨酯弹性体

综述了基于聚四亚甲基醚二醇、反式环己烷－1,4－二异氰酸酯（CHDI）和1,4－丁二醇的聚氨酯弹性体的合成工艺和机械性能,介绍了CHDI和其它二异氰酸酯的反应活性差异,并将CHDI型聚氨酯弹性体与二苯基甲烷二异氰酸酯（MDI）、对苯二异氰酸酯（PPDI）、亚甲基二环己基－4,4'－二异氰酸酯（HMDI）制成的聚氨酯弹性体的主要物性进行了对比。CHDI型聚氨酯弹性体在较低的硬段含量下就具有较高的硬度,比MDI型、HMDI型,甚至比PPDI型弹性体具有更好的高温力学性能。     

Fabrication and characterisation of nanofibrous polyurethane scaffold incorporated with corn and neem oil using single stage electrospinning technique for bone tissue engineering applications

In bone tissue engineering, the design of scaffolds with ECM is still challenging now-a-days. The objective of the study to develop an electrospun scaffold based on polyurethane (PU) blended with corn oil and neem oil. The electrospun nanocomposites were characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), contact angle measurement, atomic force microscopy (AFM) and tensile strength. The assays activated prothrombin time (APTT), partial thromboplastin time (PT) and hemolysis assay were performed to determine the blood compatibility parameters of the electrospun PU and their blends of corn oil and neem oil. Further, the cytocompatibility studies were performed using HDF cells to evaluate their proliferation rates in the electrospun PU and their blends. The morphology of the electrospun PU blends showed that the addition of corn oil and corn/neem oil resulted in reduced fiber diameter of about 845?±?117.86?nm and 735?±?126.49 nm compared to control (890?±?116.911?nm). The FTIR confirmed the presence of corn oil and neem oil in PU matrix through hydrogen bond formation. The PU blended with corn oil showed hydrophobic (112°?±?1) while the PU together with corn/neem oil was observed to hydrophilic (64°?±?1.732) as indicated in the measurements of contact angle. The thermal behavior of prepared PU/corn oil and PU/corn/neem oil nanocomposites were enhanced and their surface roughness were decreased compared to control as revealed in the AFM analysis. The mechanical analysis indicated the enhanced tensile strength of the developed nanocomposites (PU/corn oil - 11.88 MPa and PU/corn/neem oil - 12. 96 MPa) than the pristine PU (7.12 MPa). Further, the blood compatibility assessments revealed that the developed nanocomposites possess enhanced anticoagulant nature compared to the polyurethane. Moreover, the developed nanocomposites was non-toxic to red blood cells (RBC) and human fibroblast cells (HDF) cells as shown in the hemolytic assay and cytocompatibility studies. Finally, this study concluded that the newly developed nanocomposites with better physio-chemical characteristics and biological properties enabled them as potential candidate for bone tissue engineering.     

Effect of oleic acid content and chemical crosslinking on the properties of palm oil‐based polyurethane coatings

Polyurethanes (PU) were prepared by reacting palm oil‐based polyols and aromatic diisocyanate (toluene 2, 4 diisocyanates). The content of oleic acid was varied in the polyester polyols and the hydroxyl value was fixed to be 140 mg KOH g^?1. The NCO/OH ratios were varied to 1.2, 1.4, and 1.6. Crosslinking density of the PU was measured by swelling in toluene at room temperature. It was found that the crosslinking increased with decreasing oleic acid content and increasing NCO/OH ratio. The samples were assessed by thermogravimetric analysis, differential scanning calorimetric, and short‐term creep measurements. The highest rupture strength of the PU films was 36 MPa and thermostability improved as the oleic acid content and the NCO/OH ratios were increased in the sample. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biobased chain extended polyurethane and its composites with silk fiber

The biobased chain extended polyurethane (PU) was synthesized by reacting castor oil based polyol with different diisocyanates [toluene‐2,4‐diisocyanate (TDI) and hexamethylene diisocyanate (HMDI)] and chain extender such as glutaric acid. Biocomposites have been fabricated by incorporating the silk fiber into both TDI‐ and HMDI‐based PUs. The effect of incorporation of silk fiber into TDI‐ and HMDI‐based neat PU on the physicomechanical properties such as density, surface hardness, tensile strength, and percentage elongation have been investigated. The dynamic mechanical properties and the thermal stability of neat PUs and the silk fiber incorporated PU composites have been evaluated. The TDI‐based neat PU has showed higher mechanical properties compared to HMDI‐based PU. The incorporation of 10% silk fiber into TDI‐ and HMDI‐based PU resulted in an enhancement of tensile strength by 1.8 and 2.2 folds, respectively. The incorporation of silk fiber into biobased chain extended PU increased the glass transition temperature (T_g) of the resultant biocomposites. The morphology of tensile fractured neat PUs and their biocomposites with silk fiber was studied using scanning electron microscope (SEM). POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Biocompatibility and microscopic evaluation of polyurethane–poly(methyl methacrylate)–titnanium dioxide based composites for dental applications

We prepared and then blended polyurethanes (PUs) with poly(methyl methacrylate)s (PMMAs) and TiO₂ by varying the percentage compositions to form pellets. The chemistry of all of the blended samples was confirmed by Fourier transform infrared spectroscopy. The incorporation of TiO₂ into the PU–PMMA matrix was confirmed with scanning electron microscopy analysis. Differential scanning calorimetry analysis and compression testing was performed, and the results are discussed. The cytotoxicity level of the prepared blends displayed dependence on the composition ratio of the PU–PMMA blends. The results reveal that the optimum PU contents in the PU–PMMA–TiO₂ blend were responsible for its better biocompatibility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39806.     

Morphology of polyurethane modified by plasticizing,blending, or reinforcing

The morphology of modified thermoplastic PU has been studied by SEM and DSC. The PU was modified by addition of various amounts of dibutyl phthalate (DBP) plasticizer, vinyl polymers (PVA, PVAc, PVC, VAc–VC copolymer), polysiloxane or fiber reinforcement (glass or cotton) to diolpolyether, followed by mixing and vigorous stirring with dephenylmethane diisocyanate. SEM observations indicated that PU and its modifications have a cellular (foam) structure. A homogeneous matrix was observed in binary blends of PU and DBP in ratios of 20:1 down to 6.6:1; PVA, PVAc, VAc–VC copolymer with a weight ratio of 40:1, PU containing glass fiber (20:1) or cotton fiber (40:1). Blends of PU—with PVA at a weight ratio of 20:1, with PVC in ratios from 20:1 down to 5:1, or with polysiloxane polymer—were heterogeneous and thus not miscible, as evidenced by SEM observations. With the exception of the PU—PSO mixtures, the thermal behavior of the heterogeneous blends did not permit any conclusion regarding miscibility.     

Curcumin loaded chitin nanogels for skin cancer treatment via the transdermal route

In this study, curcumin loaded chitin nanogels (CCNGs) were developed using biocompatible and biodegradable chitin with an anticancer curcumin drug. Chitin, as well as curcumin, is insoluble in water. However, the developed CCNGs form a very good and stable dispersion in water. The CCNGs were analyzed by DLS, SEM and FTIR and showed spherical particles in a size range of 70-80 nm. The CCNGs showed higher release at acidic pH compared to neutral pH. The cytotoxicity of the nanogels were analyzed on human dermal fibroblast cells (HDF) and A375 (human melanoma) cell lines and the results show that CCNGs have specific toxicity on melanoma in a concentration range of 0.1-1.0 mg mL(-1), but less toxicity towards HDF cells. The confocal analysis confirmed the uptake of CCNGs by A375. The apoptotic effect of CCNGs was analyzed by a flow-cytometric assay and the results indicate that CCNGs at the higher concentration of the cytotoxic range showed comparable apoptosis as the control curcumin, in which there was negligible apoptosis induced by the control chitin nanogels. The CCNGs showed a 4-fold increase in steady state transdermal flux of curcumin as compared to that of control curcumin solution. The histopathology studies of the porcine skin samples treated with the prepared materials showed loosening of the horny layer of the epidermis, facilitating penetration with no observed signs of inflammation. These results suggest that the formulated CCNGs offer specific advantage for the treatment of melanoma, the most common and serious type of skin cancer, by effective transdermal penetration.     

Thermal stability of poly(vinyl chloride)/polyurethane blends

The thermal stability of poly(vinyl chloride) (PVC) and thermoplastic polyurethane (PU) blends has been studied in this work. It has been found that the PVC/PU blends possess lower thermal stability than unmodified PVC. No effect of the structure of polyurethanes or their content on the stability of PVC/PU system has been found.     

HTPB/液化MDI型PU与PMMA的共混研究

用同步聚合法制备了一系列HTPB／液化MDI型PU与PMMA的共混材料，分别用FTIR、DSC、SEM和拉力实验机对共混材料的反应进度、玻璃化转变温度、力学性能和微观形态进行了考查和研究；结果表明，体系中PMMA优先于PU聚合，共混材料的玻璃化转变温度Tg2随PMMA质量分数的增加略呈上升趋势；材料的拉伸强度和硬度均随体系中PMMA质量分数的增加而增大，断裂伸长率则逐渐减小；体系微观呈两相分离，当PMMA占50％时，相畴最小。     

Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings

Novel two pack polyurethane wood finished coatings are prepared from renewable sources, such as vegetable oil based fatty acid and dimer fatty acid. In actual experimental part oleic acid was reacted with diethanolamine to obtain amide which was on condensation polymerization with dimer fatty acid converted into the polyesteramide polyol. These are all being used to prepare polyurethanes. The functional and structural elucidation of dimer fatty acid based polyesteramide and diethanolamide were carried out by end group analysis, spectral studies such as FTIR and ¹H NMR. Average molar masses of the polyesteramide were estimated by gel permeation chromatography (GPC). The polyesteramide was used in the preparation of wood finished polyurethane coatings by reacting it with aromatic diisocyanates. Thermogravimetric analysis (TGA) was used to study the thermal behavior of coatings. Physico-chemical and coating properties of the coatings were investigated by using standard methods. The results indicated that the bio-based wood finished PU coatings provided good mechanical, weather resistance as well possessed adequate coating properties for wood surface protections.     

Synthesis and characterization of novel polyurethanes based on 4,4’-{1,4-phenylenebis[methylylidenenitrilo]}diphenol

A series of novel segmented polyurethanes (PUs) containing imine units in the main chain were prepared by polyaddition reaction of various diisocyanates like 4,4’-diphenyl-methane diisocyanate, tolylene 2,4-diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate with 4,4’-{1,4-phenylenebis[methylylidenenitrilo]} diphenol based diol. The structure of the diol and segmented PUs were determined by Fourier transform infrared, ultraviolet-visible spectrometry and fluoroscence spectroscopy. PUs were soluble is polar aprotic solvents. Thermal properties were done by using differential scanning calorimetry (DSC) and thermogravimetric analysis. DSC data display the PUs having multiple endotherm peaks. MDI based PU show the more thermal stable compared to other PUs.     

Preparation and properties of starch thermoplastics modified with waterborne polyurethane from renewable resources

A waterborne polyurethane (PU) aqueous dispersion was synthesized from castor oil, and blended with thermoplastic starch (TPS) to obtain a novel biodegradable plastic with improved physical properties. The effect of PU content on the morphology, miscibility and physical properties of the resulting blends was well investigated by scanning electron microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis and measurements of mechanical properties and water sensitivity. The research results show that the blends exhibit a higher miscibility when PU content is lower than 15 wt% due to the hydrogen bonding interaction between urethane groups and hydroxyl groups on starch, whereas obviously phase separation occurs in the blends with more than 15 wt% PU. Incorporating PU of 4-20 wt% in TPS results in the blends with improved Young's modulus (40-75 MPa), tensile strength (3.4-5.1 MPa), elongation at break (116-176%). Further, PU also plays an important role in improving the surface- and bulk-hydrophobicity and water resistance of the resulting blends.     

Novel biocompatible waterborne polyurethane using L‐lysine as an extender

Polyurethane (PU) prepolymers based on isophorone diisocyanates, dimethylolpropionic acid, and polycaprolactone were prepared and chain‐ extended in water using L ‐lysine (PU–L), ethylenediamine (PU–E), and their mixture (PU– L–E) as extenders, respectively. The produced emulsion exhibited satisfactory freeze/thaw stability. Films cast from emulsions exhibited excellent mechanical properties and good antiblood coagulation character. Although the water‐swelling ratio for 24 h for PU–L was higher than those of PU–L–E and PU–E, it possessed the smallest hydrolysis rate among the three samples. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2474–2480, 2002     

Synthesis,characterization and dielectric properties of nickel-based polyoxometalate/polyurethane composites

The aim of this study was to synthesis, characterization and investigation of the influence of the polyoxometalate concentrations (1, 3, 5 and 10 wt%) on chemical, thermal, physical and morphological properties of nickel-based polyoxometalate/polyurethane composite (Ni-POM/PU) materials. Firstly, nickel-based polyoxometalate (Ni-POM) compound has been synthesized and characterized through various spectroscopic techniques. Synthesized Ni-POM compounds have been used for preparation of polyurethane composites as a reinforcement. Three different Ni-POM/PU composites containing Ni-POM were prepared by solution mixing and casting techniques. The chemical structure and morphology of prepared Ni-POM/PU composite samples were confirmed by Fourier transform infrared spectroscopy (FTIR), elemental analysis and SEM techniques. Effects of Ni-POM on thermal stability, glass transition temperature, optical transparency, hydrophilicity and physical properties of polyurethane composites were examined. Thermal stabilities and glass temperatures of the materials have been checked by differential thermal analysis (DTA), thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC). The SEM results confirmed the highly porous structure and the formation of Ni-POM structures in the polymer matrix. Synthesized composites showed high chemical stability, good processability, and low Tg values. The dielectric properties of the prepared Ni-POM/polyurethane composites were also investigated at room temperature. These results displayed that the dielectric constant of the POM/polyurethane composites decreased with the increase of the Ni-POM content in polymeric matrix.