Phase segregation and viscoelastic behavior of poly(ether urethane urea)s

Two poly(ether urethane urea)s were synthesized, one based on poly(propylene glycol) and another one on poly(tetramethylene glycol). Hydrogenated MDI was used as the diisocyanate and propylenediamine as the chain extender. The diisocyanate : polyol : diamine molar ratio was 2 : 1 : 1 for both copolymers. Data from stress-relaxation tests were adjusted to a power law and to the Kohlraush-William-Watts equation. Phase separation and viscoelastic behavior were correlated through the calculation of the time-relaxation spectrum, the steady-state tensile compliance, and the tensile viscosity. The results indicated that the material based on poly(tetramethylene glycol) was the more effectively phase-segregated block copolymer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2227–2236, 1997     

Surface and bulk properties of poly(ether urethane)s/fluorinated phosphatidylcholine polyurethanes blends

As a part of long‐term project aimed at biomembrane mimicking polyurethanes (PU) with excellent biocompatibility and good mechanical properties, in this work, we report the surface and bulk properties of two series blends of fluorinated phosphatidylcholine polyurethanes (FPCPU) with poly(ether urethane)s (PEU). The blend films were prepared by solution mixing, and the surface and bulk properties were investigated by contact angle measurement, XPS, DSC, and Instron. Our results demonstrated that the surface with high percentage of phosphorus, fluorine, and nitrogen content could be achieved by blending FPCPU with PEU, because of the migration of FPCPU to the surface, resulting in a decreased water contact angle and increased hystersis. The blend films showed a reversible rearrangement of surface structure according to the change of environment from dry state to hydrated state. DSC result suggested that FPCPU could be phase miscible with PEU well in a broad composition region (as the content of FPCPU is less than 50 wt %). The blends showed an increased tensile strength and elongation at break compared with FPCPU, and increased modulus compared with PEU. Combined with the improved mechanical properties and much reduced price, together with the excellent blood compatibility, it can be expected these materials may play important roles in future medical application. © 2008 Wiley Periodicals, Inc. JAppl Polym Sci, 2008     

Hydrolytic resistance of model poly(ether urethane ureas) and poly(ester urethane ureas)

Poly(ester urethane ureas) (PesURUs) and poly(ether urethane ureas) (PetURUs) synthesized from diphenylmethane-4,4′-diisocyanate and poly(butylene adipate) diol, and poly(tetramethylene oxide) diol or poly(propylene oxide) diol, respectively, were hydrolyzed at 70°C for various periods up to 16 weeks. Differences in thermal and mechanical properties of as-received dry samples are correlated with the number and strength of hydrogen bonds formed between urea/urethane groups of hard segments and polyester or polyether groups of soft segments. Gel permeation chromatography measurements show that the molar mass of linear PesURUs markedly decreases with the hydrolysis time, whereas that of linear PetURUs remains almost unaffected. PesURU crosslinked by polymeric isocyanate has lower crystallinity, but shows somewhat better resistance to hydrolysis than its linear counterpart because of its more stable three-dimensional molecular structure. Water uptake at 37°C, dynamic mechanical thermal analysis, and differential scanning calorimetry thermograms determined for redried hydrolyzed specimens concurrently show that advancing hydrolysis accounts for decrease in the crystallinity (if any) of soft polyester segments, in the efficacy of hydrogen bonding and in crosslinking density. Experimental data indicate that hydrolytic resistance of PetURUs is primarily determined by (1) the hydrolytic stability of individual types of present groups, (2) steric hindrances affecting the access of water molecules to these groups, and (3) the hydrophilicity of backbones. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 577–586, 1998     

Structure–property relationship of sodium deoxycholate based poly(ester ether)urethane ionomers for biomedical applications

New sodium deoxycholate based poly(ester ether)urethane ionomers were prepared for the development of biomedical materials. A structure–property relationship in the tested biomaterials was established by cross‐examination of the dynamic mechanical and dielectric properties, attenuated total reflection–Fourier transform infrared investigation, thermogravimetric analysis, and surface morphology characterization. A stronger ionic interaction and solvation capacity of the ions and a higher ionic conductivity were manifested in the case of poly(ethylene oxide)‐rich segments than for poly(propylene oxide)‐rich segments in these polyurethane ionomers. The molecular and ionic interactions of the bile‐salt moiety with different polyether cosoft segments influenced chain packing and conformation, supramolecular organization, and the resulting surface morphological microstructures of the polyurethane biomembranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42921.     

Heat stabilization of segmented copoly(ether ester)s

Oxidative degradation of segmented copoly(ether ester)s can be suppressed by interference of the following basic processes: a. degradative radical chain reactions. Effective inhibition is possible by means of primary antioxidants. b. initiation of the radical chain reactions by means of hydroperoxides formed. Such initiation reactions can be suppressed by inactivation of the hydroperoxides with the aid of secondary antioxidants. c. polyester segmental chain scission by formic acid formed during oxidative degradation of the polyether segments. By scavenging the formic acid, or its precursor formaldehyde, this serious process can be restricted. Combined addition of stabilizers, simultaneously influencing the basic processes a., b. and c. can lead to synergism. Examples of the activity of the different stabilizers are given.     

Structure of segmented poly(ether urethane)s containing amino and hydroxyl functionalized polyhedral oligomeric silsesquioxanes (POSS)

Polyhedral oligomeric silsesquioxanes (POSS) with an empirical formula [RSiO_1.5]_n (where n = 6, 8,…14, and R is a reactive organic group) represent a new type of nanomodifiers for polyurethanes (PUs) to produce organic–inorganic hybrids (OIHs), which are promising candidates for modern applications spreading from biomedical to airspace technologies. In this paper we report on the synthesis and structural organization of two different series of PU–POSS copolymers (branched and cross-linked) based on a mixture of variable size oligomeric silsesquioxanes (POSS-M) of a general formula [(HOCH₂CH(OH)CH₂)₂N(CH₂)₃SiO_1,5]_n. Chemical structure of the synthesized POSS-M containing PUs has been confirmed by gel permeation chromatography and IR spectroscopic studies. Complex several-level hierarchy of their physical structural organization could be recognized from small angle X-ray scattering (SAXS) and atomic force microscopic (AFM) studies. SAXS experiments revealed that processes of microphase segregation and formation of nano-sized domains enriched with the inorganic phase (POSS fragments) take place during synthesis of the OIH systems. These nano-heterogeneity regions contain up to 66 vol.% of SiO_1.5 and form a paracrystalline lattice with hexagonal symmetry and characteristic interplanar periodicity of around 15 nm. The average size of inorganic phase nano-inclusions can be estimated as 2–3 nm, which corresponds to several POSS moieties in size. Cross-linked POSS-M containing PUs, as topologically more complex systems, is characterized with a diffusion-limited microphase segregation features. In the latter case the regions of nano-heterogeneity are smaller in size, have smaller content of the inorganic phase (ca. 54 vol.%), and form a less perfect paracrystalline order with the periodicity of 9.7 nm. Generally, we demonstrate that replacement of regular POSS moieties with the mixed POSS-M ones can lead to nanocomposite systems with an ordered supramolecular structural organization and simultaneous reduction of their production cost due to relative simplicity of their synthesis.     

Synthesis and properties of waterborne poly(urethane urea)s containing polydimethylsiloxane

To obtain flexible waterborne poly(urethane urea) (WBPU) coatings with functionalities such as shape recovery and water resistance, we synthesized a series of WBPUs by a prepolymer mixing process from hexamethylene diisocyanate, polyol, 2,2‐bis(hydroxymethyl) propionic acid, ethylenediamine, and triethylamine with polyol blends [hydroxyl‐terminated polydimethylsiloxane (PDMS) with a number‐average molecular weight of ≈ 550 and poly(tetramethylene oxide) glycol (PTMG) with a number‐average molecular weight of 650] of different molar ratios. The effects of the PDMS content in PDMS/PTMG on the dynamic thermal and mechanical properties, hardness, tensile properties, water resistance (water absorption, contact angle, and surface energy), and shape‐memory properties of WBPU films were investigated. As the molar percentage of PDMS in WBPUs increased, the storage modulus, tensile strength and modulus, elongation at break, hardness, and shape‐retention rate (30–15%) decreased; however, the water resistance and shape‐recovery rate (80–90%) increased. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrospinning of linear and highly branched segmented poly(urethane urea)s

Electrospun fibrous mats were formed from linear and highly branched poly(urethane urea)s. The highly branched poly(urethane urea)s were synthesized using an A₂+B₃ methodology, where the A₂ species is an oligomeric soft segment. Since the molecular weight of the A₂ oligomer is above the entanglement molecular weight, the highly branched polymers formed electrospun fibers unlike typical hyperbranched polymers that do not entangle. Stress-strain experiments revealed superior elongation for the electrospun fibrous mats. In particular, the highly branched fiber mats did not fail at 1300% elongation, making the electrospun mats promising for potential applications where enhanced tear strength resistance is required.     

Investigation of structure and mechanical properties of toughened poly(l‐lactide)/thermoplastic poly(ester urethane) blends

In this study, poly(l ‐lactide) (PLA) is melt‐blended with thermoplastic polyurethane (TPU) to modify the brittleness of PLA. An aliphatic ester‐based TPU was selected in order to have an ester sensitivity for degradation and an inherent biocompatibility. Using this compatible TPU, there was no need to apply problematic compatibilizers, so the main positive properties of PLA such as biocompatibility and degradability were not challenged. The detected microstructure of PLA/TPU blends showed that when the TPU content was lower than 25 wt %, the structure appeared as sea‐islands, but when the TPU content was increased, the morphology was converted to a cocontinuous microstructure. A higher interfacial surface area in the blend with 25 wt % TPU (PLA25) resulted in a higher toughness and abrasion resistance. The various analyses confirmed interactions and successful coupling of two phases and confirmed that melt‐blending of PLA with the aliphatic ester‐based TPU is a convenient, cost‐effective, and efficient method to conquer the brittleness of PLA. The prepared blends are general‐purpose plastics, but PLA25 showed an optimum mechanical strength, toughness, and biocompatibility suitable for a wide range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43104.     

Structural investigations of segmented block copolymers. II. The morphology of poly(ether ester)s based on poly(tetramethylene oxide) “soft” segments: Comparison between poly(ether ester)s and poly(ether esteramide)s

The morphology of poly(ether ester)s (PEES) of the general formula [(4GT)_k-PTMO]_z has been investigated by wide and small angle X-ray scattering and electron microscopy techniques. The copolymers are based on poly(tetramethylene terephthalate) (4GT) “hard” segments (containing an average number k of consecutive 4GT units) alternating poly(tetramethylene oxide) (PTMO) “soft” segments of constant length (MW ～ 900). The fraction of crystallized 4GT slightly increases by increasing the weight fraction of PTMO up to ca. 0.5; then it rapidly decreases so that an amorphous material is obtained for a PTMO weight fraction of 0.76. PEES display a lamellar-type morphology in which lamellar domains of crystalline 4GT alternate with slightly heterogeneous interlamellar amorphous regions containing both 4GT and PTMO. For high contents of PTMO these domains evolve toward amorphous domains formed by short 4GT segments (k = 2, 3). PEES and the structurally related poly(ether esteramide)s are compared in terms of their morphological structure.     

嵌段聚醚酯弹性纤维的老化及热分解

通过测定以PBT为硬段 ,聚乙二醇 (PEG)和聚丁二醇 (PTMG)为软段的嵌段聚醚酯弹性纤维在老化前后的特性粘数、断裂强度、断裂伸长率和弹性回复率的变化 ,发现添加抗氧剂能明显改善该弹性纤维的抗老化性能并提高纤维的力学性能和回弹性能 ;采用热失重测定了PBT -PTMG2嵌段聚醚酯弹性纤维的热分解性能 ,热分解动力学计算表明其热分解活化能较低 ,为 69.6kJ ,容易热分解 ,热分解为 1级反应     

Improvement of thermal stability of new heteroaromatic poly(azomethine urethane)s

New poly(azomethine urethane)s were synthesized in the conventional literature manner by reacting a new bisphenol‐containing azomethine group, N,N′‐bis(4‐hydroxyl‐3‐methoxy benzylidine)‐2,6‐diaminopyridine (I) with various diisocyanates, such as hexamethylene diisocyanate (HDI) (a), methylene‐4,4′‐diphenyl diisocyanate (MDI) (b), and toluene‐2,4‐diisocyanate (TDI) (c). The resulting polymers I(a–c) were confirmed by ¹H‐NMR, FTIR, UV, and CHN analyses. Thermogravimetric analysis (TGA) revealed that the polymers have high thermal stability. A semicrystalline behavior was noticed for polymers by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1198–1204, 2006     

Synthesis and characterization of poly(ester ether siloxane)s

A series of novel thermoplastic elastomers based on ABA‐type triblock prepolymers, poly[(propylene oxide)–(dimethylsiloxane)–(propylene oxide)] (PPO‐PDMS‐PPO), as the soft segments, and poly(butylene terephthalate) (PBT), as the hard segments, was synthesized by catalyzed two‐step melt transesterification of dimethyl terephthalate (DMT) with 1,4‐butanediol (BD) and α,ω‐dihydroxy‐(PPO‐PDMS‐PPO) (M?_n = 2930 g mol^?1). Several copolymers with a content of hard PBT segments between 40 and 60 mass% and a constant length of the soft PPO‐PDMS‐PPO segments were prepared. The siloxane‐containing triblock prepolymer with hydrophilic terminal PPO blocks was used to improve the compatibility between the polar comonomers, i.e. DMT and BD, and the non‐polar PDMS segments. The structure and composition of the copolymers were examined using ¹H NMR spectroscopy, while the effectiveness of the incorporation of α,ω‐dihydroxy‐(PPO‐PDMS‐PPO) prepolymer into the copolyester chains was controlled by chloroform extraction. The effect of the structure and composition of the copolymers on the transition temperatures (T_m and T_g) and the thermal and thermo‐oxidative degradation stability, as well as on the degree of crystallinity, and some rheological properties, were studied. Copyright © 2006 Society of Chemical Industry     

Synthesis, characterization and biodegradation studies of poly(ester urethane)s

Bis-isocyanoto polyester was synthesized by the polymerization of PPSe with MDI and reacted with 1,3-propanediol chain extender to obtain poly(ester urethane)s. The effect of chain extender and PPSe content in polyurethane was investigated. The polymers were characterized by ¹H NMR, FT-IR, viscosity measurement, TGA and XRD. Their biodegradability was investigated by the hydrolytic degradation in NaOH solution (3% and 10%); enzymatic degradation by Rhizopus delemar lipase and soil burial degradation using garden-composted soil. Furthermore, the degraded film was characterized by molecular weight, intrinsic viscosity, DSC, XRD, FT-IR and surface morphology by SEM. The biodegradation study revealed that hydrolysis and soil burial degradation affected morphology of the PEUs. Hydrophobicity and hard segment seem to resist the hydrolytic and enzymatic degradability of PEU. Hydrolytic degradation was very rapid in 3% and 10% NaOH solutions at 37 °C, within 2 days 20% weight loss was observed. PEUs showed a much slower degradation rate under the R. delemar lipase at 37 °C. Experimental data showed that as soft segment increases biodegradation rate decreased. A significant rate of degradation was occurred in all PEU samples under soil burial condition. Surface morphology, which interconnected to good adhesion of bacteria on polymer surface, is considered to be a factor sensible for the biodegradation rate under soil burial condition.     

Synthesis and evaluation of biodegradable segmented multiblock poly(ether ester) copolymers for biomaterial applications

Based on 1,4‐succinic acid, 1,4‐butanediol, poly(ethylene glycol)s and dimethyl terephthalate, biodegradable segmented multiblock copolymers of poly[(butylene terephthalate)‐co‐poly(butylene succinate)‐block‐poly(ethylene glycol)] (PTSG) were synthesized with different poly(butylene succinate) (PBS) molar fractions and varying the poly(ethylene glycol) (PEG) segment length, and were evaluated as biomedical materials. The copolymer extracts showed no in vitro cytotoxicity. However, sterilization of the copolymers by gamma irradiation had some limited effect on the cytotoxicity and mechanical properties. A copolymer consisting of PEG‐1000 and 20 mol% PBS, assigned as 1000PBS20 after SO₂ gas plasma treatment, sustained the adhesion and growth of dog vascular smooth muscle cells. The in vivo biocompatibility of this sample was also measured subcutaneously in rats for 4 weeks. The assessments indicated that these poly(ether ester) copolymers are good candidates for anti‐adhesion barrier and drug controlled‐release applications. Copyright © 2004 Society of Chemical Industry     

Degradation of a poly(ester urethane) elastomer. IV. Sorption and diffusion of water in PBX 9501 and its components

In preparation for studying the hydrolytic degradation of Estane® 5703 in the plastic‐bonded explosive PBX 9501, the sorption (solubility) and diffusion of water in PBX 9501 and each of its components are studied experimentally and modeled theoretically. Experiments are reported that measure the weight gain or loss due to a change in the relative humidity (RH). For all of the components, the equilibrium amount of water sorbed per gram of sample is linear in the RH at low relative humidities but curves upwards at higher relative humidities. This behavior is modeled with a water cluster model. Diffusion coefficients are determined by modeling the time dependence of the water concentrations assuming Fickian diffusion, and that fits the data for some of the materials. However, all the samples that contain the explosive HMX show much more complicated behavior at high relative humidities, and that is presented and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Simple and versatile method for the one‐pot synthesis of segmented poly(urethane urea)s via in situ‐formed AB‐type macromonomers

We present a one‐pot method for the synthesis of poly(urethane urea)s (PUUs) with uniform (monodisperse) hard segments that eliminates tedious approaches to control the exothermic nature of isocyanate–amine reaction, is less sensitive to impurities and involves no isolation of intermediates. Reaction of two moles of hexamethylene diisocyanate with one mole of polycaprolactone of various molecular weights under optimum time and temperature led to NCO‐terminated polyurethane prepolymers. Addition of an equimolar quantity of benzoic acid and excess dimethylsulfoxide at ambient temperature produced quantitative yields of PUUs with high molecular weight. The structure of the PUUs was fully characterized using spectroscopic methods and a reasonable mechanism for the reaction sequences was determined via preparation and characterization of a model compound. Dynamic mechanical thermal analysis data confirmed the phase‐separated structure of the PUUs. Evaluation of stress‐strain curves revealed the wide‐ranging mechanical properties depending on soft‐segment molecular weight. Monitoring the remaining weight and molecular weight of polymers incubated in phosphate‐buffered saline showed hydrolytic degradability with rate depending on soft‐segment molecular weight. Also, a preliminary investigation of the interaction of L929 fibroblast cells with the prepared polymers confirmed no cytotoxicity and acceptable cytocompatibility for the PUUs. Copyright © 2010 Society of Chemical Industry     

Incorporation of different crystallizable amide blocks in segmented poly(ester amide)s

High molecular weight segmented poly(ester amide)s were prepared by melt polycondensation of dimethyl adipate, 1,4-butanediol and a symmetrical bisamide-diol based on ε-caprolactone and 1,2-diaminoethane or 1,4-diaminobutane. FT-IR and WAXD analysis revealed that segmented poly(ester amide)s based on the 1,4-diaminobutane (PEA(4)) give an α-type crystalline phase whereas polymers based on the 1,2-diaminoethane (PEA(2)) give a mixture of α- and γ-type crystalline phases with the latter being similar to γ-crystals present in odd-even nylons. PEA(2) and PEA(4) polymers with a hard segment content of 25 or 50 mol% have a micro-phase separated structure with an amide-rich hard phase and an ester-rich flexible soft phase. All polymers have a glass transition temperature below room temperature and melt transitions are present at 62-70 °C (T_m,1) and at 75-130 °C (T_m,2) with the latter being highest at higher hard segment content. The two melt transitions are ascribed to melting of crystals comprising single ester amide sequences and two or more ester amide sequences, respectively. These polymers have an elastic modulus in the range of 159-359 MPa, a stress at break in the range of 15-25 MPa combined with a high strain at break (590-810%). The thermal and mechanical properties are not influenced by the different crystalline structures of the polymers, only by the amount of crystallizable hard segment present.