Fabrication of tissue engineering scaffold from poly(vinylalcohol-co-ethylene)/poly(D,L-lactic-co-glycolic acid) blend: Miscibility,thermomechanical properties,and morphology

A series of poly(DL-lactide-co-glycolic acid) (PLGA) with poly(vinylalcohol-co-ethylene) (PEVAL) blends were prepared by solution casting method. The miscibility, thermal and mechanical properties have been investigated using FTIR, DSC, and DMA techniques. The miscibility of this pair of polymers throughout compositions was proved by these methods through the single T_g and the presence of interactions between the constituents. The TGA analysis revealed three degradation zones and no sensible enhancement in the thermal stability of PLGA was noted with addition of PEVAL content. The SEM analysis revealed that the draying method dramatically influence the surface morphology of copolymers and blend. The cross section micrograph of blend scaffold containing 50 wt% of PEVAL presents microcavities of diameter pores ranged between 70 and 170 µm interconnected and uniformly distributed in the polymer matrix.     

Toughening effect of poly(methyl methacrylate) on an immiscible poly(vinylidene fluoride)/polylactide blend

In this work, a mutually miscible third polymer, poly(methyl methacrylate) (PMMA), was incorporated into an immiscible poly(vinylidene fluoride)/polylactide (PVDF/PLA) blend (weight ratio 70:30). It was found that incorporation of PMMA in an appropriate amount (30–60 wt%) induced a marked improvement in fracture toughness. A five times enlargement of the elongation at break can be achieved by introducing 30 wt% PMMA. In order to understand the underlying toughening mechanism, SEM, dynamic mechanical analysis (DMA), XRD and DSC were applied to study the variations in morphology, the interaction between the three components and the crystallization behavior. SEM micrographs showed that the PMMA preferred to locate at the interface of PVDF and PLA, which was attributed to the mutual miscibility of PVDF with PMMA and PLA. Furthermore, a variety of thermal characteristics such as T_g and T_m induced by the entanglement of PVDF, PMMA and PLA at the interface were illustrated in DMA and DSC curves. Obviously, the interface consisting of the entanglement of PVDF, PLA and PMMA acted as a linkage to improve interfacial adhesion, which was regarded as the main toughening mechanism. This work provides a potential strategy to realize the interfacial enhancement of an immiscible blend via the incorporation of a mutually miscible third polymer. © 2016 Society of Chemical Industry     

Effects of europium (III) acetylacetonate doping on the miscibility and photoluminescent properties of polycarbonate and poly(methyl methacrylate) blends

Blends stand out as simple and cheap materials with unique properties. The miscibility of blends formed by bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) doped with europium (III) acetylacetonate have been studied by differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and photoluminescent (PL) spectroscopy. DSC studies demonstrated that undoped PC/PMMA blends obtained by precipitation method present one glass transition temperature, evidencing their apparent miscibility. FTIR spectra revealed synergic effects in the PC/PMMA system as well as the incorporation of the Eu³⁺ complex. TGA analysis suggested that the Eu³⁺ complex remains preferably in the PC micro-phase. SEM analysis showed that europium (III) acetylacetonate is homogeneously distributed within the blend and PL spectra evidenced the photoluminescence of Eu³⁺ incorporated into the blend.     

Miscibility enhancement on the immiscible poly (vinyl pyrrolidone) and poly (ethyl methacrylate) with poly (vinyl phenol)

The miscibility behavior of ternary blends of poly (vinyl phenol) (PVPh)/poly (vinyl pyrrolidone) (PVP)/poly (ethyl methacrylate) (PEMA) was investigated mainly with calorimetry. PVPh is miscible with both PVP and PEMA on the basis of the single T_g observed over the entire composition range. FTIR was used to study the hydrogen bonding interaction between the hydroxyl group of PVPh and the carbonyl group of PVP and PEMA at various compositions. Furthermore, the addition of PVPh is able to enhance the miscibility of the immiscible PVP/PEMA and eventually transforms it into a miscible blend, especially when the ratio between PVP/PEMA is 3:1, probably because of favorable physical interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1205–1213, 2006     

Miscibility of poly (etherimide) and poly (butylene naphthalate) blends

Summary Differential scanning calorimeter (DSC), optical microscopy (OM) and scanning electron microscopy (SEM) were performed to characterize the miscibility of a blend system comprising poly (butylene naphthalate) (PBN) and poly (ether imide) (PEI). DSC scans showed there was only one single Tg for each blend and the glass transitions increase monotonously with the increase of PEI content. The glass transition temperatures of the blends fitted the Fox equation well implying that the blends exhibited fine segmental scale of mixing. No lower critical solution temperature (LCST) was observed by OM for the blends. SEM micrographs showed the fracture surface of quenched sample exhibited a homogeneous structure. No obvious IR peak shift of C=O absorption at 1780 cm⁻¹ was observed suggesting a relatively low level of specific interaction between two molecules. It was concluded that these blends were miscible with non-specific intermolecular interactions. Received: 5 January 2001/Accepted: 27 February 2001     

Solution and solid‐state blend compatibility of poly(vinyl alcohol) and poly(methyl methacrylate)

The blend miscibility of poly(vinyl alcohol) and poly(methyl methacrylate) in N,N′‐dimethylformamide solution was investigated by viscosity, density, ultrasonic velocity, refractive index, and UV and fluorescence spectra studies. Differential scanning calorimetry and scanning electron microscopy were used to confirm the blend miscibility in the solid state. Blends were compatible when the concentration of poly(vinyl alcohol) was greater than 60 wt %. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2415–2421, 2006     

Processability enhancement of poly(lactic acid-co-ethylene terephthalate) by blending with poly(ethylene-co-vinyl acetate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(butylene succinate)

Processability enhancement feasibility of an in-house synthesized poly(lactic acid-co-ethylene terephthalate), PLET, is investigated by blending with commercial poly(ethylene-co-vinyl acetate), EVA, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, and poly(butylene succinate), PBS. The three blend systems are prepared by varying PLET contents, and their properties are characterized. DSC, SEM, and FTIR results indicate that PLET/EVA blends are immiscible, while the corresponding PLET/PBS and PLET/PHBV blends are miscible and partially miscible, respectively. DMA results show that the three blend systems have storage modulus comparable to those of commercial EVA, PHBV, and PBS, when PLET content is kept lower than 50, 25, and 25 wt%, respectively. PLET/EVA blends show higher thermal stability, compared to those of the other two blend systems. Results on degradability tests indicate that PLET/PBS blends show highest hydrolytic degradability, compared to the other two blends, as both blend constituents are associated in the hydrolytic degradation.     

Influence of tacticity of poly(methyl methacrylate) on the compatibility with poly(vinyl phenol)

Isotactic, atactic, and syndiotactic poly(methyl methacrylate) (PMMA) were mixed with poly(vinyl phenol) (PVPh) separately in tetrahydrofuran to make three polymer blend systems. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to study the miscibility of these blends. Isotactic PMMA was found to be more miscible with PVPh than atactic or syndiotactic PMMA. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1773–1780, 1997     

Miscibility and specific interactions in blends of poly(vinyl phenyl ketone hydrogenated) with poly(2,6‐dimethyl‐1,4‐phenylene oxide)

The miscibility behavior of poly(vinyl phenyl ketone hydrogenated) (PVPhKH) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) are studied by differential scanning calorimetry, thermomechanical analysis, and FTIR spectroscopy. Two miscibility windows between 10 to 40 and 60 to 90 wt % PPO are detected. Only the blend with 50 wt % PPO is immiscible. The best fit of the Gordon–Taylor equation of the experimental glass‐transition temperatures for miscible PVPhKH/PPO blends is shown. A study by FTIR spectroscopy suggests that hydrogen bonding interactions are formed between the hydroxyl groups of PVPhKH and the ether groups of PPO. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1887–1892, 2004     

Super‐tough biodegradable poly(vinyl alcohol)/poly(vinyl pyrrolidone) blends plasticized by glycerol and sorbitol

Tough biodegradable films were prepared using a poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP) (1:1) blend with plasticizers of glycerol (GLY), sorbitol (SOR), and their (one to one) mixture. We studied the effect of plasticization on the structural, thermal, and mechanical properties of the PVA/PVP blend films. Fourier transform infrared spectra indicated good miscibility of the two components due to the H‐bonding between the PVA and PVP molecules. The addition of plasticizers reduced the interaction between PVA and PVP, evidenced by an increase in the intensity of PVA diffraction peaks observed in the X‐ray diffraction (XRD) characterization. Thermal degradation of the blends increased as a function of the plasticizer used. GLY affected thermal degradation more than SOR and the mixtures. The incorporation of the plasticizers promoted the growth of PVA crystals as evidenced by XRD patterns and the enthalpy of fusion (ΔH_f) obtained by differential scanning calorimetry measurements. The introduction of SOR to the binary blend increased toughness seven times and imparted simultaneous and pronounced improvements to maximum tensile stress and elongation at break. This behavior holds out great promise for the development of a new generation of mechanically robust, yet thoroughly biodegradable materials that could effectively supplant conventional polymers in demanding applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46406.     

Miscibility and mechanical properties of tetrafunctional epoxy resin/phenolphthalein poly(ether ether ketone) blends

Phenolphthalein poly(ether ether ketone) (PEK‐C) was found to be miscible with uncured tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM), which is a type of tetrafunctional epoxy resin (ER), as shown by the existence of a single glass transition temperature (T_g) within the whole composition range. The miscibility between PEK‐C and TGDDM is considered to be due mainly to entropy contribution. Furthermore, blends of PEK‐C and TGDDM cured with 4,4′‐diaminodiphenylmethane (DDM) were studied using dynamic mechanical analysis (DMA), Fourier‐transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). DMA studies show that the DDM‐cured TGDDM/PEK‐C blends have only one T_g. SEM observation also confirmed that the blends were homogeneous. FTIR studies showed that the curing reaction is incomplete due to the high viscosity of PEK‐C. As the PEK‐C content increased, the tensile properties of the blends decreased slightly and the fracture toughness factor also showed a slight decreasing tendency, presumably due to the reduced crosslink density of the epoxy network. SEM observation of the fracture surfaces of fracture toughness test specimens showed the brittle nature of the fracture for the pure ER and its blends with PEK‐C. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 598–607, 2001     

Miscibility behaviour of bisphenol-A polycarbonate and poly(para-chlorostyrene)

The miscibility behaviour of bisphenol-A polycarbonate (PC) and poly(para-chlorostyrene) (PpCIS) has been investigated. Special attention has been paid to the influence of the molar mass of PpCIS. Molar masses varying from 10 to > 1,000 kg/mol were used. The blends were studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and scanning and transmission electron microscopy (SEM and TEM). It was concluded that the blends of all three PpCIS grades and PC phase separate. In the low concentration region, some intermixing was found, especially for the blend with the low molar mass PpCIS. The most important effect of lowering the molar mass of PpCIS was an acceleration of the phase separation. The combination of SEM with electron probe X-ray microanalysis (EPMA) gave qualitative information on the miscibility behaviour and was found to be a useful extension of routine microscopy techniques used in blend studies.     

Miscibility enhancement on the immiscible binary blend of poly(vinyl acetate) and poly(vinyl pyrrolidone) with bisphenol A

The miscibility behavior and hydrogen bonding of ternary blends of bisphenol A (BPA)/poly(vinyl acetate) (PVAc)/poly(vinyl pyrrolidone) (PVP) were investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). The BPA is miscible with both PVAc and PVP based on the observed single T_g over the entire composition range. FTIR was used to study the hydrogen-bonding interaction between the hydroxyl group of BPA and the carbonyl group of PVAc and PVP at various compositions. Furthermore, the addition of BPA is able to enhance the miscibility of the immiscible PVAc/PVP binary blend and eventually transforms into miscible blend with single T_g, when a sufficiently quantity of the BPA is present due to the significant Δχ and the ΔK effect.     

Molecular modeling simulations and thermodynamic approaches to investigate compatibility/incompatibility of poly(l-lactide) and poly(vinyl alcohol) blends

This paper investigates the molecular modeling simulation approaches for understanding the blend compatibility/incompatibility of poly(l-lactide), PLL and poly(vinyl alcohol), PVA. Blends of PLL/PVA have been widely used in biotechnology as well as membranes in separation science. Realizing their importance, we thought of investigating to verify experimental observations on their compatibility/incompatibility aspects by calculating thermodynamic interactions between PLL and PVA over the entire range of blend compositions. In doing so, Flory-Huggins interaction parameter, χ, was computed for different blends using atomistic simulations to predict blend miscibility. It was found that at 1:9 blend composition of PLL/PVA, miscibility was observed, but increasing immiscibility was prevalent at higher compositions of PLL component. Computed results confirmed the literature findings on differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) and mechanical property studies, suggesting the validity of modeling strategies. Plots of Hildebrand solubility parameter, δ, and cohesive energy density, CED, supported these findings. Miscibility of PLL and PVA polymers is attributed to hydrogen-bonding effect. Literature findings have been validated to understand the nature of interactions between different groups of the polymers by computing radial distribution function, RDF, for groups that are tentatively involved in such interactions, leading to miscibility or immiscibility. RDF plot was constructed to identify the exact contribution of particular atoms of polymers to confirm miscibility/immiscibility of blends. Results of this study are correlated well with the reported data. Kinetics of phase separation was examined using density profiles calculated from the MesoDyn approach to examine miscibility/immiscibility aspects of the blends. Computed free energy from the mesoscopic simulation of blends reached equilibrium, particularly when simulation was performed at higher time step, indicating the stability of the blend at certain compositions. X-ray diffraction profiles have been constructed for individual polymers as well as for their blends, which agreed well with the reported data.     

Mechanical properties and morphological changes of poly(lactic acid)/polycarbonate/poly(butylene adipate‐co‐terephthalate) blend through reactive processing

The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate‐co‐terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twin‐screw extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC = 42/18/40 (wt/wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05–1 μm for RP, whereas it was approximately 10 μm without RP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Blends of poly(ethylene oxide) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate): thermal analysis, morphological behaviour and specific interactions

DSC and optical microscopy were used to determine the miscibility and crystallinity of blends of poly(ethylene oxide) (PEO) with poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM). A single glass transition temperature was observed for all blends, indicating miscibility. A progressive decrease in the degree of crystallinity and in the size of the PEO spherullites is observed, as PVPh-HEM is added. FTIR was used to probe the intermolecular specific interactions of the blends and the miscibility of the blend is mainly attributed to PVPh-HEM/PEO intermolecular interactions via hydrogen bonding.     

Dielectric and dynamic mechanical behavior of poly(vinyl acetate) containing small concentrations of cholesteryl additives

Dielectric loss measurements at four temperatures and as a function of frequency are presented for the poly(vinyl acetate) (PVAc) systems containing small concentrations of cholesterol, cholesteryl acetate, cholesteryl oleate, cholesteryl nonanoate, cholesteryl benzoate, cholesteryl oleyl carbonate, p-methoxy benzilidine-p-n-butyl aniline, diphenyl ether, and cetyl acetate. For the first five systems, the α-relaxation temperature for sure PVAc was found to be increased in the presence of the said additives. The results of the dielectric depolarization spectroscopy at 1 kHz and the dynamic mechanical analysis also conform with these observations. It is inferred that the segmental motion in PVAc is hindered by these first five additive molecules through a specific dipolar interaction. These additives are therefore described as antiplasticizers to PVAc as they extend the glassy region over a wider temperature interval. The analysis of the dielectric data to give the dielectric decay function and the β parameter reveals that the two types of the additives, viz., plasticizers and antiplasticizers, can be distinguished by the opposite signs obtained for the ratio Δβ/ΔC, where C is the concentration. The analysis based on the WLF theory shows that the WLF reference temperature T⁰ is higher than that for pure polymer if the additive is an antiplasticizer while the same is lower for the plasticizing additives. The apparent enthalpy of activation for the dielectric relaxation process is found to be higher in the case of additives which show antiplasticization of PVAc.     

Preparation,characterization, electrical and antibacterial properties of sericin/poly(vinyl alcohol)/poly(vinyl pyrrolidone) composites

In this study, we focused on the fabrication of poly(vinyl alcohol) (PVA)/poly(vinyl pyrrolidone) (PVP)/sericin composites via a simple solution‐blending method. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, UV spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry, thermogravimetric analysis (TGA), and measurements of the conductivity, tensile strength, and antibacterial activity against Staphylococcus aureus. The results of FTIR and UV spectroscopy implied the occurrence of hydrogen bonding between sericin and the PVA/PVP blend. The structure and morphology, studied by XRD and SEM, revealed that the sericin particles were well dispersed and arranged in an orderly fashion in the blend. The glass‐transition temperature (T_g) of the composite was higher than that of the pure blend, and the T_g value shifted toward higher temperatures when the volume fraction of sericin increased. TGA indicated that sericin retarded the thermal degradation; this depended on the filler concentration. The mechanical and electrical properties, such as the tensile strength, alternating‐current electrical conductivity, dielectric constant, and dielectric loss of the composites, were higher than those of the pure blend, and these properties were enhanced when the concentration of sericin was increased up to 10 wt % filler content, whereas the elongation at break of the composite decreased with the addition of sericin particles. The antibacterial properties of the composite showed that sericin had a significant inhibitory effect against S. aureus. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43535.     

Miscibility and hydrolytic degradation in alkaline solution of poly(l-lactide) and poly(methyl methacrylate) blends

Poly(l-lactide) (PLLA) was melt blended with poly(methyl methacrylate) (PMMA) using a two-roll mill. The miscibility and hydrolytic degradation of the blend films were characterized. It was found that PLLA/PMMA blend has high miscibility in the amorphous state because only single T_g was observed in the DSC and DMA measurements. In alkaline solution, the hydrolytic degradation rate of the blends whose PMMA content is higher than 30 wt% was decelerated while the rate of the blends whose PMMA content is lower than 30 wt% was accelerated. That is, the hydrolytic degradation rate of the blends could be widely controlled by PMMA content in the blend. It was also found that only PLLA was hydrolyzed and eluted into alkaline solution, while PMMA remained during alkaline hydrolysis.     

Polysulfone/poly(ether sulfone) blended membranes for CO2 separation

Polymer blending as a modification technique is a useful approach for augmenting the gas‐separation and permeation properties of polymeric membranes. Polysulfone (PSF)/poly(ether sulfone) (PES) blend membranes with different blend ratios were synthesized by conventional solution casting and solvent evaporation technique. The synthesized membranes were characterized for miscibility, morphology, thermal stability, and spectral properties by differential scanning calorimetry (DSC), field emission scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared (FTIR) spectroscopy, respectively. The permeation of pure CO₂ and CH₄ gases was recorded at a feed pressure of 2–10 bar. The polymer blends were miscible in all of the compositions, as shown by DSC analysis, and molecular interaction between the two polymers was observed by FTIR analysis. The thermal stability of the blend membranes was found to be an additive property and a function of the blend composition. The morphology of the blend membranes was dense and homogeneous with no phase separation. Gas‐permeability studies revealed that the ideal selectivity was improved by 65% with the addition of the PES polymer in the PSF matrix. The synthesized PSF/PES blend membranes provided an optimized performance with a good combination of permeability, selectivity and thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42946.