Urea Elastomers Research Articles

Biocompatible waterborne polyurethane-urea elastomer as intelligent anticancer drug release matrix: A sustained drug release study

Waterborne biodegradable polyurethane–urea (WPUU) elastomer is a revolutionary step in the field of green polymer chemistry. In the present study, emulsifier–free biodegradable WPUU elastomer was synthesized by using lysine as an internal emulsifier as well as a chain extender. WPUU elastomer was used as the stimuli–responsive drug release matrix, loaded by cisplatin as a model anticancer drug. Sustained drug release was studied by changing pH (4.4–7.4), drug release medium, and NCO/OH ratio (3–4). Furthermore, significantly inhibitory effect against Sw–620 cancer lines was observed. Highest cumulative drug release of 71.9% was observed at pH of 7.4 in phosphate buffer saline (PBS) by the system having NCO/OH=3 for 250h. The oxidative degradation was evaluated in CoCl2/H2O2 solution. Mechanical properties were tested by using the mechanical testing machine. The synthesized WPUU films exhibited high thermal stability, hardness, tensile strength and hydrophobicity.

Thermomechanical and dielectric properties of novel pyridine-based polyurethane urea elastomers

In this article, novel pyridine-based polyurethane urea elastomers were synthesized from 1,6-hexamethylene diisocyanate and poly(tetramethylene oxide) glycol of molecular weight 1400 which was chain extended with 3,4-diaminopyridine. These new heterocyclic polyurethane urea elastomers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and static mechanical measurements as a function of pyridine moieties content and the crosslinkers structure from the hard domains. This settlement of the amine groups on the pyridine rings realizes weak intermolecular hydrogen bonds compared with other pyridine derivatives studied by us. The molecular dynamics and local relaxation of these polyurethane urea elastomers were investigated using broadband dielectric spectroscopy. Results show that pyridine content slightly increases the glass transition temperature and has low dielectric strength of the segmental relaxation as a result of weaker cohesive domains.

Sustained drug delivery of doxorubicin as a function of pH, releasing media, and NCO contents in polyurethane urea elastomers

A novel diamine 4-(4-aminophenoxy)butyl-4-aminophenyl ether (ABAE) was synthesized as a chain extender (CE) by a quick and facile method using microwave reactor. CE was used for the preparation of stimuli-responsive Polyurethane-urea elastomer (PUU) with the ratio of NCO/OH from 2 to 2.5. Synthesized PUU was characterized with the help of Fourier transform infrared spectroscopy (FTIR), derivative thermogravimetric analysis (DTG), and scanning electron microscopy SEM. PUU films were loaded with an anti-cancer drug “doxorubicin”. Drug release kinetics were studied in different solvents, at different pH values and with different NCO contents of PUU. The maximum of 45% cumulative drug release was observed in DMSO while the drug release increased with the decrease in pH and a maximum cumulative release of 47% was observed at acidic pH of 4.4. The minimum drug was released from the one, which was crosslinked with highest ratio (2.5) of NCO/OH. So, we can say that drug release can easily be adjusted under different conditions and environments with the help of these stimuli-responsive media.

Tunable softening and toughening of individualized cellulose nanofibers-polyurethane urea elastomer composites

A series of elastomeric nanocomposites with superior tensile strength and extensibility, simultaneously exhibiting softening, was prepared using in situ polymerization by homogeneously dispersing TEMPO-oxidized cellulose individualized nanofibers (TOCNs) in a polyurethane urea (PUU) matrix. The structure of these PUU composites covalently cross-linked with the TOCNs was characterized. It was interesting to find that the amount and size of the hard domains in the composites gradually decreased by introducing crosslinkable TOCNs. With only 2wt% of TOCNs incorporated, a 10.4-fold increase in tensile strength, 5.5-fold increase in strain-to-failure, and a decrease of 35% in the coefficient of thermal expansion were achieved, compared with those of neat PUU. However, the elastic modulus of the nanocomposites gradually decreased with up to 1wt% of TOCNs. Conversely, with 2wt% of TOCNs, the stiffness of the elastomers again increased, due to filler-filler interaction over the CNFs percolation in the nanocomposites.

Biodegradable poly(ester urethane)urea elastomers with variable amino content for subsequent functionalization with phosphorylcholine

While surface modification is well suited for imparting biomaterials with specific functionality for favorable cell interactions, the modification of degradable polymers would be expected to provide only temporary benefit. Bulk modification by incorporating pendant reactive groups for subsequent functionalization of biodegradable polymers would provide a more enduring approach. Towards this end, a series of biodegradable poly(ester urethane)urea elastomers with variable amino content (PEUU–NH2 polymers) were developed. Carboxylated phosphorycholine was synthesized and conjugated to the PEUU–NH2 polymers for subsequent bulk functionalization to generate PEUU–PC polymers. Synthesis was verified by proton nuclear magnetic resonance, X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. The impact of amine incorporation and phosphorylcholine conjugation was shown on mechanical, thermal and degradation properties. Water absorption increased with increasing amine content, and further with PC conjugation. In wet conditions, tensile strength and initial modulus generally decreased with increasing hydrophilicity, but remained in the range of 5–30MPa and 10–20MPa, respectively. PC conjugation was associated with significantly reduced platelet adhesion in blood contact testing and the inhibition of rat vascular smooth muscle cell proliferation. These biodegradable PEUU–PC elastomers offer attractive properties for applications as non-thrombogenic, biodegradable coatings and for blood-contacting scaffold applications. Further, the PEUU–NH2 base polymers offer the potential to have multiple types of biofunctional groups conjugated onto the backbone to address a variety of design objectives.

Ultrasonic properties of composites of polymers and inorganic nanoparticles

The temperature dependencies of ultrasonic velocity and attenuation were measured in composites of inorganic nanoparticles with two types of polymers, poly(urea) elastomer with inorganic Mo6S4I6 nanowires and poly(ϵ-caprolactone) (PCL) with Mo6S3I6 nanowires. Below room temperature large ultrasonic relaxation attenuation maxima and velocity dispersion were observed. It was found that the attenuation peak in the elastomer shifted to higher temperature after doping with nanoparticles and this behavior was related to the shift of glass transition temperature. The ultrasonic attenuation data was fitted to a relaxation equation with a single temperature dependent relaxation time. The thermal activation energy of the relaxation process, which was calculated from ultrasonic data, was found to increase in the poly(urea) elastomer doped with MoSI nanowires. The low temperature ultrasonic velocity increased in the poly(urea) with nanowires added and is determined by the increase in elastic modulus. Similar ultrasonic behavior was obtained for PCL composites with inorganic MoSI nanowires. In this case, the increase in elastic modulus was smaller in comparison to the composites of poly(urea) and nanowires. Therefore, reinforcement of PCL was less pronounced.

Synthesis and characterization of novel linear and cross-linked polyurethane urea elastomers with 2,3-diaminopyridine in the main chain

Novel polyurethane urea containing pyridine moieties in their main chains have been prepared by a two-step solution polymerization procedure. These polyurethane urea elastomers were synthesized by chain-extending isocyanate end-capped prepolymers with 2,3-diaminoyridine and different cross-linkers. The isocyanate-terminated prepolymers were obtained from poly(tetramethylene oxide) glycol of molecular weight 1400 (Terathane 1400) and 1,6-hexamethylene diisocyanate. Including pyridine derivatives into the structural compositions leads to a change in properties that were investigated using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), mechanical measurements and contact angle and fluorescence analysis. The results show that intermolecular hydrogen bonds have formed between pyridine groups and urethane or urea groups, affecting all the obtained properties.

The influence of the chemical structure on the dielectric behavior of triazine derivative-based polyurethane–urea elastomers

Three series of linear and crosslinked polyurethane urea with heterocyclic triazine moieties in the main chain were synthesized and the films were prepared by casting and thermal curing. The molecular dynamics of the polyurethane urea have been studied by dielectric spectroscopy in the wide frequency range of 100–106 Hz and in the temperature range of −100 to 100 °C, by variation of the hard segments structure. Relaxation processes were observed in the dielectric spectra in proximity of the glass transition temperatures. All of the investigated samples showed two local relaxations (γ and β) and a primary relaxation (α), depending on the temperature and frequency range. For crosslinked samples, the α relaxation temperature increases with increasing the amount of crosslinkers. The dangling chains of castor oil (used as crosslinker) lead to the formation of imperfections in the network structure, affecting the relaxation process. It was found that inserting triazine derivatives in the hard segments modified dielectric behavior in comparison with linear chain extenders.

Preparation and Characterization of Structurally Graded Poly(urethane urea) Elastomers

Poly(urethane urea) elastomers with graded structure in the thickness direction were prepared using gradient temperature molding. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize the gradual change of structures within the elastomers. The degree of microphase separation in prepared samples would increase gradually with the increase of the curing temperature. Moreover, the interfaces between hard and soft segments also exhibit gradual changing trend, becoming more significant along the same direction. Effect of chain extender content and magnitude of temperature gradient on structure gradient was investigated. Mechanical properties of graded poly(urethane urea) elastomers were also studied.

Synthesis and trans-ureation of N,N’-diphenyl-4,4′-methylenediphenylene biscarbamate with diamines: a non-isocyanate route (NIR) to polyureas

A non-isocyanate route (NIR) of making polyureas of high molecular weight has been found through trans-ureation of N,N’-diphenyl-4,4′-methylenediphenylene biscarbamate (4,4′-DP-MDC) with a variety of diamines and mixed diamines. The preparation of 4,4′-DP-MDC was achieved readily by carbonylation of 4,4′-methylenedianiline (4,4′-MDA) with diphenyl carbonate (DPC) using organic acids as catalysts. It was found that the highest yield (99%) of pure 4,4′-DP-MDC can be isolated in a toluene solution under mild conditions co-catalyzed by benzoic acid and tertiary amine. Trans-ureation of 4,4′-DP-MDC with aliphatic amines indicated that the process is a highly solvent dependent process and was found to be extremely facile in dimethyl sulfoxide (DMSO) at 80 °C and in tetramethylene sulfone (TMS) at 140 °C in absence of any catalyst. Particularly, the most effective polymerization process was developed using tetramethylene sulfone (TMS) as the solvent under reduced pressure for concurrently distilling off phenol from the reaction mixture during the polymerization in a shifting equilibrium towards polyurea. However, this solvent-assisted trans-ureation was found to be in-efficient when N,N’-dimethyl-4,4′-methylenediphenylene biscarbamate (4,4′-DM-MDC) was used in a similar condition for comparison. Thus, an efficient green-chemistry process has been developed based on 4,4′-DP-MDC in making urea prepolymers, urea elastomers and urea plastics all in excellent yields without using reactive methylenediphenylene diisocyanate (MDI) or any catalysts in the trans-ureation polymerizations.

Biocompatibility of Polyurethane Urea Elastomers for Cardiac Tissue Engineering

ABSTRACTCardiac disease is the main cause of death in men and women in México and the U.S.A. When heart muscle suffers an injury, i.e. cardiac infarction, the tissue dies and is replaced by a fibrotic scar that does not allow for normal organ function. To alleviate scar tissue, the objective of this work was to investigate and synthesize polyurethane ureas from polycaprolactone diol, methylene bis(4-cyclohexilisocyanate), and butanediamine with different hard segment contents, characterize them, and prove their biocompatibility by seeding SCA-1+/CD45-cardiac progenitor cells obtained from mice cardiospheres. Ultimately, this work aims to explore how polyurethane urea elastomers can aid in therapeutic cardiac tissue regeneration.

Synthesis and characterization of linear and crosslinked poly(urethane urea) elastomers with triazine moieties in the main chain

A series of new poly(urethane urea) is synthesized via a two-step poly-addition process from polyether, 1,6-hexamethylene diisocyanate, 2,4-diamino-6-phenyl-1,3,5-triazine and different crosslinkers: glycerin or castor oil. The hard to soft segment ratio (OHpolyol/NCO/NH2chain extender) was varied systematically from 1/2/1 to 1/4/3. Poly(tetramethylene glycol) of molecular weight 1,400 was used as the soft segment. The structural behavioral characterization of these polymers was performed through FTIR spectroscopy, thermogravimetric analysis, dynamic mechanical and thermal analysis, stress–strain measurements, and water contact angle measurements. The resulting linear polyurethane urea elastomers exhibit good mechanical properties with breaking strains of 300–890% and tensile strengths of 8–13.5 MPa. Thermogravimetric analysis indicated that the thermal degradation of poly(urethane urea) started at about 280–300 °C, higher than the degradation temperature of conventional polyurethane. The improvement of properties was influenced by the hard segment content and the nature of the crosslinker, but most of all by the structure and amount of the urea introduced through 2,4-diamino-6-phenyl-1,3,5-triazine into the polymer backbone chain.

Biodegradable Polyurethane Ureas with Variable Polyester or Polycarbonate Soft Segments: Effects of Crystallinity, Molecular Weight, and Composition on Mechanical Properties

Biodegradable polyurethane urea (PUU) elastomers are ideal candidates for fabricating tissue engineering scaffolds with mechanical properties akin to strong and resilient soft tissues. PUU with a crystalline poly(ε-caprolactone) (PCL) macrodiol soft segment (SS) showed good elasticity and resilience at small strains (<50%) but showed poor resilience under large strains because of stress-induced crystallization of the PCL segments, with a permanent set of 677 ± 30% after tensile failure. To obtain softer and more resilient PUUs, we used noncrystalline poly(trimethylene carbonate) (PTMC) or poly(δ-valerolactone-co-ε-caprolactone) (PVLCL) macrodiols of different molecular weights as SSs that were reacted with 1,4-diisocyanatobutane and chain extended with 1,4-diaminobutane. Mechanical properties of the PUUs were characterized by tensile testing with static or cyclic loading and dynamic mechanical analysis. All of the PUUs synthesized showed large elongations at break (800-1400%) and high tensile strength (30-60 MPa). PUUs with noncrystalline SSs all showed improved elasticity and resilience relative to the crystalline PCL-based PUU, especially for the PUUs with high molecular weight SSs (PTMC 5400 M(n) and PVLCL 6000 M(n)), of which the permanent deformation after tensile failure was only 12 ± 7 and 39 ± 4%, respectively. The SS molecular weight also influenced the tensile modulus in an inverse fashion. Accelerated degradation studies in PBS containing 100 U/mL lipase showed significantly greater mass loss for the two polyester-based PUUs versus the polycarbonate-based PUU and for PVLCL versus PCL polyester PUUs. Basic cytocompatibility was demonstrated with primary vascular smooth muscle cell culture. The synthesized families of PUUs showed variable elastomeric behavior that could be explained in terms of the underlying molecular design and crystalline behavior. Depending on the application target of interest, these materials may provide options or guidance for soft tissue scaffold development.

Fabrication of a model continuously graded co-electrospun mesh for regeneration of the ligament–bone interface

Current scaffolds for the regeneration of anterior cruciate ligament injuries are unable to capture intricate mechanical and chemical gradients present in the natural ligament–bone interface. As a result, stress concentrations can develop at the scaffold–bone interface, leading to poor osseointegration. Hence, scaffolds that possess appropriate mechano-chemical gradients would help establish normal loading properties at the interface, while promoting scaffold integration with bone. With the long-term goal of investigating regeneration of the ligament–bone interface, this feasibility study aimed to fabricate a continuously graded mesh. Specifically, graded meshes were fabricated by co-electrospinning nanohydroxyapatite/polycaprolactone (nHAP-PCL) and poly(ester urethane) urea elastomer solutions from offset spinnerets. Next, mineral crystallites were selectively deposited on the nHAP-PCL fibers by treatment with a 5× simulated body fluid (5× SBF). X-ray diffraction and energy-dispersive spectroscopy indicated calcium-deficient hydroxyapatite-like mineral crystallites with an average Ca/P ratio of 1.48. Tensile testing demonstrated the presence of a mechanical gradient, which became more pronounced upon treatment with 5× SBF. Finally, biocompatibility of the graded meshes was verified using an MC3T3-E1 osteoprogenitor cell line. The study demonstrates that graded meshes, for potential application in interfacial tissue engineering, can be fabricated by co-electrospinning.

Effect of Fiber Diameter and Alignment of Electrospun Polyurethane Meshes on Mesenchymal Progenitor Cells

Effective strategies to guide cell alignment and the deposition of an oriented extracellular matrix are critical for the development of anisotropic engineered tissues suitable for the repair of ligament defects. Electrospinning is a promising means to create meshes that can align adherent cells, but the effect of fiber mesh architecture on differentiation has not been examined closely. Therefore, the goal of this study was to determine the effect of fiber diameter and the degree of fiber alignment on mesenchymal progenitor cell morphology, proliferation, and ligament gene expression. Specifically, a poly(ester urethane)urea elastomer was electrospun onto rigid supports under conditions designed to independently vary the mean fiber diameter (from 0.28 to 2.3 microm) and the degree of fiber alignment. Bone marrow stromal cells--seeded onto supported meshes--adhered to and proliferated on all surfaces. Cells assumed a more spindle-shaped morphology with increasing fiber diameter and degree of fiber alignment, and oriented parallel to fibers on aligned meshes. Expression of the ligament markers collagen 1alpha1, decorin, and tenomodulin appeared to be sensitive to fiber diameter and greatest on the smallest fibers. Concurrently, expression of the transcription factor scleraxis appeared to decrease with increasing fiber alignment. These results suggest that the formation of a ligament-like tissue on electrospun scaffolds is enhanced when the scaffolds consist of aligned submicron fibers.

Electrospinning of degradable elastomeric nanofibers with various morphology and their interaction with human fibroblasts

Artelon® (degradable poly(urethane urea) elastomer) was electrospun into scaffolds for tissue engineering. The diameter of the electrospun fibers, studied by scanning electron microscopy, ranged from 100 nm to a few μm, with an average diameter of 750 nm. The molar mass of the polymer had a major influence on the morphology of the scaffold. Furthermore, aging of the polymer solution caused changes in viscosity, as measured by stress sweeps between 13.5–942 Pa that affected the morphology. The electrospun Artelon mats exhibited about the same elongations to break, both exceeding 200%, measured by tensile tests. The degradation study showed similar degradation behavior in electrospun mats and solids. In vitro study showed that human fibroblasts not only adhere to the surface but also migrate, proliferate, and produce components of an extracellular matrix. These results strongly support the use of electrospun Artelon as a scaffold in tissue engineering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation, morphology, and properties of polyurethane–urea elastomers derived from sulphone‐containing aromatic diamine

AbstractAn aromatic diamine containing both sulfone and diphenyl ether groups, bis[4‐(4‐aminophenoxy)phenyl]sulfone, was synthesized in a two‐step way, whose structure was confirmed through Fourier transform infrared spectrometry, nuclear magnetic resonance, and elemental analysis. Then, the obtained BAPS was used as the chain‐extender to prepare a polyurethane–urea elastomer, whose morphology, thermal stability and mechanical properties were examined by means of attenuated total reflection, DSC, thermogravimetric analysis, dynamic mechanical thermal analysis, and stress–strain measurements. The results showed that the PUU elastomer based on BAPS showed good heat‐resistance and mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3554–3561, 2007

Biodegradable poly(ether ester urethane)urea elastomers based on poly(ether ester) triblock copolymers and putrescine: synthesis, characterization and cytocompatibility

Polymers with elastomeric mechanical properties, tunable biodegradation properties and cytocompatibility would be desirable for numerous biomedical applications. Toward this end a series of biodegradable poly(ether ester urethane)urea elastomers (PEEUUs) based on poly(ether ester) triblock copolymers were synthesized and characterized. Poly(ether ester) triblock copolymers were synthesized by ring-opening polymerization of ε-caprolactone with polyethylene glycol (PEG). PEEUUs were synthesized from these triblock copolymers and butyl diisocyanate, with putrescine as a chain extender. PEEUUs exhibited low glass transition temperatures and possessed tensile strengths ranging from 8 to 20 MPa and breaking strains from 325% to 560%. Increasing PEG length or decreasing poly(caprolactone) length in the triblock segment increased PEEUU water absorption and biodegradation rate. Human umbilical vein endothelial cells cultured in a medium supplemented with PEEUU biodegradation solution suggested a lack of degradation product cytotoxicity. Endothelial cell adhesion to PEEUUs was less than 60% of tissue culture polystyrene and was inversely related to PEEUU hydrophilicity. Surface modification of PEEUUs with ammonia gas radio-frequency glow discharge and subsequent immobilization of the cell adhesion peptide Arg-Gly-Asp-Ser increased endothelial adhesion to a level equivalent to tissue culture polystyrene. These biodegradable PEEUUs thus possessed properties that would be amenable to applications where high strength and flexibility would be desirable and exhibited the potential for tuning with appropriate triblock segment selection and surface modification.

Polyurethane Urea Elastomer Having Monodisperse Poly(oxytetramethylene) as a Soft Segment with a Uniform Hard Segment

Polyurethane Urea Elastomer Having Monodisperse Poly(oxytetramethylene) as a Soft Segment with a Uniform Hard Segment

Effect of the chemical structure of the rigid block on the properties of polyester urethane urea elastomers

A thermomechanical analysis has been made of polyester urethane ureas with non-crystallizable rigid blocks and an amorphous flexible matrix. The glass transition temperature, the devitrification interval and the compression modulus depending on the degree of phase separation are regulated not only by change in the solubility parameter of the rigid block but also by the number and position of the “hinge” groups in it. The behaviour of the polyester urethane urea elastomers at high temperatures is determined by the same factors and also by the polarity of the rigid block reflected in the temperature of the onset of devitrification of the rigid phase and the interval of its devitrification which in the end determines the performance of polyester urethane urea elastomers at high temperatures.