Miscibility Of Poly Research Articles

Miscibility behavior of hydroxyethyl cellulose/poly(vinyl pyrrolidone) blends in the presence of some imidazolium based ionic liquids

In this study, the effect of 1–butyl–3–methyl imidazolium bromide ([BMIm]Br); 1–hexyl–3–methyl imidazolium bromide ([HMIm]Br) and 1–octyl–3–methyl imidazolium bromide ([OMIm]Br) ionic liquids on the miscibility of poly(vinyl pyrrolidone) and hydoxyethyl cellulose (PVP/HEC) blends were examined. The polymer solvent method was used to study miscibility of PVP/HEC blends. Two miscibility criterions on the based Δ[η] and ΔK were used to evaluate miscibility. Both Δ[η] and ΔK miscibility criterions confirmed that the PVP/HEC blends are miscible. PVP/HEC blends in the solid state were characterized with attenuated total reflective-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC) and field emission-scanning electron microscopy (FE-SEM). The miscibility of PVP/HEC blends was confirmed by ATR-FTIR, DSC and FE-SEM results. This miscibility was attributed to the strong intermolecular hydrogen bonding interactions between the –OH groups of HEC and –C = 0 groups of PVP.

Electrical conductivity of carbon nanotube-filled miscible poly(phenylene oxide)/polystyrene blends prepared by melt compounding

Conductive polymer composites (CPCs) have attracted tremendous attention from both academia and industry for several decades. Unfortunately, high conductive filler loadings required for current CPCs to obtain insulator/conductor transition (usually defined as percolation threshold) significantly limit their development. Although some methods have been put forward over the past decades, no-one is cost effective and not compatible with industrial production. Here we reported a low cost and high processing efficiency method to develop high-performance CPCs with low percolation threshold. Miscible poly(phenylene oxide)/polystyrene (PPO/PS) blends with different compositions were used as the matrices, and the dispersion of carbon nanotubes (CNTs) was tuned by the viscosity of the matrices which result from different blend ratio. The best dispersion state of CNTs as well as the best electrical conductivity of the nanocomposites were found at the intermediate matrix viscosity that had balanced effects on infiltration of polymer molecules and breakage of primary CNT agglomerates. The percolation threshold of PPO/PS(35/65)/CNTs nanocomposites is 63% lower than that of PS/CNTs nanocomposites because of the significantly better dispersion state of CNTs. The electrical resistivity of PPO/PS(35/65)/2%CNTs is about 103 Ω cm which is 9 orders of magnitude lower than that of PS/2%CNTs.

Bioinspired cellular sheath-core electrospun non-woven mesh

Fibers are valuable to biomedical applications. Used as sutures or meshes, there is an increased dual need to provide functionality such as drug delivery. Porosity represents a high surface area to volume architecture. Coaxial fibers with porous and non-porous layers offer a new design framework for fiber design that can resolve dual needs of mechanical robustness with transport phenomena. Using preferential solubility of a polymer in supercritical CO2, we develop a new architecture using biocompatible polymers based on porous core-sheath fiber fabrication technique. Polycaprolactone was selected as the CO2 miscible phase and Poly(butyrate adipate terephthalate)(PBAT) as the immiscible phase. The mechanical performance of the fibers was investigated using quasi static and dynamic loading. SEM images indicate no physical detachment of the two polymer surface after CO2 exposure indicating a successful amalgamation of polymers at the boundary of core and sheath. PCL as a sheath and as a core showed an increase of 650% and 468% in tensile strength compared to pristine PCL and PBAT. Introduction of porosity on the surface of coaxial fiber fPCL(cPBAT) further enhanced the yield strength increases by 40%. Dynamic mechanical analysis was used to analyze the viscoelastic properties of the fibers. The storage and loss modulus for coaxial fibers shows superior modulus throughout the glassy, glass transition and rubbery region as compared to the pristine PCL and PBAT, showing enhancement in both the elastic and viscous response of the material. The results indicate a new approach that is free of volatile organic solvents to manipulate the architecture of the cross-section of the electrospun fiber and tailor mechanical properties to the required application.

Structural and physicochemical properties of melt-quenched poly(ethylene carbonate)/poly(lactic acid) blends

The effect of the melt-quench process on the thermal, structural and mechanical properties of partially miscible poly(ethylene carbonate) (PEC)/poly (lactic acid) (PLA) blends was investigated. The differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements found a largely amorphous phase of melt-quenched PEC/PLA blends, with crystallinity in the range 6–12%, depending on the PEC and PLA ratios. The high chain mobility of PEC reduces the cold-crystallization temperature of PLA for the melt-quenched PEC/PLA blends by more 12 °C, as in the PEC60/PLA40 blend. Upon the rapid cooling, however, the morphology of PEC/PLA blend changes to enhance the toughness, especially for the PLA-rich blend. Addition of 10 wt% PEC to PLA slightly improved the tensile toughness, from 5.1 MJ/m3 to 5.5 MJ/m3, in which ductile PEC improves the toughness of PLA. SEM images of the quenched fracture cross-section of melt-quenched PEC/PLA blends confirmed that PEC and PLA are compatible, with a two-phase structure in which small PLA domains are distributed in the continuous PEC phase. This structure is responsible for the high interfacial adhesion in the sea-island morphology of PEC-rich blends, giving improved resistance to failure of PEC.

Solvent and polymer H/D isotope effects on miscibility in Poly(ethylene oxide)/Ethanol system

Various combinations between deuterated/nondeuterated poly(ethylene oxide) and (fully and partly) deuterated/nondeuterated ethanol solvents were investigated by small-angle neutron scattering. It was found that the deuteration process has strong effects on the polymer solution behavior when approaching the solubility limit upon cooling. Deuteration of the polymer and/or of the solvent can change the character of mixing/demixing and even 'flip' the upper/lower critical solution temperature trends in experimental temperature range.

Miscibility of Poly(hydroxybutyrate)/Poly(vinyl alcohol) Melt Blends Plasticized With Glycerol

Miscibility of Poly(hydroxybutyrate)/Poly(vinyl alcohol) Melt Blends Plasticized With Glycerol

Novel biodegradable and non-fouling systems for controlled-release based on poly(ε-caprolactone)/Quercetin blends and biomimetic bacterial S-layer coatings.

Quercetin is a strong antioxidant with low bioavailability due to its high crystallinity. A further drawback is that Quercetin has potentially toxic effects at high concentrations. To improve this low water solubility, as well as control the concentration of the flavonoid in the body, Quercetin is incorporated into a polymeric matrix to form an amorphous solid dispersion (ASD) stable enough to resist the recrystallization of the drug. For this purpose, miscible poly(ε-caprolactone) (PCL) and Quercetin (Q) blends are prepared, provided that they have complementary interacting groups. For compositions in which the flavonoid remains in an amorphous state thanks to the interactions with polymer chains, various PCL/Q drug release platforms are fabricated: micrometric films by solvent casting, nanometric films by spin coating, and nanofibers by electrospinning. Then, the potential use of bacterial S-layer proteins as release-preventive membranes is tested on PCL–Quercetin blends, due to their ability to construct a biomimetic coating including nanometric pores. For all the platforms, the SbpA coating can maintain a stable release under the toxicity level of Quercetin. Accordingly, a PCL/Q system with an S-layer coating allows the design of versatile bioavailable Quercetin eluting devices that prevent toxicity and biofouling issues.

Hydrogen bond mediated partially miscible poly(N-acryloyl piperidine)/poly(acrylic acid) blend with one glass transition temperature

In this work, we have systematically studied the miscibility and phase structure of a hydrogen-bonded polymer blend composed of short rigid poly(N-acryloyl piperidine) (PAP) and long flexible poly(acrylic acid) (PAA). Ultrathin PAP/PAA blend films with various compositions were prepared by solution-casting method. It was found that the spin-coated blend films had distinct surface features with many protuberant domains that can be extracted by toluene. Composition analysis of the isolated protrusion domains and matrix domains revealed that PAP/PAA blend is a partially miscible system with PAP-rich protrusion phase (dispersed phase) and PAA-rich matrix phase. The hydrogen-bonding interaction between the amide carbonyl of PAP and hydroxyl of PAA (O=C⋯H-O) was found to account for the partial miscibility of these two components. Interestingly, only one positively shifted glass transition temperature (Tg) was detected for this blend. This behavior is very different from other reported partially miscible polymer blends, in which two inward shifted Tgs are usually observed. Thermal analysis further disclosed that Tgs of PAP-rich dispersed phase and PAA-rich matrix phase are very close to each other, thus merged into one broad Tg presented in the blend. The close Tgs of these two phases is attributed to the strong hydrogen-bonding interaction between PAP and PAA, which surpasses the compositional difference between them. At high PAP concentrations (above 60 mol percent), the separation of excess PAP in dispersed phase contributed to the appearance of a second Tg that corresponds to that of PAP. Such phase behavior was further confirmed in the free-standing films of PAP/PAA blends.

Towards the development of electrospun mats from poly(ε-caprolactone)/poly(ester amide)s miscible blends

In this work, electrospun mats made from miscible poly(ε-caprolactone) (PCL)/poly(ester amide) (PEA) blends were prepared, for the first time. The well-known immiscibility issues between these two type of polymers were overcome through the synthesis of a novel tailor-made compatibilizer blocky PEA, comprising well defined PCL and PEA8L6 blocks (PCL-PEA8L6). The PCL-PEA8L6 was synthesized for the first time in this work and was characterized in terms of its chemical structure and thermal properties. Regarding the mats, it was found that their properties (morphology, porosity, wettability, thermomechanical) can be easily adjusted by the ratio of the components of the mixture to be electrospun. Increasing amounts of PEA led to more hydrophilic mats, with enhanced in vitro degradability, both hydrolytic and enzymatic. The in vitro cytotoxicity tests carried out with normal human dermal fibroblasts (NHDF) revealed that the samples do not elicit any acute adverse effect on the cells. Moreover, the NHDF were able to grow and proliferate in the surface of the electrospun mats. The data presented in this contribution is a proof-of-concept that can be used to address immiscibility issues between different types of polymers broadly used in biomedical applications.

Miscibility of Poly(Ethylene-co-Vinylalcohol)/Poly(δ-Valerolactone) Blend and Tissue Engineering Scaffold Fabrication Using Naphthalene as Porogen

ABSTRACTHerein, various poly(ethylene-co-vinylalcohol)/poly(δ-valerolactone) blends were prepared at different ratios by solvent casting for use in tissue engineering. The miscibility of these polymers was studied in detail using differential scanning calorimetry, Fourier-transform infra-red spectroscopy, and X-ray diffraction. The Avrami model have been applied for determining the isothermal crystallization kinetics of poly(ethylene-co-vinyl alcohol), poly(δ-valerolactone) and their blend with equal compositions, in which the Avrami parameters, the maximum crystallization time and the half-time were deducted. Cell adhesion and cell proliferation of the resultant materials were examined by an (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide)MTT assay; the blend containing equal amounts of the two polymers showed the best performance. Micropores and their connections were formed by using a new porogen under vacuum at temperatures slightly less than the glass transition temperature. The produced micropores and their interconnections were studied using scanning electron microscopy.

Impact of Molecular Weight on the Thermal Stability and the Miscibility of Poly(ε-caprolactone)/Polystyrene Binary Blends

Poly(e-caprolactone) (PCL) and two different molecular weight (6K and 650K) of polystyrene (PS) were mixed in solution to prepare binary blends of PCL/PS with various compositions. The impact of the molecular weight of PS in the blends was studied on thermal stability and miscibility by the thermogravimetric analysis (TGA) and the differential scanning calorimetry (DSC) method. The TGA results under dynamic conditions in an inert atmosphere show that the thermal stability of the blends depends on the length of PS molecules. The increase of the low molecular weight PS into the PCL/PS blend reduces the thermal stability while the high molecular weight PS improves the thermal stability. The crystallization peak temperature, enthalpy, and crystallinity of the blends are found molecular weight dependent; these parameters with blend compositions deviate from linearity of additive law for low molecular weight PS, while they do follow the additive law for high molecular weight PS. A significant melting point depression of PCL crystals with composition was observed for the blends with the incorporation of the low molecular weight PS, while the no significant melting temperature depression was observed for the high molecular weight PS. The experimental results clearly indicate that in the PCL/PS blends, the thermal stability and the interaction between the neat components strongly depend on the molecular weight of the PS.

Evolution and disappearance of solvent drops on miscible polymer subphases

Traditionally, an interface is defined as a boundary between immiscible phases. However, previous work has shown that even when two fluids are completely miscible, they maintain a detectable “effective interface” for long times. Miscible interfaces have been studied in various systems of two fluids with a single boundary between them. However, this work has not extended to the three-phase system of a fluid droplet placed on top of a miscible pool. We show that these three-phase systems obey the same wetting conditions as immiscible systems, and that their drop shapes obey the Augmented Young-Laplace Equation. Over time, the miscible interface diffuses and the shape of the drop evolves.We place 2-microliter drops of water atop miscible poly(acrylamide) solutions. The drop is completely wetted by the subphase, and then remains detectable beneath the surface for many minutes. An initial effective interfacial tension can be approximated to be on the order of 0.5 mN/m using the capillary number. Water and poly(acrylamide) are completely miscible in all concentrations, and yet, when viewed from the side, the drop maintains a capillary shape. Study of this behavior is important to the understanding of effective interfaces between miscible polymer phases, which are pervasive in nature.

Miscibility and degradation of polymer blends based on biodegradable poly(butylene adipate-co-terephthalate)

The aim of this work is to analyse the effect of the preparation method on the miscibility of poly(butylene adipate-co-terephthalate) (PBAT) and poly(hydroxy ether of bisphenol A) (PH) blends and to provide a better understanding on the effect of a non-degradable component (PH) in the degradation of biodegradable PBAT. Blends have been prepared by different methods and the miscibility has been studied in a deeper way by means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). Depending on the preparation method miscible or partially miscible blends are obtained. Furthermore, for miscible blends the hydrolytic degradation has been carried out for 405 days. It has been observed that adipate sequences on poly(butylene adipate-co-terephthalate) copolymer are more prone to degradation which leads to changes on glass transition temperature, crystallinity and chemical structure. The degradation rate is decelerated with the addition of PH, however the rate is similar or higher than other biodegradable polymers. Therefore the degradation rate can be controlled varying the composition of the blend and tailored materials with adequate properties can be obtained.

Crystallization and concentration fluctuation of miscible poly(vinylidene fluoride)/poly(methyl methacrylate) blends containing carbon nanotubes: Molecular weight dependence of poly(methyl methacrylate)

In this work, poly(vinylidene fluoride)/poly(methyl methacrylate) (PVDF/PMMA) blend (50/50, wt/wt) and its blend composites containing carbon nanotubes (CNTs, 0.2 and 0.5 wt%) were prepared. Two types of PMMA with relatively large (PMMA-L) and small (PMMA-S) molecular weights were used to prepare the materials. It was observed that PVDF had higher crystallization ability in the samples containing PMMA-S. CNTs exhibited nucleation effect on the crystallization of PVDF and their nucleation efficiency was influenced by the molecular weight of PMMA. Rheological measurements showed that concentration fluctuation occurred during the melt annealing process even if the blend should be miscible at this temperature range, and more apparent concentration fluctuation was observed for the samples containing PMMA-S. Incorporating CNTs restrained the concentration fluctuation of the blend under the shear condition. Further results showed that larger concentration fluctuation in the melt state facilitated the higher crystallization ability of PVDF in the subsequent cooling process.

Miscibility of poly(acrylic acid)/poly(methyl vinyl ketone) blend and in vitro application as drug carrier system

ABSTRACTA series of poly(acrylic acid)/poly(methyl vinyl ketone) (PAA/PMVK) blends with different compositions were prepared by the solvent casting method. The miscibility of this pair of polymers was investigated by differential scanning calorimetry(DSC), Fourier transform infra-red (FTIR) and X-Ray diffraction (XRD) techniques. An in-vitro cytotoxicity test of the drug-carrier system via MTT (3-(4,5-demethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay revealed no significant cytotoxic effects at concentrations up to 100 µg· ml−1. The STX/PAA-50 drug carrier systems were also prepared by solvent casting of solutions containing the sulfamethoxazole (STX) used as drug model and PAA/PMVK blend in N.N-dimethylformamide then crosslinked with acidified ethylene glycol. The release dynamic of STX from the prepared hydrogels was investigated in which the diffusion through the polymer matrix, the enhancement of the water solubility of STX, the influence of the initial drug concentration, the pH of the medium, and the effect of the degree of swelling of the polymer matrix on the release dynamic was evaluated. According to the total gastrointestinal transit time estimated by Belzer, the estimate distribution of STX released in the different organs indicated that the performance is obtained with the drug – carrier-system containing equal ratios of polymer and 10 wt% of STX (STX-10/PAA-50).

Transparency, ultraviolet transmittance, and miscibility of poly(lactic acid)/poly(methyl methacrylate) blends

Poly(lactic acid)/poly(methyl methacrylate) (PLA/PMMA) blends were prepared by melt compounding technique. The miscibility of PLA/PMMA blends at various blending ratios (i.e. 80/20, 60/40, 40/60, and 20/80) was investigated using a dynamic mechanical analyzer (DMA) and solvent uptake experiment. The solvent uptake experiment was conducted to estimate the interaction of PLA/PMMA blends based on the calculation of Flory–Huggins interaction parameter ( χ12). DMA results revealed that only single glass transition temperature ( Tg) existed along the PLA/PMMA blends. Smallest χ12 (i.e. −0.03) was found on the PLA/PMMA20 blend, suggesting interaction between PLA and PMMA at this composition. The incorporation of PMMA slightly improved the UV protection properties of the PLA/PMMA blend, while maintaining their optical transparency.

Crystallization of poly(l-lactide) in the miscible poly(l-lactide)/poly(vinyl acetate) blend induced by carbon nanotubes

In this work, carbon nanotubes (CNTs) were introduced into miscible poly(l-lactide)/poly(vinyl acetate) (PLLA/PVAc) blend and the crystallization behaviors of PLLA with the presence of PVAc and CNTs are systematically discussed. The dispersion state of CNTs was characterized using scanning electron microscope, and the crystallization behaviors of PLLA in different conditions including melt crystallization and cold crystallization were comparatively investigated using polarized optical microscope, differential scanning calorimetry and wide angle X-ray diffraction. The results showed that the crystallization of PLLA was greatly restricted by PVAc. CNTs exhibit apparent nucleation effect, promoting the occurrence of both melt crystallization and cold crystallization. However, the nucleation effect of CNTs in the ternary composites is weakened as compared with that in the binary PLLA/CNTs composites. It was suggested that the relatively higher interfacial affinity between PVAc and CNTs, which possibly resulted in more PVAc molecule rather than PLLA molecule around the surface of CNTs, was the main reason for the reduced nucleation efficiency.

Crystallization kinetics and the fine morphological evolution of poly(ethylene oxide)/ionic liquid mixtures

The overall crystallization kinetics and spherulite morphologies of miscible poly(ethylene oxide) (PEO)/1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) mixtures were studied by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and rheological measurements. The finer crystal structures were further detected by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). Crystallization of PEO is largely suppressed by [BMIM][PF6] addition especially at higher ionic liquid (IL) concentrations above 20 wt%. Both the overall crystallization rate and the spherulite growth decrease with the increase of IL content and crystallization temperature; however, the crystallization mechanism keeps unchanged as evidenced by the similar Avrami exponent n and WAXD results. The addition of [BMIM][PF6] could induce more nuclei to some extent, but the induction time of crystallization is evidently prolonged, and a linear to non-linear transition of the spherulite growth (R ∝ t to R ∝ t 1/2) can be observed. At higher IL concentration, the spherulite texture changes apparently from particular serrated to branch surface due to the diffusion-controlled growth and the dilution effect, which also as a main factor contributes to the increasing trend of the long period of crystals.

Tg-confinement effects in strongly miscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene: Roles of bulk fragility and chain segregation

The glass transition temperature (Tg)-confinement effects in single-layer, supported films of strongly miscible poly(2,6-dimethyl-1,4-phenylene oxide)/polystyrene (PPO/PS) blends are characterized using ellipsometry and fluorescence, both of which report a single, reduced blend Tg upon confinement. These results indicate that PPO/PS blends exhibit strong miscibility under conditions of nanoscale confinement and that there is a lack of strong attractive polymer-substrate interactions in PPO/PS films supported on Si/SiOx. The strength of the Tg-confinement effect obtained via ellipsometry scales with bulk blend fragility in PPO/PS blends and exhibits a weaker dependence on bulk fragility than that observed previously [Evans et al. Macromolecules 2013, 46, 6091] in supported films of linear homopolymers lacking attractive polymer-substrate interactions. We further compare Tg results obtained from fluorescence of both pyrenyl labels (covalently attached to PS) and dopants (freely dispersed in PPO/PS blends) along with those from ellipsometry. In the confined state, pyrenyl dopant fluorescence reports blend Tg values that agree relatively well with Tg values reported by ellipsometry; in contrast, pyrenyl label fluorescence reports blend Tg values that are significantly lower than those reported by both ellipsometry and pyrenyl dopant fluorescence. We attribute this difference to the combined effects of the distribution of pyrenyl dye across the film and underlying surface segregation. Our results indicate that the combination of ellipsometry and fluorescence provides a powerful methodology to study interface-induced chain segregation in nanoconfined miscible polymer blends, whether in film geometry or in nanocomposites.

Mechanical properties and state of miscibility in poly(racD,L-lactide-co-glycolide)/(L-lactide-co-ε-caprolactone) blends

Polymers based on lactic acid (PLA) are a very promising category of biopolymers. As they are multi-stimuli responsive, can, in many ways, positively interact with the host, stimulating the innate reparative machinery of the human body. Since biopolymers for medical applications are subject to restrictive regulations, blending stands out as an effective method for obtaining tailored properties within a reduced time to market if compared to synthesis. Hence, in this study a set of PDLGA/PLCL blends was obtained by means of thermoplastic techniques and then further characterized. Evaluation techniques include GPC, NMR, DSC, tensile testing and SEM. Although mixtures proved to be immiscible, a full range of tensile properties was achieved. Observation of the surfaces of fracture provided visual evidence of the deformation mechanisms that occurred during the tensile tests which in the end led to failure. Interpretation of the thermal events based on molecular characterization parameters revealed phase separation, crystallization and plasticisation mechanisms that are relevant to any potential applications based on mechanical performance and shape memory behaviour.