Adhesion properties of phosphate‐ and siloxane‐containing polyurethane dispersions to steel: An analysis of the metal–coating interface

Polyurethane dispersions containing phosphate and siloxane groups in the main chain were investigated as possible self‐assembling metal coatings. Improved adhesion of the polymer to the metal was observed because of the formation of an insoluble metal phosphate layer at the metal–coating interface. The neutralizing amine of the dispersions affected the formation of this metal phosphate, and the metal phosphate formation was dependent on the curing temperature and boiling point of the amine used for neutralization. A crosscut comparative study of adhesion proved that the phosphate‐containing coatings had better adhesion because of the formation of ionic bonds at the metal–coating interface. A solid‐state adhesion prediction method based on thermodynamic considerations was used. The results of the solid‐state adhesion method correlated well with that obtained from the crosscut adhesion test method. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 900–907, 2003     

Self‐assembled honeycomb polyurethane nanofibers

Electrospinning uses a high voltage electric field to produce fine fibers. A new phenomenon of self‐assembly in the electrospinning of polyurethane nanofibers is observed. This report is the first known self‐assembling phenomenon in polyurethane electrospun nanofibers. Electrospun polyurethane nanofibers self‐assemble into unique honeycomb patterns on the collector surface. This novel observation opens up new and interesting opportunities for electrospun fibers in the areas of drug delivery devices, protective clothing, filters, and tissue scaffolds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3121–3124, 2006     

Self‐assembling amphiphilic PEGylated block copolymers obtained through RAFT polymerization for drug‐delivery applications

In this work, ring‐opening polymerization and reversible addition‐fragmentation chain transfer polymerization (RAFT) have been employed for the production of block copolymers where the backbone is brushed with poly(ethylene glycol) (PEG) and polyester chains. Because of their amphiphilic properties, they are able to self‐assemble in water, forming micelles. Molecular dynamics simulations have been accomplished to study the behavior of the copolymer single chain in water, and the self‐assembly properties have been characterized and correlated to the copolymer structure in terms of critical micellar concentration and particle size. As a proof of their flexibility, these materials have been employed for the production of polymer–lipid hybrid nanoparticles with tunable dimensions (from 120 to 260 nm) adopted for the controlled release of anticancer compounds (paclitaxel and curcumin). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43084.     

Hydrophobic and oil‐resistant coatings based on advanced green polyurethane dispersions

In recent years, there have been significant interests among scientists around the world to design smart coatings that combine the standard desirable mechanical and chemical resistance properties with additional functionalities such as oil and water repellency, hydrophobicity, self‐cleaning and gas barrier properties. In the present research work, advanced aqueous polyurethane dispersion (PUD) systems have been designed and developed using three different types of polyols as soft‐segments. These polyols differ in their chemical structure, functionality, polarity, and interfacial properties. The effects of soy‐based polyol, hydroxy‐terminated perfluoropolyether, and hydroxy‐terminated polydimethylsiloxane—on various mechanical properties of their uncross‐linked and cross‐linked films, and more specifically on their hydrophobicity and oil‐resistance (oleophobicity) have been studied. Hydrophobicity of these coatings has been characterized by their Dynamic Contact Angle measurements and their oleophobicity by n‐octane absorption method. The investigations showed that presence of fluorine and siloxane structures significantly improve the hydrophobicity and oil resistance of these coatings and it is possible to optimize these properties using suitable composition of PUDs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3874–3884, 2013     

Examination of radio‐opacity enhancing additives in shape memory polyurethane foams

Three microparticle additives, tungsten (W), zirconium oxide (ZrO₂) , and barium sulfate (BaSO₄) were selected to enhance the radio‐opacity in shape memory polymer (SMP) foam biomaterials. The addition of filler causes no significant alterations of glass transition temperatures, density of the materials increases, pore diameter decreases, and total volume recovery decreases from approximately 70 times in unfilled foams to 20 times (4% W and 10% ZrO₂). The addition of W increases time to recovery; ZrO₂ causes little variation in time to shape recovery; BaSO₄ increases the time to recovery. On a 2.00 mean X‐ray density (mean X.D.) scale, a GDC coil standard has a mean X.D. of 0.62 ; 4% W enhances the mean X.D. to 1.89, 10% ZrO₂ to 1.39 and 4% BaSO₄ to 0.74. Radio‐opacity enhancing additives could be used to produce SMP foams with controlled shape memory kinetics, low density , and enhanced X ‐ray opacity for medical materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42054.     

Dry‐peelable temporary protective coatings from waterborne self‐crosslinkable sulfourethane–silanol dispersions

Novel temporary protective coatings were prepared by the addition of release additives to waterborne polyurethane dispersions. New types of self‐crosslinkable sulfourethane–silanol (SUS) dispersions were utilized as the peelable coatings. These dispersions are stable, low‐volatility organic chemical (VOC) waterborne dispersions that spontaneously crosslink upon drying without extra additives or processing steps. Tensile strengths up to 6000 psi with elongations between 300–600% were obtained for the crosslinked films. The adhesion of the films to a variety of substrates can be controlled by the addition of hydrophilic additives, including glycerol, oligomers of glycerol, and poly(ethylene glycol) derivatives. Alternatively, hydrophobic additives that are water dispersible, such as paraffin waxes and sulfated castor oil, can also be used to control adhesion. In addition, this technique can be utilized for the release of films derived from a wide variety of waterborne urethane dispersions, including carboxylated polyurethane ureas. The removable coatings are useful for the temporary protection of plastic surfaces during thermoforming processes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1443–1449, 2004     

Studies on self‐assembly and characterization of polyelectrolytes and organic dyes

Four polyelectrolyte complexes were formed through the self‐assembly of poly‐N‐ethyl‐N,N‐ dimethylamino ethyl methacrylate (PEDEM) and poly‐ N‐ethyl‐4‐vinylpyridinium (PEVP) cations with methyl orange (MO) and metanil yellow (MY) anions in water. The FTIR spectra showed that the assembly was formed chiefly through electrostatic force and hydrophobic interaction between polyelectrolytes and organic dyes without new bonds emerging. The fluorescence spectra revealed that the emission waves of the complexes of PEDEM‐MY and PEDEM‐MO in alcohol were blue‐shift in comparison with those of dyes in alcohol, and the emission waves of the PEVP‐MY and PEVP‐MO complexes in alcohol were red‐shift in comparison with those of dyes in alcohol. The structure of the complexes in solid state were also investigated by differential thermal analysis (DTA) and X‐ray diffraction experiments. It was proved that the complexes were new materials formed through weak interactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 638–644, 2002     

Self‐assembly of pH‐responsive acrylate latex particles at emulsion droplets interface

The self‐assembly of pH‐responsive poly (methyl methacrylate‐co‐acrylic acid) latex particles at emulsion droplet interfaces was achieved. Raising pH increases the hydrophilicity of the latex particles in situ and the latex particle acts as an efficient particulate emulsifier self‐assembling at emulsion droplet interface at around pH 10–11 but exhibits no emulsifier activity at higher pH. This effect can be reversibly induced simply by varying the aqueous phase pH and thus the latex emulsifier can be reassembled. The effect factors, including the aqueous phase pH, the surface carboxyl content, ζ‐Potential of the latex particles and oil phase solvent have been investigated. Using monomer as oil phase, the latex particles could stabilize emulsion droplets during polymerization and cage‐like polymer microspheres with hollow core/porous shell structure were obtained after polymerization. The mechanism of the latex particles self‐assembly was discussed. The morphologies of emulsion and microspheres were characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and properties of polyurethane/clay nanocomposite by clay modified with polymeric methane diisocyanate

A polyurethane (PU)/clay nanocomposite was synthesized from polyol, polymeric 4,4′‐diphenyl methane diisocyanate (PMDI), and modified clay with PMDI. To achieve the modified clay with PMDI, the silanol group of the clay and the NCO group of the PMDI were reacted for 24 h at 50°C to form urethane linkage. Fourier transform IR analysis of the clay modified with the PMDI demonstrated that the NCO characteristic peak was observed in the clay after a modification reaction with PMDI. The results of the X‐ray pattern suggested that the clay layers were exfoliated from the PU/clay nanocomposite. From the results of the mechanical properties, the maximum values of the flexural and tensile strength were observed when 3 wt % clay based on PMDI was added into the PU/clay nanocomposites. The glass‐transition temperature and change in the heat capacity at glass transition temperature (ΔC_p) of the PU/clay nanocomposite decreased with an increase in the modified clay content. We suggested that the decrease in the ΔC_p with the modified clay content might be due to the increase of steric hindrance by the exfoliated clay layers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2879–2883, 2006     

Novel phenyl‐POSS/polyurethane aqueous dispersions and their hybrid coatings

A facile and rapid preparation of 3‐(2‐aminoethylamino)propylheptaphenylPOSS (AA‐POSS), a special phenyl‐POSS that contains two functional amino groups (Scheme 1), is demonstrated by the corner‐capping method. Then AA‐POSS forms a series of novel phenyl‐POSS/PU aqueous dispersions. The structure of AA‐POSS has been confirmed by ¹H, ¹³C, ²⁹Si NMR, and ESI‐MS. The POSS/PU hybrid films are studied by Fourier transform infrared spectrometer (FT‐IR), gel permeation chromatography (GPC), scanning electron microscope (SEM), X‐ray diffraction (XRD) spectra, differential scanning calorimetry (DSC) analysis, and thermal gravimetric analyzer (TGA). FT‐IR and GPC are conducted to validate the chemical structure of the hybrid PU. The properties of hybrid films display significant changes with notable increases in T_g, thermal properties, tensile strength, as well as surface hydrophobicity. These changes are attributed to the incorporation of novel POSS into PU. Moreover, these significant material property enhancements are achieved at low levels of POSS incorporation (only 4%). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1611–1620, 2013     

Synthesis and characterization of calcium‐containing poly(urethane‐urea)s

A calcium salt of mono(hydroxyethoxyethyl)phthalate [Ca(HEEP)2] was synthesized by the reaction of diethylene glycol, phthalic anhydride, and calcium acetate. Four different bisureas like hexamethylene bis(ω,N‐hydroxyethylurea), tolylene 2,4‐bis(ω,N‐hydroxyethylurea), hexamethylene bis(ω,N‐hydroxypropylurea), and tolylene 2,4‐bis(ω,N‐hydroxypropylurea) were prepared by reacting ethanolamine or propanolamine with hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI). Calcium‐containing poly(urethane‐urea)s (PUUs) were synthesized by reacting HMDI or TDI with 1:1 mixtures of Ca(HEEP)2 and each of the bisureas using di‐n‐butyltin dilaurate as a catalyst. The PUUs were well characterized by Fourier transform infrared, 1H‐ and 13C‐NMR (nuclear magnetic resonance), solid‐state 13C cross‐polarization–magic angle spinning NMR, viscosity, solubility, elemental, and X‐ray diffraction studies. Thermal properties of the polymers were also studied by using thermogravimetric analysis and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3488–3496, 2003     

High‐performance waterborne coatings based on epoxy‐acrylic‐graft‐copolymer‐modified polyurethane dispersions

Polyurethane dispersions (PUDs) have been an active area of research since the early 1940s because of legislative restrictions on the use of organic solvents in conventional solvent‐based products and also because PUDs exhibit almost the same high performance levels as solvent‐borne polyurethanes. In the present study, properties of conventional waterborne PUDs are modified with epoxy‐acrylic graft copolymer blocks. The epoxy‐acrylic graft copolymers were first modified with ethylene diamine to give amine‐terminated blocks which in turn reacted with isocyanate‐terminated prepolymer (prepolymer mixing process) to give modified PUDs. Several experimental sets were prepared with varying compositions. The experimental sets were also prepared using conventional poly(ethylene glycol) blocks and ethylene diamine chain‐extenders. The physico‐chemical properties and film characteristics of the experimental sets show the dramatic improvement in important mechanical properties of PUDs due to grafting with epoxy‐acrylic copolymer blocks. Copyright © 2004 Society of Chemical Industry     

Hybrid polyaniline–TiO2 nanocomposite Langmuir–Blodgett thin films: Self‐assembly and their characterization

Polyaniline (PANi)–titanium dioxide (TiO₂) nanocomposite materials were prepared by chemical polymerization of aniline doped with TiO₂ nanoparticles. Surface pressure–area (π‐A) isotherms of these nanocomposites show phase transformations in the monolayer during compression process. Multiple isotherms indicate that the monolayer of the nanocomposite material can retain its configuration during compression‐expansion cycles. Langmuir–Blodgett thin films of PANi–TiO₂ nanocomposite were deposited on the quartz and indium tin oxide coated conducting glass substrates. Fourier transfer infrared spectroscopy and UV–visible spectroscopy study indicates the presence of TiO₂ in PANi, whereas X‐ray Diffraction study confirmed the anatase phase of TiO₂ and particle size (～nm) of PANi–TiO₂. The morphology of Langmuir–Blodgett films of these nanocomposites was also characterized by atomic force microscopy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41386.     

Self‐healing supramolecular elastomers based on the multi‐hydrogen bonding of low‐molecular polydimethylsiloxanes: Synthesis and characterization

Novel self‐healing supramolecular elastomers based on polydimethylsiloxanes (SESi) were synthesized from a mixture of polydimethylsiloxanes derivers with single, di‐, or tri‐carboxylic acid groups (PDMS–COOH_x, where x = 1, 2, and 3, respectively), diethylene triamine, and urea with a two‐stage procedure. The reactions and the final products were tracked, characterized, and confirmed by Fourier transform infrared spectroscopy, ¹H‐NMR, differential scanning calorimetry, dynamic mechanical analysis, and gel permeation chromatography. Compared with a supramolecular rubber based on dimer acid (reported previously) with a similar synthesis procedure, the SESi showed a lower glass‐transition temperature of about ?113°C for the softer chain of polydimethylsiloxane and showed real rubberlike elastic behavior and self‐healing properties at room temperature or even lower temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Production of polyols and waterborne polyurethane dispersions from biodiesel‐derived crude glycerol

This study investigated the preparation of polyols and waterborne polyurethane dispersions (CG‐WPUDs) from biodiesel‐derived crude glycerol. The polyols were produced from biodiesel‐derived crude glycerol via a thermochemical conversion process, which converted crude glycerol components such as glycerol, free fatty acids, and methyl esters of fatty acids (FAMEs) into polyols under optimized reaction conditions. CG‐WPUDs with different hard segments (41.0% to 63.2 wt %) were prepared from the crude glycerol‐based polyols produced. PU coating films cast from CG‐WPUDs showed increasing glass transition temperatures (T_g) from 63°C to 81°C when hard segment content increased from 41.0% to 63.2% and had good thermal stability up to 240°C. CG‐WPUD‐based coatings showed excellent adhesion to steel panel surfaces, pencil hardness as high as F, but relatively low flexibility. This study demonstrated the potential of biodiesel‐derived crude glycerol for the production of bio‐based polyols and WPUDs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41425.     

Study on effect of duration of the ultrasonication process on solvent‐free polyurethane/organoclay nanocomposite coatings: Structural characteristics and barrier performance analysis

In this study, effect of duration of ultrasonication process on structural characteristics and barrier properties of solvent‐free castor oil‐based polyurethane (PU)/organically modified montmorillonite (OMMT) nanocomposites was investigated. A series of PU/OMMT composites were synthesized by in situ polymerization technique through an ultrasonication‐assisted process at various processing durations. Effect of ultrasonication duration on de‐agglomeration of clay stacks in castor oil dispersions was evaluated by optical microscopy, sedimentation test, and viscosity measurement. Wide angle X‐ray diffraction and Fourier‐transform infrared spectroscopy were employed to investigate the effect of processing time on degree of delamination of clay platelets and interfacial strength between clay layers and PU matrix. Also, surface morphology of the nanocomposites was analyzed by atomic force microscopy. The results showed that by increasing the ultrasonication time up to 60 min, the size of clay agglomerates decreased and the interlayer spacing of clay platelets increased. To evaluate the effect of ultrasonication duration on transport properties of the PU/OMMT composites, diffusion coefficient and permeability were determined through water uptake test. Electrochemical impedance spectroscopy was carried out to analyze the barrier properties and to evaluate the corrosion performance of these composite coatings on carbon steel panels. It was found that by increasing sonication time, the barrier property of nanocomposites against diffusion of water molecules improved, which is due to further separation of clay platelets, enhancement of the traveling pathways for water molecules and improvement of interactions between the two components. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Self‐reinforcing elastomer composites based on ethylene–propylene–diene monomer rubber and liquid‐crystalline polymer

In this study, the prime factor determining the size, shape, and distribution of liquid‐crystalline polymer (LCP) was the viscosity ratio at the processing conditions. The fiber‐forming capacity of the LCP depended on the viscosity of the ethylene–propylene–diene monomer rubber (EPDM). With increasing LCP content, the tensile and tear strengths did not increase, perhaps because of incompatibility between the EPDM and LCP. The hardness increased because of the hard mesogenic groups in the LCP. The percentage swelling decreased as the LCP content increased. With increasing LCP content, processability became easier because of a lower melt viscosity. The scorch time increased at higher LCP levels. A higher percentage crystallinity was observed with increasing LCP content. Scanning electron microscopy clearly showed the fiber phase formation, which was two‐dimensionally isotropic in nature, confirming fiber formation even in a shear field. The addition of LCP improved the thermal stability. The onset degradation temperatures shifted to higher values with increasing LCP content. Dynamic mechanical thermal analysis revealed that with the addition of LCP, the mechanical damping increased at its lower level. High‐temperature processing increased the effective amorphous zone. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 711–718, 2004     

Comparison between the self‐assembling behaviors of PLLA‐PEO‐PLLA triblock copolymers and PLLA‐PEO‐PPO‐PEO‐PLLA pentablock copolymers

Poly(L ‐lactic acids) (PLLAs) were grafted to both ends of poly(ethylene oxide) (PEO) to produce biocompatible amphiphilic PLLA‐PEO‐PLLA triblock copolymers. The self‐assembling behaviors of two PLLA‐PEO‐PLLA copolymers in aqueous solutions were examined by Dynamic Light Scattering and Transmission Electron Microscopic techniques. PLLA‐PEO‐PLLA formed spherical micelles, whereas PLLA‐PEO‐PPO‐PEO‐PLLA pentablock copolymers were reported to produce vesicles. It is believed that the PPO segment within the PLLA‐PEO‐PPO‐PEO‐PLLA pentablock copolymers has a dominant role in the formation of vesicles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of aqueous polyurethane dispersions with well‐defined soft segments

Novel aqueous polyurethane (PU) hybrid dispersions were successfully prepared with 5–15 mol % functionalized hexamethylene diisocynate trimer modified by N‐(n‐butyl)‐3‐aminopropyltriethoxysilane and dihydroxylpropyl‐terminated siloxane oligomers (TS). The results of the differential scanning calorimetry and X‐ray diffraction tests show that the degree of segment order was reduced by the introduction of TS. The hybrid polymer films with TS introduced into the PU backbone displayed excellent water and xylene resistance. Atomic force microscopy showed that the films had a smooth surface. It was noticeable that the tensile strength (σ_b) and Young's modulus of the films increased simultaneously when TS was incorporated into PU; σ_b of the PU15 film with 15 mol % TS was much higher than that of the neat PU0 film, and the breaking elongation of the film with 10 mol % TS was clearly higher than that of the other films. The results indicate that an appropriate content of TS significantly improved the properties of the aqueous PU hybrids. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Self‐assembled nanoblends of functional polystyrene and a reactive aramid: Morphological and thermomechanical profile

Various blends composed of pure polystyrene (PS) and modified PS [amino‐functionalized polystyrene (PS–NH₂)] were prepared with a new aromatic polyamide obtained through the polycondensation of 1,5‐diaminonaphthalene and 1,4‐phenylenediamine with isophthaloyl chloride. The variation in the morphological and thermophysical profiles in the two blend systems with aramid loading were investigated. The amine functionality introduced to PS enhanced its compatibility with the polyamide because of the formation of an aramid‐graft‐PS copolymer. The grafting, hydrogen bonding, and phenylene‐ring (π–π) stacking between the chains of the two components finally nurtured self‐assembled nanostructured blends. A strong compatibilizing effect was observed for the 50, 60, and 70 wt % aramid blends, where an exceptionally inimitable cocontinuous self‐assembled morphology was formed by PS–NH₂/aramid. Significant developments in the morphology along with thermal and mechanical stability were observed for the reactive PS/aramid system. The most favorable mechanical and thermal data supported by the finest nanostructure were observed with 70 wt % polyamide addition. Future prospects may involve the formation of nanotemplates and nanostructured membranes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39954.