Flory-Huggins Parameter Research Articles

Screening of Polymers for Oral Ritonavir Amorphous Solid Dispersions by Film Casting.

Background/Objectives: Drug-polymer interactions and miscibility promote the formation and performance of amorphous solid dispersions (ASDs) of poorly soluble drugs for improved oral bioavailability. The objective of this study was to employ drug-polymer interaction calculations and small-scale experimental characterization to screen polymers for potential ASDs of ritonavir. Methods: Seven polymers across four polymer types were screened as follows: an enteric one (EudragitS100), amphiphilic ones (HPMCAS-L, HPMCAS-H, and their 1:1 combination), hydrophilic ones (PEG-6000, PVP-VA), and a surfactant (Soluplus), including PVP-VA as a positive control, as the commercial ASD employs PVP-VA. Drug-polymer interaction calculations were performed for Hansen solubility parameter, Flory-Huggins parameter, and glass transition temperature. ASDs were prepared via film casting. Experimental characterizations included drug solubility in polymer solutions, polymer inhibition of drug precipitation, polarized light microscopy, differential scanning calorimetry, solubilization capacity, and dissolution studies. Results: HPMCAS-L, HPMCAS L:H, and Soluplus, along with the positive control PVP-VA, were identified as polymers for potential ASDs of ritonavir, with HPMCAS-L and PVP-VA being preferable. HPMCAS-L and the positive control PVP-VA were always viable for both 20% and 40% drug loads across all tests. Films with each of these four polymers showed improved dissolution compared to amorphous ritonavir without polymer. Drug-polymer interaction calculations anticipated the unfavorable small-scale experimental results for PEG-6000 and EudragitS100. Conclusion: Overall, the results contribute towards a resource-sparing approach to identify polymers for ASDs.

Combined extension and torsion of hydrogels with chemo-mechanical coupling: Revealing positive poynting effect

In this paper, combined extension and torsion of hydrogel subject to a chemo-mechanical coupled loading is described in the framework of continuum mechanics, where the free energy density consists of the elastic, mixing and chemical contributions. A simplified, closed-form and exactly analytical solution to the mechanical response is obtained, which accounts for the coupling effect of external loading, chemical potential and microstructural parameters, such as crosslinking degree, Flory-Huggins parameter, etc. In particular, the effect of free swelling and microscopic diffusion on deformation of the hydrogel at equilibrium state is discussed, reaching some fundamental conclusions. Negative axial forces are captured, revealing the typical positive Poynting effect where the cylinder tends to elongate on twisting, and an inhomogeneous deformation, induced by torsion, along the radial direction is demonstrated. Furthermore, the dynamic competition between external loading and solvent environment is revealed and investigated, where the direct connection between internal micro-physical parameters and macroscopic deformation is demonstrated. The theoretical results presented in this paper may provide predictions and guidance for the mechanical analysis and design of hydrogel cylinder subject to extension and torsion in a solvent.

Amphiphilic Nanogels as Versatile Stabilizers for Pickering Emulsions.

Pickering emulsions (PEs) are stabilized by particles at the water/oil interface and exhibit superior long-term stability compared to emulsions with molecular surfactants. Among colloidal stabilizers, nano/microgels facilitate emulsification and can introduce stimuli responsiveness. While increasing their hydrophobicity is connected to phase inversion from oil-in-water (O/W) to water-in-oil (W/O) emulsions, a predictive model to relate this phase inversion to the molecular structure of the nano/microgel network remains missing. Addressing this challenge, we developed a library of amphiphilic nanogels (ANGs) that enable adjusting their hydrophobicity while maintaining similar colloidal structures. This enabled us to systematically investigate the influence of network hydrophobicity on emulsion stabilization. We found that W/O emulsions are preferred with increasing ANG hydrophobicity, oil polarity, and oil/water ratio. For nonpolar oils, increasing emulsification temperature enabled the formation of W/O PEs that are metastable at room temperature. We connected this behavior to interfacial ANG adsorption kinetics and quantified ANG deformation and swelling in both phases via atomic force microscopy. Importantly, we developed a quantitative method to predict phase inversion by the difference in Flory-Huggins parameters between ANGs with water and oil (χwater - χoil). Overall, this study provides crucial structure-property relations to assist the design of nano/microgels for advanced PEs.

An automated calculation pipeline for differential pair interaction energies with molecular force fields using the Tinker Molecular Modeling Package

An automated pipeline for comprehensive calculation of intermolecular interaction energies based on molecular force-fields using the Tinker molecular modelling package is presented. Starting with non-optimized chemically intuitive monomer structures, the pipeline allows the approximation of global minimum energy monomers and dimers, configuration sampling for various monomer–monomer distances, estimation of coordination numbers by molecular dynamics simulations, and the evaluation of differential pair interaction energies. The latter are used to derive Flory–Huggins parameters and isotropic particle–particle repulsions for Dissipative Particle Dynamics (DPD). The computational results for force fields MM3, MMFF94, OPLS-AA and AMOEBA09 are analyzed with Density Functional Theory (DFT) calculations and DPD simulations for a mixture of the non-ionic polyoxyethylene alkyl ether surfactant C10E4 with water to demonstrate the usefulness of the approach.Scientific ContributionTo our knowledge, there is currently no open computational pipeline for differential pair interaction energies at all. This work aims to contribute an (at least academically available, open) approach based on molecular force fields that provides a robust and efficient computational scheme for their automated calculation for small to medium-sized (organic) molecular dimers. The usefulness of the proposed new calculation scheme is demonstrated for the generation of mesoscopic particles with their mutual repulsive interactions.

Accomplishing High-Performance Organic Solar Sub-Modules (≈55 cm2) with >16% Efficiency by Controlling the Aggregation of an Engineered Non-Fullerene Acceptor.

The fabrication of environmentally benign, solvent-processed, efficient, organic photovoltaic sub-modules remains challenging due to the rapid aggregation of the current high performance non-fullerene acceptors (NFAs). In this regard, design of new NFAs capable of achieving optimal aggregation in large-area organic photovoltaic modules has not been realized. Here, an NFA named BTA-HD-Rh is synthesized with longer (hexyl-decyl) side chains that exhibit good solubility and optimal aggregation. Interestingly, integrating a minute amount of new NFA (BTA-HD-Rh) into the PM6:L8-BO system enables the improved solubility in halogen-free solvents (o-xylene:carbon disulfide (O-XY:CS2)) with controlled aggregation is found. Then solar sub-modules are fabricated at ambient condition (temperature at 25±3 °C and humidity: 30-45%). Ultimately, the champion 55 cm2 sub-modules achieve exciting efficiency of >16% in O-XY:CS2 solvents, which is the highest PCE reported for sub-modules. Notably, the highest efficiency of BTA-HD-Rh doped PM6:L8-BO is very well correlated with high miscibility with low Flory-Huggins parameter (0.372), well-defined nanoscale morphology, and high charge transport. This study demonstrates that a careful choice of side chain engineering for an NFA offers fascinating features that control the overall aggregation of active layer, which results in superior sub-module performance with environmental-friendly solvents.

Thermodynamics of solvent sorption by layers of carbon-chain polymers in damping rubber blankets

The paper addresses the study of the thermodynamic compatibility of carbon-chain polymer compositions of offset rubber blankets with low-molecular-weight liquids, paint solvents and care agents for rubber damping machine parts used in transport, mechanical engineering and printing industries. The Flory-Huggins parameters χ were determined by inverted gas chromatography and calculation performed using the mathematical model of sorption, and the correlation between χ obtained by these two independent methods was found. The excess thermodynamic characteristics of the studied systems G E, H E and S E were calculated to predict the compatibility of components in these systems. The relationship was found between χ that characterizes the thermodynamic quality of the solvent and the equilibrium swelling index of polymer networks.

Microscopic Properties of Asphalt and Polyethylene at an Extraordinary High Dosage through Molecular Dynamics Simulation

Using waste plastics in asphalt mixtures could be an exploratory way to dispose of waste plastics. This study aims to investigate the microscopic properties between asphalt and polyethylene (PE) at an extraordinary dosage of 20 wt.%. Various types of PE with different degrees of polymerization (DP) and structural configurations were considered. Molecular dynamics simulations were used to calculate the mechanical parameters, free volume ratio (FVR), and Flory–Huggins parameter of the resulting PE-modified asphalt (PEA). Two types of PEA were made and characterized by fluorescence microscopy. The simulation results indicate that the addition of PE reduces the density of modified asphalt by less than 5%, and a higher density of PEA is associated with a lower FVR. When the FVR is close, the mechanical properties are greatly influenced by the DP and configuration. The DP and the number of chains are the main parameters impacting the compatibility between PE and asphalt, based on the Flory–Huggins parameter analysis. Decreasing the DP of PE (e.g., 50, with a minimum Flory–Huggins parameter and a relative molecular mass of 1300) will significantly increase the compatibility between asphalt and PE. LDPE−2 has better compatibility with asphalt, possibly because LDPE−2 has higher purity. These findings provide valuable insights into plastic thermal cracking and industrial modification practices.

Determination of interaction parameters in a bottom-up approach employed in reactive dissipative particle dynamics simulations for thermosetting polymers.

The limitations in previous dissipative particle dynamics (DPD) studies confined simulations to a narrow resin range. This study refines DPD parameter calculation methodology, extending its application to diverse polymer materials. Using a bottom-up approach with molecular dynamics (MD) simulations, we evaluated solubility parameters and bead number density governing nonbonded interactions via the Flory-Huggins parameter and covalent-bonded interactions. Two solubility parameter methods, Hildebrand and Krevelen-Hoftyzer, were compared for DPD simulations. The Hildebrand method, utilizing MD simulations, demonstrates higher consistency and broader applicability in determining solubility parameters for all DPD particles. The DPD/MD curing reaction process was examined in three epoxy systems: DGEBA/4,4'-DDS, DGEBA/MPDA and DGEBA/DETA. Calculations for the curing profile, gelation point, radial distribution function and branch ratio were performed. Compared to MD data for DGEBA/4,4'-DDS, the maximum deviation in secondary reactions between epoxy and amine groups according to DPD simulations with Krevelen-Hoftyzer was 14.8%, while with the Hildebrand method, it was 1.7%. The accuracy of the DPD curing reaction in reproducing the structural properties verifies its expanded application to general polymeric material simulations. The proposed curing DPD simulations, with a short run time and minimal computational resources, contributes to high-throughput screening for optimal resins and investigates mesoscopic inhomogeneous structures in large resin systems.

Swelling of Polypropylene Separators and Its Effect on the Lithium-Ion Battery Performance

The safety of lithium-ion batteries (LIBs) depends on separators -- porous materials providing ionic transport between the electrodes while preventing them from direct contact. Many commercial separator materials are polymers, e.g., polypropylene. Polypropylene has a non-polar structure, so it tends to interact favorably with non-polar solvents, such as carbonates used in LIBs as electrolyte solvents. These favorable interactions result in two effects: separator plasticization (softening) [1] and swelling [2]. Both swelling and plasticization affect the battery performance and cause safety concerns.Here we present a model which predicts the swelling of a porous polymer separator based on the molecular structures of the polymer and the solvent. The model is based on Flory's theory of polymer solutions and the Flory–Huggins parameter for polymer–solvent interactions. We introduced two additional parameters to Flory's theory, taking into account the complex structure of the porous polymers. These two parameters can be obtained from experimental data on two solvents. The Flory–Huggins parameter is calculated based on the UNIFAC-FV group contribution method for a given polymer–solvent pair. Our model predicts swelling of polypropylene separators in various solvents, matching the experimental data [3] quite well. By relating the swelling of the separator to the change in its porosity and tortuosity, we estimated the increase of cell impedance as a result of the swelling.Finally, the plasticization of the separator makes it less persistent to mechanical impacts, increasing the chances of failure. Since the solvent-induced plasticization of the separator is correlated with its swelling [3], our model can also be utilized to assess this effect. Therefore, our model can be used to quickly evaluate various polymer–solvent pairs for application in lithium-ion batteries.1. Sheidaei, A.; Xiao, X.; Huang, X.; Hitt, J. Mechanical behavior of a battery separator in electrolyte solutions. J. Power Sources 2011, 196, 8728−8734.2. Cannarella, J.; Liu, X. Y.; Leng, C.; Sinko, P.; Gor, G. Y.; Arnold, C. B. Mechanical properties of a battery separator under compression and tension. J. Electrochem. Soc. 2014, 161, F3117−F3122.3. Gor, G. Y.; Cannarella, J.; Leng, C. Z.; Vishnyakov, A.; Arnold, C. B. Swelling and softening of lithium-ion battery separators in electrolyte solvents. J. Power Sources 2015, 294, 167−172.4. Maksimov, A. V.; Molina, M.; Maksimova, O. G.; Gor, G. Y. Prediction of Swelling of Polypropylene Separators and Its Effect on the Lithium-Ion Battery Performance. ACS Appl. Polym. Mater. 2023, 5(3), 2026-2031.

Predicting Polymer Brush Behavior in Solvents Using the Steepest-Entropy-Ascent Quantum Thermodynamic Framework.

The steepest-entropy-ascent quantum thermodynamic (SEAQT) framework is utilized to study the effects of temperature on polymer brushes. The brushes are represented by a discrete energy spectrum, and energy degeneracies obtained through the replica-exchange Wang-Landau algorithm. The SEAQT equation of motion is applied to the density of states to establish a unique kinetic path from an initial thermodynamic state to a stable equilibrium state. The kinetic path describes the brush's evolution in state space, as it interacts with a thermal reservoir. The predicted occupation probabilities along the kinetic path are used to determine the expected thermodynamic and structural properties. The polymer density profile of a polystyrene brush in cyclohexane solvent is predicted using the equation of motion, and it agrees qualitatively with the experimental density profiles. The Flory-Huggins parameter chosen to describe brush-solvent interactions affects the solvent distribution in the brush but has a minimal impact on the polymer density profile. Three types of nonequilibrium kinetic paths with differing amounts of entropy production are considered: a heating path, a cooling path, and a heating-cooling path. Properties such as tortuosity, radius of gyration, brush density, solvent density, and brush chain conformations are calculated for each path.

Development and investigation of high‐flux antifouling NF PES membranes decorated by aniline oligomers and application for wastewater treatment

AbstractIn this research, first branched aniline oligomers functionalized polyethersulfone (BAO‐PES) were prepared by diazonium‐induced grafting, and then the embedded membranes were fabricated at five different compositions using the conventional phase inversion process. The influence of BAO‐PES as a modifier on membrane preparation was investigated in terms of membrane topography, membrane morphology, hydrophilicity, permeability, antifouling performance, and chemical stability. The function of blended membranes was evaluated by computational analysis, Fourier transform infrared (FTIR) analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle (WCA) measurement. Our computational analysis has substantiated that BAO‐PES (25 wt. %)/PES, characterized by a lower Flory–Huggins parameter (0.65), emerges as a promising contender for the blending of BAO‐PES with PES. The maximum water flux of 67.6 kg/m2 h was observed for the M1 membrane with the optimum dosage of BAO‐PES (25 wt. %) at a low pressure of 3 bar. To assess the nanofiltration performance of the mixed matrix BAO‐PES/PES membranes, the removal efficiency was studied for Direct Red 16 and tannic acid dye. From the results, it was found that the loose BAO‐PES/PES membranes had great dye rejection ability (more than 97%) compared to the bare membrane (88%–89%). The fouling resistance property of the loosely prepared membranes was tested by protein rejection, and the results revealed that the best antifouling property was observed at optimum dosage of the BAO‐PES modifier (25%, FRR = 98.37%). The embedded BAO‐PES/PES membranes, after exposure to harsh environments, exhibited such long‐term chemical stability that it is an important specification for real management in industry.

PLA aerogel as a universal support for the typical organic phase change energy storage materials

We first prepared Polylactic acid (PLA) aerogels with high porosity based on a facile and efficient thermal induced phase separation technique. In view of the excellent internal nano structure of PLA aerogel, high porosity and suitable interfacial affinity, it was selected as a support material to encapsulate four common organic phase change materials (PCMs), thereby preparing anti-leakage, shape-stable and sustainable PCMs with ultra-high latent heat (178.9–224.9 J g−1). PLA aerogel encapsulated PCMs perform high enthalpy efficiency (>92 %), which may benefit from the highly internal compatible nanostructure of PLA. Thermally conductive fillers (Boron nitride and Graphene nanoplatelet) were introduced to improve thermal conductivity. An important factor of PLA aerogel as a universal encapsulation matrix is analyzed based on the solubility parameters and Flory-Huggins parameters. The application cases of smart container and thermal regulation in confined spaces further prove the practical application value in the thermal regulation and energy saving area.

Experimental and computational design tools for industrial drying processes: Challenges in process‐limit prediction

AbstractThe coating and drying of inks and slurries are important steps to manufacture a plethora of products. Drying processes, particularly, comprise energy‐intensive steps that affect product cost and quality. Prior work has highlighted failures of various multicomponent diffusivity models to conserve mass in dryer modeling and challenges in predicting process limits given variability in published values of key thermodynamic parameters. Herein, we develop a computational model and benchtop drying experiments to investigate these concerns for drying polymer‐laden coatings. Model predictions of process limits in a single‐zone drying oven demonstrate that published variability in Flory–Huggins parameter yields large variations in predicted operating temperatures above which blistering occurs. This indicates that caution should be exercised when choosing approaches to obtain or predict the Flory–Huggins parameter, and that both benchtop drying experiments and a set of additional experiments, such as sorption experiments, are needed to fully characterize and optimize a given drying process.

Enhancing the compatibility of cold-mixed epoxy asphalt binder via graphene oxide grafted plant oil-based materials

Cold-mixed epoxy asphalt (CEA) has attracted extensive attention in overloaded and steel bridge pavement and maintenance engineering because of its room temperature construction and low energy consumption. However, the compatibility of epoxy resin and asphalt in CEA is still a challenge, limiting its application to some extent. This study aims to enhance the compatibility of CEA with low amounts of plant oil-based compatibilizers and suggest appropriate methods for assessing the compatibility of CEA. GO-grafted epoxidized soybean oil (GOESO) and GO-grafted soybean oil (GOSO) were synthesized and used to modify CEA. The GO and ESO (or SO) solutions were prepared at concentrations of 0.5 mg/mL and 5 mg/mL, respectively. The pH of the solution was adjusted to 5∼6 before heating. The results showed that 0.2 wt% of GO-modified oil-based compatibilizers had similar effects as 30 wt% of oil-based compatibilizers and did not significantly alter the crystal and chemical structures of the CEAs. GOESO is the preferred recommended GO-modified compatibilizer because of the enhanced compatibilizing ability of the epoxy groups in ESO. The compatibilization mechanism involved the effects of the oils on the chemical structures, curing reaction rate, and microstructures of CEAs. The proportion of asphalt particles larger than 20 μm and the reaction rate had strong correlations with the mechanical properties of the cured CEAs. Molecular dynamics simulations revealed that GOSO reduced the solubility parameter (δ) and Flory-Huggins parameter (χ) difference between components A and B by 39.4% and 65.8%, respectively, while GOESO increased the δ and χ difference between components A and B by 10.4% and 15.8%, respectively.

Temperature Transferable and Thermodynamically Consistent Coarse-Grained Model for Binary Polymer Systems

For the simulations of polymer systems, coarse-grained (CG) models are often developed to tackle the length and time scale limitations that are not feasible by all-atom molecular dynamic simulations. However, due to the necessary simplification or reduction in atomistic degrees of freedom, CG models usually have poor transferability over various temperatures, compositions, or thermodynamic states. In this work, the structure-based iterative Boltzmann inversion (IBI) method is further developed to obtain temperature transferable and thermodynamically consistent CG potentials for binary polymer systems. In particular, the conventional IBI procedure is first utilized to optimize single-component CG potentials from homopolymer systems while cross-interaction potentials from a random block copolymer system. Afterward, a thermodynamic integration method is applied to refine the cross-interaction potential between two constituent components in binary systems until the Flory–Huggins parameter (χ) between two components is matched with experimental value. We apply the above optimization procedure for the polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) as an example, which is widely studied experimentally, and the χ value can be easily obtained in the literature. To validate the transferability of the obtained CG potential, systems of both PS and PMMA homopolymers, random block copolymers, diblock copolymers, and PS/PMMA blends with various compositions are simulated. Many properties, including the mass density, radius distribution function, and bonded distribution functions, between CG beads generated from CG simulations match very well with those from atomistic simulations in the simulated temperature range, i.e., from 453 to 500 K. More importantly, phase morphologies of diblock copolymers and phase diagram of PS/PMMA binary blends over wide temperature and compositional ranges generated from CG simulations using our model are in good agreement with experimental results and predictions from self-consistent field theory.

The Process-Directed Self-Assembly of Block Copolymer Particles.

The kinetic paths of structural evolution and formation of block copolymer (BCP) particles are explored using dynamic self-consistent field theory (DSCFT). It is shown that the process-directed self-assembly of BCP immersed in a poor solvent leads to the formation of striped ellipsoids, onion-like particles and double-spiral lamellar particles. The theory predicts a reversible path of shape transition between onion-like particles and striped ellipsoidal ones by regulating the temperature (related to the Flory-Huggins parameter between the two components of BCP, χAB ) and the selectivity of solvent toward one of the two BCP components. Furthermore, a kinetic path of shape transition from onion-like particles to double-spiral lamellar particles, and then back to onion-like particles is demonstrated. By investigating the inner-structural evolution of a BCP particle, it is identified that changing the intermediate bi-continuous structure into a layered one is crucial for the formation of striped ellipsoidal particles. Another interesting finding is that the formation of onion-like particles is characterized by a two-stage microphase separation. The first is induced by the solvent preference, and the second is controlled by the thermodynamics. The findings lead to an effective way of tailoring nanostructure of BCP particles for various industrialapplications.

Modelling studies of the diffusivity and intersolubility of semi volatile organic compounds in water

Semi-volatile organic compounds (SVOCs) are hazardous contaminants found in several products - ranging from personal care products to plastic products and the environment. Their chemical migration into food substances, raising environmental and health concerns, has been well documented. The dispersion/diffusion and solubility of SVOCs in food simulants is an indicator of their migration from food packaging materials. Here, we employed molecular dynamics simulations to investigate molecular mass transfer/diffusivity and intersolubility of three (S)VOCs from various sources into water. The simulation results illustrated that the molecular weight of SVOCs affects their dispersion and solubility in water. SVOC molecules are also much easier to diffuse into water at higher temperatures and longer time periods. The intersolubility of SVOCs in water according to the Flory-Huggins parameter (χ) and Hildebrand solubility parameter (δ) occurs in the following order: methyl isocyanate > caprolactam > naphthalene. The solubility of SVOCs increases with temperature, as evident by the decreasing δSVOCs and χsvocs. These results will play a key role in expanding the knowledge base of chemical migration of small molecules into food simulants.

Prediction of Swelling of Polypropylene Separators and Its Effect on the Lithium-Ion Battery Performance

The safety and reliability of lithium-ion batteries depend on porous separators, many of which are made of polymer materials, such as polypropylene. Favorable interactions between a separator and organic electrolyte solvents used in the batteries often induce separator swelling. Swelling increases the electric resistance of the cell and is accompanied by plasticization of the separator, which also affects the battery’s performance. Here we propose a model based on Flory’s theory of polymer solutions which can predict the swelling of a porous polymer separator based on the Flory–Huggins parameter for polymer–solvent interactions. Despite the complexity of the polymer structure, introducing only two additional parameters provides predictive capability for the model. These two parameters can be obtained based on experimental measurements of separator swelling in two different solvents; the model also requires the Flory–Huggins parameter as an input, which can be calculated based on the UNIFAC-FV group contribution method for a given polymer–solvent pair. We illustrated the applicability of this model to recent experimental data on the swelling of polypropylene separators in various solvents. We also showed a simple relation between the separator swelling and an increase in cell resistance. Our model can be used for a quick assessment of various polymer–solvent pairs for application in lithium-ion batteries.

Investigation of the interaction between curcumin and hydroxypropyl methylcellulose acetate succinate in solid and solution media

Solubility and bioavailability are the main factors that affect the use of drugs and active ingredients, including curcumin (CUR). Among the ways to improve the properties of CUR are the polymeric matrices. This work aims to investigate the solubilization of CUR in the presence of macromolecular hydroxypropyl methyl cellulose succinate acetate (HPMCAS). Through the group contribution method, the compatibility between CUR and HPMCAS, which presented similar solubility components (Δδt < 7 MPa1/2), was analyzed. DSC measurements showed a depression of the CUR melting point in the presence of HPMCAS. The calculated Flory-Huggins parameter (−2.057 ± 0.25) indicates compatibility between the polymer and the CUR. The degree of crystallinity (Xc) of the CUR in the solid state (by XRPD) and in the molten state (by DSC) was calculated, noting that in the solid state the Xc was significantly higher. The intrinsic solubility of CUR in HPMCAS ranged from 102.84 to 62.40 when the temperature was raised from 293 K to 313 K with an enthalpy change of −18.01 ± 2.34 kJ mol−1 and entropy of 80. 9 ± 7.8 J mol−1 K−1. This process had a Gibbs free energy change with temperature variation of about −1.56 kJ mol−1 due to the solubilization of CUR in the internal hydrophobic core of HPMCAS. Particle sizes were detected indicating two populations of particles. The first (31.1 to 86 nm) and second (0.23 to 6.6 μm) populations were classified as unstable (< ±20 mV) by zeta potential (ζ). These results indicate that HPMCAS reorganization in the presence of CUR promotes a hydrophobic core capable of stabilizing CUR in solution. The formation of colloidal nanoparticles was confirmed by TEM which exhibited an effective diameter of 92 to 353 nm. As verified by ζ, colloidal instability was confirmed after 48 h, after which there was no change in the solubility of CUR in the system, showing that HPMCAS promotes a metastable state. The solubilization process and the formation of colloidal aggregates indicate how the drug dispersion process in the matrix can help in the production of pharmaceutical formulas.

Molecular Dynamic and Dissipative Particle Dynamic Simulation on the Miscibility of NR/CR Blends.

Natural rubber (NR) exhibits good elasticity, flexural resistance, wear resistance, and excellent mechanical properties, and it has been widely used in aerospace, transportation, medical, and health fields. For NR, however, the resistance to thermal-oxidation and ozone aging is fairly poor. Although aging properties of NR can be significantly improved with the incorporation of chloroprene rubber (CR) according to some references, the miscibility between NR and CR, the morphologies of the binary blends, and so on are revealed ambiguously. In this work, molecular dynamics simulation (MD) and dissipative particle dynamics (DPD) simulation were carried out to predict the compatibility between natural rubber and chloroprene rubber in view of Flory-Huggins parameters. The morphologies of the blends were obtained with the use of the DPD method. The simulation results were furtherly examined by means of Fourier transform infrared spectroscopy (FT-IR) and dynamic mechanical analysis (DMA). It was found that the miscibility between NR and CR is poor. Nevertheless, the miscibility could be improved when the content of CR is 50% or 90%. In addition, spinodal decomposition with a critical temperature of 390 K would take place according to the phase diagram. Microphase structure such as spherical, lamellar, and bicontinuous phases can be found with different contents of CR in the blends with the results of morphologies analysis.