Polymer Blends Of Poly Research Articles

Unusual Fractional Crystallization Behavior of Novel Crystalline/Crystalline Polymer Blends of Poly(ethylene suberate) and Poly(ethylene oxide) with Similar Melting Points

Novel crystalline/crystalline polymer blends of biodegradable poly(ethylene suberate) (PESub) and biocompatible poly(ethylene oxide) (PEO) were prepared through a solution and casting method. The basic thermal properties, including both glass transition temperature and melting point, of both of the components are very close to each other. The two components are miscible as no obvious phase separation can be detected, forming novel miscible polymer blends of two crystalline polymers. PESub/PEO blends show two or three crystallization exotherms at different supercoolings. The complex crystallization behaviors are attributed to the occurrence of the fractional crystallization of the minor component of the blends. Depending on the blend composition, the major component of the blend crystallizes first and the minor component crystallizes later. During the crystallization of the major component, the amorphous minor component is completely included the interlamellar region of the major component or most of the amorphous minor component is expelled out of the interlamellar region while only a few is incorporated between the lamellae of the major component. In both cases, the fractional crystallization of the minor component occurs at large supercooling because of the confinement effect of the lamellae of the major component. In the present work, the fractional crystallization of PESub or PEO may occur at large supercooling when its content is low. PESub/PEO blends may be the first model that the fractional crystallization of each component occurs at large supercooling when its content is low; thus, they provide a rare system to study the unique crystalline morphology and crystallization behavior of miscible crystalline/crystalline polymer blends. Such research is very interesting and challenging for a better understanding of the crystalline morphology and crystallization behavior of crystalline polymer blends from both academic and practical viewpoints.

Morphology and rheological properties of silica-filled poly(carbonate)/poly(methyl methacrylate) blends

The effect of silica nanoparticles on the morphology and the rheological properties was investigated in the immiscible polymer blend poly(carbonate)/poly(methyl methacrylate) (PC/PMMA). In the melt state, the linear viscoelastic properties of the nanocomposite showed a reduction effect of the silica nanoparticles on the mobility of one of the polymer which is related to the state of distribution of the silica nanoparticles. Hydrophilic and hydrophobic silica particles were used to study particle migration and their effects on the morphology and it was shown that the distribution of the nanoparticles depends on the balance of interactions between the surface of the particles and the polymer components. The effect on the coarsening kinetics was investigated in both hydrophilic and hydrophobic silica-filled blends. Compared to the hydrophilic silica, a better compatibilization can be obtained by introducing the hydrophobic silica particles at the PC/PMMA interface as the solid barrier. POLYM. ENG. SCI., 55:1951–1959, 2015. © 2014 Society of Plastics Engineers

Notch Sensitivity of Poly(Acrylonitrile-Butadiene-Styrene)/Poly(Methyl Methacrylate)/Ethylene Methacrylate Co-Polymer (EMA) Composites

Polymer blends of poly (acrylonitrile-butadiene-styrene)/poly (methyl methacrylate) with ethylene methacrylate copolymer (EMA) were injection molded, and the notch sensitivity of the bends were examined by Izod impact and tensile tests. Investigations revealed that the toughness of ABS/PMMA composites were greatly improved and appeared a linear increase with the addition of EMA. However, the blends also show strong notch sensitivity due to the EMA component but the EMA content seems not a factor responsible for it. Tensile tests of the blends revealed that notches in any depth have great detrimental effects on the elongation at break of the materials, which is not consistent with the calculated notch sensitivity factor (kS) data.

Characterization of poly (vinyl alcohol)/poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) polymer blend: structure, optical absorption, electrical and dielectric properties

Polymer blends of poly (vinyl alcohol) (PVA) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)), were prepared by casting from aqueous solution. They were characterized by x-ray diffraction, scanning electron microscopy, differential scanning calorimetery, thermo gravimetric analysis, Fourier transform infrared, ac spectroscopy and optical UV–visible absorption techniques. The thermal analysis did not illustrate significant variations of PVA when blended with different concentrations of PEDOT:PSS. The bulk conductivity of PVA/PEDOT:PSS blend illustrated a two orders increase, while the activation energy reduced from 0.52 to 0.16 eV with an increasing PEDOT:PSS concentration to 4 wt%. In addition, the frequency dependence of conductivity obeyed the power relation σ ∼ ωs, 0.3 < s < 0.45, which predicts ionic diffusion. The dielectric constant and dielectric loss ε″ obeyed, at ambient temperature, the Debye dispersion relations in a wide range of frequencies. A new significant optical broad absorption peak appeared in the visible range around 926 nm. Its height increased by increasing the PEDOT:PSS concentration, which was attributed to a direct energy band gap, in the range 1.05–1.2 eV, and plasmon–exciton interaction.

Characterization of the Microstructure and Mode I Fracture Property of Biodegradable Poly(L-lactic acid) and Poly(ϵ-caprolactone) Polymer Blends with the Additive Lysine Triisocyanate

Biodegradable polymer blends of poly(L-lactic acid) (PLLA) and poly(ϵ-caprolactone) (PCL) with the addition of 2 phr lysine triisocyanate (LTI) were investigated using the Fourier transform infrared (FT-IR) spectroscopy, field-emission electron scanning microscope (FE-SEM), and mode I fracture testing technique. It was found that the addition of LTI dramatically improved the phase-separation morphology of the PLLA/PCL blends, hence increase the mode I fracture properties. The FT-IR analysis suggested that LTI acted as a compatibilizer by inducing secondary interaction between the NCO groups of LTI with the OH groups of PLLA and PCL.

Miscibility, water uptake, ion exchange capacity, conductivity and dielectric studies of poly(methyl methacrylate) and cellulose acetate blends

ABSTRACTIn the last few decades, polymer blends with good miscibility and conductivity have been the focus of study for material scientists. Here, polymer blends of Poly(methyl methacrylate) (PMMA) and Cellulose acetate (CA) of varying blend compositions have been prepared by solution casting method and their miscibility, water uptake, ion exchange capacity (IEC) proton conductivity, and dielectric properties have been studied. Dimethyl formamide (DMF) was used as solvent. Fourier transform infrared spectra (FTIR) and Differential scanning calorimetry (DSC) measurements have been used to analyze the miscibility of the blends. Up to 50/50 PMMA/CA, water uptake showed an increasing trend and for other compositions the value decreased. Ion exchange capacity and conductivity of the blends decreased with increase in PMMA content of the blends. The variations in the blend properties have been attributed to the presence of specific interactions and exchangeable groups in the blend system. The proton conductivity of the blends is in the order of 10−3 S cm−1. Impedance analysis of the blends indicated the absence of any relaxation phenomenon in the blend system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3074–3081, 2013

Effect of lower critical solution temperature phase separation on crystallization kinetics and morphology of poly(butylenes succinate)/poly(ethylene oxide) blend

The crystalline/crystalline polymer blend of poly(butylenes succinate)/poly(ethylene oxide) (PBS/PEO) exhibited lower critical solution temperature (LCST) phase separation behavior at temperatures above the melting point of PBS, which was measured by phase contrast optical microscopy (PCOM) technique. In this work, we determined the LCST phase diagram of PBS/PEO blends, and then investigated the effect of liquid–liquid phase separation (LLPS) on the crystallization kinetics and morphologies of PBS/PEO (40/60 wt/wt) blend. Based on polarized optical microscopy (POM), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC) results, we found that the spherulite morphology and crystallization kinetics of PBS were strongly influenced by the initial LLPS structure; because the kinetics of liquid–liquid phase dissolution was much slower than that of crystallization. The effect of LLPS on the primary nucleation density and crystal growth rate of PBS were strongly dependent on the crystallization temperature of PBS. After a second quench to a temperature below the melting point of PEO, the fractionated crystallization of PEO was observed. The competition between the kinetics of LLPS and the driving force of PBS crystallization controlled the spatial distribution of PEO in PBS spherulites, thus essentially determined the confined conditions of the PEO crystallization. The results indicated that the LLPS was an effective process to control the crystallization kinetics and morphology in crystalline/crystalline polymer blend systems.

Effects of blending on the molecular dynamics of highly interacting binary polymer blends of poly(methyl methacrylate) and poly[styrene-co -(maleic anhydride)

The molecular dynamics and miscibility of highly interacting binary polymer blends of poly(methyl methacrylate) (PMMA) and poly[styrene-co-(maleic anhydride)] random copolymer with 8 wt% maleic anhydride content (SMA) were investigated as a function of composition over a wide range of frequency (10−2–106 Hz) at different constant temperatures (30–160 °C). Only one common glass relaxation process (α-process) was detected for all measured blends, and its dynamics and broadness were found to be composition dependent. The existence of only one common α-relaxation process located at a temperature range between those of the pure polymer components indicated the miscibility of the two polymer components over the entire range of composition. The miscibility was also confirmed by measuring the glass transition temperatures of the blends, Tg, using differential scanning calorimetry. The composition dependence of Tg of the blends showed a positive deviation from the linear mixing rule and well described by the Gordon–Taylor–Kwei equation. The relaxation spectrum of the blends was resolved into α- and β-relaxation processes using the Havriliake–Negami (HN) equation and ionic conductivity. The dielectric relaxation parameters obtained from HN analysis, such as broadness of relaxation processes, maximum frequency, fmax, and dielectric strength, Δϵ (for the α- and β-relaxation processes), were found to be blend composition dependent. The kinetics of the α-relaxation process of the blends were well described by the Meander model, while an Arrhenius-type equation was used to evaluate the molecular dynamics of the β-relaxation process. Blending of PMMA and SMA was found to have a considerable effect on the kinetics and broadness of the β-relaxation process of PMMA, indicating that the strong interaction and miscibility between the two polymer components could effectively change the local environment of each component in the blend. © 2013 Society of Chemical Industry

Charge mosaic membranes with semi-interpenetrating network structures prepared from a polymer blend of poly(vinyl alcohol) and polyelectrolytes

Charge mosaic (CM) membranes with semi-interpenetrating network structures were prepared by blending poly(vinyl alcohol) as a membrane matrix, poly(allyl amine) as a polycation and poly(vinyl alcohol-co-2-acrylamido-2-methyl propane sulfonic acid) as a polyanion with varying polyelectrolyte contents under different cross-linking conditions. Our method can prepare CM membranes of a large area easily at low manufacture cost. Although the flux of electrolytes through the membrane is less than that through a typical charge mosaic membrane such as Desalton® (Tosoh Co., Ltd.), which was prepared using micro-phase separation, the permselectivity for electrolytes through the CM membrane was more than 4 times higher than Desalton®. These CM membranes have enough mechanical strength to form thin layer on a porous support membrane, thereby increasing the flux of electrolytes.

Energy transfer from conjugated polymer to bacterial light-harvesting complex

Energy transfer from a conjugated polymer blend (poly(9,9-dioctylfluorenyl-2,7-diyl):poly (2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene) to a light-harvesting complex 2 from purple bacteria has been demonstrated using time-resolved fluorescence spectroscopy. For our hybrid nanostructure, we observe a 30% reduction of the fluorescence lifetime of the polymer emission as compared to the pure polymer layer. This result is an important step towards integrating naturally evolved biomolecules with synthetic materials into biohybrid organic electronic systems.

Polymer Blends of Poly(Vinyl Chloride) and Lower-Melting Point Polyamide-6 Compatibilized by Epoxy

Lower-melting point polyamide-6 (LPA6) with the melting point of 198°C was prepared through melting extrusion. Blends of poly (Vinyl Chloride) (PVC) and LPA6 which use epoxy (EP) as compatibilizer were prepared by blending PVC and LPA6. The effects of the composition of PA6 and epoxy on the morphology and mechanical properties were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The behavior of the blends was also determined experimentally using the dynamic mechanical analysis (DMA). Experiments revealed that, the epoxy resin F51 plays a compatibilizer. The more of the content of epoxy resin, the better of compatibility between PVC and PA6. With the increase of PA6, the degree of crystallization, crystallization rate and the regularity of crystal grain increased, the tensile strength declinged, the flexural strength and notched impact strength increase first and then decrease, both of then had an extreme value when the content of PA6 is 20wt%.

Effect of secondary forces in the compatibility of two incompatible biodegradable polymers

Poly(ethylene adipate) (PEA) and polytetramethylene ether glycol (PTMEG) were used as compatibilizers in the biodegradable polymer blend of poly(l-lactic acid)/poly(butylene succinate-co-l-lactate) (PLLA/PBSL). The compatibilizers of various contents were incorporated into the blend using a Haake internal mixer. The compatibilization between PEA and PTMEG on the blends was measured using thermogravimetric analysis (TGA), flexural test, field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy. From the TGA results, it was found that the thermal stability of the blend improved with the addition of PEA. The flexural strength showed a dependency on the extent of the secondary forces interaction between PEA and PTMEG with the blends. This observation corresponded well with the FESEM micrographs. Based on the FTIR analysis, the physical interaction between PEA and PLLA/PBSL was due to the presence of secondary forces.

Enhanced visualization of biodegradable polymeric vascular scaffolds by incorporation of gold, silver and magnetite nanoparticles

Due to improved tissue regeneration and the enabling of post-operative minimally invasive interventions in the same vessel segment, biodegradable polymeric scaffolds represent a competitive approach to permanent metallic stents in vascular applications. Despite these advantages some challenges, such as the improvement of the scaffold mechanics and enhancement of scaffold visibility during the implantation procedure, are persisting. Therefore, the scope of our studies was to investigate the potential of gold, silver and magnetite nanoparticles incorporated in a polymeric blend of poly(L-lactide)/poly(4-hydroxybutyrate) for image enhancement in X-ray, magnetic resonance or near-infrared imaging. Their impact on mechanical properties of such modified scaffold materials was also evaluated.

The Effect of Thermal Pretreatments on the Mechanical Properties of the Blend Consisting of Poly(Ethyl Methacrylate) and Poly(Ethylene Oxide)

The solution cast technique for the preparation of polymer blends of poly(ethylmethacrylate) (PEMA) and poly(ethylene oxide)(PEO) is described. Polymer blends of poly(ethylmethacrylate) (PEMA) and poly(ethylene oxide) (PEO) with different weight percentage ratio of the two polymers have been prepared. Effect of thermal pretreatments like annealing and quenching on the mechanical properties of polymer blends of PEMA and PEO have been reported using Vicker's microhardness testing. The thermal pretreatment produces morphological changes in the blend system investigated. These thermal pretreatments results in hardening and softening of blend systems under investigation.

Factorial Study of Compressive Mechanical Properties and Primary In Vitro Osteoblast Response of PHBV/PLLA Scaffolds

For bone tissue regeneration, composite scaffolds containing biodegradable polymers and nanosized osteoconductive bioceramics have been regarded as promising biomimetic systems. Polymer blends of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) and poly(L‐lactic acid) (PLLA) can be used as the polymer matrix to control the degradation rate. In order to render the scaffolds osteoconductive, nano‐sized hydroxyapatite (nHA) particles can be incorporated into the polymer matrix. In the first part of this study, a factorial design approach to investigate the influence of materials on the initial compressive mechanical properties of the scaffolds was studied. In the second part, the protein adsorption behavior and the attachment and morphology of osteoblast‐like cells (Saos‐2) of the scaffolds in vitro were also studied. It was observed that nHA incorporated PHBV/PLLA composite scaffolds adsorbed more bovine serum albumin (BSA) protein than PHBV or PHBV/PLLA scaffolds. In vitro studies also revealed that the attachment of human osteoblastic cells (SaOS‐2) was significantly higher in nHA incorporated PHBV/PLLA composite scaffolds. From the SEM micrographs of nHA incorporated PHBV/PLLA composite scaffolds seeded with SaOS‐2 cells after a 7‐day cell culture period, it was observed that the cells were well expanded and spread in all directions on the scaffolds.

Compressive mechanical properties and deformation behavior of porous polymer blends of poly(ε-caprolactone) and poly(l-lactic acid)

Porous biodegradable polymeric scaffolds are developed by physically blending two different kinds of biodegradable polymers, PCL, and PLLA, for application in tissue engineering. The main objective of the development of this material is to control the mechanical properties, such as, elastic modulus and strength. The results from mechanical testing showed that the compressive mechanical properties of PCL/PLLA scaffold can be varied by changing the blend ratio. It also showed that these properties can be well predicted by the rule of mixture. The primary deformation mechanism of the scaffolds was found to be localized buckling of struts surrounding the pores. Localized ductile failure caused by PCL phase tends to be suppressed with increasing PLLA content. The immiscibility of PCL and PLLA caused the phase-separation morphology that strongly affected the macroscopic mechanical properties and the microscopic deformation behavior.

Charge Transport and Recombination in Low‐Bandgap Bulk Heterojunction Solar Cell using Bis‐adduct Fullerene

AbstractCharge transport and recombination are studied for organic solar cells fabricated using blends of polymer poly[(4,4′‐bis(2‐ethylhexyl)dithieno[3,2‐b:2′,3′‐d]silole)‐2,6‐diyl‐alt‐(4,7‐bis(2‐thienyl)‐2,1,3‐benzothiadiazole)‐5,5′‐diyl] (Si‐PCPDTBT) with [6,6]‐phenyl‐C61‐butyric acid methyl ester (mono‐PCBM) and the bis‐adduct analogue of mono‐PCBM (bis‐PCBM). The photocurrent of Si‐PCPDTBT:bis‐PCBM devices shows a strong square root dependence on the effective applied voltage. From the relationship between the photocurrent and the light intensity, we found that the square‐root dependence of the photocurrent is governed by the mobility‐lifetime (μτ) product of charge carriers while space‐charge field effects are insignificant. The fill factor (FF) and short circuit current density (Jsc) of bis‐PCBM solar cells show a considerable increase with temperature as compared to mono‐PCBM solar cells. SCLC analysis of single carrier devices proofs that the mobility of both electrons and holes is significantly lowered when replacing mono‐PCBM with bis‐PCBM. The increased recombination in Si‐PCPDTBT:bis‐PCBM solar cells is therefore attributed to the low carrier mobilities, as the transient photovoltage measurements show that the carrier lifetime of devices are not significantly altered by using bis‐PCBM instead of mono‐PCBM.

Restricted Molecular Rotation and Enhanced Emission in Polymer Blends of Poly(fluorene-alt-naphthol) and Poly(vinyl pyrrolidone) with Mutual Hydrogen-Bond Interactions

In this study, fluorescent alternative copolymer poly(fluorene-alt-1,6-naphthol) (PFN) with inherent hydroxyl (OH) groups was blended with poly(vinyl pyrrolidone) (PVR) through facile hydrogen-bond (H-bond) interactions. The emission intensities of the resultant PFN/PVR mixtures of different compositions were shown to increase with increasing PVR content in both the chloroform solution and in the solid film states. The H-bond interactions between PFN and PVR resulted in the restricted molecular rotations of the fluorophores, which lead to the blockage of nonradiative energy decay channels and the accompanied emission enhancement. With the efficient H-bond interactions, the PFN/PVR blend with the low content (2.33 wt %) of fluorescent PFN component actually has a high quantum efficiency of 0.93, comparatively higher than other blends containing higher fluorescent PFN. The role of the H-bonding on the restricted molecular rotations of the PFN/PVR blends was therefore evaluated by the infrared, the 1H NMR sp...

Rheology and phase separation of polymer blends with weak dynamic asymmetry

Abstract Rheological methods have been frequently used to study the phase separation behavior of partially miscible polymer blends. Usually the binodal temperature can be determined from the failure of time–temperature superposition (TTS) principle in isothermal experiments, or the deviation of the storage modulus from the apparent extrapolation of modulus in miscible regime in non-isothermal experiments. However, these methods are shown in this work to be not widely applicable even in blends with weak dynamic asymmetry due to the thermo-rheological complexity. A rheological model which is an integration of the double reptation model and the self-concentration model is found to describe the linear viscoelasticity of miscible blends quite satisfactorily, from which it is possible to follow the contribution from the miscible blends even in the two phase regime. Then, the binodal temperature is readily defined as the deviation of experimental data from such model prediction for miscible blends. Such method is successfully applied in a model polymer blend (poly(methyl methacrylate)/poly(styrene-co-maleic anhydride), PMMA/SMA) with weak dynamic asymmetry.

Orienting Periodic Organic−Inorganic Nanoscale Domains Through One-Step Electrodeposition

One of the challenges in the synthesis of hybrid materials with nanoscale structure is to precisely control morphology across length scales. Using a one-step electrodeposition process on indium tin oxide (ITO) substrates followed by annealing, we report here the preparation of materials with preferentially oriented lamellar domains of electron donor surfactants and the semiconductor ZnO. We found that either increasing the concentration of surfactant or the water to dimethyl sulfoxide ratio of solutions used resulted in the suppression of bloomlike morphologies and enhanced the density of periodic domains on ITO substrates. Furthermore, by modifying the surface of the ITO substrate with the conductive polymer blend poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), we were able to alter the orientation of these electrodeposited lamellar domains to be perpendicular to the substrate. The long-range orientation achieved was characterized by 2D grazing incidence small-angle X-ray scattering. This high degree of orientation in electronically active hybrids with alternating nanoscale p-type and n-type domains is of potential interest in photovoltaics or thermoelectric materials.