Micro‐phase‐separation behavior of amphiphilic polyurethanes involving poly(ethylene oxide) and poly(tetramethylene oxide)

The temperature dependence of thermal, morphological, and rheological properties of amphiphilic polyurethanes was examined with differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXS), small‐angle X‐ray scattering (SAXS), rheological measurements, and Fourier transform infrared spectroscopy. Multiblock (MPU) and triblock (TPU) polyurethanes were synthesized with two crystallizable segments—poly(ethylene oxide) (PEO) as a hydrophilic block and poly(tetramethylene oxide) (PTMO) as a hydrophobic block. DSC and WAXS measurements demonstrated that the microphase of MPUs in the solid state is dominantly affected by the PEO crystalline phase. However, high‐order peaks were not observed in the SAXS measurements because the crystallization of the PEO segments in MPUs was retarded by poor sequence regularity. The microphase in the melt state was induced by the hydrogen bonding between the N? H group of hexamethylene diisocyanate linkers and the ether oxygen of PEO or PTMO blocks. As the temperature increased, the smaller micro‐phase‐separated domains were merged into the larger domains, and the liquidlike ordering was eventually disrupted because of the weakening hydrogen bonding. However, the fully homogeneous state of an MPU with a molar ratio of 5/5 PEO/PTMO (MPU55) was not confirmed even at much higher temperatures with both SAXS and rheological measurements. However, the SAXS patterns of TPU showed weak but broad second‐order peaks below the melting temperature of the PEO block. Compared with MPU55, the ordering of the TPU crystalline lamellar stacks was enhanced because of the high sequence regularity and the low hydrogen‐bonding density. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2365–2374, 2003     

Poly(urethane-oxazolidone): Synthesis, characterisation and shape memory properties

Poly(urethane-oxazolidone) were synthesized by reacting isocyanate-terminated oxazolidone with hydroxy-telechelic poly(tetramethylene oxide) (PTMO). The molar ratios of the reactants were varied to get polymers of varying oxazolidone and urethane compositons. The polymers were characterized by DSC, FTIR, XRD, dynamic mechanical thermal analysis and chemical analyses. An increase in the concentration of urethane and oxazolidone groups caused a decrease in tensile strength and elongation of the poly(urethane-oxazolidone). The polymers possessed crystallites of PTMO whose melting transition temperature decreased on enhancing the oxazolidone concentration. The polymers exhibited thermo-responsive shape memory properties, which was confirmed and quantified by cyclic tensile tests. The influence of oxazolidone modification and the consequent soft/hard segment variation on the thermal, mechanical, dynamic-mechanical and shape recovery properties of the resultant polymers was investigated. The oxazolidone moities conferred enhanced shape recovery and shape fixity to the polyurethane.     

端羟基芳香酯二醇扩链的聚氨酯－酯的DSC研究

端羟基芳香酯二醇扩链的聚氨酯－酯的ＤＳＣ研究陈静，余学海，杨昌正（南京化工学院应化系南京２１０００９）（南京大学化学系南京２１００９３）关键词嵌段聚醚聚氨酯－酯，结晶性，微观相结构，差示扫描量热法，形态结构众所周知，聚氨酯嵌段共聚物是一类结构特殊、用...     

Microstructural evolution underlying the ternary stages of the elastic behaviors for poly(ether‐b‐amide) copolymer elastomers

Three stages of elastic behavior were observed during cyclic deformations for poly(ether‐b‐amide) (PEBA) segmented copolymers based on crystalline hard segments of polyamide 12 (PA12) and amorphous soft segments of poly(tetramethylene oxide) (PTMO). The underlying microstructural evolution was characterized by a combination of in situ Fourier transform infrared spectroscopy (FTIR), wide‐angle X‐ray diffraction (WAXD), and small‐angle X‐ray scattering (SAXS) technologies. The γ–α″ phase transition of crystalline PA12 occurred upon stretching, and the orientation of the α″ phase was less reversible under larger strains. PTMO chain orientation cannot be restored to the initial state, contributing to plastic deformation. Driven by the entropy effect, the strain‐induced crystallization of PTMO can fuse during sample retarding, exerting little influence on the residual strain. For PEBA with a shore D hardness of 35 D, the long period (L) can be restored to the initial L after the sample was unloaded until system fibrillation. The tie molecules between adjacent oriented lamellae can be by drawn out high stress in a PEBA material with a shore D hardness of 40 D, and the relaxation led to a second long period. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 855–864     

Thermal properties of poly(lactic acid)/organo-montmorillonite nanocomposites

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (T _m), glass transition temperature (T _g), crystallization temperature (T _c), degree of crystallinity (χ_c), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.     

端羟基芳香酯二醇扩链的聚氨酯－酯的DSC研究

端羟基芳香酯二醇扩链的聚氨酯－酯的ＤＳＣ研究陈静，余学海，杨昌正（南京化工学院应化系南京２１０００９）（南京大学化学系南京２１００９３）关键词嵌段聚醚聚氨酯－酯，结晶性，微观相结构，差示扫描量热法，形态结构众所周知，聚氨酯嵌段共聚物是一类结构特殊、用...     

Temperature‐dependent changes in the hydrogen bonded hard segment network and microphase morphology in a model polyurethane: Experimental and simulation studies

Hydrogen bonding between hard segments has a critical effect on the morphology and properties of polyurethanes. Influence of temperature on hydrogen bonded urethane network and melting behavior of a model semicrystalline segmented polyurethane was investigated by experiments and simulations. Polyurethane was synthesized by the stoichiometric reaction between p‐phenylene diisocyanate and poly(tetramethylene oxide) (PTMO) with a molecular weight of 1000 g/mol. Simulations were carried out using dissipative particle dynamics (DPD) and molecular dynamics (MD) approaches. Experimental melting behavior obtained by various techniques was compared with simulations. DPD simulations showed a room temperature microphase morphology consisting of a three‐dimensional hydrogen‐bonded urethane hard segment network in a continuous and amorphous PTMO matrix. The first‐order melting transitions of crystalline urethane hard segments observed during the continuous isobaric heating in DPD and MD simulations (340–360 K) were in reasonably good agreement with those observed experimentally, such as AFM (320–340 K), WAXS (330–360 K), and FTIR (320–350 K) measurements. Quantitative verification of the melting of urethane hard segments was demonstrated by sharp discontinuities in energy versus temperature plots obtained by MD simulations due to substantial decrease in the number of hydrogen bonds above 340 K. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 182–192     

Synthesis and properties of segmented block copolymers based on mixtures of poly(ethylene oxide) and poly(tetramethylene oxide) segments

The synthesis and characterisation of segmented block copolymers based on mixtures of hydrophilic poly(ethylene oxide) and hydrophobic poly(tetramethylene oxide) polyether segments and monodisperse crystallisable bisester tetra-amide segments are reported. The PEO length was varied from 600 to 8000 g/mol and the PTMO length was varied from 650 to 2900 g/mol. The influence of the polyether phase composition on the thermal mechanical and the elastic properties of the resulting copolymers was studied.The use of high melting monodisperse tetra-amide segments resulted in a fast and almost complete crystallisation of the rigid segment. The copolymers had only one polyether glass transition temperature, which suggests that the amorphous polyether segments were homogenously mixed. Thermal analysis of the copolymers showed one polyether melting temperature that was lower than in the case of ideal co-crystallisation between the two polyether segments. However, at PEO or PTMO lengths larger than 2000 g/mol two polyether melting temperatures were observed. The copolymer with the best low temperature properties was based on a mixture of PEO and PTMO segments, both having a molecular weight of 1000 g/mol, at a weight ratio of 30/70.     

Glass transition and melting behavior of poly(ether-ester) multiblock copolymers with poly(tetramethylene isophthalate) hard segments

The glass transition and melting behavior of poly(ether-ester) multiblock copolymers with poly(tetramethylene isophthalate) (PTMI) hard segments and poly(tetramethylene oxide) (PTMO) soft segments are studied by differential scanning calorimetry (DSC) and small- and wide-angle x-ray scattering (SAXS and WAXS). Thermodynamic melting parameters for the PTMI homopolymer are estimated by WAXS and from the dependence of melting point on crystallization temperature. The melting behavior of PTMI is characterized by dual endotherms which are qualitatively representative of the original morphology, although reorganization effects are present. The composition dependence of the glass transition temperature parameters after rapid quenching from the melt are well described by mixed phase correlations for copolymers in the range 30-100 wt% hard segment. Combined with SAXS characterization at melt temperatures, a single phase melt is suggested in these materials which extends to temperatures below the hard segment melting point. © 1994 John Wiley & Sons, Inc.     

Synthesis and Characterization of Thermoplastic Polyurethaneureas based on Polyisobutylene and Poly(tetramethylene oxide) Segments

New thermoplastic polyurethaneureas (TPUU) based on polyisobutylene (PIB) and poly(tetramethylene oxide) (PTMO) segments have been synthesized possessing tensile properties comparable to conventional PTMO based TPUs. PIB based TPUU containing 35 weight (wt)% hard segment was synthesized by chain extension of H₂N-Allyl-PIB-Allyl-NH₂ with 4,4′ -methylene bis(phenylisocyanate) (MDI) and 1,4-butanediol (BDO) in toluene. The ultimate tensile strength (UTS) = 12 MPa and ultimate elongation = 70% were inferior to PTMO based polyurethane (UTS = 35 MPa, elongation at break = 600%). H₂N-Allyl-PIB-Allyl-NH₂ and HO-PTMO-OH in different proportions were chain extended in presence of MDI and BDO to obtain TPUUs containing 35 wt% hard segment. The polymers exhibited M _ns = 84000–138000 with polydispersity indices (PDIs) = 1.7–3.7. The UTS = 23–32 MPa and elongation at break = 250–675% was comparable to that of PTMO based polyurethane and significantly higher than the PIB based TPUU with the same Shore hardness. The Young's modulus of the polymers was strongly dependent and directly proportional to the PIB wt% in the SS of the TPUUs.     

Tailoring the morphology and properties of waterborne polyurethanes by the procedure of cellulose nanocrystal incorporation

Polyurethane waterborne synthesis was performed using a two-step method, commonly referred to as a prepolymer method. Nanocomposites based on waterborne polyurethane and cellulose nanocrystals were prepared by the prepolymer method by altering the mode and step in which the nanofillers were incorporated during the polyurethane formation. The morphology, structural, thermal, and mechanical properties of the resulting nanocomposite films were evaluated by Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and tensile tests. FTIR results indicated that the degree of interaction between the nanofillers and the WPU through hydrogen bonds could be controlled by the method of cellulose nanocrystal incorporation. Data obtained from SAXS experiments showed that the cellulose nanocrystals as well as the step of the reaction in which they are added influenced the morphology of the polyurethane. The reinforcing effect of CNCs on the nanocomposites depends on their morphology.     

Synthesis and ESCA surface studies of octadecyl chain-extended polyurethanes

Poly(ether urethane)s as biomaterials display certain favorable mechanical and biocompatibility properties. Earlier studies suggest that improved blood compatibility might be attained by introducing hydrocarbon groups at the surface. We synthesized and characterized a series of polyurethanes in which a N-2,3-dihydroxypropyl-N′-octadecyl urea chain extender (ODCE) was incorporated into the poly(tetramethylene glycol) (PTMO)/4,4′-methylenebis(phenylene isocyanate) (MDI) system. Molecular weights of the polymers varied between 40,000 and 250,000. An electron spectroscopy for chemical analysis (ESCA) study of the ODCE polyurethane surface revealed a substantially enhanced hydrocarbon concentration compared to a control PTMO/MDI/ethylene diamine (ED) polyurethane surface. Also, bulk composition analyses and ESCA data of the ODCE polymers indicated that the percentage of carbon was higher in the surface region than in the bulk. Thus, the ODCE polymer showed a marked increase in hard-segment concentration in the surface region compared to the bulk region and to the ED polymer.     

Effect of sample preparation conditions and degree of neutralization on the dynamic mechanical properties of poly(styrene-co-sodium methacrylate) ionomers

A study was undertaken of the effect of sample preparation conditions, especially moisture content, annealing conditions, and degree of neutralization, on the dynamic mechanical properties of poly(styrene-co-sodium methacrylate) ionomers. Water plasticizes the ionic cores; however, very small amounts of water do not affect the cluster glass transition mechanism. The study of the annealing effect showed that the morphology of ionomers is fixed during sample molding. No clustering was observed in samples below a degree of neutralization of 50%, possibly due to a decrease in the lifetime of the multiplets. The 50 and 75% neutralized samples showed weak clustering, with the cluster tan δ peaks shifting to higher temperatures with increasing degree of neutralization. The addition of neutralizing agents causes an increase in the size of multiplets; as a result, the strength of the electrostatic interaction between ion pairs increases. The 100–150% neutralized samples showed identical tan δ peaks and also very similar SAXS peaks. Therefore, it is speculated that excess NaOH resides in or near the multiplets and does not affect the electrostatic interaction between ion pairs. The 200–300% neutralized samples showed increased flow above the cluster T_g, as well as a strong small-angle upturn in the SAXS profile. In agreement with previous results, it appears that in these materials, the excess NaOH resides in the hydrocarbon phase in the form of NaOH crystals, which can act as sites on which the carboxylate ion pairs can reside temporarily; the binding, however, is believed to weaken at high temperatures, which allows flow to occur. The 200% overneutralized Ba²⁺ sample showed the cluster T_g at much higher temperatures than the 100% neutralized sample, which implies that, for this sample, the stability of the multiplets is higher. © 1995 John Wiley & Sons, Inc.     

Polyisobutylene‐based polyurethanes. III. Polyurethanes containing PIB/PTMO soft co‐segments

The synthesis, characterization, and structure–property behavior of polyurethanes containing polyisobutylene (PIB)/poly(tetramethylene oxide) (PTMO) soft co‐segments and bis(4‐isocyanatocyclohexyl)methane (HMDI)/hexanediol (HDO) hard segments is presented. The mechanical (stress/strain, hardness, and hysteresis) properties of these novel polyurethanes were investigated over a broad composition range. PIB‐based polyurethanes with HMDI/HDO hard segments showed better mechanical properties than earlier polyurethanes containing highly crystalline hard segments. The addition of moderate amounts (20% by weight) of PTMO significantly increased both tensile strengths and elongation. In the presence of larger amounts of PIB, these polyurethanes are expected to possess oxidative/hydrolytic/enzymatic stabilities superior to commercially available polyurethanes. These polyurethanes are softer and exhibit hysteresis superior to or comparable with conventional polyurethanes. According to initial thermal studies, these materials show good melt processibility. Overall, the mechanical properties of PIB based hybrid polyurethanes are similar to commercially important polyurethane type biomaterials. Our results show that the incorporation of PTMO segments to PIB‐based polyurethanes significantly improves elastomeric properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5278–5290, 2009     

Structure and morphology of HDPE-g-MA/organoclay nanocomposites: Effects of the preparation procedures

Nanocomposites comprising high density polyethylene (HDPE) or maleic anhydride-grafted HDPE (HDMA) as the host polymers and Cloisite^® 20A (20A) as the organoclay filler were prepared by melt-compounding, solution-blending and static annealing of polymer/clay powder mixtures. The dependence of their structure and morphology on the preparation conditions was studied by X-ray diffraction (XRD and SAXS), polarized optical microscopy (POM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that intercalated nanocomposites based on HDPE or HDMA cannot be obtained by solution-blending, as long as solvent removal is made at room temperature. In fact, wide angle XRD patterns of solution blended composites are similar to those of mechanical blends of clay and polymer. However, as demonstrated by XRD and SAXS, fast intercalation or even complete delamination was obtained when the HDMA composites prepared from solution were annealed statically at temperatures higher than the polymer melting point. This implies that solution-blending causes efficient fragmentation of the clay agglomerates into thin tactoids (though unintercalated) homogeneously dispersed in the polymer matrix. This conclusion, supported by the finding that annealing mechanical blends of polymer and clay powders only leads to intercalated structures, was confirmed by TEM and SEM analyses. Morphology investigation revealed that, in contrast to melt-compounding, solution-blending followed by static annealing fails to produce significant orientation of clay platelets and polymer crystallites. However, repeated compression molding cycles were shown by XRD and SAXS to cause increasing levels of orientation of the platelets and the polymer matrix parallel to the sample flat surface.     

Thermogravimetric study of rubber waste-polyurethane composites

Granulated rubber obtained from used tyres, below 1.5 mm granularity (fine rubber) and polyurethane prepolymers (Chemolan M, Chemolan M50 and Chemolan B3) were used for the synthesis of rubber waste-polyurethane composites, containing 90, 85, 80, 75 and 70% w/w of fine rubber. The influence of the kind of polyurethane resin on hardness, elasticity, glass transition temperature and thermal stability of composites was studied. Kinetic parameters of the thermal degradation process of composites were calculated from thermogravimetric analysis (TG) data.This work has been financially supported by the State Committee for Scientific Research, Poland (research project-grant no. 3 T09B 043 19).     

Studies on thermoplastic polyurethanes based on new diphenylethane-derivative diols. II. Synthesis and characterization of segmented polyurethanes from HDI and MDI

Various new thermoplastic segmented polyurethanes were synthesized by a one-step melt polymerization from aliphatic-aromatic α,ω-diols containing sulfur in the aliphatic chain, including 4,4′-(ethane-1,2-diyl)bis(benzenethioethanol), 4,4′-(ethane-1,2-diyl)bis(benzenethiopropanol) and 4,4′-(ethane-1,2-diyl)bis(benzenethiodecanol) as chain extenders, hexane-1,6-diyl diisocyanate (HDI) or 4,4′-diphenylmethane diisocyanate (MDI) and 20-80 mol% poly(oxytetramethylene)diol (PTMO) with molecular weight of 1000 g/mol as a soft segment. The reaction was conducted at the molar ratio of NCO/OH = 1 and 1.05, and in the case of the HDI-based polyurethanes in the presence of dibutyltin dilaurate as a catalyst. The effect of the diisocyanate used on the structure and some physicochemical, thermal and mechanical properties of the segmented polyurethanes were studied. The structures of these polyurethanes were examined by FTIR and X-ray diffraction analysis. The thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. Shore hardness and tensile properties were also determined. All the synthesized polymers showed partially crystalline structures. The MDI-based polyurethanes were products with lower crystallinity, higher glass-transition temperature (T_g) and better thermal stability in comparison with the HDI-based ones. The MDI series polymers also exhibited higher tensile strength (up to ∼36 MPa vs. ∼23 MPa) and elongation at break (up to ∼3900% vs. ∼900%), but lower hardness than the analogous HDI series polyurethanes. In both series of the polymers an increase in PTMO soft-segment content was associated with decreased crystallinity, T_g, hardness and tensile strength. An increase in PTMO content also involved an increase in elongation at break.     

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     

Preparation and characterization of polyurethan‐block‐poly(trifluoro‐ propylmethyl)siloxane elastomers

A series of polyurethane‐block‐poly(trifluoropropylmethyl)siloxane (PUFS) elastomers were prepared via a two‐step process from toluenediisocyanate (TDI), α ω‐bis(3‐aminopropyldiethoxylsilane) poly(trifluoropropylmethyl)siloxane (APFS), and poly(tetramethylene oxide) (PTMO). The PUFS films were formed through moisture curing and characterized by DSC, DMTA, TGA, mechanical testing, and water contact angle. It was found that the extent of microphase separation of the PUFS system would increase with the increase in APFS content, and result in the decrease in the tensile strength and the thermal stability. On the other hand, the crosslink density of the PUFS system would apparently increase with the increase in the TDI content, which reduced the microphase separation and improved the tensile properties and the thermal stability of the PUFS elastomers. Copyright © 2009 John Wiley & Sons, Ltd.     

固体变温核磁共振碳谱研究主链型热致液晶聚醚聚氨酯弹性体

固体变温核磁共振碳谱研究主链型热致液晶聚醚聚氨酯弹性体陈群，杨光，王源身（华东师范大学分析测试中心上海２０００６２）余学海（南京大学高分子系南京２１０００８）黑子弘道，安藤勋（日本东京工业大学高分子工学科）关键词主链型热致液晶聚氨酯弹性体，固体变温高...