Water transport properties of thermoplastic polyurethane films

Two linear segmented polyurethanes, based on poly(oxyethylene) (POE) as a soft segment and 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol as hard segments and differing in their soft segment length, have been studied from a water vapor transport point of view. For both polyurethanes, the water sorption is governed by a Fickian process, and the thermoplastic polyurethane with the longer POE segments displays the higher water diffusion rate. The water sorption isotherms are Brunauer Emmet Teller (BET) type III for both thermoplastic polyurethanes, and the water uptakes are directly related to the polymer POE content. The Flory–Huggins theory cannot correctly describe the sorption isotherms. More sophisticated approaches (Koningsveld–Kleinjtens or Guggenheim‐Anderson‐de Boer (GAB) models) are needed to fit the experimental water uptakes. The positive deviation from Henry's law and the decrease in the apparent diffusion coefficient observed at a high activity have been particularly studied. In this activity range, an isotherm analysis based on the cluster integral of Zimm and Lundberg suggests some clustering phenomenon, which seems consistent with the diffusion coefficient variation. In agreement with the sorption results, the water permeability coefficients are small at low activities, and they increase greatly with the relative pressure of water. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 473–492, 2004     

Electrospinning of biostable polyisobutylene-based thermoplastic polyurethanes

Electrospinning of a previously synthesized biostable polyisobutylene (PIB)-based thermoplastic polyurethanes (TPU) have been performed as materials with potential applications as vascular grafts. Electrospun mats were generated with fiber diameters in the submicron to 2 μm range as observed using scanning electron microscopy. Porosity of electrospun TPU fiber mats was investigated using Hg intrusion porosimetry. Fiber mats were found to have a distribution of pore sizes between 100 nm and 100 μm, with overall porosity between 50 and 70%. Thermal analysis of electrospun mats showed orientation of the TPU chains compared to the bulk as-synthesized material. Tensile failure properties were characterized, showing ultimate tensile strength of 1.6–6.5 MPa and ultimate elongation of ∼300–100% with TPUs of increasing hardness from Shore 60A to 100A. Strain-recovery experiments showed good recovery of tensile strain at significant stresses. The previously demonstrated biostability of these PIB-based TPUs, together with the excellent reported mechanical properties, indicates great promise for these materials as biostable vascular grafts. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Effects of polymerization method on structure and properties of thermoplastic polyurethanes

The effects of the dynamic polymerization method and temperature on the molecular aggregation structure and the mechanical and melting properties of thermoplastic polyurethanes (TPUs) were successfully clarified. TPUs were prepared from poly (ethylene adipate) glycol (M_n = 2074), 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol by the one‐shot (OS) and the prepolymer (PP) methods in bulk at dynamic polymerization temperatures ranging from 140 to 230 °C. Glass‐transition temperatures (T_gs) of the soft segment and melting points (T_ms) of the hard segment domains of OS‐TPUs increased and decreased, respectively, with increasing polymerization temperatures, but those of PP‐TPUs were almost independent of the polymerization temperature. T_gs of the soft segment and T_ms of the hard segment domains of these TPUs polymerized above 190 °C were almost the same regardless of the polymerization method. Solid‐state nuclear magnetic resonance spectroscopy (NMR) analyses of OS‐ and PP‐TPUs showed that the relative proton content of fast decay components, which corresponds to the hard segment domains, in these TPUs decreased with increasing polymerization temperatures. These results clearly show that the degree of microphase separation becomes weaker with increasing polymerization temperatures. The temperature dependence of dynamic storage modulus and loss tangent of OS‐TPUs coincided with those of PP‐TPUs at polymerization temperature above 190 °C. The apparent shear viscosity for OS‐ and PP‐TPUs polymerized above 190 °C approached a Newtonian behavior at low shear rates regardless of the polymerization method. These results indicate that TPUs polymerized at higher temperatures form almost the same molecular aggregation structures irrespective of the dynamic polymerization method. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 800–814, 2007     

Shear‐induced structuring kinetics in thermoplastic segmented polyurethanes monitored by rheological tools

Thermoplastic segmented polyurethanes (TPUs) are an important class of thermoplastic elastomers with a two‐phase microstructure arising from the thermodynamic incompatibility between hard (HSs) and soft segments. This microphase separation observed on cooling from a homogeneous state is often combined with the solidification of either or both types of segments. In this study, the structuring mechanism of two TPUs with HSs based on 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol was investigated from rheological measurements. Hence, in addition to the structuring temperature influence, the effect of an applied preshear flow in the melt polymer was analyzed, in particular. The results clearly show an enhancement of the solidification kinetics by the preshear. Indeed, the measured structuring time can be reduced by more than 1 decade. Rheo‐optical microscopy observations coupled with a shearing hot stage corroborated these results and showed the modification of the microstructure by the shear. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 190–201, 2010     

Linear polyurethanes made from naturally occurring tartaric acid

Naturally occurring tartaric acid was used as raw material for the synthesis of novel linear polyurethanes (PURs) bearing two carboxylate side‐groups in the repeating unit. Aliphatic and aromatic PURs were obtained by reaction in solution of alkyl and benzyl tartrates with hexamethylene diisocyanate and 4,4′‐methylene‐bis(phenyl isocyanate), respectively. All the novel PURs were thermally stable and optically active. The aliphatic carboxylate‐containing PURs had M_w in the 40–70 kDa range, with PD between 2.1 and 2.5; all were semicrystalline polymers with melting temperatures between 100 and 150 °C and T_g in the 50–80 °C range. The aromatic PURs were amorphous materials with molecular weights between 18 kDa and 25 kDa and T_g above 130 °C. Hydrogenolysis of the PUR made from hexamethylene diisocyanate and benzyl tartrate yielded PURs containing up to 40% of free carboxylic side‐groups. The tartrate‐derived PURs displayed enhanced sensitivity to hydrolysis compared with their unsubstituted 2,6‐PUR homologs. The PURs bearing free carboxylic groups were unique in being degraded by water upon incubation under physiological conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2391–2407, 2009     

Low‐temperature route to thermoplastic polyamide elastomers

Thermoplastic polyamide elastomers were obtained by polymerization of aminobenzoyl‐substituted telechelics derived from poly(tetrahydrofuran)‐diols (number‐average molecular weight: 1400 or 2000 g mol^?1) with several diacid dichlorides (terephthaloyl dichloride, 4,4′‐biphenyldicarbonyl dichloride, or 2,6‐naphthalenedicarbonyl dichloride) and chlorotrimethylsilane in N,N‐dimethylacetamide at 0–20 °C. The as‐prepared polymers had melting temperatures above 190 °C and exhibited elastic properties at room temperature, as evidenced by dynamic mechanical analysis and stress–strain measurements. The polymer with 2,6‐naphthalenedicarboxamide hard segments had the widest rubbery plateau within the series, the highest extension at break, and good recovery properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1449–1460, 2004     

Synthesis,structural characterization,and properties of polyurethane elastomers containing various degrees of unsaturation in the chain extenders

We prepared polyurethane block copolymers with both 50 and 70% soft segment concentrations, using 4,4′‐diphenylmethane diisocyanate–poly(propylene glycol) prepolymer and 1,4‐butanediol, cis‐2‐butene‐1,4‐diol, and 2‐butyne‐1,4‐diol as chain extenders. The effects of the different chain extenders were observed during synthesis and in the final products. A comparison of spectroscopic, mechanical, and thermal data reveals that polymer properties can be significantly altered by differences in chemical bonding within the chain extender backbone. Although all data support the expected differences in phase morphology between the two series of samples, they also suggest that increasing chain extender unsaturation reduced reactivity with isocyanate, adversely affected hydrogen bonding, lowered the degree of crystallinity of the hard segments, and decreased phase separation. The tensile strength, elongation, modulus, and elastic recovery decreased and the electrical conductivity of iodine‐doped samples increased with increasing chain extender unsaturation. The thermal stability of the urethane group was also lower in samples with increased unsaturation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1316–1333, 2002     

Study of slabstock flexible polyurethane foams based on varied toluene diisocyanate isomer ratios

The morphological features of three flexible slabstock polyurethane foams based on varied contents of 2,4 and 2,6 toluene diisocyanate (TDI) isomers are investigated. The three commercially available TDI mixtures, that is, 65:35 2,4/2,6 TDI, 80:20 2,4/2,6 TDI, and 100:0 2,4/2,6 TDI were used. The foams were characterized at different length scales with several techniques. Differences in the cellular structure of the foams were noted with scanning electron microscopy. Small‐angle X‐ray scattering was used to demonstrate that all three foams were microphase‐separated and possessed similar interdomain spacings. Transmission electron microscopy revealed that the aggregation of the urea phase into large urea‐rich regions decreased systematically on increasing the asymmetric TDI isomer content. Fourier transform infrared spectroscopy showed that the level of bidentate hydrogen bonding of the hard segments increased with the 2,6 TDI isomer content. Differential scanning calorimetry and dynamic mechanical analysis (DMA) were used to note changes in the soft‐segment glass‐transition temperature of the foams on varying the diisocyanate ratios and suggested that the perfection of microphase separation was enhanced on increasing the 2,6 TDI isomer content. The preceding observations were used to explain why the foam containing the highest content of the symmetric 2,6 TDI isomer exhibited the highest rubbery storage modulus, as measured by DMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 258–268, 2003     

生物降解型聚氨酯研究进展

本文综述了生物降解型聚氨酯的研究现状，并探讨了影响其生物降解性的因素，指出了其应用前景，特别是医学上的应用．     

Crystallization studies on linear aliphatic n‐polyurethanes

A detailed crystallization study of the linear n‐polyurethane (n‐PUR) family for n ranging from 5 to 12 was carried out by DSC supported by polarizing optical microscopy. The study embraces crystallization of all the n‐PUR under both nonisothermal and isothermal conditions. The odd and even series of n‐PUR defined by the parity of the number of methylenes (n) contained in the polymer repeating unit are considered and separately analyzed. All the members of the two series showed a thermal behavior consistent with their chemical constitution. Isothermal crystallization data were analyzed by the kinetics Avrami approach which revealed that the “crystallizability” of n‐PUR increases steadily with the flexibility of the polyurethane chain. Melting and enthalpy temperatures of isothermally and nonisothermally crystallized n‐PUR were found to vary with n according to a zig‐zag plot characteristic of odd–even effect. Given the structural similitude of n‐PUR with (n + 2)‐nylons, results were referenced to those reported for this family of polyamides. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1368–1380, 2009     

Synthesis and thermal transition behavior of model thermoplastic polyurethanes containing MDI/butanediol‐based monodisperse hard segments

Amine‐terminated monodisperse hard segments (MDHSs) containing two to four 4,4′‐methylenebis (phenyl isocyanate) extended by 1,4‐butanediol have been synthesized using carboxybenzyl protecting‐deprotecting strategy. Pure MDHSs in large scale were obtained in good yield and their structures were confirmed by ¹H‐, ¹³C‐NMR spectroscopy and GPC‐MALLS. Differential scanning calorimetry (DSC) showed that as the hard segment (HS) size increased, the melting and glass transition temperature and the change of heat capacity at glass transition of ethyl capped MDHSs increased. Model thermoplastic polyurethanes (TPUs) were synthesized using the reaction of bischloroformate of poly (tetramethylene oxide) (PTMO) diol or polyisobutylene (PIB) diol with amine‐terminated MDHSs. X‐ray diffraction results indicated the amorphous structure of model TPUs. DSC revealed HS related endotherms, regardless of SS, which were attributed to the local ordering of the HSs. Additional endotherms in PTMO based model TPUs might arise from the dissociation of hydrogen bonding between PTMO and HSs. The lower T_g in model TPUs compared to the polydisperse analogues observed by dynamic mechanical analysis (DMA) indicated higher microphase separation of monodisperse HSs. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3171–3181     

Morphology and tensile properties of model thermoplastic polyurethanes with MDI/butanediol based monodisperse hard segments

Morphology and tensile properties of model thermoplastic polyurethanes (TPUs) containing polyisobutylene (PIB) or poly(tetramethylene oxide) (PTMO) based soft segment and 4,4‐methylene bis(phenyl isocyanate) (MDI) and 1,4‐butanediol (BDO) based monodisperse hard segments (HSs), consisting of exactly two to four MDI units extended by BDO, were investigated. Using FT‐IR spectroscopy, increased hydrogen bonded C?O fraction was observed in model TPUs as the HS size increased. The hydrogen bonded C?O fraction was higher in PIB based TPUs compared with PTMO based TPUs, indicating higher phase separation in PIB based TPUs. The morphology of TPUs was investigated using AFM phase imaging, which showed ribbon‐like or interconnected hard domains in PTMO based model TPUs and randomly dispersed hard domains in PIB based model TPUs. SAXS revealed that the degree of phase separation in the model TPUs was higher than in their polydisperse analogues. Domain spacing as well as interfacial thickness increased with the increasing HS size, and both values were higher in PTMO based TPUs. The tensile analysis indicated that model TPUs exhibited higher modulus and slightly higher elongation compared with their polydisperse analogues. Only in PTMO based model TPUs, strain induced crystallization was observed above 300% elongation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2485–2493     

Soy-oil-based segmented polyurethanes

Segmented polyurethanes were prepared from soy polyol, diphenyl methane diisocyanate (MDI), and ethylene glycol or butane diol as chain extenders. Samples were prepared with true hard-segment concentrations (HSC) of about 0, 10, and 40%. Both the soft MDI–polyol and hard MDI/diol segments are glassy at room temperature. These samples were also crosslinked through the polyfunctional polyol soft segment. Partial crystallinity and phase separation were detected in samples with 40% HSC, on the basis of DSC data. Small-angle X-ray scattering shows the existence of phase separation with domain sizes of about 10 nm in the 40% HSC samples, but not in the others. The distribution of domain sizes is considerably broader for the ethylene-glycol extended system compared with that for the butane-diol case. Although the presence of hard segments lowers the crosslink density, samples with higher HSC had higher glass transition temperatures, higher strengths, higher moduli, lower swelling, lower elongation at break, and lower impact strengths. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3178–3190, 2005     

Synthesis and properties of renewable nonisocyanate polyurethanes (NIPUs) from dimethylcarbonate

Novel fully renewable AA‐BB type nonisocyanate polyurethanes (NIPUs) were synthesized using the transurethanization approach. Dicarbamate monomers were prepared by the reaction of a diamine with an excess of dimethylcarbonate (DMC), in presence of 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) as catalyst. Then, the dicarbamate was reacted with a diol to afford the polymer, in presence of TBD or K₂CO₃ as catalyst. Several renewable diamines and diols were tested. The two steps were conducted under neat conditions. The obtained materials exhibited T_g values varying from ?38 to 42 ° C, T_m values varying from 42 to 204 °C , and thermal stabilities above 200 ° C. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1351–1359     

Thermal stability enhancement of polyurethanes by surface treatment

Both oxidation and methoxymethylation of the surfaces of a series of MDI (methylene diphenyl isocyanate) and TDI (toluene diisocyanate) polyether and polyester soft segment 1–4 butanediol polyurethanes result in increased thermal stability as measured by TG. Explosive loss of mass above the hard segment melting temperature suggests that the diffusion of the dissociated diisocyanate moiety is hindered at lower temperatures. Thus suppression of the depolycondensation reaction by chemical blockage of the surface may result in a material with an increased service life at use temperatures as thermal stability of a polyurethane may depend upon the low diffusivity of its diisocyanate comonomer. The effect of vacuum, oxygen and water vapor on the kinetics of mass-loss of several of the polyurethanes is presented. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Polyurethanes containing sulfur. I. New thermoplastic polyurethanes with benzophenone unit in their structure

New thermoplastic nonsegmented thiopolyurethanes were obtained from the low-melting aliphatic–aromatic thiodiols 4,4′-bis(2-hydroxyethylthiomethyl)benzophenone (BHEB), 4,4′-bis(3-hydroxypropylthiomethyl)benzophenone (BHPB), and 4,4′-bis(6-hydroxyhexylthiomethyl)benzenophenone(BHHB) as well as hexamethylene diisocyanate (HDI), both by melt and solution polymerization with dibutyltin dilaurate as the catalyst. The effect of various solvents on molecular-weight values was examined. The polymers with the highest reduced viscosities (0.63–0.88 dL/g) were obtained when the polymerization was carried out in a solution of tetrachloroethane, N,N-dimethylacetamide, and N,N-dimethylacetamide or N,N-dimethylformamide for BHEB-, BHPB-, and BHHB-derived polyurethanes, respectively. These polymers with a partially crystalline structure showed glass-transition temperatures (T_g) in the range of −1 to 39 °C, melting temperatures (T_m) in the range of 107 to 124 °C, and thermal stabilities up to 230 to 240 °C. The BHEB-derived polyurethane is a low-elasticity material with high tensile strength (ca. 50 MPa), whereas the BHPB- and BHHB-derived polyurethanes are more elastic, showing yield stress at approximately 16 MPa. We also obtained segmented polyurethanes by using BHHB, HDI, and 20 to 80 mol % poly(oxytetramethylene) glycol (PTMG) of M̄_n = 1000 as the soft segment. These are high-molecular thermoplastic elastomers that show a partially crystalline structure. Thermal properties were investigated by thermogravimetric analysis and differential scanning calorimetry. The increase in PTMG content decreases the definite T_g and increases the solubility of the polymers. These segmented polyurethanes exhibit the definite T_g (−67 to −62 °C) nearly independent of the hard-segment content up to approximately 50 wt %, indicating the existence of mainly phase-separated soft and hard segments. Shore A/D hardness and tensile properties were also determined. As the PTMG content increases, the hardness, modulus of elasticity, and tensile strength decrease, whereas elongation at break increases. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4140–4150, 1999     

Roles of rhenium diimine complexes as metal‐ion probes and photosensitizers in functional polyurethanes

Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10^?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003     

Synthesis and characterization of thermotropic liquid crystalline polyurethanes from 4,4′‐bis(6‐hydroxyhexoxy) biphenyl and aliphatic diols

A series of thermotropic liquid crystalline polyurethanes (LCPUs) were synthesized by the polyaddition reactions of 2,4‐toluene diisocyanate (2,4‐TDI) with 4,4′‐bis(6‐hydroxyhexoxy)biphenyl (BHHBP) and aliphatic diol. The intrinsic viscosities of the polymers were measured by Ubbelohde viscometer, and the chemical structure was confirmed by Fourier transform infrared spectroscopy (FT‐IR). The LCPUs were examined by differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide angle X‐ray diffraction (WAXD), and thermogravimetric analysis (TGA). The intrinsic viscosities were 0.56–0.83 dl/g. According to the melting point (T_m) and the isotropic temperature (T_i) of the LCPUs, the temperature range of the liquid crystalline phase became wider with increased number of methylene spacers in the polyurethane. The LCPUs exhibited a nematic phase with a threaded texture and had a wide mesophase temperature range. The decomposition temperature of the LCPUs was >300°C. On WAXD, the LCPUs give a dispersing peak at 2θ ≈ 20°, and a strong diffraction peak at 2θ ≈ 25°. Copyright © 2008 John Wiley & Sons, Ltd.     

Composition effects of thermoplastic segmented polyurethanes on their nanostructuring kinetics with or without preshear

In this work, the structuring mechanism from the molten state of various thermoplastic polyurethanes was analyzed with respect to their composition [polyether or polyester soft segments (SSs), aromatic or aliphatic hard segments (HSs)]. As a preliminary study, the molar mass evolution of the materials with the temperature was quantified. Then, based on rheological experiments and in situ rheo‐small angle X‐ray scattering (SAXS) measurements, the structuring was examined at different temperatures and, particularly, the effect of a preshear treatment was analyzed. The temperature effect can be accounted by an Arrhenius‐like law with an activation energy depending mainly on the HS nature. Moreover, the shear induced structuring phenomenon is highlighted for all the studied thermoplastic segmented polyurethanes. Nevertheless, for the studied range of shear treatments, the SAXS analyses did not reveal any specific orientation. Finally, arguments based on the modification of the quench depth (ΔT = T_ODT ? T) by the shear are given to explain the shear induced structuring phenomenon. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011