Synthesis,characterization and thermal dissociation of 2‐butoxyethanol‐blocked diisocyanates and their use in the synthesis of isocyanate‐terminated prepolymers

A series of blocked diisocyanates has been synthesized from toluene diisocyante (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4′‐diphenylmethane diisocyanate (MDI) and 2‐butoxyethanol. The synthesis of blocked diisocyanate adducts was confirmed by Fourier transform infrared, ¹H NMR, electron impact mass spectrometry and nitrogen analysis. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and carbon dioxide evolution were used to determine the minimum de‐blocking temperatures. De‐blocking temperatures determined by these three techniques were found to be in the order DSC > TGA > CO₂ evolution. The effect of different metal catalysts on thermal de‐blocking reaction of the blocked diisocyanates was studied, using the carbon dioxide evolution method. It was found that iron(III) oxide has the maximum catalytic activity on de‐blocking. The solubility of the blocked diisocyanate adducts was determined in different solvents. The study revealed that at 30 °C blocked IPDI and HDI adducts show better solubility than adducts based on TDI and MDI. Isocyanate‐terminated prepolymers of blocked diisocyanates and hydroxyl‐terminated polybutadiene (HTPB) were prepared. The storage stability and gelation times of the prepolymers were studied. Results showed that all the diisocyanate‐HTPB compositions are stable at 50 °C for more than three months. However, aliphatic diisocyanate‐HTPB compositions require greater gelation time than aromatic diisocyanate‐HTPB compositions at their respective de‐blocking temperatures. Copyright © 2007 Society of Chemical Industry     

Synthesis and dissociation of amine‐blocked diisocyanates and polyurethane prepolymers

Substituted N‐methylanilines are shown to act as blocking agents for toluenediisocyanate. N‐methylaniline‐, N‐methyl‐p‐anisidine‐ and N‐methyl‐p‐nitroaniline‐blocked toluene diisocyanates have been prepared and characterized by FTIR, ¹H NMR and ¹³C NMR spectroscopies, and nitrogen content analysis. A new method for determining the minimum deblocking temperature of the blocked isocyanate is described. The method has advantages in that it can be used to find the minimum deblocking temperature of even non‐volatile blocking agents. The minimum deblocking temperature of the adducts is found to be in the following order: N‐methyl‐p‐anisidine–TDI adduct < N‐methyaniline–TDI adduct < N‐methyl‐p‐nitroaniline–TDI adduct. The anilines exhibit the same trend when they block a polyurethane prepolymer prepared using polypropylene glycol of molecular weight 2000 g mol^?1 and tolylene‐2,6‐diisocyanate. The deblocking temperatures are lower in the case of blocked prepolymers than in the blocked adducts. The blocked adducts and prepolymers are reacted with pyromellitic dianhydride (PMDA) in dimethylpropylene urea (DMPU) and the evolution of carbon dioxide is monitored to study the completion of imidization. The reaction time is in accordance with the deblocking ability of the adducts. The regeneration of the blocking agent is confirmed by gas chromatography. © 2002 Society of Chemical Industry     

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     

Ozone Degradation Study of Novel Chain Extended Energetic Polymers Containing Carbon‐Carbon Double Bonds

A range of chemically modified energetic polymers has been synthesized. The structural modification involves the incorporation of a double bond into the polymeric binder which allows subsequent degradation of the material by ozonolysis thus providing an environmentally safe method for the disposal of munitions. This was achieved by reacting the energetic prepolymer, poly‐NIMMO, with a range of unsaturated diisocyanates where the double bond was incorporated into the cross‐linking i.e. “curing” agent. Firstly, poly‐NIMMO and cis‐1,4‐but‐2‐ene diol were reacted with hexamethylene diisocyanate. Secondly, three unsaturated diisocyanates (two novel) were prepared in situ from their corresponding diacyl azides and reacted with poly‐NIMMO. The three diisocyanates prepared were 1,4‐diphenoxy‐trans‐2‐butene‐diisocyanate, phenylene diacrylic di‐isocyanate, and trans‐2‐butene‐1,4‐diisocyanate. The latter has been reported previously^(1,2) although never isolated and characterized; however, this has been achieved successfully in this study. GPC of the chain extended polymers prepared by both methods showed the expected increase in molecular weight distribution. A corresponding decrease following ozonolysis occurred particularly with the polymers prepared from 1,4‐diphenoxy‐trans‐2‐butene‐diisocyanate and phenylene diacrylic diisocyanate.     

Polyurethane powder coatings crosslinked with allophanate structures containing polyisocyanates

With the use of alicyclic diisocyanates, aliphatic alcohols and dibutyltin dilaurate as well as triethylamine as a catalysts internally‐blocked polyisocyanate crosslinkers which contained allophanate bonds were synthesized. The chemical structure of those compounds were characterized by IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. Their molecular weight distribution (MWD) parameters were determined by gel permeation chromatography (GPC). Those blocked polyisocyanates were used for the production of ecological lacquer compositions and coatings. The unblocking and curing reactions were investigated on the DTA, TG, and DSC thermograms. The resulting powder lacquers exhibit an excellent appearance; they are transparent, smooth, and nonyellowing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of poly(urethane‐ester)s based on calcium salt of mono(hydroxybutyl)phthalate

Calcium‐containing poly(urethane‐ester)s (PUEs) were prepared by reacting diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and hydroxyl‐terminated poly(1,4‐butylene glutarate) [HTPBG₁₀₀₀], using di‐n‐butyltin‐dilaurate as catalyst. About six calcium‐containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:HTPBG₁₀₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4, and 1:3:4. Two blank PUEs were synthesized by the reaction of HTPBG₁₀₀₀ with diisocyanate (HMDI or TDI). The polymers were characterized by IR, ¹H NMR, Solid state ¹³C‐CP‐MAS NMR, TGA, DSC, XRD, solubility, and viscosity studies. The T_g value of PUEs increases with increase in the calcium content and decreases with increase in soft segment content. The viscosity of the calcium‐containing PUEs increases with increase in the soft segment content and decreases with increase in the calcium content. X‐ray diffraction patterns of the polymers show that the HMDI‐based polymers are partially crystalline and TDI‐based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium‐containing PUEs based on HMDI shows that with increase in the calcium content of polymer, modulus (g′ and g″) increases at any given temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1720–1727, 2006     

Synthesis and characterization of novel polyurethanes based on N1,N4‐bis[(4‐hydroxyphenyl)methylene]succinohydrazide hard segment

This article deals with the synthesis and characterization of novel polyurethanes (PUs) by the reaction between two aromatic diisocyanates (4,4′‐diphenylmethane diisocyanate and tolylene 2,4‐diisocyanate) and two aliphatic diisocyanates (isophorone diisocyanate and hexamethylene diisocyanate) with N¹,N⁴‐bis[(4‐hydroxyphenyl)methylene]succinohydrazide, which acted as hard segment. UV–vis, FTIR, ¹H NMR, ¹³C NMR, and DSC/TGA analytical technique has been used to determine the structural characterization and thermal properties of the hard segmented PUs. X‐ray diffraction revealed that PUs contained semicrystalline and amorphous regions that varied depending upon the nature of the backbone structures. PUs were soluble in polar aprotic solvents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization of novel dihydrazide containing polyurethanes based on N1,N2‐bis[(4‐hydroxyphenyl)methylene]ethanedihydrazide and various diisocyanates

Four novel types of polyurethanes (PUs) were prepared from N¹,N²‐bis[(4‐hydroxyphenyl)methylene]ethanedihydrazide with two aromatic diisocyanates (4,4′‐diphenylmethane diisocyanate and tolylene 2,4‐diisocyanate) and two aliphatic diisocyanates (isophorone diisocyanate and hexamethylene diisocyanate). The chemical structure of both diol and PUs was confirmed by UV–vis, fluoroscence, FTIR, ¹H NMR, and ¹³C NMR spectral data. DSC data show that PUs have multiple endotherm peak. X‐ray diffraction revealed that the PUs contained semicrystalline and amorphous regions that varied with the nature of the backbone structures. PUs were soluble in polar aprotic solvents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(ether urethane)s from aromatic diisocyanates based on lignin‐derived phenolic acids

A series of new bio‐based aromatic diisocyanates, namely bis(4‐isocyanato‐2‐methoxyphenoxy)alkane and bis(4‐isocyanato‐2,6‐dimethoxyphenoxy)alkane, were synthesized starting from lignin‐derived phenolic acids, namely vanillic acid and syringic acid, via the Curtius rearrangement. The diisocyanates were employed to synthesize poly(ether urethane)s by reacting them with potentially bio‐based aliphatic diols, namely 1,10‐decanediol and 1,12‐dodecanediol. The chemical structures of diisocyanates and poly(ether urethane)s were confirmed using Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopy. Inherent viscosities and number‐average molecular weights of the poly(ether urethane)s were in the ranges 0.58–0.68 dL g^?1 and 32 100–58 500 g mol^?1, respectively, indicating the formation of reasonably high molecular weight polymers. The poly(ether urethane)s exhibited 10% weight loss in the temperature range 304–308 °C. The glass transition temperatures of the poly(ether urethane)s were in the range 49–74 °C and were dependent both on the number of methylene units in the diols and on the number of methoxy substituents on the aromatic rings of the diisocyanate component. © 2017 Society of Chemical Industry     

Synthesis,characterization, and properties of a linear poly(ester‐amide) containing ethylene glycol lactate sequences

A novel linear lactic acid‐based poly(ester‐amide) (LLPEA) was prepared via polyaddition of toluene‐2,4‐diisocyanate (TDI) with ethylene lactate succinic half‐ester diacid (ELDA), which contained ethylene glycol lactate sequences and derived from lactic acid. LLPEA was characterized with FTIR, GPC, DSC, TGA, and XRD. The weight average molecular weight and its polydisperse index of LLPEA could be 1.0 × 10⁵ and 2.0, respectively. DSC and XRD analysis showed that LLPEA was a semicrystalline polymer. The glass transition temperature, melting temperature, and the thermal decomposition temperature (50 wt %) of LLPEA were ?2, 94, and ～415°C, respectively. The contact angle determination indicated that LLPEA was a hydrophilic polymer. It was found that the yield strength, tensile strength, and elastic module of LLPEA could be 8.8, 9.6, and 176 MPa, respectively. In addition, the weight loss percentage of LLPEA was 2.5% after 157‐days immersion in activated sludge at ambient temperature, which suggested that LLPEA was degradable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3805–3808, 2006     

Preparation and characterization of novel polyurethanes containing 4,4′‐{oxy‐1,4‐diphenyl bis(nitromethylidine)}diphenol schiff base diol

Four novel segmented polyurethanes (PUs) based on4,4′‐{oxy‐1,4‐diphenyl bis(nitromethylidine)}diphenol (ODBNMD) diol with different diisocyanates such as 4,4′‐diphenylmethane diisocyanate, toluene 2,4‐diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate have been prepared by solution method. The structures of ODBNMD and PUs have been confirmed by Fourier transform infrared (FTIR), nuclear magnetic resonance (¹H‐NMR and ¹³C‐NMR), UV‐visible, and fluorescence spectroscopies. The segmented PUs were further characterized by thermogravimetry (TGA), differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction. FTIR confirmed hydrogen bonding interactions, whereas TGA and DSC suggested that introduction of aromatic/phenyl ring in the main chain considerably increased the thermal stability. POLYM. ENG. SCI., 54:24–32, 2014. © 2013 Society of Plastics Engineers     

Chain‐linked lactic acid polymers by benzene diisocyanate

Chain‐linked lactic acid polymers with high molecular weight were synthesized by two‐step polymerization method, including polycondensation and chain extending reactions. The effects of chain extender toluene diisocyanate (TDI) on the chain‐linked lactic acid polymers were studied. The polymers obtained were characterized by gel permeation chromatography, fourier transform infrared spectroscopy, ¹H NMR, and differential scanning calorimeter. Reactions between 1,4‐butanediol and lactic acid oligomers led to hydroxyl‐terminated prepolymer, which provided significant increase of molecular weight in the chain extending reaction. In addition, the glass transition temperature (T_g) and the melting temperature (T_m) were increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1045–1049, 2006     

Synthesis and thermal dissociation of phenol- and naphthol-blocked diisocyanates

Phenol-, 2-naphthol-, and 1-nitroso-2-naphthol-blocked toluene diisocyanate (TDI) and isophorone diisocyanate (IPDI) adducts and their polymers with PPG-1000 were prepared and characterized by nitrogen estimation, IR, and ¹H-NMR spectroscopy. The absence of an IR absorption band at 2270 cm^?1 confirmed the completion of the reaction between the isocyanate and the blocking agents, whereas the presence of a band at 1075–1150 cm^?1 confirmed the formation of poly(ether urethanes). The deblocking temperatures were determined by the use of DSC and by the carbon dioxide evolution methods. The thermal stabilities of the 2-naphthol-blocked diisocyanates were less than the phenol-blocked diisocyanates. Dissociation temperature was also reduced by the nitroso group in the blocking agent. Mass spectral data confirmed the product analysis. The solubility of the adducts were determined in the different polyols. Adducts based on IPDI showed better solubility than did those based on TDI. © 1994 John Wiley & Sons, Inc.     

Microwave‐assisted and classical heating polycondensation reaction of bis(p‐amido benzoic acid)‐N‐trimellitylimido‐L‐leucine with diisocyanates as a new method for preparation of optically active poly(amide imide)s

A new class of optically active poly(amide imide)s were synthesized via direct polycondensation reaction of diisocyanates with a chiral diacid monomer. The step‐growth polymerization reactions of monomer bis(p‐amido benzoic acid)‐N‐trimellitylimido‐L‐leucine (BPABTL) (5) as a diacid monomer with 4,4′‐methylene bis(4‐phenylisocyanate) (MDI) (6) was performed under microwave irradiation, solution polymerization under gradual heating and reflux condition in the presence of pyridine (Py), dibuthyltin dilurate (DBTDL), and triethylamine (TEA) as a catalyst and without a catalyst, respectively. The optimized polymerization conditions according to solvent and catalyst for each method were performed with tolylene‐2,4‐diisocyanate (TDI) (7), hexamethylene diisocyanate (HDI) (8), and isophorone diisocyanate (IPDI) (9) to produce optically active poly(amide imide)s by the diisocyanate route. The resulting polymers have inherent viscosities in the range of 0.09–1.10 dL/g. These polymers are optically active, thermally stable, and soluble in amide type solvents. All of the above polymers were fully characterized by IR spectroscopy, ¹H NMR spectroscopy, elemental analyses, specific rotation, and thermal analyses methods. Some structural characterization and physical properties of this new optically active poly(amide imide)s are reported. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1647–1659, 2004     

Synthesis and characterization of novel polyureas based on benzimidazoline‐2‐one and benzimidazoline‐2‐thione hard segments

Six novel polyureas were prepared from benzimidazolin‐2‐one and benzimidazolin‐2‐thione, which acted as hard segments, with two aromatic diisocyanates (4,4′‐diphenylmethane diisocyanate and toluene 2,4‐diisocyanate) and one aliphatic diisocyanate (hexamethylene diisocyanate). The polymers that formed were fully characterized with Fourier transform infrared spectroscopy, ¹³C‐NMR cross‐polarization/magic‐angle spinning, differential scanning calorimetry, and thermogravimetry. X‐ray diffraction revealed that the polymers contained crystalline and amorphous regions that varied with the nature of the backbone structures. All the polyureas were insoluble in common organic solvents, and this made it difficult to investigate their solution properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 576–583, 2006     

Synthesis and characterization of a novel liquid crystalline star‐shaped polymer based on α‐CD core via ATRP

Well‐defined side‐chain liquid crystalline star‐shaped polymers were synthesized with a combination of the “core‐first” method and atom transfer radical polymerization (ATRP). Firstly, the functionalized macroinitiator based on the α‐Cyclodextrins (α‐CD) bearing functional bromide groups was synthesized, confirmed by ¹H‐NMR, MALDI‐TOF, and FTIR analysis. Secondly, the side‐chain liquid crystalline arms poly[6‐(4‐methoxy‐4‐oxy‐azobenzene) hexyl methacrylate] (PMMAzo) were prepared by ATRP. The characterization of the star polymers were performed with ¹H‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). It was found that the liquid crystalline behavior of the star polymer α‐CD‐PMMAzo_n was similar to that of the linear homopolymer. The phase‐transition temperatures from the smectic to nematic phase and from the nematic to isotropic phase increased as the molecular weight increased for most of these samples. All star‐shaped polymers show photoresponsive isomerization under the irradiation with Ultraviolet light. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, and hydrolytic degradation of biodegradable poly(ether ester)‐urethane copolymers based on ε‐caprolactone and poly(ethylene glycol)

In this article, a new kind of biodegradable poly(ε‐caprolactone)‐poly(ethylene glycol)‐poly(ε‐caprolactone)‐based polyurethane (PCEC‐U) copolymers were successfully synthesized by melt‐polycondensation method from ε‐caprolactone (ε‐CL), poly(ethylene glycol) (PEG), 1,4‐butanediol (BD), and isophorone diisocyanate (IPDI). The obtained copolymers were characterized by ¹H‐nuclear magnetic resonance (¹H‐NMR), FTIR, and gel permeation chromatography (GPC). Thermal properties of PCEC‐U copolymers were studied by DSC and TGA/DTG under nitrogen atmosphere. Water absorption and hydrolytic degradation behavior of these copolymers were also investigated. Hydrolytic degradation behavior was studied by weight loss method. ¹H‐NMR and GPC were also used to characterize the hydrolytic degradation behavior of PCEC‐U copolymers. The molecular weight of PCL block and PEG block in soft segment and the content of hard segment strongly affected the water absorption and hydrolytic degradation behavior of PCEC‐U copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Starch‐g‐polycaprolactone copolymerization using diisocyanate intermediates and thermal characteristics of the copolymers

Starch‐g‐polycaprolactone copolymers were prepared by two‐step reactions. The diisocyanate‐terminated polycaprolactone (NCO–PCL) was prepared by introducing NCO on both hydroxyl ends of PCL using diisocyanates (DI) at a molar ratio between PCL and DI of 2:3. Then, the NCO–PCL was grafted onto corn starch at a weight ratio between starch and NCO–PCL of 2:1. The chemical structure of NCO–PCL and the starch‐g‐PCL copolymers were confirmed by using FTIR and ¹³C‐NMR spectrometers, and then the thermal characteristics of the copolymers were investigated by DSC and TGA. By introducing NCO to PCL (M_n : 1250), the melting temperature (T_m ) was reduced from 58 to 45°C. In addition, by grafting the NCO–PCL (35–38%) prepared with 2,4‐tolylene diisocyanate (TDI) or 4,4‐diphenylmethane diisocyanate (MDI) onto starch, the glass transition temperatures (T_g 's) of the copolymers were both 238°C. With hexamethylene diisocyanate (HDI), however, T_g was found to be 195°C. The initial thermal degradation temperature of the starch‐g‐PCL copolymers were higher than that of unreacted starch (320 versus 290°C) when MDI was used, whereas the copolymers prepared with TDI or HDI underwent little change. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 986–993, 2000     

Synthesis and characterization of diethylene glycol monobutyl ether—Blocked diisocyanate crosslinkers

Typically blocked isocyanate systems are used to obtain the performance of two component polyurethane (PU) system in a one-component mixture. In this study four types of isocyanates namely, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) were blocked with diethylene glycol monobutyl ether (DEGMBE). Elimination of the isocyanate groups and the formation of urethane bonds were studied by FTIR spectroscopy and titration methods. Thermal dissociation of blocked diisocyanates was analyzed by DSC and TGA techniques.     

An NMR Comparison of the Whole Lignin from Milled Wood,MWL, and REL Dissolved by the DMSO/NMI Procedure

Abstract

Lignins isolated from pine milled wood, milled wood lignin (MWL), and residual enzyme lignin (REL) were compared using modified thioacidolysis, modified DFRC, gel permeation chromatography (GPC), two‐dimensional Heteronuclear Multiple Quantum Coherence (HMQC) NMR, and quantitative ¹³C NMR. Dissolution of the lignin for solution‐state NMR was accomplished by utilizing the recently reported DMSO/N‐methylimidazole/acetic anhydride solvent system. Contrary to previous reports, comparison of the lignin preparations by thioacidolysis indicated that REL was more structurally similar to the lignin in the milled wood and Wiley wood meal than MWL. Total monomer yields indicated that the MWL was lower in β‐aryl ether content than the other preparations, and this was verified by quantitative ¹³C NMR. NMR analysis indicated that the inter‐unit linkages present in all the lignin preparations are consistent with the present knowledge about lignin biosynthesis. The contribution of minor end group structures in the MWL are further decreased in the milled wood, indicating that they are preferentially isolated as low molecular weight material, possibly generated during the milling process. All other structural moieties were similar in all preparations. GPC data indicated that the milled wood and REL both contain a portion of lignin with a molecular weight of 55,000 g/mol. Data indicate that the inefficiency of the DFRC method may be related to molecular mobility or accessibility in higher molecular weight portions of the lignin polymer.