Miscible Blends Research Articles

Biodegradable binary blends of poly (butylene succinate) or poly (ε-caprolactone) with poly (butylene succinate-ran-ε-caprolactone)copolymers: Crystallization behavior

Poly (butylene succinate) (PBS) and polycaprolactone (PCL) are two immiscible biocompatible and biodegradable polymers. Aiming to combine the properties of these biodegradable polymers, this work explores for the first time blending PBS or PCL with PBS-ran-PCL copolymers (BSxCLy) at 75/25, 50/50, and 25/75 wt% compositions, with various copolymer contents: BS78CL22, BS46CL54, and BS15CL85. The crystallization behavior of these novel binary blends was systematically studied with non-isothermal and isothermal differential scanning calorimetry (DSC), polarized light optical microscopy (PLOM), and simultaneous wide- and small-angle X-ray scattering (WAXS and SAXS). All the blends displayed a miscible character in the amorphous state, judging by a single glass transition temperature, and in the melt state (as indicated by SAXS), but their miscibility in the crystalline state depends on the specific blend. In both PBS/BS78CL22 and PCL/BS15CL85 evidences of co-crystallization between the matrix and the crystallizable fraction of the copolymer were found. However, high comonomer exclusion, higher in the BS15CL85 than in the BS78CL22, greatly affects blend miscibility. Thus, the results show that the PBS/BS78CL22 blend is miscible, in the crystalline state, at high PBS (homopolymer) content, i.e., 75/25 and 50/50 compositions, whereas its “counterpart”, the PCL/BS15CL85 displays partial miscibility, even for high PCL (homopolymer) content. For the 25/75 blends, i.e., copolymer-rich, the homopolymer addition favors the crystallization of the copolymer-rich component. Blending PBS or PCL with BS46CL54 leads to blends that exhibit a much lower miscibility in the crystalline state than the blends prepared with BS or CL-rich copolymers, independently of the composition. But, interestingly, a novel behavior is found, since the BS46CL54 copolymer can crystallize either in PBS type crystals or in PCL type crystals depending on the polymeric matrix (PCL or PBS). The PBS favors the crystallization of the BS component, while the PCL favors the crystallization of the CL component within the random copolymer. The crystallization behavior found in this work evidences the interactions of the PBS or PCL with the BSxCLy copolymer, representing a potential strategy to combine the properties of the PBS and PCL through blending.

Critical Percolation Threshold for Solvation-Site Connectivity in Polymer Electrolyte Mixtures

Poly(ethylene oxide) (PEO)-based polymer electrolytes are often mixed with rigid, nonconductive polymers to improve mechanical strength. The suppressed conductivity of the mixture typically arises from a reduced segmental mobility and a diminished connectivity between conductive PEO sites. To decouple these two mechanisms, we compare transport in symmetric miscible blends and disordered block copolymers (BCP) of PEO and poly(methyl methacrylate) (PMMA). Because the two systems have identical physicochemical properties, differences in their conductivity directly reflect the underlying PEO network connectivity. We find that, at short distances (<5 Å), the Li+ solvation networks are identical for the two systems; however, a distinct variation in the network connectivity arises at length scales between 5 and 10 Å. Specifically, the BCP exhibits a lower connectivity, and therefore a lower conductivity than the blend. A quantitative model is proposed that associates long-range Li+ transport with local miscibility; the concept of network connectivity discussed here could be useful for designing polymer electrolyte systems.

Critical Percolation Threshold for Solvation Site Connectivity in Polymer Electrolytes Mixtures

To address the tradeoff between mechanical strength and Li+ conductivity in Poly(Ethylene Oxide) (PEO)-based electrolytes, a rigid nonconductive polymer is frequently added to the electrolyte via blending or copolymerization. The ionic conductivity of mixed PEO electrolytes is generally lower than that of unmixed PEO electrolytes. The suppressed ionic conductivity is attributed to the reduced segmental mobility and connectivity of the conductive PEO cites. Most experimental systems make it difficult to decouple the two mechanisms and accurately examine their impact on conductivity. We compare two symmetric polymer mixtures (50:50 wt%): a miscible polymer blend PEO/PMMA and a disordered block copolymer (BCP) PEO-b-PMMA, both with the same amount of Li salt. Because their chemical and physical properties are the same, changes in ionic conductivity can be attributed solely to local changes in PEO network connectivity. We discover that the mixtures' immediate Li+ solvation sites (<5 Å) are identical to those of unmixed PEO electrolytes. The presence of non-conducting PMMA near the PEO, on the other hand, causes local concentration changes at longer range scales. The BCP is more mixed than the blend electrolyte at these length scales, resulting in a factor of two drop in conductivity. To that end, we propose a quantitative computational model that considers Li+ transport within and across PEO clusters at the appropriate length scales. This new understanding of network connectivity in polymer electrolyte mixtures is critical for the design of future multiphase polymer electrolyte systems.

A deep insight of solubility behavior, mechanical quantum, thermodynamic, and mechanical properties of Pebax-1657 polymer blends with various types of vinyl polymers: A mechanical quantum and molecular dynamics simulation study

Molecular dynamics (MD) simulations are a key method frequently used to develop and design new blend polymers and predict their properties. In this study, frontier molecular orbital (FMO) and mechanical quantum (MQ) methods were used to determine the partial charges, energy values, phase behavior, regioselectivity, chemical reactivity, and surface properties of Pebax-1657 (Px) and three vinyl group polymers. Subsequently, the blend compatibility, miscibility, and mechanical behavior of poly (vinyl fluoride) (PVF), poly (vinyl chloride) (PVC), and poly (vinyl acetate) (PVAc) with Px were analyzed for a range of combinations using atomistic simulation systems. Accordingly, MD simulations were performed for the Px/PVAc, Px/PVC, and Px/PVF blend models with different composition ratios (80/20, 70/30, and 60/40, by weight) at a temperature T = 298 K and pressure P = 1 bar. For all the systems, the electron affinity (A) and ionization energy (I) were determined to calculate the global softness (σ), global hardness (η), polarizability, chemical potential (µ), and electrophilicity index (ω). The softness decreased in the following order: PVC > Px > PVF > PVAc. It can be deduced that PVC and PVAc are the most polarizable and exhibit the lowest chemical reactivities. Additionally, PVF and PVC exhibited the highest and lowest chemical hardness values, respectively. Accordingly, based on the calculated solubility parameters, PVAc, PVC, and PVF were miscible with Px and reached the same glass transition temperature (Tg). Moreover, the χ (chi) parameters of the Px-PVAc, Px-PVC, and Px-PVF polymer blends were ranked as follows: Px-PVF (∼2.66) > Px-PVC (∼1.59) > Px-PVAc (∼0.64), suggesting that Px-PVAc and Px-PVF exhibited high and low miscibility, respectively. Furthermore, the mechanical properties of Px-PVAc, Px-PVC, and Px-PVF blend polymers reduced when the content of PVAc, PVC, and PVF exceeded 30% wt.

Inclusion/Exclusion Behaviors of Small Molecules during Crystallization of Polymers in Miscible PLLA/TAIC Blend.

In this work, PLLA/TAIC has been taken as a model system to investigate the inclusion and exclusion of small molecules during the crystallization of polymers in their miscible blend. Our results indicate that it is the growth rate and diameter of PLLA spherulites that dominate the localization of TAIC. On the one hand, crystallization temperature plays an important role. Crystallization at higher temperature corresponds to higher growth rates and a greater diameter of PLLA spherulites. The former improves the ability of PLLA crystals to trap TAIC while the latter leads to a lower volume fraction of space among neighboring PLLA spherulites. The combination of the two contributes to the enhanced inclusion behaviors. On the other hand, when compared to melt crystallization, cold crystallization results in much smaller spherulites (from higher nucleation density) and sufficient space among spherulites, which accounts for the enrichment of TAIC in interspherulitic regions and for its enhanced exclusion. In the adopted polymer–small molecule blend, TAIC can enrich in interspherulitic regions even in its miscible blend with PLLA, which can be attributed to its stronger diffusion ability.

Intra- and Intermolecular Hydrogen Bonding in Miscible Blends of CO2/Epoxy Cyclohexene Copolymer with Poly(Vinyl Phenol).

In this study, we synthesized a poly(cyclohexene carbonate) (PCHC) through alternative ring-opening copolymerization of CO2 with cyclohexene oxide (CHO) mediated by a binary LZn2OAc2 catalyst at a mild temperature. A two-dimensional Fourier transform infrared (2D FTIR) spectroscopy indicated that strong intramolecular [C–H···O=C] hydrogen bonding (H-bonding) occurred in the PCHC copolymer, thereby weakening its intermolecular interactions and making it difficult to form miscible blends with other polymers. Nevertheless, blends of PCHC with poly(vinyl phenol) (PVPh), a strong hydrogen bond donor, were miscible because intermolecular H-bonding formed between the PCHC C=O units and the PVPh OH units, as evidenced through solid state NMR and one-dimensional and 2D FTIR spectroscopic analyses. Because the intermolecular H-bonding in the PCHC/PVPh binary blends were relatively weak, a negative deviation from linearity occurred in the glass transition temperatures (Tg). We measured a single proton spin-lattice relaxation time from solid state NMR spectra recorded in the rotating frame [T1ρ(H)], indicating full miscibility on the order of 2–3 nm; nevertheless, the relaxation time exhibited a positive deviation from linearity, indicating that the hydrogen bonding interactions were weak, and that the flexibility of the main chain was possibly responsible for the negative deviation in the values of Tg.

Synthesis and structural characterization of elastin-based polypentapeptide/hydroxypropylmethylcellulose blend films: Assessment of miscibility, thermal stability and surface characteristics

This work portrays the synthesis of Elastin-based polymer poly(GVGIP) (where; G-Glycine, V-Valine, I-Isoleucine, P-Proline) through the solution-phase strategy by stepwise approach followed by characterization with modern analytical tools. The miscibility attributes of the polypeptide were explored with hydroxypropylmethylcellulose (HPMC) using dilute solution viscometry method, spectroscopic, thermal, SEM, and XRD analysis. Explicitly the Huggins coefficient [KH], the intrinsic viscosity [η], parameters such as α by Sun, ∆[η]m by Garcia ∆B, and µ suggested by Chee, ∆K, and β advocated by Jiang and Han, recommend the miscibility up to 50% of the polypeptide. In the solid phase, DSC and TGA analysis showed that miscible blends possessed a higher glass transition temperature (Tg) and thermal stability, respectively. The Scanning Electron Microscopy (SEM) evinced the smooth morphology for miscible blends. Besides, XRD showed broadening of the diffraction pattern ratified the miscibility. The change in frequency and intensity of FTIR peaks demonstrated the existence of intermolecular interchanges between two polymers. Overall, the approach successfully synthesized poly(GVGIP)/HPMC miscible blends up to 50%, make it an excellent choice for biomedical and pharmaceutical purposes.

Miscibility study of thermoplastic starch/polylactic acid blends: Thermal and superficial properties

In this work, the miscibility of blends of thermoplastic Achira Starch (AS) and polylactic acid (PLA) was evaluated, assisted by Pluronic® F127 an amphiphilic triblock copolymer that acts as a surfactant and promotes the reduction of surface tension among AS and PLA in solution by emulsion stabilization. Different formulations of AS/PLA blends were obtained at 75:25, 50:50, and 25:75 containing 0 %, 4 %, and 8 % of Pluronic® F127, and glycerol was used as a plasticizer. Solvent casting was the method used to obtain blended polymeric films, which were characterized by Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric Analysis (TGA), differential scanning calorimetry (DSC) and wettability by contact angle measurements. The results demonstrate that miscibility of PLA in AS or vice versa was achieved. The stability of emulsion and posterior drying of the different formulations allows the production of films for packaging, pharmaceutical, or biomedical applications.

Miscibility and rigid amorphous phase in blends of polypropylene with poly(propylene‐co‐ethylene)

AbstractThermal and mechanical properties of binary blends of polypropylene (PP) with a statistical copolymer (85 wt% propylene and 15 wt% ethylene, abbreviated here as VM) have been investigated. Both components were found to be miscible in the melt in the whole range of compositions. No separate domains of VM have been detected by polarizing optical microscopy, and the size of spherulites is going down with increasing VM content. The crystallization temperature of PP as detected by DSC, is going down to 83°C, for PP/VM blends 10:90. This is another evidence for miscibility in the melt. Viscoelastic properties of the melt were measured. Regarding the solid state, the melting enthalpy is exactly proportional to the PP content in the blend. The DSC step height at the glass transition is exactly proportional to the VM content. These results are suggesting a three‐phase model (crystalline, rigid amorphous, and mobile amorphous phase), where the VM component is mainly located in the mobile amorphous regions, while the amorphous part of PP is in the rigid amorphous regions. Stress–strain curves show a systematic increase of elongation at break with increasing VM%, to be extended from 7.8% to more than 550%.

Viscoelastic and Properties of Amphiphilic Chitin in Plasticised Polylactic Acid/Starch Biocomposite.

The enhancement of the PLA thermomechanical properties is significant due to its suitability as a replacement for primary synthetic polymer use in diverse industrial production. The amphiphilic chitin was used as a compatibilizer in PLA/starch biocomposite. The properties of plasticised polylactic acid blended with starch, and amphiphilic chitin was studied for enhanced thermomechanical and viscoelastic properties. Chitin was modified using acetylated substitution reaction and blended with plasticised PLA/starch biocomposite. The biocomposite was prepared with combined compression and melt extrusion techniques. The biocomposite’s thermomechanical, thermal, mechanical, and morphological properties were studied using dynamic mechanical analysis, TGA-DSC, tensile test, and scanning electron microscopy. The storage and loss modulus were significantly enhanced with increased amphiphilic chitin content. Similarly, the single peak of tan delta showed good miscibility of the polymeric blend. Additionally, the modulus increases with frequency change from 1 Hz to 10 Hz. The thermal stability of the biocomposite was observed to be lower than the neat PLA. The tensile properties of the biocomposite increased significantly more than the neat PLA, with P4S4C having the highest tensile strength and modulus of 87 MPa and 7600 MPa. The SEM images show good miscibility with no significant void in the fractured surface. The viscoelastic properties of PLA were enhanced considerably with plasticizer and amphiphilic chitin with improved biodegradability. The properties of the biocomposite can be adapted for various industrial applications.

The Development Study of a Prototype of Sodium Carboxymethylcellulose and Poly(Vinyl Alcohol) Wound Dressings Using a Mixer Torque Rheometer

The search for new materials that serve as dressings and promote the proper means for wound healing, without yielding toxic waste to the wound bed and at low cost, is currently the subject of research. In this sense, the present study aimed to develop a prototype of a poly(vinyl alcohol) (PVA) polymeric film, sodium carboxymethylcellulose (NaCMC). PVA and NaCMC as miscible polymer blend films for wound dressings was developed using internal mixing chamber processing in a mix torque rheometer (MTR) without the use of binders or crosslinks in different mixing conditions that were investigated by thermal characteristics (differential scanning calorimetry (DSC)) and thermogravimetric analysis (TGA) and crystallinity (X-ray Diffraction Technique (XRD)). The films obtained by pouring from this starting material were characterized by DSC, TGA, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), optical microscopy and swelling assay. All stages of development of this prototype are discussed, from the quality control of the raw materials, through the development of the preparation technique of the blends in 14 different processing conditions. The processed PVA/NaCMC film showed physical crosslinking which may have promoted its ability to resist dissolution in water (unprocessed PVA/NaCMC films’ characteristic). The results demonstrated that the processing of the PVA and NaCMC polymers in the MTR constitutes a viable technique to obtain membranes for use as dressings.

Blends Containing Amphiphilic Biopolymers and their Compatibility Behavior

Abstract: This mini-review deals with the miscibility behaviour of two biopolymers, chitosan and alginate. It is well known that the miscibility in multifunctional polymer blends is favoured due to specific interactions, which origin a negative heat of mixing. Particular interest is focused on functionalized polymers because they are the most suitable way to obtain interacting polymers, producing a single-phase material. Due to the polyfunctionality of chitosan (CS) and other biopolymers, they can be taken into account as a basis of a strongly interacting polymer. They would allow obtaining compatible polymeric materials. For this reason, blends containing CS with different vinyl polymers have been studied. The most significant polymeric blends with these natural polymers will be analyzed in this review. Chitosan is obtained from the biopolymer chitin through sequential processes of demineralization, deproteinization and deacetylation. The native chitin is obtained by direct separation from the marine crustaceans shell, which is abundant on the sea coasts. Some classic results that relate to the polymeric blends containing amphiphilic polymers will be discussed. Another biopolymer of the coast is Sodium Alginate (SA). Alginate also allows the formation of compatible polymer blends. Results in this regard will also be analyzed in this review.

Effect of Tm of blend components on the isothermal melt-crystallization process of PHB/PLLA blends investigated using spectroscopic imaging and DSC

The understanding of morphology and crystallization in biopolymer blends offers the ability to tune these properties for specific uses. In this study, the isothermal melt-crystallization process of poly (3-hydroxybutyrate) (PHB)/poly ( l -lactic acid) (PLLA) blends with different weight loadings and molecular weights was investigated using in-situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic imaging and differential scanning calorimetry (DSC). When the isothermal crystallization temperature is constant, increasing the fraction of blend component with a lower T m results in the decreasing T m of both blend components, which is indicated in DSC thermograms. The reduced T m delays the crystallization of both blend components and then the restrained crystallization leads to a greater extent of phase separation, which is shown in ATR-FTIR spectroscopic images. Likewise, at a constant isothermal crystallization temperature, with the decreasing molecular weights of blend components, the miscibility of polymer blend should be enhanced because of the shift of the phase boundary in phase diagram to lower temperatures. However, the decreasing overall crystallization rate and the delay of crystallization indicated in the integrated absorbance profiles and the decreasing T m indicated in the DSC thermograms can be used to explain the greater extent of phase separation in the PHB/PLLA blend shown in the spectroscopic images. A phase diagram was prepared to show the effect of polymer molecular weight on the miscibility of PHB/PLLA blends. Thus, increasing the fraction of the blend component with a higher T m , choosing polymers with a higher molecular weight and decreasing the isothermal crystallization temperature have been demonstrated to be effective methods to promote the miscibility of upper critical solution temperature (UCST) crystallizable polymer blends. Moreover, it was concluded that in-situ ATR-FTIR spectroscopic imaging can be combined with integrated absorbance profiles and DSC thermograms to deepen the understanding of multicomponent polymer systems. • A phase diagram was prepared to show the effect of M w on the miscibility of PHB/PLLA blends. • Effective methods are found to promote the miscibility of UCST polymer blends during isothermal crystallization process. • Spectroscopic imaging can be combined with DSC thermograms to deepen the understanding of multicomponent polymer systems.

Understanding the miscibility of polyoxymethylene dimethyl ethers (OMEn) and diesel blend using molecular dynamics simulation

Polyoxymethylene dimethyl ethers (OMEn) as an alternative fuel have attracted considerable interest in recent years, owing to their much reduced environmental impact. Since OMEn is often blended with diesel, the miscibility and stability of OMEn/diesel mixtures are important for engine operation. In this study, molecular dynamics method was used to investigate the miscibility of OME1-6 and diesel blends. The results suggest that the miscibility of OMEn and diesel blends decreases with the increasing number of oxymethylene units. The aromatics and heteroatomic molecules help maintain the stability of OMEn/diesel blends. The intermolecular interactions between OME1-6 and diesel molecules were investigated, which revealed that the electrostatic interaction plays a significant role in the liquid–liquid equilibrium of OMEn/diesel blends. The molecules in diesel having strong electrostatic interaction with OMEn are prone to accumulate around OMEn. The electrostatic interaction between diesel and OMEn molecules depends on the molecular structure and electronegativity differences of atoms in diesel molecules. The analyses of MD results coupled to minimum-distance distribution functions show an accumulation of paraffins and naphthenes close to OMEn at ∼ 2.36 Å, and suggest a strong interaction of OMEn with diesel carbazole molecules via hydrogen bonds. The results also indicate that the chain length and structure of alkanes have little impact on the molecular distribution around OMEn.

Investigating the Potential of Ethyl Cellulose and a Porosity-Increasing Agent as a Carrier System for the Formulation of Amorphous Solid Dispersions.

In the present work, an insoluble polymer, i.e., ethyl cellulose (EC), was combined with the water-soluble polyvinylpyrrolidone (PVP) as a carrier system for the formulation of amorphous solid dispersions. The rationale was that by conjoining these two different types of carriers a more gradual drug release could be created with less risk for precipitation. Our initial hypothesis was that upon contact with the dissolution medium, PVP would be released, creating a porous EC matrix through which the model drug indomethacin could diffuse. On the basis of observations of EC as a coating material, the effect of the molecular weight of PVP, and the ratio of EC/PVP on the miscibility of the polymer blend, the solid state of the solid dispersion and the drug release from these solid dispersions were investigated. X-ray powder diffraction, modulated differential scanning calorimetry, and solid-state nuclear magnetic resonance were used to unravel the miscibility and solid-state properties of these blends and solid dispersions. Solid-state nuclear magnetic resonance appeared to be a crucial technique for this aspect as modulated differential scanning calorimetry was not sufficient to grasp the complex phase behavior of these systems. Both EC/PVP K12 and EC/PVP K25 blends were miscible over the entire composition range, and addition of indomethacin did not alter this. Concerning the drug release, it was initially thought that more PVP would lead to faster drug release with a higher probability that all of the drug molecules would be able to diffuse out of the EC network as more pores would be created. However, this view on the release mechanism appeared to be too simplistic as an optimum was observed for both blends. On the basis of this work, it could be concluded that drug release from this complex ternary system was affected not only by the ratio of EC/PVP and the molecular weight of PVP but also by interactions between the three components, the wettability of the formulations, and the viscosity layer that was created around the particles.

Segregation Behavior of Miscible PC/PMMA Blends during Injection Molding.

Miscible blends composed of bisphenol-A polycarbonate (PC) and poly(methyl methacrylate) (PMMA), in which one of them has low molecular weight, were employed to study the surface segregation behavior during flow. The blend samples showed typical rheological behaviors, such as simple polymer melts without a long-time relaxation mechanism ascribed to phase separation, demonstrating that they were miscible. After injection molding, the amounts of a low molecular weight component on the blend surface were found to be larger than the actual blend ratio. Because the injection-molded products were transparent despite a huge difference in refractive indices between PC and PMMA, they showed no phase separation. This result demonstrated that surface segregation of a low molecular weight component occurred under flow field, which expands the material design such as tough plastics with good scratch resistance and optical fibers with tapered refractive index.

New Method Based on Direct Analysis in Real-Time Coupled with Time-of-Flight Mass Spectrometry (DART-ToF-MS) for Investigation of the Miscibility of Polymer Blends.

The miscibility of a series of binary blends such as polystyrene/poly(methyl methacrylate) (PS/PMMA), polystyrene/poly(vinyl chloride)(PS/PVC), poly(vinyl chloride)/poly(polymethyl methacrylate)(PVC/PMMA) and poly(ethylene-co-vinyl alcohol)/poly(lactide-co-glycolide acid) PEVAL/PLGA with equal ratios and poly(ethylene oxide)/poly(hydroxyl propyl methyl cellulose) (PEO/PHPMC) containing 30 and 70 wt% PEO, which were randomly chosen among the widely systems reported in the literature, was investigated by a new method based on a direct analysis in real-time coupled with time-of-flight mass spectrometry (DART-ToF-MS). To reach this goal these pairs of polymers and copolymers were prepared by solvent casting method. As a first step, the DSC technique was undertaken in this work to highlight the published results on the miscibility of these binary systems. The thermogravimetry analysis (TGA) was used to define the optimum decomposition temperature of these blends programmed for the study of miscibility using the DART-ToF-MS technique. The results obtained by this method based on the comparison of the nature of the fragments resulting from the isothermal decomposition of the blend with those of their pure components have been very effective in demonstrating the character of miscibility of these systems. Indeed, it was found that the PS/PMMA-50 and PS/PVC-50 blends were immiscible, PVC/PMMA-50 and PEVAL/PLGA-50 miscible, and the PEO/PHMC partially miscible. This method, which is rapid and uses a very small amount of sample (1–2 mg) can be extended in its application to other blends whose other methods used have shown their limits due to the intrinsic properties of the polymers involved.

Complicated Structure Change during Capillary Extrusion of Binary Blends of Polycarbonate and Poly(methyl methacrylate).

The effects of pressure and shear rate on the miscibility of binary blends comprising bisphenol-A polycarbonate (PC) and low molecular weight poly(methyl methacrylate) (PMMA) were investigated using a capillary rheometer. Both pressure and shear rate affected the miscibility. The examination of an extruded strand of the blend provided information about the cause of the phase change. Under high pressure, pressure-induced demixing occurred at temperatures below the lower critical solution temperature (LCST) of the blend. Consequently, the extruded strand became opaque throughout. During shear-induced mixing/demixing, a part of the strand became opaque because of the distribution of the shear rate in the strand. For example, during shear-induced demixing, only the exterior of the strand, i.e., the high shear rate region, became opaque. Above the LCST, shear-induced mixing occurred, and only the center region of the strand became opaque.

Morphology manipulation for highly miscible photovoltaic blend of carboxylate-substituted polythiophene:Y6

Polythiophenes and its derivatives (PTs) have attracted extensive research interest in the field of organic solar cells (OSCs) owing to their benefits of low synthesis cost and high scalability of synthesis. However, the efficiency of PT-based photovoltaic devices is far lower than that of the popular push-pull conjugated polymer-based devices. To elevate the photovoltaic performance, pairing PTs with low-bandgap acceptors is highly desirable. Nevertheless, when pairing the prevailing low-bandgap non-fullerene acceptor Y6 with a representative PT derivative named PDCBT-Cl, the OSC delivered an extremely low efficiency of ∼0.1%. The crucial reason for the abysmal performance is the poor morphology with insufficient phase separation induced by the high miscibility between PDCBT-Cl and Y6. How to tune the morphology and promote phase separation is challenging and important for the highly miscible blend system to achieve performance breakthrough. Given that PDCBT-Cl and Y6 are crystalline, in the present study, we promote the formation of phase separation for PDCBT-Cl:Y6 blend by control molecular crystallization, using thermal annealing (TA) at various temperatures. We observed that, phase-separated morphology appeared when TA temperature was higher than the aggregation transition temperature of PDCBT-Cl. Upon TA at 160 °C, ordered molecular packing and appropriate phase separation were obtained for PDCBT-Cl:Y6 blend film, and the device efficiency increased dramatically to ∼10%, which was ∼90 times higher than that of the as-cast counterpart. This study demonstrates that promoting crystallization is an effective means to induce phase separation for the highly miscible blend system with crystallinity.

Study some specifications of copolymer (PLA-PEG)

This study about the blends of Poly Lactic Acid/ Poly Ethylene Glycol (PLA/PEG) 4000 copolymer at concentrations (9%,6%,3%,0%)) wt%) from (PEG) and (PLA) (5%) (w/w) by using casting solvent method to production films. The nonwoven nano fibrous mats were obtained by electro spinning of (PLA/PEG) solutions in chloroform, at weight ratios (70/30) (v/v), respectively. DSC is employed to measure the crystallinity difference between (PLA/PEG) blends and their nonwovens mats. the thermal properties (DSC) of (PLA/PEG) copolymer blends films and electrospun nano fiber mats such as (Tm) melting temperature, (Tg) glass transition temperature, (Tc) crystallization, Xc crystallinity rate and enthalpy . the FTIR test was done for all samples to figure the nature linking between (PLA) and (PEG),the results were that (6%) (w/w) of (PEG) was the optimized rate to apply Electrospinning method , data of DSC test defined that (Tg) and (Tm) were decreased, and that refer to occurrence physicist cross linking between the used substances (Completely miscible blend) when the electrospinning method was applied, also Xc for these nonwoven mats was decreased which has in turn an important effect on the speed of biodegradble for poly lactic acid (PLA).