Mixed Poly Research Articles

Nanocomposite polymer electrolyte membranes based on poly (vinylphosphonic acid)/sulfated nano-titania

Proton conductors comprising phosphonic acid units are very promising due to their oxidative stability as well as high proton conductivity. In the present work, the membrane materials were produced by mixing of poly(vinylphosphonic acid) (PVPA) with sulfated nano-titania at various concentrations to get PVPATSx where x designates the molar ratio of the polymer repeating units to sulfate units (varied from 1 to 4). The structure of the nanocomposite polymer membrane is confirmed by FT-IR spectroscopy. The TGA results verify that the presence of sulfated nano-titania in the complex polymer electrolytes suppressed the formation of phosphonic acid anhydrides up to 200°C. DSC results indicate that the Tg of the materials shifts to higher temperatures as sulfated nano-titania content increases. In the anhydrous state, the proton conductivity of PVPATS is found to be 0.03 (Scm−1) at 150°C. Proton conductivity of these membranes are also measured and compared with previous studies. The results suggest that proton conduction is occurred between surface of the nano-titania particles with the aid of sulfonic acid and phosphonic acid units.

PDMS network blends of amphiphilic acrylic copolymers with poly(ethylene glycol)‐fluoroalkyl side chains for fouling‐release coatings. I. Chemistry and stability of the film surface

AbstractAmphiphilic copolymers of a methacrylic monomer (SiMA) carrying a polysiloxane side chain and an acrylic monomer (ZA) with a mixed poly(ethylene glycol) (PEG)‐fluoroalkyl side chain (10–85 mol % ZA) were incorporated as the surface‐active components into poly(dimethylsiloxane) (PDMS) network blends at different loadings (1 and 4 wt % with respect to PDMS). Wettability of the coating surfaces was investigated by contact angle measurements, and their surface chemical composition was determined by angle‐resolved X‐ray photoelectron spectroscopy. It was found that the surface segregation of the fluoroalkyl segments of the amphiphilic copolymers was responsible for the high enrichment in fluorine concentration within 10 nm of the coating surface. The PEG segments were also concentrated at the polymer−air interface. The chemical composition of the films was proven to be relatively little affected by immersion in water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

New piezoelectric damping composites of poly(vinylidene fluoride) blended with clay and multi‐walled carbon nanotubes

AbstractDamping materials are used to control mechanical vibrations, and piezoelectric damping composite is a very promising material due to its unique mechanism. In this study, a potential piezoelectric damping composite was developed by simply melt mixing poly(vinylidene fluoride) (PVDF) with small amounts of organic modified montmorillonite (OMMT) and multi‐walled carbon nanotubes (MWCNTs). The piezoelectric, mechanical and electrical properties were investigated using a dynamic mechanical analyser, direct current electrical resistivity measurements, X‐ray diffraction, Fourier transform infrared spectroscopy and the direct quasi‐static d33 piezoelectric coefficient method. It was found that the damping property of PVDF can be greatly improved by adding both MWCNTs and OMMT, and the composite containing 1.9 wt% of MWCNTs and 3 wt% of OMMT showed the best damping property. A model and an approximate calculation were applied to explain the improved damping property. Moreover, similar mechanical properties of PVDF composites were observed in the tensile testing and dynamic mechanical analyser measurements. Copyright © 2012 Society of Chemical Industry

Cross-Linked Benzoxazine–Benzimidazole Copolymer Electrolyte Membranes for Fuel Cells at Elevated Temperature

Here we report new H3PO4-doped cross-linked benzoxazine–benzimidazole copolymer membranes showing high proton conductivity and long-term durability for use in proton-exchange membrane fuel cells at elevated temperatures (>100 °C). The cross-linked copolymer membranes were prepared by mixing of poly[2,2′-(m-phenylene)-5,5′-bibenzimidazole] (PBI) with 3-phenyl-3,4-dihydro-6-tert-butyl-2H-1,3-benzoxazine (pBUa) in N,N-dimethylacetamide, with subsequent stepwise heating to 220 °C, and even large-sized films (30 cm × 140 m) could be easily prepared. The membranes showed high proton conductivities of up to 0.12 S cm–1 at 150 °C under anhydrous conditions. Membrane–electrode assemblies (MEAs) employing the membranes showed operating voltages of 0.71 V at 0.2 A cm–2. Furthermore, the MEAs displayed long-term durability up to 1999 cycles, with much slower performance decay, −0.03 mV h–1, than those prepared using the PBI membrane in in situ accelerated lifetime mode (load cycling testing).

Analysis of Gas Permeability Characteristics of Poly(Lactic Acid)/Poly(Butylene Succinate) Nanocomposites

Gas permeability and morphological properties of nanocomposites prepared by the mixing of poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and clay was investigated. While the composition of PLA and PBS polymers was fixed as 80% and 20% by weight, respectively, for all the nanocomposites, clay contents varied from 1 to 10 wt%. From the morphological studies using both wide angle X‐ray diffraction and transmission electron microscopy, the nanocomposite having 1 wt% of clay was considered to have a mixed morphology of intercalated and delaminated structure, while some clusters or agglomerated particles were detected for nanocomposites having 3 and more than 3 wt% of clay content. However, the average particle size of the dispersed PBS phase was reduced significantly from 7 μm to 30–40 nm with the addition of clay in the blend. The oxygen barrier property was improved significantly as compared to the water vapor. A model based on gas barrier property was used for the validation of the oxygen relative permeabilities of PLA/PBS/clay nanocomposites. PLA/PBS/clay nanocomposites validated the Bharadwaj model up to 3 wt% of clay contents only, while for nanocomposites of higher clay contents the Bharadwaj model was invalid due to the clusters and agglomerates formed.

Mixed poly (ethylene glycol) and oligo (ethylene glycol) layers on gold as nonfouling surfaces created by backfilling

Backfilling a self-assembled monolayer (SAM) of long poly (ethylene glycol) (PEG) with short PEG is a well-known strategy to improve its potential to resist fouling. Here it is shown, using x-ray photoelectron spectroscopy, contact angle, and atomic force microscopy, that backfilling PEG thiol with oligo (ethylene glycol) (OEG) terminated alkane thiol molecules results in underbrush formation. The authors also confirm the absence of phase separated arrangement, which is commonly observed with backfilling experiments involving SAMs of short chain alkane thiol with long chain alkane thiol. Furthermore, it was found that OEG addition caused less PEG desorption when compared to alkane thiol. The ability of surface to resist fouling was tested through serum adsorption and bacterial adhesion studies. The authors demonstrate that the mixed monolayer with PEG and OEG is better than PEG at resisting protein adsorption and bacterial adhesion, and conclude that backfilling PEG with OEG resulting in the underbrush formation enhances the ability of PEG to resist fouling.

Redox-responsive self-healing materials formed from host-guest polymers.

Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host–guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host–guest interactions. We employ cyclodextrin (CD) as a host molecule because it is environmentally benign and has diverse applications. A transparent supramolecular hydrogel quickly forms upon mixing poly(acrylic acid) (pAA) possessing β-CD as a host polymer with pAA possessing ferrocene as a guest polymer. Redox stimuli induce a sol−gel phase transition in the supramolecular hydrogel and can control self-healing properties such as re-adhesion between cut surfaces.

Interpolymer Complexes of Poly(N,N‐Dimethylacrylamide/Poly(Styrene‐co‐Acrylic Acid): Thermal Stability and FTIR Analysis

AbstractSummary: This contribution will focus on the elaboration and characterizations of new materials with optimal properties as interpolymer complexes, upon mixing poly (styrene‐co‐acrylic acid containing 18, 27 and 32 mol % of acrylic acid (SAA‐x) and poly (N,N‐dimethylacrylamide) (PDMA), through the control of the densities, strength, self‐association and accessibility of the interacting species. These elaborated interpolymer complexes, of different structures, investigated by DSC and TGA, exhibited a significant improved thermal stability. Their DSC analysis showed that all these materials showed one composition‐dependence glass transition temperature Tg, indicating the formation of a single homogeneous phase. The different behaviors of Tg‐initial composition observed with these systems were analyzed by the approaches of Kwei and Brostow et al., recently developed. The specific interactions that occurred within the elaborated materials were evidenced qualitatively by ATR/FTIR spectroscopy, from the appearance of new bands in the 1800–1550 cm−1 region.

Local thermal-mechanical analysis of ultrathin interfacially mixed poly(ethylene oxide)/poly(acrylic acid) layer-by-layer electrolyte assemblies

Ion conductivities of layer-by-layer (LBL) assemblies of solid thin film polyelectrolyte systems involving poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) were found to be a strong function of the number of bilayer stacks, n, with conductivities approaching 10 − 7 S/cm for n < 10, compared to 10 − 9 S/cm for n ≥ 10 and 10 − 10 S/cm for bulk PEO. Increased ion conductivity for low LBL stack numbers ( n < 10) originated to part from an effective suppression of the PEO crystallization via PEO/PAA blending, which could be inferred from local glass transition temperature measurements involving shear modulation force microscopy. Another phenomenon responsible for high conductivity in thin films was found in the in-plane phase heterogeneity of PEO and PAA. Increased ion conductivity for larger LBL stacks ( n ≥ 10) were attributed to low concentration autoblending caused by PEO-PAA hydrogen bonding, and an average layer thickness of noticeably less than 100 nm. The effect of interfacial constraints was evident in the degree of intermixing, addressed by a thin film extended Fox blend analysis, in the glass and melting transitions of PEO and PAA pure film components. While the glass transition value of PAA decreased by 55% to 46 °C for an 8 nm film, the melting transition for PEO decreased by 15% to 64 °C caused by surface tension effects.

Microgravimetric study on the formation and redox behavior of poly(2-acrylamido-2-methyl-1-propanesulfonate)-doped thin polyaniline layers

A comparative study on the potentiostatic polymerization of polyaniline (PANI) in inorganic (sulfuric and perchloric) acid and mixed poly(2-acryalamido-2-methyl-1-propane-sulfonic) (PAMPSA)/inorganic acid solutions is carried out through combined electrochemical and microgravimetric techniques. It is established that polymerization in the presence of small amounts of PAMPSA in the mixed solutions results in immobilization of the polyanions in the PANI layers. The redox behavior of the PAMPSA-doped PANI layers, studied in acidic, neutral and slightly alkaline solutions shows that the electroactivity is preserved up to pH 9. PAMPSA seems to operate as a buffer, providing the necessary protons for the PANI layer in the range pH 7 to pH 9. Detailed microgravimetric measurements in buffer solutions with various cationic (Na + and Cs +) and anionic (Cl − and ClO 4 −) species are used to elucidate the ionic transport occurring in the course of the PANI redox transition in neutral solutions. It is found that cations (different than protons) are involved in the early stage of oxidation whereas the participation of anionic species seems to be limited. Small mass fluxes and minor changes in the viscoelastic properties are observed during the redox transition in neutral and slightly alkaline solutions.

Improvement of the thermal stability of streptavidin immobilized on magnetic beads by the construction of a mixed poly(ethylene glycol) tethered-chain layer

Streptavidin-immobilized magnetic beads and poly(ethylene glycol) covalently immobilized streptavidin-immobilized magnetic beads were prepared to investigate the heat resistance of streptavidin surrounded by a densely packed poly(ethylene glycol) tethered-chain layer on the magnetic bead surface. The covalent immobilization of poly(ethylene glycol) tethered-chains on the streptavidin-immobilized magnetic beads surface was carried out using α-methoxy-poly(ethylene glycol)-pentaethylenehexamine (N6-PEG) after streptavidin immobilization. Figure shows changes in the capture efficiency of biotinylated single-stranded DNA by poly(ethylene glycol)/streptavidin-immobilized magnetic beads (red plots) and streptavidin-immobilized magnetic beads (blue plots) as a function of the number of heat-treatment cycles (75 °C for 5 min). Surprizingly, the heat resistance of the poly(ethylene glycol) tethered-chain covalently immobilized on the streptavidin-immobilized magnetic beads surface was found to improve.

Mechanical and Dynamic Mechanical Properties of Degradable Polyurethane Foams with PEG/PCL Mixed Soft Segments

Polyurethane (PU) with mixed poly(ethylene glycol) / poly(ε-caprolactone) (PEG/PCL) soft segments is a representatively kind of degradable polyurethane material. Polyurethane foams (PUF) with mixed PEG/PCL soft segments were synthesized by using one pot method, and their mechanical and dynamic mechanical properties were investigated. Influences of PEG/PCL weight ratio and molecular weight of soft segments on PUF's mechanical and dynamic mechanical properties were studied. The results showed that: with increasing content of PCL, PUF's tensile strength, elongation at break, stress at certain tensile/compressive strain and storage modulus increased gradually; with increasing molecular weight of soft segment, PUF's elongation at break increased, but tensile strength, stress at certain tensile/compressive strain and storage modulus all decreased accordingly; glass transition temperature (Tg) of PUF with various soft segments decreased according to the following sequence: PEG-400, PCL-210N, PEG-1000 and PTMG1000; loss factor of PUF with PEG/PCL mixed soft segments was higher than that of PUF with individual PEG or PCL soft segments.

Effects of kaolin and maleic anhydride contents on melt elasticity and flexural behaviour of polypropylene/kaolin and unplasticised poly(vinyl chloride)/kaolin composites

AbstractPolypropylene/kaolin and unplasticised poly(vinyl chloride)/kaolin composites were prepared by directly melt mixing polypropylene (PP) and unplasticised poly(vinyl chloride) (UPVC) with maleic anhydride (MAH) and low cost kaolin via in situ extrusion process. The influences of kaolin particles and MAH in PP and UPVC matrix were discussed through investigating the flexural and morphological properties of filled PP and UPVC composites. The extrudates obtained from the extrusion process were carefully collected in order to investigate the elastic properties (extrudate swell and melt fracture). Results revealed that the above mentioned properties are strongly dependent on the presences of kaolin and MAH in both composite systems. Observation on scanning electron microscopy (SEM) analysis showed that the kaolin books (stacks of kaolin particles) were successfully delaminated thus lead to a well dispersed of kaolin particles in PP and UPVC matrix.

Microphase Separation of High Grafting Density Asymmetric Mixed Homopolymer Brushes on Silica Particles

A set of high grafting density mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with PtBA number-average molecular weight (Mn) fixed at 18.6 kDa and PS Mn ranging from 8.7 to 28.0 kDa was synthesized from 172 nm asymmetric difunctional initiator (Y-initiator)-functionalized silica particles by sequential surface-initiated atom transfer radical polymerization of tert-butyl acrylate and nitroxide-mediated radical polymerization (NMRP) of styrene. The Y-initiator-functionalized particles were prepared by the immobilization of a triethoxysilane-terminated Y-initiator onto the surface of bare silica particles via a hydrolysis/condensation process. The overall grafting densities of the obtained mixed brushes were 0.9−1.2 chains/nm2, which were significantly higher than those of mixed brushes prepared from silica particles that were surface functionalized by a monochlorosilane-terminated Y-initiator (0.6−0.7 chains/nm2). Differential scanning calorimetry analysis showed that all high density mixed...

Evolution of Phase Morphology of Mixed Poly(tert-butyl acrylate)/Polystyrene Brushes Grafted on Silica Particles with the Change of Chain Length Disparity

We report in this article the synthesis of a series of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes with PtBA number-average molecular weight (Mn) being fixed at 24.5 kDa and PS Mn ranging from 14.8 to 30.4 kDa on 160 nm silica particles and the study of their microphase separation behaviors using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The samples were synthesized by a two-step “grafting from” process from asymmetric difunctional initiator (Y-initiator)-functionalized silica particles using two different “living”/controlled radical polymerization techniques. PtBA brushes were grown first from Y-initiator-functionalized particles by surface-initiated atom transfer radical polymerization of tert-butyl acrylate at 75 °C in the presence of a free initiator, followed by nitroxide-mediated radical polymerization (NMRP) of styrene at 120 °C. The “living” nature of NMRP allowed the synthesis of mixed PtBA/PS brushes with different PS molecular weights (14.8, 18.7, 24.9, and 30.4 kDa) in a one-pot polymerization. DSC studies showed that all thermally annealed mixed brush samples exhibited two glass transitions with the middle points located at ∼47 and ∼90 °C, suggesting that the two tethered polymers microphase separated in the brush layer. For TEM studies, the samples were dispersed in CHCl3, a good solvent for both PtBA and PS, drop-cast onto carbon films, thermally annealed in vacuum at 120 °C for 3 h, and then stained with RuO4 vapor. All samples showed clear microphase separation, consistent with the DSC results. With increasing PS Mn from 14.8, to 18.7, and 24.9 kDa, the morphology of mixed brushes evolved from isolated, nearly spherical PS microdomains buried inside the PtBA matrix, to short PS cylindrical microdomains in the PtBA matrix, and to nearly bicontinuous nanostructures. Further increasing the molecular weight of PS to 30.4 kDa resulted in the formation of isolated PtBA microdomains which were covered by PS chains.

Highly selective GC stationary phases consisting of binary mixtures of polymeric ionic liquids

GC stationary phases composed of binary mixtures of two polymeric ionic liquids (PILs), namely, poly(1-vinyl-3-hexylimidazolium) bis[(trifluoromethyl)sulfonyl]imide (poly(ViHIm-NTf(2)))/poly(1-vinyl-3-hexylimidazolium) chloride (poly(ViHIm-Cl)) and poly(1-vinyl-3-hexadecylimidazolium) bis[(trifluoromethyl)sulfonyl]imide (poly(ViHDIm-NTf(2)))/poly(1-vinyl-3-hexadecylimidazolium) chloride (poly(ViHDIm-Cl)), were evaluated in terms of their on-set bleed temperature and separation selectivity. A total of six neat or binary PIL stationary phases were characterized using the solvation parameter model to investigate the effects of the polymeric cation and anion and PIL composition on the system constants of the resulting stationary phases. The hydrogen bond basicity of the mixed poly(ViHIm-NTf(2))/poly(ViHIm-Cl) stationary phases was enriched linearly with the increase in the poly(ViHIm-Cl) content. Results revealed that tuning the composition of the stationary phase allowed for fine control of the retention factors and separation selectivity for alcohols and carboxylic acids as well as selected ketones, aldehydes, and aromatic compounds. A reversal of elution order was observed for particular classes of analytes when the weight percentage of the chloride-based PIL was increased.

Poly Aryl Amide and Multiwalled Carbon Nanotube Composite Supported Laccase Electrode and Its Electrochemical Behavior

A novel strategy for the immobilization of laccase onto a glassy carbon electrode with high stability and electrocatalytic performance is presented. Laccase is attached to a matrix of mixed poly aryl amide (PAA) and multiwalled carbon nanotubes (MWCNTs) (denoted Lac/PAA-MWCNTs/GCE) by covalently bonding the surface amine group of laccase to the terminal carboxyl group of PAA and hydrophobic-hydrophobic interaction between MWCNTs and the laccase. The PAA backbone avoids the detachment and denaturing of the laccase, and the intermixed MWCNTs provide high electronic conductivity. The loading of laccase is 56.0 mg·g-1 and more than 68% shows electrochemical activity. The electrode delivers direct electron transfer between the redox center of the laccase and the electrode with two pairs of redox peaks at 0.73 and 0.38 V, which is close to the formal potential of the T1 and T2 Cu-sites (0.78 and 0.39 V (vs NHE)), respectively. The onset potential for O2 reduction reaction (ORR) is ca 0.55 V in a phosphate buffer solution (pH=4.4). The Michaelis constant (KM) of the Lac/PAA-MWCNTs/GEs for O2 is 55.8 μmol·L-1 and the detection limit of oxygen reaches 0.57 μmol·L-1. After 2 months of storage at 4 ℃ the ORR activity of the Lac/PAA-MWCNTs/GC electrode retains ca 86% of its initial values and the peak potential of the ORR shifts negatively by ca 50 mV. Given the excellent catalytic performance towards ORR and its high stability this strategy will be widely applicable to the development of an enzyme-based cathode for biofuel cells and amperometric biosensors for oxygen.

SPIN SELF-ASSEMBLY OF A POLYACRYLATE-BASED AZO POLYELECTROLYTE AND MULTILAYER PHOTORESPONSIVE BEHAVIOR

Multilayer films of a polyacrylate-based azo polyelectrolyte were fabricated by a spin self-assembly method.By spin-coating solutions of the azo polyelectrolyte in DMF/H_2O mixed solvent and poly_(diallyldimethylammonium chloride)(PDAC) in water,high quality multilayer films were obtained.Dichroism was optically induced in the self-assembled films under the irradiation of a polarized Ar~+ laser beam at 488 nm.The dichroism was easily detected from UV-Vis spectra and exhibited long term stability.The orientational order parameter obtained was about 0.06 for the film.With interfering illumination of Ar~+ laser beams,significant surface relief gratings formed on the self-assembled multiplayer films were observed.

Macromol. Chem. Phys. 22/2009

Cover: Mixing poly(L-lactide), poly(D-lactide), and diphenyl ether (DE) produced a crystallosolvate, consisting of homo-chiral (hc) and stereocomplex (sc) crystals of the polymers and amorphous DE domains. Nanoscopic analysis revealed that sc granules with a diameter of 20 nm were formed via the solvation-induced collapse of rod-like hc lamellae. Further details can be found in the article by H. Nakajima, I. Wataoka, H. Ohara, and Y. Kimura* on page 1915.

Stereoblock Polylactides as High-Performance Bio-Based Polymers

Mixing of poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) affords stereocomplex-type PLA (sc-PLA) having a high melting temperature of 230°C, and its use provides higher thermal properties for PLA materials. The stereocomplex formation, however, is always accompanied by homochiral crystallization of PLLA and PDLA, causing deterioration of properties, when their molecular weight is higher than 100 kDa. Therefore, stereoblock-type PLAs (sb-PLA) consisting of PLLA and PDLA stereosequences are developed by utilizing new synthetic methodologies. The sb-PLAs exclusively generate the stereocomplex because of the better mixing state of their enantiomeric sequences and can be utilized as high-performance bio-based materials.