On the role of aminolysis and transesterification in the synthesis of ɛ-caprolactone and L-lactide based polyurethanes

Summary Polyurethanes based on a 50/50 copoly(L-lactide/ɛ-caprolactone) prepolymer and butanediisocyanate were made. Chain extending a diisocyanate terminated prepolymer with butanediamine was not possible due to the susceptibility of the lactide bond to aminolysis. Chain extension with butanediol resulted in a polymer with poor mechanical properties due to transesterification. When the copolymer prepolymer was chain-extended with an isocyanate terminated block, transesterification with the chain-extender was avoided and the mechanical properties were increased. When the length of the hard segments was increased the mechanical properties increased further. A L-lactide/ɛ-caprolactone based polyurethane with a tensile strength and modulus of respectively 45 MPa and 60 MPa was made. The polymer contained no poly(L-lactide) crystals and was easy to process. Compared to the high molecular weight 50/50 copoly(L-lactide/ɛ-caprolactone) the polyurethane showed better mechanical properties, is expected to have the same adhesive properties and is expected to have a slower degradation rate. These factors makes this polymer excessively useful for in-vivo tissue engineering in for instance meniscal reconstruction material, nerve guide and artificial skin. Received: 12 March 1998/Revised version: 26 June 1998/Accepted: 26 June 1998     

The effect of chain extenders structure on properties of new polyurethane elastomers

Two series of polyurethane elastomers were synthesized to investigate what effect does the incorporation of various new chain extenders have on the mechanical and thermal properties of polyurethane elastomers. The polyurethane soft segments were based on poly(ε-caprolactone) polyol. The hard segment was based on 1,6-hexamethylene diisocyanate in combination with 2,5-dimethyl-3-hexine-2,5-diol (DHD), hexaethylene glycol, glycerin, or castor oil. The results showed that the degradation rate and mechanical properties of the final products can be controlled through the structure of diol chain extenders or/and hard segment cross-linking present in the polyurethane elastomers. The DHD-based polyurethane displayed a relatively low glass transition temperature of −57 °C and a tensile strength of 11–14 MPa and elongation at break of 600–700%. These kinds of materials have potential application in many domains.     

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 (OH_polyol/NCO/NH_{2chain 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.     

新型水性聚氨酯脲-丙烯酸酯复合乳液的制备与性能

以乙烯脲(EU)为新型扩链剂,异佛尔酮二异氰酸酯(IPDI)、二羟甲基丙酸(DMPA)为硬段,聚四氢呋喃醚二醇(PTMG1000)为软段,先合成水性聚氨酯脲(PU-EU);然后利用互穿聚合物网络(LTPN)改性的方法将丙烯酸丁酯(BA)、甲基丙烯酸缩水甘油醚(GMA)在PU-EU乳液中共聚,利用乙二胺(EDA)与其交联,制备出具有核-壳结构的水性聚氨酯脲-丙烯酸酯复合乳液(PUEU/PA)。结果表明,PU-EU/PA复合乳液具有良好的耐热性、力学性能和较高的硬度,形成了具有化学交联的核-壳互穿网络结构聚合物。     

Synthesis of hydrolytically stable low elastic modulus polyurethane‐urea for biomedical applications

Polyurethane‐urea without ether linkages was synthesised using dicyclohexyl‐methane diisocyanate (SMDI), hydroxy‐terminated polybutadiene (HTPBD) and m‐phenylenediamine (PDA). The hydrolytic stability of this polymer was investigated under in vitro conditions using Ringer's solution and phosphate‐buffered saline, and the stability of candidate polyurethane‐urea polymers was compared with that of polyurethane prepared with SMDI, HTPBD and 1,4‐butanediol [BD]. The change of tensile properties, hardness and surface properties in the aged polymer is significant for polyurethane when compared with those of polyurethane‐urea polymer. The in vitro study revealed possible applications of polyurethane‐urea for long‐term biomedical applications. © 2000 Society of Chemical Industry     

Characterization of Thermoplastic Polyurethanes Prepared Using Different Macroglycols

Three polyurethane elastomers (PU_s) were prepared using macroglycols of different nature (varepsilon-polycaprolactone, polyadipate of 1,6-hexanediol) and length of the hydrocarbon chain (polyadipate of 1,4-butanediol, polyadipate of 1,6-hexanediol). The PU_s were characterized using Gel Permeation Chromatography, Differential Scanning Calorimetry, Wide X-ray angle Diffraction, Dynamic Thermal Mechanical Analysis, stress-controlled rheometry and stress-strain experiments. The surface properties were evaluated from contact angle measurements. The PU_s were used as raw materials for solvent-based adhesives, whose adhesion properties were measured from T-peel strength of plasticized poly(vinyl chloride) (PVC)/polyurethane adhesive joints. The use of polyadipate of 1,6-hexanediol produced a polyurethane with high crystallinity (i.e. poor rheological and mechanical properties) and enhanced interactions between soft segments. Low adhesion was obtained in joints produced with this polyurethane and a cohesive failure of the adhesive was produced. The decrease in the polyadipate hydrocarbon chain length decreased the degree of crystallinity between polymer chains, therefore, no reduction in rheological and mechanical properties was obtained; a higher joint strength was also obtained. In this study the best performance was obtained with the polyurethane based on varepsilon-polycaprolactone, presumably because of its higher surface energy and reduced crystallinity. The properties of the polyurethanes prepared in this study were more affected by the characteristics of the macroglycol, and the crystallinity of the polyurethane had a more marked effect on the properties than the degree of phase separation.     

Application of zirconium (IV) acetylacetonate to the copolymerization of glycolide with ɛ-caprolactone and lactide

Summary A study on the copolymerization of glycolide with lactide and glycolide with ɛ-caprolactone was performed in the presence of zirconium (IV) acetylacetonate at moderate temperatures (100° and 150°C). Zirconium acetylacetonate appeared to be an efficient initiator of copolymerization. The obtained polymers were characterized by high molecular weights. Considerable influence of transesterification on the polymer chain microstructure was found. Received: 13 October 1998/Revised version: 4 January 1999/Accepted: 4 January 1999     

Novel side chain dendronized polyurethane: synthesis,characteristics, and cell responses

Novel side chain dendronized polyurethane was synthesized by the sequential conjugation of amine-terminated fourth generation polyester dendrons with carboxyl groups at the side chain of polyurethane and deprotection of acetonide groups at the surface of dendrons. The effect of each step on the properties of the polymers was measured by GPC, DSC, SEM, AFM, and water contact angle measurement. The results showed that immobilization of polyester dendrons improve the compatibility of hard and soft segments in polyurethane and decrease the tendency of crystallinity due to the bulkiness of the substituents. After deprotection of the acetonide groups, both bulk and surface hydrophilicity of the polymer were evidently enhanced. Cell toxicity analysis showed that the side chain dendronized polyurethane synthesized in this study has exhibited excellent biocompatibility to human embryonic kidney 293T cells. The cells can effectively adhere to and proliferate on the surface of the polymer film. Overall, the present study demonstrated an efficient modification method for polyurethanes to improve their cell compatibility with high potential in biomedical applications.     

Molecular dynamics, thermo-mechanical and optical studies on benzidine chain extended polyurethane-urea

This paper reports the effect that the aromatic diamines and crosslinker nature have on the physico-mechanical and dielectric properties of linear and crosslinked polyurethane-urea. These elastomers were prepared using poly(tetramethylene glycol) (Terathane 1400), 1,6-hexamethylene diisocyanate and 4,4′-diaminobiphenyl (benzidine) as chain extender and glycerin or castor oil as crosslinkers. The polyurethane-ureas were characterized through Fourier transform infrared spectroscopy, thermogravimetric analysis, differential dynamic mechanical analysis, dielectric properties. The effects of the hard segments structure on physical, dielectric, mechanical and dynamic mechanical properties of the polyurethane-urea elastomers were investigated. The presence of more urea groups in the hard segment leads to high tensile strength (60–70 MPa), high elongation (700%–950%), increased thermally stability and superior dielectric properties.     

Synthesis and characterization of biocompatible poly(ethylene glycol)-functionalized polyurethane using click chemistry

Functionalization of azide moiety-containing polyurethane (PU) with alkyne-decorated poly(ethylene glycol) (PEG) was accomplished by Cu(I)-catalyzed Huisgen [3+2] dipolar cycloaddition click chemistry. The azide moiety containing poly(ε-caprolactone)diol was synthesized by the copolymerization of α-chloro-ε-caprolactone with ε-caprolactone using ring-opening polymerization and further used for PU synthesis. The PEG-functionalized PU was characterized using FT-IR, NMR, and GPC. The hydrophilicity of synthesized polymers was measured using contact angle and water content tests. In vitro cytotoxicity results showed that the amphiphilic PEG-functionalized PU exhibits good biocompatible behavior, which supports the importance of functionalized PU for biomedical applications.     

Structure and Mechanical Properties of Shape Memory Polyurethane Based on Hyperbranched Polyesters

Summary Hyperbranched shape memory polyurethane (HB-SMPU) were prepared from 4,4’-diphenylmethane diisocyanate, poly (butylenes adipate) glycol, and hyperbranched polyester as chain extender via a two-step process. The morphology of the HB-SMPU films was investigated by the use of wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), DSC and dynamic mechanical analysis (DMA). It was found that the PBAG soft segments in HB-SMPU with 15–35 wt. % of hard segments were in a crystalline state, however, the PBAG segments were in an amorphous state in the HB-SMPU with 40 wt. % hard segments. The increase of the hard segment content resulted in the decrease of the melt transition temperature of the HB-SMPU. The HB-SMPU with 25 wt. % of hard segment content possessed highest loss tangent. Heat of crystallization was dependent on the content of hard segment in the HB-SMPU. 96–98 wt. % shape recovery could be obtained for the HB-SMPU with 15–35 wt. % of hard segment. The content of hard segments in HB-SMPU was very important in determining their physical properties.     

Evaluation of disulfide chain extender effect on the mechanical properties of unsaturated polyurethane‐urea networks

4‐Aminophenyl disulfide and bis(4‐aminophenyl)methane chain extenders containing hydroxyl‐terminated polybutadiene‐based polyurethane‐ureas are prepared one‐shot to explore the effect of the chain extender structure on the elastomers mechanical properties. However, the results revealed that the participation of the disulfide chain extender in side reactions like thiol‐ene and proton abstraction prevented disulfide metathesis reaction due to decomposing chain extender in the polyurethane‐urea matrix. Also, these side reactions improved the phase mixing via chemical crosslinking between polyurethane‐ureas soft and hard segments, too. Tensile test results showed higher stress strength of the elastomers in the presence of the disulfide chain extender in comparison with the nondisulfide bond containing elastomers. This result was in agreement with the observed result in dynamical mechanical analysis. Dynamic mechanical analysis results established that the absence of the disulfide bond in the polyurethane‐urea matrix led to the higher viscous modulus. The swelling test revealed chemical crosslinking increased in the presence of the disulfide bond. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46309.     

Imide-modified polyurethanes,syntheses, thermal,and mechanical characteristics

Polyurethanes based on polyethylene glycol and hydroxy-terminated polybutadiene, bearing pyromellitimide groups in the backbone, were synthesised via a sequential method. The diisocyanate and diamine telechelic precursor polymers, the polyamic acid intermediate and the polyimides were characterized by physicochemical and thermoanalytical techniques. The imide content could be varied in the chain through selection of the polyol of desired molecular weight or by a chain extension process of the diisocyanate precursor. The thermal and mechanical properties of the imide-modified polyurethane increased proportionate to the hard segment content, constituted by the imide and the urea groups. The presence of the imide group resulted in better thermomechanical profile and caused enhancement in glass transition temperature of the modified polyurethane vis-à-vis the unmodified resin. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1483–1491, 1998     

Novel Polyurethane Scaffolds Containing Sucrose Crosslinker for Dental Application

In this paper, the synthesis, characterization, and properties of crosslinked poly(ε-caprolactone)-based polyurethanes as potential tissue replacement materials are reported. The polyurethane prepolymers were prepared from poly(ε-caprolactone)diol (PCD), polyethylene glycol (PEG)/polylactic acid diol (PLAD), and 1,6-hexamethylene diisocyanate (HDI). In these segmented polyurethanes, the role of PEG/PLAD was to tune the hydrophobic/hydrophilic character of the resulting polymer while sucrose served as a crosslinking agent. PLAD was synthesized by the polycondensation reaction of D,L-lactic acid and investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and nuclear magnetic resonance spectroscopy (NMR). The crosslinked polyurethane samples (SUPURs) obtained were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy (AT-FT-IR), swelling, and mechanical (uniaxial tensile tests) experiments. The thermo and thermomechanical behavior were studied by differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA). The viability of dental pulp stem cells was investigated in the case of polyurethanes composed of fully biocompatible elements. In our studies, none of our polymers showed toxicity to stem cells (DPSCs).     

Preparation and Characterization of Footwear Soling Materials Based on Biodegradable Polyurethane

The aim of this research work is to prepare biodegradable polyurethane composites and study their physical, mechanical, thermal, and biodegradation properties. Rigid biodegradable polyester-based polyurethane was synthesized by reacting excess of isocyanate with poly(ε-caprolactone)diol to obtain prepolymer which was then reacted with chain extender. The polyurethane composites are prepared with nanoclay and titanium(IV)oxide nanopowder in different concentrations, and polyurethane containing 2% w/w of nanopowder had shown better properties. Biodegradation studies showed that the developed polyurethane materials when used as shoe soles will retain their strength while storage and use, but will decompose only after disposal into the environment.     

Hybrid polymer latexes: acrylics-polyurethane from miniemulsion polymerization: properties of hybrid latexes versus blends

Hybrid polymer latexes polyurethane/polyacrylic esters, are prepared through miniemulsion polymerization of polyurethane solutions in acrylic monomers. The polyurethanes are prepared by condensation of isophorone diisocyanate on polypropylene glycol (M_n=1000) and butane diol as chain extender. The NCO chain ends being reacted with water (which act as a further chain extender producing some urea bonds). They are miniemulsified in a mixture of methylmethacrylate and butylacrylate monomers, and the miniemulsion are polymerized using benzoylperoxide as initiator. Films were obtained for different hybrid latexes of various compositions. Their mechanical properties have been compared with those of films from the basic components (polyurethane and acrylic latexes), as well as films from blends of these components. Some specific features of the surface of these films are also discussed from microscope images (TEM and AFM) as well as from contact angle measurements.     

Nanostructured hyperbranched polyurethane elastomer hybrids that incorporate polyhedral oligosilsesquioxane

Novel thermoplastic hyperbranched polyurethane (HBP) elastomer hybrids containing polyhedral oligomeric silsesquioxane (POSS) have been synthesized using an A₂ + B₃ approach. Different compositions of these hybrid nanomaterials were obtained from reactions of POSS-diol, triethanolamine, poly(ε-caprolactone)diol, and 4,4′-methylenebis(phenyl isocyanate) with a chain extender. The covalent attachment of POSS molecules to the backbone of the polyurethane chain was characterized with FT-IR and NMR spectroscopies. The non-agglomerated homogeneous dispersion obtained through the covalent attachment of POSS molecules and the HBP matrix was observed by SEM imaging. The mechanical properties, including the tensile and yield strengths, Young’s modulus, and toughness, significantly increased after the introduction of POSS molecules into the hybrids; this increase can be ascribed to the nano-reinforcement effect of the POSS cages and the long-range branched structure of the polymer. Thermogravimetric analyses indicated that the thermal stability of the polymer matrix was improved by the introduction of a small amount of POSS.     

Synthesis and evaluation of mechanical and thermal properties of segmented condensation polyurethanes

Abstract

Condensation polyurethanes with different hard segment (HS) content were prepared by condensation reaction of urea, phenol sulphonic acid and formaldehyde and tested for their mechanical, physical and thermal properties. Obtained polyurethane (PUR) films were first heated at 50°C for 120 min and then treated at 135°C for 15 min or 160°C for 10 min. The tensile strength of samples thermally treated at 50°C then at 135°C was 120% higher than for samples treated only at 50°C. The obtained polyurethanes exhibited segmented structures with phase separation between HSs and soft segments (SSs). Films containing 19 and 21%HSs heated at 50°C then 135°C exhibited acceptable mechanical properties and water resistance. The lower and higher end use temperatures of PUR films were affected mainly by the polymer composition. Moreover, the polyurethane samples containing 19 and 21%HSs have shown the highest decomposition temperature (i.e. >165°C), compared to 80°C for polymers with 32%HSs.     

Synthesis and characterization of polyurethane urea acrylates: Effects of the hard segments structure

A series of poly(ester‐urethane‐urea) acrylates were synthesized using poly(ethylene adipate) diol (PEA), 4,4′‐diphenyl methane diisocyanate (MDI), different diamines and acrylic acid. On the basis of IR, stress–strain, thermogravimetric, and differential scanning calorimetry measurements of their cured materials, relations between their structure and physical properties were investigated systematically. The properties were compared with a polyurethane acrylate (PUA) elastomer in which the variable was the diamine modification. The mechanical analysis indicated that, when the short chain of diamine was used, the strength and strain at break of the polymer was enhanced. The thermal stability and the glass transition of PUA increased with increased of diamine chain. The crosslinking process depresses crystallization of the soft segments and can be used to obtain protective films and finishing materials for the leather industry. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis of polymer having β,β-triketone unit in the main chain and its copper (II) complex

Summary A novel polymer having β,β-triketone unit in the main chain was prepared by polycondensation of triethylene glycol bis(p-butoxycarbonylphenyl) ether (1) with triethylene glycol bis(p-acetylacetophenyl) ether (4). The obtained polymer was soluble in CHCl₃, DMF, and DMSO. The structure of the polymer was confirmed by ¹H-NMR. Insoluble brownish yellow copper (II) chelate was obtained by adding a methanol solution of copper (II) acetate to a chloroform solution of the polymer. The IR analysis and the measurement of copper content by iodometric titration showed the quantitative formation of binuclear copper (II) complex. Received: 20 March 1998/Accepted: 17 April 1998