Effects of Temperature on Morphology and Properties of Films Prepared from Poly(ester‐urethane) and Nitrochitosan

Summary: Novel elastic materials were prepared by mixing semicrystalline polyester‐based polyurethane (PU) synthesized at 100 °C with nitrochitosan (NCH) and 1,1,1‐tris(hydroxylmethyl)propane as crosslinker, and then by curing the mixture at 18, 25, 40, 60, and 80 °C. The effects of cure temperature on the crystallization behavior, miscibility, and mechanical properties of the PUNCH materials were studied by attenuated total reflection Fourier transform IR, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, X‐ray photoelectron spectroscopy, and tensile test. The results indicated that the crystalline structure of the blend films was more easily interrupted as the cure temperature increased, leading to a decrease of the degree of crystallinity. With an increase of cure temperature, the blend films exhibited high crosslinking density and tensile strength, and the phase separation between hard and soft segments of PU enhanced, resulting in a decrease in the glass transition temperature (T_g) of soft segment. Interestingly, the composite films keeping high elongation at break possessed tensile strength higher than that of the native poly(ester‐urethane). The enhanced mechanical properties of the blend films can be attributed to the relatively dense crosslinking network and strong intermolecular hydrogen bonding between NCH and PU. Therefore, this study not only provided a novel way by adding NCH into PU matrix to prepare elastic materials, which would remain functional characteristic of chitosan, but also expanded the application field of chitosan.

The cure temperature dependence of the tensile strength and elongation at break for the PEPU‐100 and PUNCH‐100 films.     

The infulence of aromatic diols on thermotropic Poly(ester-amide)s synthesized by direct polycondensation

Thermotropic Poly(ester-amide)s containing triethyleneglycol bis(4-carboxyphenyl) ether (PEG₃), o-Tolidine (OT) and various aromatic diols such as hydroquinone (HQ) and 4,4-biphenol (BP) were synthesized by direct polycondensation with DPCP (diphenyl chlorophosphate) as direct condensation agent in the presence of pyridine and LiCl. The polymer structures were characterized by infrared spectroscopy and elemental analysis. The influence of structure, substituents and contents of various aromatic diols on the phase transitions were studied by Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy. These revealed that the structure and substituents of diols affected the mesophase while most of the synthesized polymers exhibit nematic mesophase. Addition of HQ decreased the melting temperature of the polymers, but, in contrast to others diols, did not affect thermal resistance.     

Carbohydrate‐based poly(ester‐urethane)s: A comparative study regarding cyclic alditols extenders and polymerization procedures

A set of segmented poly(ester‐urethane)s were prepared from diisocyanates HDI or MDI and using 1,4‐butanediol and D ‐glucose‐derived cyclic diols (1,4 : 3,6‐dianhydro‐D ‐glucitol (isosorbide) or 2,4;3,5‐di‐O‐methylidene‐D ‐glucitol (gludioxol) or mixtures of them) as extenders. Hydroxyl end‐capped polycaprolactone with a molecular weight of 3000 g·mol^?1 was used as soft segment. Two polymerization methods, in solution and in bulk, were applied for the synthesis of these poly(ester‐urethane)s. The influence of the preparation procedure and composition in cyclic extender on synthesis results, structure, and properties of the novel poly(ester‐urethane)s was comparatively evaluated and discussed. The effect of replacement of 1,4‐butanediol by isosorbide or gludioxol on hydrodegradability was also assessed; the hydrolysis rate increased noticeably with the presence of glucitol derived units, although degradation of the polymers took place essentially by hydrolysis of the polyester soft segment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ternary‐phase poly(ester‐urethane)/elastomer/filler composites

Impact‐modified and reinforced composites, consisting of biodegradable poly(ester‐urethane) (PEU), poly(L ‐lactic acid‐co‐ϵ‐caprolactone‐urethane) elastomer, and various organic and inorganic fillers, were prepared by melt blending, and their properties were investigated. The impact strength increased with elastomer addition, and the addition of particulate or fibrous fillers as a third component increased the stiffness. Therefore, the balance between the impact strength and stiffness of the amorphous PEU was significantly improved. Composites with elastomer and 15 wt % particulate fillers, that is, wollastonite, Aktisil, and talc, showed excellent impact strength. However, effective impact modification was lost in highly constrained systems. Dynamic mechanical thermal analysis confirmed the phase separation of elastomer and showed a marked increase in the glass‐transition temperature for the PEU matrix in binary blends with wollastonite, talc, and glass fiber. Scanning electron microscopy studies showed good adhesion of the components. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1531–1539, 2001     

Synthesis,characterization and evaluation of novel methoxypolyethyleneglycol‐ grafted‐ poly(ester‐urethane)s for controlled release of repaglinide

Novel biodegradable aliphatic poly(ester‐urethane)s (PEUs) based on polycaprolactone diol (PCL) and methoxypolyethyleneglycol grafted onto trimethylol propane (mPEG‐g‐TMP) were synthesized by solution polymerization technique and characterized using a variety of techniques. Microspheres ranging in size from 7 to 25 μm were prepared by the solvent evaporation technique and loaded with repaglinide up to 71 to 96%. Increasing molar ratios of mPEG‐g‐TMP propane with respect to polycaprolactone diol gave increase in particle size along with increase in % encapsulation efficiency. Surface morphology and spherical nature of the microspheres were confirmed by scanning electron microscopy (SEM). The release of repaglinide varied, depending upon the molar ratios of mPEG‐g‐TMP moieties with respect to PCL. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Effect of structure modification on rheological properties of biodegradable poly(ester‐urethane)

Biodegradable lactic acid based poly(ester‐urethanes) (PEU) were polymerized and their structure and rheological properties were characterized. The polymerization process comprised two steps: lactic acid monomer was oligomerized to low molecular weight prepolymer, and this was then linked to high molecular weight PEU with chain extender, 1,6‐hexamethylene diisocyanate. The properties of PEU were modified by varying the amount of chain extender from 1.05:1 to 1.35:1 (NCO/OH ratio). The modification was mostly seen in the molecular weight distribution of the polymers, which was broadened from 2.2 to 3.5 as the amount of chain extender was increased. The telechelicity of the prepolymer was found to play an essential role in successful linking of the prepolymer units. In addition, the rheological properties of poly(ester‐urethane) were determined with capillary and dynamic rheometers. All PEU samples were pseudoplastic and broadening of their molecular weight distribution was accompanied by increased viscosity and complex viscosity at low shear rates and increased shear thinning. The temperature dependency of the measurement was pronounced. Rheological measurements also showed that PEU starts to degrade at 100°C and further rise in temperature increases the rate of degradation significantly.     

Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)

Poly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T_g) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T_g and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006     

Optically active poly(ester‐amide)s: synthesis and characterization

The synthesis and characterization of a new series of chiral poly(ester‐amide)s are reported. They were prepared by the simple reaction of diacid chlorides with biphenolic azo chromophores and optically active dihydroxy compound (isosorbide) in dimethyl acetamide at 100 °C. The polymers containing isosorbide units were optically active. The polymers showed T_g between 100 and 190 °C and were stable up to 400 °C. These poly(ester‐amide)s showed a positive solvatochromism in UV–visible absorption spectra. Second harmonic generation activities were measured by the powder method. © 2001 Society of Chemical Industry     

Novel amphiphilic poly(ester‐urethane)s based on poly[(R)‐3‐hydroxyalkanoate]: synthesis,biocompatibility and aggregation in aqueous solution

BACKGROUND: The aim of this work was to develop polyhydroxyalkanoates (PHAs) for blood contact applications, and to study their self‐assembly behavior in aqueous solution when the PHAs are incorporated with hydrophilic segments. To do this, poly(ester‐urethane) (PU) multiblock copolymers were prepared from hydroxyl‐terminated poly(ethylene glycol) (PEG) and hydroxylated poly[(R)‐3‐hydroxyalkanoate] (PHA‐diol) using 1,6‐hexamethylene diisocyanate as a coupling reagent. The PEG segment functions as a soft, hydrophilic and crystalline portion and the poly[(R)‐3‐hydroxybutyrate] segment behaves as a hard, hydrophobic and crystalline portion. In another series of PU multiblock copolymers, crystalline PEG and completely amorphous poly[((R)‐3‐hydroxybutyrate)‐co‐(4‐hydroxybutyrate)] behaved as hydrophobic and hydrophilic segments, respectively. RESULTS: The formation of a PU series of block copolymers was confirmed by NMR, gel permeation chromatography and infrared analyses. The thermal properties showed enhanced thermal stability with semi‐crystalline morphology via incorporation of PEG. Interestingly, the changes of the hydrophilic/hydrophobic ratio led to different formations in oil‐in‐water emulsion and surface patterning behavior when cast into films. Blood compatibility was also increased with increasing PEG content compared with PHA‐only polymers. CONCLUSION: For the first time, PHA‐based PU block copolymers have been investigated in terms of their blood compatibility and aggregation behavior in aqueous solution. Novel amphiphilic materials with good biocompatibility for possible blood contact applications with hydrogel properties were obtained. Copyright © 2008 Society of Chemical Industry     

Morphology of Poly(1‐olefin)s from Poly(1‐octene) to Poly(1‐eicosene)

Poly(1‐olefin)s from poly(1‐octene) to poly(1‐eicosene) synthesized by isospecific metallocene catalysts are investigated by wide and small angle X‐ray scattering (WAXS and SAXS) and by atomic force microscopy. The crystal structure of poly(1‐eicosene) is determined and the scattering peaks are assigned. Additionally, 1‐dodecene is polymerized using a constrained geometry catalyst and the obtained atactic polymer is compared with the isotactic species. Using this sample it is possible to determine the amorphous halo in the small angle regime at room temperature. For poly(1‐decene), poly(1‐dodecene), and poly(1‐hexadecene) a long period can be measured by small angle X‐ray scattering which coincides with the results from AFM measurements.     

Monitoring of the Synthesis of Hyperbranched Poly(urea‐urethane)s by Real‐Time Attenuated Total Reflection (ATR)‐FT‐IR Spectroscopy

Summary: The reaction of 2,4‐TDI and DEA, as an A₂ + B^*B₂ polymerization system towards hyperbranched HPUs was followed using in situ ATR‐FT‐IR spectroscopy. The decrease in intensity of the NCO absorption band of the reactive isocyanate group of 2,4‐TDI along with the formation and growth of the new characteristic bands of urethane and urea groups were detected. The reactivity difference of both NH and OH groups towards the NCO group at low temperatures was proven. The rate of the reaction was found to be affected by changing the temperature, the rate of addition of the B^*B₂ monomer and the type of solvent. Moreover, the increase of the carbonyl vibration and the amide II bands of urea was very obvious during the addition of the stopper DEA. Thus, it was possible to verify the individual reaction steps of this complex polyreaction and to correlate these with the structural development of the resulting macromolecules.

Characteristic vibration bands of urethane and urea groups in the IR spectra (1 780–1 480 cm^?1) during the polymerization reaction.     

Main‐chain liquid crystalline poly(ester‐amide)s containing lithocholic acid units

A series of poly(ester‐amide)s based on an ester group containing lithocholic acid derivative [3‐(3‐carboxypropionyl) lithocholic acid] and several aromatic diamines (naphthalene‐1,5‐diamine, 4,4′‐diaminodiphenyl ether, 4,4′‐diaminodiphenylmethane, 4,4′‐diaminodiphenylsulfone, benzidine, m‐phenylenediamine, p‐phenylenediamine, and tetraphenylthiophene diamine) was synthesized and characterized by solubility, viscosity, IR, differential scanning calorimetry, thermogravimetric analysis, and optical microscopy. The polymers were soluble in most of the organic solvents and had inherent viscosities in the range of 0.21–0.38 dL/g. All the polymers exhibited a nematic mesophase, but only on shearing. Thermal transitions due to mesophase formation were not seen in the differential scanning calorimetry thermograms. However, the liquid crystalline character of the polymers was observed under an optical microscope. Thermogravimetric analyses revealed the maximum decomposition temperature was 390–435°C for these polymers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 73–80, 2006     

Light‐Stability of Poly(dialkylstannane)s

This study deals with the stability of poly(dialkylstannane)s in solution and in the bulk, in particular under exposure to light, which was found to cause degradation more severely than water or oxygen. Decomposition of the poly(dialkylstannanes) under argon atmosphere in solution proceeded by an unzipping mechanism, most likely initiated by scission of a Sn? Sn bond. While solvents and additives influenced polystannane degradation, the length of the alkyl groups was not particularly relevant, indicating that steric effects played a minor role in this process. In unreactive solvents, the polystannanes were the least stable and cyclic oligostannanes formed as decomposition products. Polystannanes in solution were found to be most stable in dichloromethane or styrene, which gave rise to the formation of Bu₂(ClCH₂)SnCl or poly(styrene), indicating that the polystannanes acted in the latter case as a photoinitiator. Addition of radical scavengers and selected dyes improved the stability of polystannanes toward light. Exposure of bulk poly(dialkylstannane)s to ambient caused the formation of (oligo‐)alkyltin‐oxides.

     

New Poly(azomethine‐urethane)s including melamine derivatives in the main chain: Synthesis and thermal characterization

Up to date, only a few kinds of poly (azomethine‐urethane)s (PAMUs) derived from aromatic hydroxy compounds were obtained and studied with thermal degradation steps. Novel PAMUs were prepared using the hydroxy‐functionalized Schiff bases derived from melamine and toluene‐2,4‐diisocyanate. Schiff base prepolymers were synthesized by the condensation reaction of melamine with 4‐hydroxybenzaldehyde and 2‐hydroxy‐1‐naphtaldehyde. Characterization was made by UV–Vis, FTIR, NMR, and SEC techniques. Thermal characterizations of the novel PAMUs were carried out by TG‐DTA and DSC techniques. Thermal decomposition steps at various temperatures were also clarified and the physical changes of the synthesized PAMUs with exposing to the thermal degradation steps were displayed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of degradable copoly(ester–amide)s: Poly(trans‐4‐hydroxy‐L‐proline‐co‐ε‐caprolactam)

Novel copolyesteramides were synthesized by reacting trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) with ε‐caprolactam (CLM) in the presence of stannous octoate [Sn(II) Oct.] as a catalyst. Various techniques, including ¹H‐NMR, IR, DSC, and viscosity, were used to elucidate structural characteristics and thermal properties of the resulting copolymers. Data showed that the optimal reaction condition for the synthesis of the copolymers was obtained by using 3 wt % Sn(II) Oct. at 170°C for 24 h. The DSC analysis demonstrated amorphous structure for most of the copolymers. The glass‐transition temperature of the copolymers shifts to a higher temperature with increasing Hpr/CLM molar ratio. In vitro degradation of these poly(N‐CBz‐Hpr‐co‐CLM)s was evaluated by weight loss measurements. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1615–1621, 2002     

Functionalization of poly(ester‐urethane) surface by radiation‐induced grafting of N‐isopropylacrylamide using conventional and reversible addition–fragmentation chain transfer‐mediated methods

The functionalization of poly(ester‐urethane) (PUR) surface was conducted using radiation‐induced grafting. A thermosensitive layer constructed from N‐isopropylacrylamide (NIPAAm) was introduced onto a polyurethane film and characterized using attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopies and contact angle measurements. Size exclusion chromatography was used to analyse the PUR‐graft‐PNIPAAm copolymers and homopolymers formed in solution. Additionally, reversible addition–fragmentation chain transfer (RAFT) polymerization was performed in order to obtain PNIPAAm‐grafted surfaces with well‐defined properties. Atomic force microscopy was used to evaluate the surfaces synthesized via conventional and RAFT‐mediated grafting methods. The results of various techniques confirmed the successful grafting of NIPAAm from PUR film. © 2015 Society of Chemical Industry     

Synthesis and characterization of a novel poly(ester‐urethane) containing short lactate sequences and PEG moieties

A novel poly(ester‐urethane) with tailor‐made structure was prepared by using lactic acid (LA) as starting material through a combination of two facile common reactions. First, a diol was prepared via the esterification between LA and poly(ethylene glycol) (PEG) with low molecular weight. Subsequently, the poly(ester‐urethane) was synthesized through the addition polymerization of the LA‐based diol and toluene 2,4‐diisocyanate with 1,4‐butanediol as chain extender. The structure, morphology, and properties of intermediate and the poly(ester‐urethane) were analyzed with Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography (GPC), X‐ray diffraction, differential scanning calorimetry, polarizing optical microscopy, and thermogravimetric analysis. The results indicated that the intermediate was a diol of conjugating quite short lactate sequences with PEG oligomer, and the structure of the poly(ester‐urethane) was as expected. The thermal transition, thermal decomposition temperature, and crystallinity of the polymer samples depended on the molecular size of PEG. In vitro degradation property of the poly(ester‐urethane) also relied on the molecular weight of PEG. The weight loss percentages varied from 11 to 36% after 12‐days immersing in phosphate‐buffer saline at 37°C. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and study of new poly(ester‐imide)s containing triptycene groups

A new triptycene‐containing dicarboxylic acid monomer was successfully synthesized by refluxing the diamine, bis(4‐aminophenoxy)phenyl triptycene with trimellitic anhydride in glacial acetic anhydride. A series of novel thermally stable poly(ester‐imide)s were prepared from dicarboxylic acid, bis(4‐trimellitimido phenoxy)phenyl triptycene with various diols by the direct polycondensation. The polymers were obtained in quantitative yields with inherent viscosities of 0.27–0.74 dL g^?1. The resulting polymers dissolved in N‐methyl‐2‐pyrrolidinone, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethyl sulfoxide, and pyridine. These polymers were fairly stable up to a temperature >450°C and lost 10% weight in the range of 477°C and 575°C in nitrogen. The UV–V is absorption spectra revealed that most of the polymers had absorption maxima around 310 and 341 nm. POLYM. ENG. SCI., 54:2252–2257, 2014. © 2013 Society of Plastics Engineers     

Poly(ester‐amine) hyperbranched polymer as toughening and co‐curing agent for epoxy/clay nanocomposites

The marriage between hardness and flexibility of epoxy resins (improved toughness) is a desired feature, which broads their application in various industrial fields, especially for high impact resistance purposes. Accordingly, this work aims to improve toughness properties of epoxy resin (Epon‐828)/Ancamine (curing agent) system using amino‐terminated hyperbranched poly(ester‐amine) [Poly(PEODA‐NPA)] (HP) as toughening and/or co‐curing agent, in presence of organo‐modified Montmorillonite clay (OMMT) as a reinforcing filler. HP was synthesized via Michael addition reaction of poly(ethylene glycol) diacrylate (PEODA) to N‐methyl‐1,3‐propanediamine (NPA). Chemical structure and molecular weight of HP were elucidated using infrared (FTIR) spectroscopy and gel permeation chromatography (GPC) techniques, respectively. Epoxy/OMMT nanocomposites toughened with HP (at different concentrations) showed remarkable improvement in their toughness without any adverse effect on the other physico‐mechanical properties. The optimum concentration of HP and OMMT was found to be 20 wt % and 1–3 wt% of the epoxy resin, respectively. The extent of exfoliation and dispersion of OMMT platelets within the epoxy cured films was assessed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. In addition, thermal gravimetric analyses (TGA‐DTA) of epoxy/OMMT nanocomposites toughened with HP showed a slight increase in their decomposition temperature, particularly at low OMMT loading. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers