Aliphatic polycarbonate‐based polyurethane elastomers and nanocomposites. II. Mechanical,thermal, and gas transport properties

Thermal, thermomechanical, tensile and gas transport properties of aliphatic polycarbonate‐based polyurethanes (PC‐PUs) and their nanocomposites with bentonite for organic systems were studied. Hard segments are formed from hexamethylene diisocyanate and butane‐1,4‐diol. All PC‐PUs and their nanocomposites feature high degree of the phase separation. Three phase transitions were detected by temperature‐modulated differential scanning calorimetry (TMDSC) and dynamic mechanical thermal analysis. TMDSC revealed the filler affinity both to soft and hard segments, even though the affinity to hard segments is much stronger. Elongation‐at‐break at ambient temperatures is mostly over 700%, which leads together with high tensile strength (in some cases) to very high toughness values (over 200 mJ/mm³). The addition of 1 wt % of bentonite does not practically affect mechanical properties implying its very good incorporation into the PU matrix. Permeabilities and other gas transport properties depend on regularity of PC‐diol and on hard segment content, but the variations are insignificant. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hydrogen bond‐mediated self‐assembly and supramolecular structures of diblock copolymer mixtures

This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self‐assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self‐assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry     

The effect of soft‐segment structure on the properties of novel thermoplastic polyurethane elastomers based on an unconventional chain extender

Thermoplastic polyurethane elastomers (TPUs) are now widely used because of their excellent properties that include high tensile and tear strength, and good abrasion, impact and chemical resistance. TPUs are multiblock copolymers with alternating sequences of hard segments composed of diisocyanates and simple diols (chain extenders) and soft segments formed by polymer diols. Commonly used hard segments for TPUs are derived from 4,4′‐diphenylmethane diisocyanate (MDI) and aliphatic diols. The aim of our research was to examine the possibility of obtaining TPUs with good tensile properties and thermal stability by using an unconventional aliphatic‐aromatic chain extender, containing sulfide linkages. Three series of novel TPUs were synthesized by melt polymerization from poly(oxytetramethylene) diol, poly(ε‐caprolactone) diol or poly(hexane‐1,6‐diyl carbonate) diol of number‐average molecular weight of 2000 g mol^?1 as soft segments, MDI and 3,3′‐[methylenebis(1,4‐phenylenemethylenethio)]dipropan‐1‐ol as a chain extender. The structure and basic properties of the polymers were examined using Fourier transfer infrared spectroscopy, X‐ray diffraction, atomic force microscopy, differential scanning calorimetry, thermogravimetric analysis, Shore hardness and tensile tests. It is possible to synthesize TPUs from the aliphatic‐aromatic chain extender with good tensile properties (strength up to 42.6 MPa and elongation at break up to 750%) and thermal stability. Because the structure of the newly obtained TPUs incorporates sulfur atoms, the TPUs can exhibit improved antibacterial activity and adhesive properties. Copyright © 2011 Society of Chemical Industry     

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     

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

Four polyelectrolyte complexes were formed through 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‐shifted in comparison with that of dyes in alcohol, and the emission waves of the PEVP–MY and PEVP–MO_ complexes in alcohol were red‐shifted in comparison with that of dyes in alcohol. The structure of the complexes in the solid state were also investigated by DTA and X‐ray diffraction experiments. It could be proved that the complexes were new materials formed through weak interactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 369–374, 2003     

Photoimaging technique on printing Al plate via self‐assembly multilayer films based on diazoresin

A photoimaging technique on a printing aluminum plate (anodized oxidation Al plate) via self‐assembly multilayer thin film from nitro‐containing diazoresin (NDR) as cationic polyelectrolyte and various anionic polyelectrolytes has been developed. It was confirmed that, under UV‐irradiation, the linkage nature of the films changes from ionic to covalent and the solubility of the films converts dramatically, that is, the exposed area of the film becomes insoluble in H₂O–DMF–LiCl (2 : 4 : 1 wt %) ternary solvent, but mainly the unexposed area will be dissolved. After developing in ternary solvent, an image that accepts ink easily appears on the printing Al plate. To resolve the ink‐stain problem, originating from a trace remainder of the NDR on the unexposed area of the Al plate, a surface modification technique by polyphosphoric acid, which reacts with NDR to form a hydrophilic surface, was developed. The thickness, homogeneity, and surface morphology of the multilayer film (on mica) determined by atomic force microscopy and UV‐vis spectra were also reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1983–1987, 2001     

Studies on the self‐assembly of neat DBS and DBS/PPG organogels

The self‐assembly behavior of neat 1,3:2,4‐dibenzylidene‐D ‐sorbitol (DBS) and DBS/poly(propylene glycol) (PPG) organogels has been investigated by scanning electron microscopy, polarizing optical microscopy, and rheological measurements. DBS molecules are capable of self‐organizing into fibrils and exhibit the birefringent spherulitic textures during cooling from the melt. On the other hand, DBS can self‐assemble into a fibrillar network in PPG to produce organogels. DBS/PPG organogels also reveal a spherulite‐like morphology. When a small amount of DBS is dispersed into a PPG matrix, we find that the spherulite sizes are much smaller than those of neat DBS. This is because the dilution of DBS causes DBS to self‐assemble in PPG at a lower temperature. Therefore, more nucleation sites and smaller spherulite sizes are found in the DBS/PPG organogel system. The rheological measurements demonstrate that the elastic modulus (G′) in DBS/PPG organogels increases as the DBS concentration increases. However, the increase in G′ is less obvious, as the DBS content exceeds 3 wt %. suggesting that the DBS networks become saturated. Also, it is found that these organogels require a certain period of time to reach thermodynamic equilibrium, depending on DBS concentrations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Hierarchical structure of phase‐separated segmented polyurethane elastomers and its effect on properties

Polyurethanes were prepared from 4,4′‐methylenebis(phenyl isocyanate), 1,4‐butanediol and poly(1,4‐butanediol adipate) polyester polyol. The hydroxyl functional group ratio of polyol/total diol was kept constant at 0.4, while the ratio of the isocyanate and hydroxyl groups (NCO/OH ratio) changed between 0.90 and 1.15. The polymers were prepared by one‐step bulk polymerization in an internal mixer. They were characterized using a number of methods including Fourier transform infrared spectroscopy, wide‐ and small‐angle X‐ray scattering, differential scanning calorimetry, dynamic mechanical analysis, light transmittance and tensile testing. Changing the stoichiometry modifies the molecular weight in accordance with the laws of stepwise polymerization, and the relative concentration of end groups also changes at the same time. Competitive interactions among various groups including chain‐end functional groups lead to the formation of slightly ordered phases of sub‐nanometre size at both ends of the composition range. These structures assemble into larger units at the 10 nm level, which associate further to even larger entities of micrometre size causing scattering of light and a decreased transparency of the samples. The order of the primary units, together with the number and size of assemblies at both higher levels, decrease as the composition approaches equimolar stoichiometry. The amount of less ordered amorphous phase has a maximum in this range. The stiffness of the polymers is determined by the amount of this phase, while ultimate properties are influenced also by molecular weight and the number of physical crosslinks formed. Copyright © 2010 Society of Chemical Industry     

Three‐dimensional crystalline supramolecular nanostructures from self‐assembly of rod–coil molecules incorporating lateral carboxyl group in the middle of the rod segment

We report the synthesis and self‐assembling behaviour of coil–rod–coil molecules 1a–1c and 2a–2c , which incorporate lateral carboxyl or ester groups in the middle of the rod segment. The self‐assembling behaviour of these molecules was investigated in the bulk using differential scanning calorimetry, polarised optical microscopy and small‐angle X‐ray scattering. Our results reveal that hydrogen bonds strongly influence the self‐assembling behaviour of rod‐like building blocks. Molecules 1a–1c , which incorporate carboxyl groups in the middle of rod segments, self‐assemble into two‐dimensional (2‐D) columnar, three‐dimensional (3‐D) body‐centred tetragonal and 3‐D hexagonal close‐packed assemblies in the crystalline state. However, molecules 2a–2c , which contain ester groups in the centre of rod segments, self‐assemble into unexpected lamellar, hexagonal perforated lamellar and 2‐D columnar nanostructures in the bulk, indicating that hydrogen bonds impede intermolecular stacking in this rod–coil system. © 2015 Society of Chemical Industry     

Synthesis and characterization of electrolyte substrate materials based on hyperbranched polyurethane elastomers for anodic bonding

A series of hyperbranched polyurethane elastomers (PEO-HBPUEs) as polymer electrolyte substrate materials was developed for anodic bonding with aluminum (Al) foil in micro-electro-mechanical system (MEMS) devices. The PEO-HBPUEs were prepared by pre-polymerization method with toluene-2,4-diisocyanate(TDI), polypropylene glycol (PPG), 1,4-butanediol(BDO), trimethylolpropane(TMP), lithium bis(trifluoromethanesulphonyl)imide (LiTFSI), and polyethylene oxide (PEO)-based electrolyte in varying proportions via solution casting technique at room temperature. All prepared PEO-HBPUEs exhibited low glass transition temperatures, good thermal stabilities, and suitable mechanical properties. The XRD results showed that PEO-HBPUEs are amorphous, and LiTFSI was well dissolved in the polymer matrix. The component of PEO-based electrolyte in PEO-HBPUEs contributed to increase the ionic conductivity, of which the highest value reached 1.23 × 10⁻³ S/cm at 75°C for PEO-HBPUE4. The anodic bonding of PEO-HBPUE substrate with Al foil was conducted by the coupling action of electric field, temperature field, and pressure field. A clear intermediate bonding layer between the substrate and Al foil was observed and the elements diffusion around bonding layer can be detected by SEM, indicating PEO-HBPUEs and Al foil have been jointed together successfully. The highest tensile strength of the bonding interface of PEO-HBPUE4/Al reached 1.88 MPa. All results demonstrated that the prepared PEO-HBPUEs materials would be promising substrates for flexible MEMS device that can be applied to flexible packaging by anodic bonding technology.     

Growth control and long‐range self‐assembly of poly(methyl methacrylate) nanospheres

A systematic investigation of the reaction time and role of a cosolvent (toluene) in inducing several beneficial effects on nanobead properties was performed to achieve the synthesis of poly(methyl methacrylate) nanospheres. In particular, good dimensional control in the range of 100–400 nm, very low polydispersity, and a spherical shape were consistently obtained. Different parameters affecting the self‐assembly mechanism leading to the deposition of hard‐sphere photonic crystals were studied, and the features underlying their role were examined. Photonic crystals were produced by the evaporation of nanosphere suspensions at different temperatures, relative humidities, and suspension ionic strengths and with different substrate materials. The proper conditions for obtaining large crystal domains were determined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4493–4499, 2006     

Emulsifier‐free synthesis and self‐assembly of an amphiphilic poly(styrene‐co‐acrylic acid) copolymer

A poly(styrene‐co‐acrylic acid) copolymer was synthesized by surfactant‐free polymerization with the assistance of power ultrasound in water. Fourier transform infrared, NMR, and differential scanning calorimetry measurements revealed that the copolymer was random. Atomic force microscopy and laser light scattering were used to investigate the self‐assembly of the copolymer, and it was found that the copolymer chains formed micelles or other self‐assemble structures in solution. Atomic force microscopy also indicated that the self‐assembled structures developed into nanospheres with a poly(acrylic acid)‐rich or polystyrene‐rich surface in a film, depending on the solvent used for the preparation of the film. In particular, a wheel‐like structure could resulted in a film when the copolymer film was prepared in a moist environment; it resulted from heterogeneous aggregates of poly(acrylic acid) at the rim of water bubbles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:3718–3726, 2006     

Preparation and self‐assembly of polyaniline nanorods and their application as electroactive actuators

To improve the performance of ion‐exchange polymer–metal composite (IPMC) actuators, an electrical pathway material for enhancing the surface adhesion between the membrane and the metal electrodes of the IPMC was studied. As an efficient electrical pathway material, polyaniline nanorods (PANI‐NRs) doped with p‐toluene sulfonic acid (TSA) were synthesized with a template‐free method. The factors affecting polyaniline morphology were studied with various dopant concentrations and oxidant feeding rates. Highly conductive PANI‐NRs were formed when they were synthesized with ammonium persulfate at a 5.0 mL/min oxidant feeding rate and doped with 0.125M TSA. The conductivity of the PANI‐NRs was 1.15 × 10^?1 S/cm, and their diameters and lengths were 120–180 nm and 0.6–2 μm, respectively. To apply the membrane as an actuator, perfluorosulfonated ionomer (Nafion)/PANI‐NR blends were prepared by solution blending and casting. The actuating ability of the three‐layered membrane consisting of Nafion/PANI‐NR blends was then examined and compared with that of Nafion only. The actuating ability of the IPMC was improved when Nafion/PANI‐NRs were used as electrical pathways. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of nano‐ and microparticles through self‐assembly of azobenzene‐pendent ionomers

The particle formation of azobenzene‐containing ionomers, through self‐assembly, in aqueous media (THF/H₂O solvent) was studied. The ionomers were synthesized by copolymerization between azobenzene‐pendent methacrylate and methacrylic acid. It was revealed by UV–vis spectra and light scattering measurements that the extent of H‐aggregation of the azobenzene units first decreased, and then increased with increasing volume fraction of H₂O of the solvent. The H₂O fraction at which the extent of H‐aggregation began to increase became lower, when the copolymers contained more azobenzene units. Colloidal particles were prepared by slow addition of various concentrations of aqueous NaOH to the copolymer THF solutions. The hydrodynamic diameters of the particles obtained by the procedures were several hundreds of nanometer. When the azobenzene unit content in the copolymer was smaller, the diameters of the particles became smaller. When the colloidal particles dispersions were cast on a carbon sheet and dried, the particles aggregated and formed larger spherical particles, with diameters of several micrometers. The size of the particles obtained by the drying process became smaller, when higher concentrations of aqueous NaOH solutions were used. Therefore, the particle sizes were controlled by the azobenzene units content in the copolymers and the concentration of aqueous NaOH solutions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3913–3918, 2006     

Synthesis and self‐assembly of hyperbranched polyethers peripherally modified with adenosine 5′‐monophosphate

The chloride functionalized hyperbranched poly(3‐ethyl‐3‐oxetanemethanol) (HBPO) was prepared via reaction of thionyl chloride with hydroxyl groups. Adenosine 5′‐monophosphate (AMP) groups were attached to HBPO in CH₂Cl₂ in the presence of triethylamine (TEA) as an acceptor of HCl. The self‐assembly of resultant hyperbranched molecules bearing self‐complementary hydrogen‐bonding patterns would allow the generation of a highly organized supramolecular architecture in a selected solvent. The morphologies of self‐assembly structures were depended on the level of AMP in polymer and the concentration in solvent. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1147–1152, 2006     

Preparation and self‐assembly of poly(diglycidyl maleate‐co‐stearyl methacrylate)

Poly(diglycidyl maleate‐co‐stearyl methacrylate) (P(DGMA‐co‐SMA)) with reactive epoxy groups was synthesized by reaction of poly(maleic anhydride‐co‐stearyl methacrylate) (P(MA‐co‐SMA)) and epichlorohydrin. The effect of precipitant on self‐assembly behaviors of the resultant copolymer was investigated. It was found that vesicles and nanotubule liked aggregates can be obtained through self‐assembly of P(DGMA‐co‐SMA) in THF solution using CH₃CH₂OH (EtOH) as precipitant while spheral aggregates can be obtained using H₂O as precipitant. The mechanism of the self‐assembly behavior was discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Ionic self‐assembly and characterization of a polysaccharide‐based polyelectrolyte complex of maleic starch half‐ester acid with chitosan

A novel polysaccharide‐based polyelectrolyte complex was formed via ionic self‐assembly (ISA) of a carboxylic derivative of starch, maleic starch half‐ester acid (MSA), with chitosan (CS) and precipitated from aqueous solution. Both Fourier transform infrared (FTIR) spectroscopy and elementary analysis results showed that there was CS in the complex. Thermogravimetric analysis (TGA) showed that the thermal resistance of the complex was higher than that of two components and the corresponding blend. X‐ray diffraction (XRD) analysis result revealed that the complex was amorphous, whereas its components were semi‐crystalline. In addition, the drug release behavior of the complex that contains 5‐fluorouracil behaved pH‐responsive. All the experimental results verified the complex was composed of MSA and CS, and also indicated that the driving force for the self‐assembly of the complex was predominantly the electrostatic interactions between two oppositely charged polyelectrolytes, cationic CS, and the anionic MSA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

In situ polymerization and characterization of polyester‐based polyurethane/nano‐silica composites

Polyester‐based polyurethane/nano‐silica composites were obtained via in situ polymerization and investigated by Fourier‐transform infrared spectroscopy (FTIR), or FTIR coupled with attenuated total reflectance (FTIR‐ATR), Transmission electron microscopy (TEM), atomic force microscopy (AFM), an Instron testing machine, dynamic mechanical analysis (DMA) and ultraviolet‐visible spectrophotometry (UV‐vis). FTIR analysis showed that in situ polymerization provoked some chemical reactions between polyester molecules and nano‐silica particles. FTIR‐ATR, TEM and AFM analyses showed that both surface and interface contained nano‐silica particles. Instron testing and DMA data showed that introducing nano‐silica particles into polyurethane enhanced the hardness, glass temperature and adhesion strength of polyurethane to the substrate, but also increased the resin viscosity. UV‐vis spectrophotometry showed that nano‐silica obtained by the fumed method did not shield UV radiation in polyurethane films. Copyright © 2003 Society of Chemical Industry     

Microcapsules prepared from a polycondensate‐based cement dispersant via layer‐by‐layer self‐assembly on melamine‐formaldehyde core templates

Novel microcapsules were prepared from colloidal core–shell particles by acid dissolution of the organic core. Weakly crosslinked, monodisperse and spherical melamine‐formaldehyde polycondensate particles (diameter ～ 1 μm) were synthesized as core template and coated with multilayers of an anionic polyelectrolyte via layer‐by‐layer deposition technique. As polyelectrolytes, an anionic naphthalenesulfonate formaldehyde polycondensate that is a common concrete superplasticizer and thus industrially available, and cationic poly(allylamine hydrochloride) were used. Core removal was achieved by soaking the core–shell particles in aqueous hydrochloric acid at pH 1.6, resulting in hollow microcapsules consisting of the polyelectrolytes. Characterization of the template, the core–shell particles, and the microcapsules plus tracking of the layer‐by‐layer polyelectrolyte deposition was performed by means of zeta potential measurement and scanning electron microscopy. The microcapsules might be useful as microcontainers for cement additives. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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