A study of polyurethanes synthesized from an arylsilane,bis(4,4′-phenylisocyanato)dimethylsilane,and its carbon analog, 2,2-bis(4,4′-phenylisocyanato)propane

Bis(4,4′-phenylisocyanato) dimethylsilane (SiDI) and 2,2-bis (4,4′-phenylisocyanato)propane (PrDI) were synthesized, polymerized to polyurethanes, and their chemical, thermal and physical properties studied. Nuclear magnetic resonance spectra confirm deshielding by silicon of both the phenyl ring and the urethane linkage. The glass transition temperatures, solubility parameters, and mechanical properties were independent of the diisocyanates. The silicon containing polyurethanes are more thermally stable than their carbon counterparts. © 1993 John Wiley & Sons, Inc.     

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.     

Synthesis and Characterization of Polyurethanes Based on Oligo(ϵ-caprolactone) Prepared by Free-Metal Method

The oligoester diols were synthesized via ring-opening polymerization of ?-caprolactone in the presence of creatinine and diethylene glycol or 1,4-butanediol as initiator systems. Thus, obtained oligomers were successfully used in the synthesis of segmented polyurethanes. The oligoester diols (poly(?-caprolactone) and dihydroxy(polyethylene adipate)) were reacted with 4,4′-methylenebis(phenyl isocyanate) in the presence of 1,4-butanediol as the chain extender to obtain polyurethanes. The physical and mechanical properties of polyurethanes were determined. The structures of the oligoesters and polyurethanes were elucidated by means of NMR, IR and MALDI-TOF MS studies.     

Properties of Polyurethanes Based on Mesogenic Diol and 4,4'-methylenebis(cyclohexyl Isocyanate)

New polyurethanes with mesogenic units in the main chain due to the use of a liquid crystalline chain extender were synthesized from 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI)using diisocyanates of different trans, trans isomer content, a low molecular diol4,4'-bis(6-hydroxyhexoxy)biphenyl (BHHBP) and a high molecular poly(hexyleneadipate)diol (PHA). The growth of trans, trans isomer content in HMDI used to syntheses of PU induces monotonic growth of melting point, rectilinear growth of crystallization temperatures and the growth of crystallization enthalpy, both for hard segment polyurethanes and block polyurethanes. The increase of trans, trans isomer content in HMDI increases also glass transition temperatures and dynamic storage modulus of the polyurethanes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Liquid crystalline polyurethane. Polyurethanes containing bis-(p-oxymethylphenyl) terephthalate

Several polyurethanes based on bis-(p-oxymethylphenyl) terephthalate (BOPT) were synthesized and studied with respect to some of their thermal properties. BOPT exhibits a mesomorphic phase at 252–264°C. Polymerization was carried out by equimolar reaction with hexamethyl-ene diisocyanate (HDI), 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI) α,α'-diisocyanate-1,3-dimethylcyclohexane (H6 XDI), 4,4′-diphenylmeth-ane diisocyanate (MDI), 2,4-tolylene diisocyanate (TDI), and phenylene diisocyanate (PDI). It became clear that polyurethanes obtained from BOPT with HDI, H₁₂MDI, H₆XDI, and TDI have mesomorphic phases at 243–291, 214–250, 172–229, and 180–234°C, respectively, as determined by DSC and polarized microscopy, and that all polyurethanes are crystalline as evidenced by x-ray diffraction.     

Framed aromatic polyurethanes based on an anionic macroinitiator, 4,4'-diphenylmethane diisocyanate,and 4,4'-dihydroxy-2,2-diphenylpropane: Metal-complex modification

Metal complexes are prepared from poly(oxyethylene glycol) and iron(III) chloride and studied as modifiers of framed aromatic polyurethanes. The latter polymers are synthesized on the basis of macroinitiators, 4,4'-dihydroxy-2,2-diphenylpropane, and polyisocyanate, which is a mixture of 4,4'-diphenylmethane diisocyanate and its branched derivatives. The interaction of iron(III) chloride with poly(oxyethylene glycol) is accompanied by redox processes that lead to its degradation and partial reduction of Fe(III) to Fe(II). Aromatic polyurethanes are modified in the concentration range of metal complexes from 0.5 to 20%. At a concentration of metal complexes of 4–7%, the polymer shows high mechanical characteristics and excellent thermal stability. The framed structure of aromatic polyurethanes hampers the effective contacts of coordinately bonded Fe atoms that are present in various oxidation states.     

Annealing effects on the thermal properties of liquid crystalline polyurethanes

This work is a continuation of our earlier investigations of liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy) biphenyl (BHBP), 2,4-tolylene diisocyanate (TDI), and poly (oxytetramethylene) diols (PTMO). The annealing effects on the thermal properties of the investigation polyurethanes are presented for three samples with the same BHBP content, different flexible spacer length, and different molecular weight of the polyurethanes. The annealed polyurethanes were investigated by means of DSC, and polarizing microscopy. The results of the thermal analysis show that the temperatures of phase transitions depend on the annealing temperature and time. These dependences are different for different molecular weights. © 1994 John Wiley & Sons, Inc.     

Sugar‐based hydrophilic polyurethanes and polyureas

Novel linear homogeneous polyurethanes and polyureas with enhanced hydrophilic character have been successfully prepared from sugar‐based monomers having their hydroxyl groups free or partially protected. By the reaction of primary hydroxyl groups of xylitol with dimethyl hexamethylene dicarbamate (HMDC) or di‐tert‐butyl‐4,4′‐diphenyl methyl dicarbamate (MDC), two new linear semicrystalline polyurethanes [PU(X‐HMDC) and PU(X‐MDC)] have been prepared. Likewise, by the reaction of xylitol with the analogous diisocyanates hexamethylene diisocyanate (HMDI) or 4,4′‐methylenebis(phenyl isocyanate) (MDI), similar polyurethanes [PU(X‐HMDI) and PU(X‐MDI)] were obtained. However, these latter polyurethanes present some degree of crosslinking because of the higher reactivity of the diisocyanate comonomers. Linear hydrophilic polyureas having free hydroxyl groups joined to the main chain have also been prepared by the reaction of the same diisocyanates (HMDI and MDI) with 1,6‐diamino‐1,6‐dideoxy‐D ‐mannitol and 1,6‐diamino‐1,6‐dideoxy‐3:4‐O‐isopropylidene‐D ‐mannitol. As far as we are aware, this kind of polyhydroxylated polyurea has not been previously described in the literature. The new polymers were characterized by standard methods (elemental analyses, gel permeation chromatography, IR, and NMR). The polyurethanes were hydrolytically degradable under physiological conditions, in contrast with less‐hydrophilic linear polyurethanes previously described. The thermal properties of the novel polymers were investigated by thermogravimetric analysis and differential scanning calorimetry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and properties of liquid crystalline polyurethanes

Liquid crystalline polyurethanes were prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP) and 2,4-tolylene diisocyanate (TDI). The effect of partial replacement of BHBP by 25–75 mol % poly(oxytetramethylene) diol (PTMO, M _n = 250) on the liquid crystalline properties was studied. The BHBP/TDI/PTMO polyurethanes were obtained by one- and two-step polyaddition. The polyurethanes were investigated by DSC, polarizing microscopy, x-ray, and IR spectroscopy. The molecular weight distribution was determined by GPC. The morphology of the polymers was investigated by the SALS method. Thermogravimetric investigations of the polyurethanes were also performed. All polyurethanes containing BHBP units have liquid crystalline properties. Partial replacement of BHBP by PTMO-250 considerably changes the phase transition temperatures and the range of mesophase occurrence. More homogeneous polyurethanes were obtained, if the two-step polyaddition method was applied. The polyaddition method affects the phase transition temperatures. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of novel liquidcrystalline polyurethanes

Novel polyurethanes have been synthesized by the condensation of two rigid diols, biphenyl-4,4'-diol (BPH(4,4')D) and 4-hydroxyphenyl-4-hydroxybenzoate (4HPH4'HB), with the flexible hexamethylene diisocyanate (HDI). Their phase diagrams were established by means of differential scanning calorimetry, nuclear magnetic resonance and polarizing optical microscopy. Poly(4HPH4'HB/HDI) was found to display a nematic phase between 140 and 199°C; poly (BPH(4,4')D/HDI) also exhibits a mesomorphic phase, but so far the nature of this phase has not been established.     

Influence of molecular weight on some properties of liquid crystalline polyurethanes

This investigation extends our previous investigations of liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP), 2,4-tolylene diisocyanate, and poly(oxytetramethylene)diols as the flexible spacers. The influence of molecular weight of investigated polyurethanes on their properties is discussed for two series with the same content of BHBP and different lengths of flexible spacers. The polyurethanes were investigated by means of DSC, polarizing microscopy, x-ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. Morphology was studied by the SALS method. The molecular weight of polyurethanes and the length of flexible spacer influence the phase transition temperature and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc.     

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

New aliphatic–aromatic α,ω-diols containing sulfur in aliphatic chain: 4,4′-(ethane-1,2-diyl)bis(benzenethioethanol) [EBTE], 4,4′-(ethane-1,2-diyl)bis(benzenethiopropanol) [EBTP], 4,4′-(ethane-1,2-diyl)bis(benzenethiohexanol) [EBTH], 4,4′-(ethane-1,2-diyl)bis(benzenethiodecanol) [EBTD], and 4,4′-(ethane-1,2-diyl)bis(benzenethioundecanol) [EBTU] were prepared by the condensation reaction of 4,4′-(ethane-1,2-diyl)bis(benzenethiol) with suitable halogen alcohols in aqueous sodium hydroxide solution. Thermoplastic nonsegmented polyurethanes containing sulfide linkages were synthesized from these diols, and hexane-1,6-diyl diisocyanate (HDI) or 4,4′-methylenediphenyl diisocyanate (MDI) by solution and melt polymerization. The reaction was carried out at 1:1 or 1.05:1 molar ratios of isocyanate and hydroxy groups in the presence of dibutyltin dilaurate as a catalyst.The structures of the diols were determined by using elemental analysis, FTIR and ¹H NMR spectroscopy, and X-ray diffraction analysis. Thermal characteristics of the diols were determined by using differential scanning calorimetry (DSC). The polymers were studied to describe their structures and physicochemical, thermal (by DSC and thermogravimetric analysis) and tensile properties as well as Shore A/D hardness.All the polyurethanes possessed partially crystalline structures. Their melting temperatures were in the range of 94–179 °C (HDI) and 105–207 °C (MDI). The MDI-based polyurethanes showed higher tensile strengths, up to ∼50 MPa.     

Effect of the poly(oxytetramethylene)diol spacer length on some properties of liquid crystalline polyurethanes

Previous studies on liquid crystalline polyurethanes prepared from 4,4′-bis(2-hydroxyethoxy)biphenyl (BHBP) and 2,4-tolylene diisocyanate (TDI) were continued. In this article, a series of polyurethanes, which differ in the flexible spacer length and BHBP content is described. Poly(oxytetramethylene)diols of different molecular weights (PTMO, M _n = 250, 650, 1000, 2000) were used as flexible spacers. The polyurethanes were investigated by DSC, polarizing microscopy, x-ray diffractometry, and IR spectroscopy. The molecular weight distribution was determined by GPC. The morphology of the polyurethanes was investigated by the SALS method. Partial replacement of BHBP by 25–75 mol % PTMO and the flexible spacer length influence the liquid crystalline properties, the phase transition temperatures, and the range of mesophase occurrence. © 1993 John Wiley & Sons, Inc.     

聚酯-聚氨酯溶液的~(13)C-NMR弛豫研究——自旋晶格弛豫与聚氨酯分子在溶液中的局部片段运动

本文对由己二酸丁二醇酯(数均分子量为2000)、4,4′-二苯基甲烷二异氰酸酯(MDI)和扩链剂1,4-丁二醇(BDO)形成的不同分子量的聚氨酯溶液进行了~(13)C核磁共振研究。在氘代二甲基亚砜溶液中,应用JEOL FX-60Q核磁共振仪测定了聚氨酯链中不同嵌段上CH_2和CH碳的自旋晶格弛豫时间(T_1)。利用所得数据对聚氨酯分子的链运动进行了分析和讨论。     

Synthesis and characterization of polyurethanes containing cholesterol and phosphatidylcholine analogous moieties

Several new polyurethanes containing cholesterol and phosphatidylcholine analogous moieties were synthesized by addition polymerization of 2-[bis(2-hydroxyethyl)methylammonio]ethyl 5-cholesten-3β-yl phosphate ( 2 ) with diisocyanates such as hexamethylene diisocyanate (HDI), 2,4-tolylene diisocyanate (TDI), 4,4′-methylenediphenyl diisocyanate (MDI) and m-xylylene diisocyanate (XDI), respectively. They were characterized by their IR and ¹H NMR spectral data and elemental analyses. Preliminary studies suggest that these polyurethanes show the viscosity behavior of common polyelectrolytes.     

Optically-active polyurethanes containing coumarin dimer component: Synthesis,characterization, and chiral recognition ability

Optically-active polyurethanes ( 2a-2c ) were prepared by polyaddition reaction of diamide ( 1a, 1b ) and diester ( 1c ) derivatives of chiral coumarin dimer with 4,4′-diphenylmethane diisocyanate (MDI) in chloroform and methyl ethyl ketone, respectively. The inherent viscosity of the polyurethanes are between 0.13 and 0.21 dL/g in N,N-dimethylacetamide (DMAc) at 30°C. Treated silica gels were absorbed with ca. 25 wt % of the polyurethanes, and packed as chiral stationary phases for direct optical resolution of 16 racemates with aromatic groups by high-performance liquid chromatography (HPLC). Polyurethanes 2a and 2b , obtained from diamide derivatives, show efficient resolution ability to some of the racemates (α = 1.06-1.79), especially the atropic ( R5 ) and trans ( R6-R9 ) isomers. The recognition ability of the polyurethanes can be attributed to the simultaneous aromatic stacking and hydrogen-bonding interactions with racemates. © 1992 John Wiley & Sons, Inc.     

Framed aromatic polyurethanes based on an anionic macroinitiator, 4,4'-diphenylmethane diisocyanate,and 4,4'-dihydroxy-2,2-diphenylpropane: Synthesis and characterization

Polyurethanes composed of aromatic components are synthesized using the catalytic effect of potassium alcoholates on the reaction of urethane formation occurring with participation of 4,4'-dihydroxy-2,2-diphenylpropane, 4,4'-diphenylmethane diisocyanate, and polyisocyanate, which is a mixture of 4,4'-diphenylmethane diisocyanate and its branched derivatives. In the case of 4,4'-diphenylmethane diisocyanate, segmented polyurethanes with the predetermined length of the rigid block are formed, while the use of polyisocyanate gives rise to framed aromatic polyurethanes. The use of macroinitiators as carriers of potassium alcoholate groups does not cause microphase separation of flexible and rigid segments.     

聚酯-聚氨酯溶液的13C-NMR弛豫研究——自旋晶格弛豫与聚氨酯分子在溶液中的局部片段运动

 本文对由己二酸丁二醇酯(数均分子量为2000)、4,4′-二苯基甲烷二异氰酸酯(MDI)和扩链剂1,4-丁二醇(BDO)形成的不同分子量的聚氨酯溶液进行了¹³C核磁共振研究。在氘代二甲基亚砜溶液中,应用JEOL FX-60Q核磁共振仪测定了聚氨酯链中不同嵌段上CH₂和CH碳的自旋晶格弛豫时间(T₁)。利用所得数据对聚氨酯分子的链运动进行了分析和讨论。     

Hydrolysis of linear polyurethanes and model monocarbamates

Alkaline hydrolysis of model carbamates, polyurethanes, and poly(urethane-ureas) has been investigated. The model carbamates were based upon phenyl, benzyl, and cyclohexyl isocyanates. The polyurethanes and poly(urethane-ureas) were prepared from tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI) and a poly(oxyethylene)glycol of 6000 molecular weight. Pseudo-first-order rate constants of hydrolysis were obtained in aqueous pyridine solution at 110°C, and second-order rate constants were obtained in aqueous KOH solution for the model biscarbamates. Pseudo-first-order rate constants of hydrolysis were obtained in alcoholic KOH solution for the polyurethanes and poly(urethane-ureas). The hydrolysis of the model carbamates showed that the stability increased in the following manner: phenyl < benzyl < cyclohexyl. The pseudo-first-order rate constants were dependent upon the pK_b of the corresponding amines. The hydrolysis of the polyurethanes and poly(urethane-ureas) showed that the stability increased in the following manner: aromatic < aralkyl < cycloaliphatic. It was shown that polyurethanes are more susceptible to alkaline hydrolysis than to acidic hydrolysis.     

Synthesis and thermal crosslinking of oxazolidine‐functionalized polyurethanes

A new oxazolidine derivative was obtained from phenol, 2‐amino‐2‐methylpropane‐1,3‐diol and paraformaldehyde. The reaction of this novel oxazolidine diol with phenylisocyanate lead to a urethane model compound which can be polymerized thermally by oxazolidine ring opening to give a Mannich bridge structure. Linear segmented polyurethanes were prepared by reaction of different ratios of oxazolidine diol and commercial polyethylenglycol (M_w ～ 400) with 4,4′‐methylenbis (cyclohexylisocyanate) (HMDI, 90% isomers mixture). The polyurethanes were thermally characterized and crosslinked by oxazolidine ring opening to obtain materials which showed improved thermal stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4965–4973, 2007