Core-shell Polymer Research Articles

Core–shell microgels having zwitterionic hydrogel core and temperature-responsive shell prepared via inverse miniemulsion RAFT polymerization

The temperature-responsive core–shell microgels comprising PMPC core and side-chain oligo(ethylene glycol) polymer shell were prepared via inverse miniemulsion RAFT polymerization using a water-soluble emulsifier with RAFT agent terminus.

Effect of Solution Miscibility on the Morphology of Coaxial Electrospun Cellulose Acetate Nanofibers.

Coaxial electrospinning (co-electrospinning) technique has greatly expanded the universality of fabricating core-shell polymer nanofibers. However, the effect of solution miscibility on the morphology of co-electrospun products remains unclear. Herein, different cellulose acetate (CA) solutions with high solution miscibility but distinctly different electrospinnability were used to survey the effect of solution miscibility on the co-electrospinning process. The structural characterizations show that co-electrospun products are composed of nanofibers with and without the core-shell structure. This indicates that partial solution mixing occurred during the co-electrospinning process instead of absolute no-mixing or complete mixing. Importantly, the solution miscibility also shows a significant influence on the product morphology. In particular, the transformation from nanofibers to microparticles was realized with the increase of core-to-shell flow ratio during the co-electrospinning of core electrosprayable CA/dimethylacetamide (DMAc) solution and shell electrospinnable CA/acetone-DMAc (2/1, v/v) solution. Results show that the solution miscibility exerts a significant effect on not only the formation of core-shell structure but also the product morphology. This work provides a new insight for the in-depth understanding of the co-electrospinning process.

Simulative study of polymeric core–shell foam particles for the enlargement of the material portfolio in 3‐D high‐frequency welding

AbstractThe steam chest molding process is currently state of the art concerning the generation of three‐dimensional polymeric foam components made from particle foams. An adaption of the high‐frequency welding process shows advantages regarding the required energy and the used water. Due to the low dielectric loss factors of the most common foam materials (PE, PP, and PS), they cannot be heated sufficiently by an electric field. To enable heating of these foams, the particles may be coated with a second material that shows a high dielectric loss. The possible heat development of the modified particles was simulatively investigated. To ensure a realistic simulation, the properties of the used materials are analyzed beforehand. The heating simulation shows clear dependence regarding the particle size and the shell thickness. By a suitable combination, sufficient heating is achievable. For single particles, an irregular temperature distribution is calculated, mainly caused by the difference of permittivity resulting in a local variation of electrical flux density. Bigger particles and thicker shells will result in faster heating ramps and higher overall temperatures. The additional calculation regarding a particle–particle interaction shows a homogenization of the temperature distribution across the particle surface.

Surface Morphology Signature of Critical Separated Length and Glass Transition Temperature during Seeded Dispersion Polymerization.

The properties of colloids are considerably affected by particles' surface morphology. In this work, for understanding the mechanism of roughness formation in polymeric core-shell (CS) particles, the surface morphology of synthesized CS particles through seeded dispersion polymerization (SDP) in the presence of poly(methyl methacrylate) seeds was investigated. The results revealed that shell polymers with higher solubility parameters (δ) and glass transition temperatures (Tg) had a rougher surface. These parameters directly affect the time needed for chain deformation, which is a critical parameter in controlling the final morphology. We suggested a relation based on these parameters to predict the surface morphology (smoothness or roughness) of CS particles synthesized through SDP in water.

Synthesis of luminescent core–shell polymer particles carrying amino groups for covalent immobilization of enzymes

Synthesis of luminescent core–shell polymer particles carrying amino groups for covalent immobilization of enzymes

Wetting properties and morphological behavior of core-shell polymer-based nanoparticle coatings

The glass transition temperature (Tg) strongly affects the physicochemical properties of a polymer. In particular, coating a material with polymer nanocapsules with two or more Tg values can endow the material with variety of properties. We introduced polymer nanocapsules onto glass substrates and analyzed the effect of polymer Tg on the surface properties of the coating. Core-shell polymer (CSP) particles were prepared by a two-step emulsion polymerization procedure using poly(methyl methacrylate) (PMMA, Tg = 105 °C) and poly(butyl acrylate) (PBA, Tg = −54 °C) in different ratios as cores, and poly(nonafluorohexyl acrylate) (PNFHA, Tg = −6 °C) as shells. The microstructural and microbehavioral properties of the coating surface were found to depend on the Tgs of the synthesized CSP. Surface elemental distributions and chemical bonding were analyzed by XPS depth profiling to determine the behavior of the CSP nanoparticles. A core/shell nanoparticle with Tg = 55.81/−9.12 °C has a high probability of its core becoming located at the coating surface. On the other hand, a core/shell nanoparticle with Tg = −33.17.81/−28.6 °C has a high probability of its shell becoming located at the surface. Because the shell has a low surface energy, test solutions with a variety of surface tensions exhibited low wettabilities. These results allow the Tg values of the CSP to access the final thermodynamic equilibrium state, reveal that the Tg values affect the surface distribution of the functional groups of the coatings, which in turn determine its surface morphology and wetting properties.

Reaction-diffusion model to quantify and visualize mass transfer and deactivation within core-shell polymeric microreactors

HypothesisThe performance of a polymeric core–shell microreactor depends critically on (i) mass transfer, (ii) catalyzed chemical reaction, and (iii) deactivation within the nonuniform core–shell microstructure environment. As such, these three basic working principles control the active catalytic phase density in the reactor. TheoryWe present a high-fidelity, image-based nonequilibrium computational model to quantify and visualize the mass transport as well as the deactivation process of a core–shell polymeric microreactor. In stark contrast with other published works, our microstructure-based computer simulation can provide a single-particle visualization with a micrometer spatial accuracy. FindingsWe show how the interplay of kinetics and thermodynamics controls the product-induced deactivation process. The model predicts and visualizes the non-trivial, spatially resolved active catalyst phase patterns within a core–shell system. Moreover, we also show how the microstructure influences the formation of foulant within a core–shell structure; that is, begins from the core and grows radially onto the shell section. Our results suggest that the deactivation process is highly governed by the porosity/microstructure of the microreactor as well as the affinity of the products towards the solid phase of the reactor.

Synthesis of Fe3O4@Zn-BDC nanocomposite for the removal of MB from aqueous solution

Coordination polymers (CPs) are a significant platform for dye adsorption. Designing Fe3O4@CP nanocomposites as easy-recoverable adsorbents could facilitate their recycling. In this research, a core-shell Fe3O4@CP nanocomposite was prepared for methylene blue (MB) adsorption and removal from aqueous solutions. The obtained nanocomposite consists of Fe3O4 core and coordination polymer shell constructed from Zn2+ and benzene-1,4-dicarboxylic acid (H2-BDC) which formed with layer-by-layer assembly. The formation of the core-shell nanostructure was approved with various physicochemical techniques. The microscopy results confirmed a core-shell nanostructure for Fe3O4@CP nanocomposite that shell thickness is about 5–7 nm. The adsorption experiments indicated that Fe3O4@CP nanocomposite not only adsorbed more than 86% of MB only after 2 min, it significantly could be separated magnetically and reused without evident loss of adsorption efficiency after four cycles.

Fabrication of two-dimensional metal-organic framework nanosheets/PDA composites as mixed-mode stationary phase for chromatographic separation.

Thesynthesis of two-dimensional metal-organic frameworks (2D MOFs)/polymer core-shell compositesis reported which were composed of polydopamine modified 2D Zr-1,3,5-(4-carboxylphenyl)-benzene (2D Zr-BTB) nanosheets and silica microspheres via a double-solvent approach. In this way, the composites were obtained under the condition of two solvents with different polarities to avoid agglomeration and uneven modification of most MOFs particles on the surface of the silica, existing inevitably in the one-pot method. Compared with the reported MOFs@silica composites adopting one-pot solvent method, the prepared composites exhibited significantly enhanced separation performance for sulfonamides, antibiotics, nucleosides, and polycyclic aromatic hydrocarbons compounds. Furthermore, the retention mechanisms were demonstrated by studying the relationships of chromatographic retention factors of tested analytes versus a variety of parameters under RPLC and HILIC modes, respectively. The superior chromatographic repeatability and stability were validated through the relative standard deviations of the retention time and/or column efficiency, which were found to be less than 0.8% and 0.9%, respectively. The material showed efficient separation ability for several types of compounds and provided another selectivity for preparing composites based on 2D MOFs nanosheets and other functional molecules.

Synthesis of core-shell bottlebrush polymers of poly(polycaprolactone-b-polyethylene glycol) via ring-opening metathesis polymerization

This research was focused on the synthesis of core-shell bottlebrush polymer poly(PCL-b-PEG) (PCL: polycaprolactone; PEG: polyethylene glycol) through a combination of ring-opening polymerization (ROP) and ring-opening metathesis polymerization (ROMP). Three main steps were involved in this synthesis: firstly, the ROP of ε-caprolactone was conducted to form an amphiphilic linear polymer PEG-b-PCL in presence of methoxypolyethylene glycols and Sn(Oct)2; secondly, macromonomers with norbornenyl-functionalization were synthesized by the esterification of the hydroxyl-terminated PEG-b-PCL with 5-norbornene-2-carboxylic acid; thirdly, the synthesized macromonomers were further polymerized by ROMP in presence of Grubbs second-generation catalyst to form a core-shell bottlebrush structured polymer. The effects of the reaction time, concentrations of small-molecule monomers, amount of catalyst and the molecular weights of macromonomers on the performance of the ROMP of the macromonomers were investigated in detail. 1H NMR and GPC analyses confirmed the structures of the resulting polymers. DSC, XRD, TGA were used to characterize the properties of PEG-b-PCL and poly(PCL-b-PEG). Compared with the linear block polymers PEG-b-PCL, the resulting polymers with core-shell bottlebrush structures have a more regular chain arrangement and better thermal stability.

Guiding Molecularly Imprinted Polymer Design by Pharmacophore Modeling.

Molecularly imprinted polymers (MIP) combine the selectivity of immunoaffinity chromatography with the robustness of common solid-phase extraction in what is referred to as molecularly imprinted solid-phase extraction (MISPE). This contribution shows how MIP design may be guided by pharmacophore modeling for the example of citrinin, which is an emerging mycotoxin from cereals. The obtained pharmacophore model allowed searching public databases for a set of citrinin-mimicking molecular surrogates. Imprinted and non-imprinted polymers were subsequently obtained through bulk and core-shell polymerization in the presence of these surrogates. Evaluation of their binding ability for citrinin and structurally related ochratoxin A revealed a promising MIP derived from rhodizonic acid. A protocol for MISPE of citrinin from cereals was subsequently developed and compared to immunoaffinity chromatography with respect to clean-up efficiency and recovery.

Functional polymeric core–shell hybrid nanoparticles overcome intestinal barriers and inhibit breast cancer metastasis

Oral delivery of therapeutic agents is complicated by issues associated with nanocarrier transfer in the gastrointestinal tract, such as physical stability, mucus penetration, and cellular uptake and transport. Various functional nanocarriers have been devised but more research is required to assure the desirable physical stability in the intestinal lumen and biology-responsive diffusion in the mucus. Here, we developed nanoparticles coated with microbial-derived sophorolipid assemblies for oral delivery of therapeutic agents, focusing on improved bioavailability and inhibition of breast cancer metastasis. Upon exposure to the intestinal lumen, the nanoparticles resisted changes in the pH and ion content, and retained their size and composition. They exhibited intestinal biologically responsive diffusion in the mucus because of a charge change from negative to nearly neutral, accompanied by a detachment of sophorolipid assemblies. The latter was possibly caused by the high sophorolipid affinity for mucin, which protected the nanoparticles during mucus penetration. The increased stability and enhanced mucus diffusion improved the intracellular uptake of nanoparticles, thus improving the oral bioavailability of the payload. Administration of silibinin and curcumin co-loaded nanoparticles resulted in an improved therapeutic effect of inhibiting breast cancer metastasis, by regulating tumor microenvironment, in 4T1 tumor bearing mice. The nanoparticles modulated epithelial–mesenchymal transition and inhibited angiogenesis. They also increased the infiltration of CD4+ and CD8+ T cells, and downregulated the immunosuppressive regulatory T cells and myeloid-derived suppressor cells in tumors. In conclusion, the novel nanocarriers are a promising oral drug delivery system.

Adsorption of Tartrazine anionic dye by novel fixed bed Core-Shell- polystyrene Divinylbenzene/Magnetite nanocomposite

In this study, the in situ chemical polymerization process was used to synthesize polystyrene/magnetite nanocomposite (PS-DVB/ Fe3O4). The prepared composite was characterized by XPS, SEM, XRD, HRTEM, FT-IR, and TGA technique. The XPS as an essential elemental analysis tool proved the proposed general formulae of the prepared nanocomposite (PS-DVB/ Fe3O4). FT-IR data proved the functional groups in the proposed structural formula of the prepared nanomaterials. The thermal analysis confirmed the high thermal stability of the prepared core–shell polymer. XRD results prove the crystallinity and single phase. Scanning electron microscope (SEM) and the presence of Fe2O3 and PS-DVB/Fe3O4 composite has been confirmed by HRTEM. The particle size analysis was used to determine the distribution of particle size within the polymer matrix. The adsorption potential of Tartrazine azo dye from polluted water samples onto cross-linked (PS-DVB/Fe3O4) using fixed-bed adsorption column was investigated. The adsorption capacity of Tartrazine onto PS-DVB greatly improved when Fe3O4 is added to the porous composite of PS-DVB copolymer to be 0.15 mol with removal efficiency reach 98%. In this respect, the effect of liquid flow rate, initial Tartrazine concentration, and PS-DVB/Fe3O4 bed height on the adsorption technique's breakthrough features was taken. In this work, the mass transfer model, which involved the two parameters of τ (50% breakthrough time) and k (adsorption rate constant), was suggested for discussion the effect of PS-DVB/Fe3O4on such values. It was found that the adsorption capacity Qe and τ values were decreased with the flow rate increases. The flow rate had little effect, at least for the PS-DVB/Fe3O4, on the k value. On the other hand, both Qe and τ values decreased with increasing the initial Tartrazine concentration, whereas the k value was slightly increased. We concluded that the liquid flow rate, initial Tartrazine concentration, and bed height were1mL/min, 5 M, and 7 cm, respectively. Finally, the PS-DVB/Fe3O4 was a suitable Tartrazine adsorbent using a fixed-bed adsorption column, which fitted well with the mass transfer model.

Multi-objective dynamic optimization of seeded suspension polymerization process

The temperature profile of the seeded suspension polymerization process was optimized to maximize molecular weight, shell thickness and monomer conversion ratio of core–shell polymer particles. Extreme learning machine radial basis function neural networks with R2 values greater than 0.93 were developed, to predict polymer properties at any point in time, using data generated by a computational fluid dynamics model. The optimal combination of input parameters for each neural network was selected from a pool of 44 variables, by using a weight-based method that uses a support vector regression model, and a global exhaustive search algorithm, consecutively. The neural networks developed were incorporated into a genetic algorithm that maximizes the molecular weight, monomer conversion ratio and shell thickness. The optimum temperature profile generated by the algorithm satisfactorily maximized all target polymer properties. This study also demonstrates that a support vector machine classifier could be reliably used for imposing nonlinear inequality constraints for solving dynamic optimization problems.

All-Conjugated Polymer Core-Shell and Core-Shell-Shell Particles with Tunable Emission Profiles and White Light Emission.

Future applications of conjugated polymer particles (CPP) in medicine, organic photonics, and optoelectronics greatly depend on high performance and precisely adjustable optical properties of the particles. To meet these criteria, current particle systems often combine conjugated polymers with inorganic particles in core-shell geometries, extending the possible optical characteristics of CPP. However, current conjugated polymer particles are restricted to a single polymer phase composed of a distinct polymer or a polymer blend. Here, a synthetic toolbox is presented that enables the synthesis of monodisperse core-shell and core-shell-shell particles, which consist entirely of conjugated polymers but of different types in the core and the shells. Seeded and fed-batch dispersion polymerizations based on Suzuki-Miyaura-type cross-coupling are investigated. The different approaches allow accurate control over the created interface between the conjugated polymer phases and thus also over the energy transfer phenomena between them. This approach opens up completely new synthetic freedom for fine tuning of the optical properties of CPP, enabling, for example, the synthesis of individual white light-emitting particles.

A one-step in vitro continuous flow assessment of protein release from core-shell polymer microcapsules designed for therapeutic protein delivery

Developing accurate methods for the assessment of therapeutic protein release from polymer drug delivery systems (microcapsules, microspheres, nanoparticles, 3D-printed systems) is of paramount importance for new formulation development. The most straightforward method for protein release assessment is spectrophotometric analysis of the release medium surrounding the formulation. However, direct spectrophotometric analysis is inapplicable to formulations releasing interfering compounds (co-encapsulated drugs, additives) absorbing light in the same spectrum as proteins. Conventional protein release assays also require frequent release medium sampling and replacement, which reduces their accuracy. We propose a one-step method to assess protein release from core/shell microcapsules eliminating the need for sampling and allowing selective real-time protein quantitation in the release medium. To prevent spectral interferences, released protein is differentiated from interfering compounds by employing a colorimetric protein assay reagent, forming a colour complex selectively with the protein, as the release medium. To eliminate sampling, we employed a continuous flow closed loop set-up, where the release medium is constantly circulating between microcapsule-containing tank and spectrophotometer. A series of colorimetric protein assay reagents (bromocresol green, tetrabromophenol blue, eosin B, eosin Y, biuret) were evaluated in terms of their applicability as the release medium in described system. Only biuret reagent was found compatible with proposed method due to formation of color complex stable over extended period of time and low adsorption to microcapsules. Presented method allowed effective evaluation of albumin release from alginate-polyethersulfone microcapsules with accuracy equal to conventional ‘sample and separate’ technique. Albumin release followed first-order kinetics with plateau reached after 19 h.

Magnetic polymeric core-shell as a carrier for gradual release in-vitro test drug delivery

At first functionalized graphene oxide was selected as a basic substrate obtained through process of functionalization of graphene oxide with diethylenetriamine as substrates. Then magnetic nanoparticle sediments were formed and coated on the functionalized graphene oxide as the core center. The core nanoparticle was added to a gel containing poly (lactic-co-glycolic acid), polyethylene glycol, and polyvinylpyrrolidone and nilotinib drug for forming a shell on the core. After separation and freeze-drying, single core-shell particles were obtained. The second shell was coated by dispersing first core-shell in a new gel containing polylactic acid, polyvinyl alcohol, polyethylene glycol, and nilotinib. The third layer was laminated on core-dual shell particle by entering in sodium alginate, polyethylene glycol, poly (lactic-co-glycolic acid), polylactic acid and nilotinib gel according to the same method used above. In order to determine the gradual release, the core-single, dual and triple shell nanoparticles dispersed in phosphate buffer saline at the several pHs (3, 5.4, 7.4) and as well as monitoring the released concentration of nilotinib by UV-Vis spectrophotometer technique. Core-triple shell particle had gradual release at three different rates over the long time. Finally, the average release rate for 400 mg of drug, in single layer, double-layer and three layers were reported to be equal to 15.8, 10.4 and 6.6 mg/h at intervals of 24, 37 and 60 h, respectively. The release rate of the drug reduced by increasing the pH value. All products were characterized using several techniques.

Self-assembly in soft matter with multiple length scales

Spontaneous self-assembly in molecular systems is a fundamental route to both biological and engineered soft matter. Simple micellization, emulsion formation, and polymer mixing are well understood. However, the principles behind emergence of structures with competing length scales in soft matter systems remain unknown. Examples include droplet-inside-droplet assembly in many biomacromolecular systems undergoing liquid-liquid phase separation, analogous multiple emulsion formation in oil-surfactant-water formulations, and polymer core-shell particles with internal structure. We develop here a microscopic theoretical model based on effective interactions between the constituents of a soft matter system to explain self-organization both at single and multiple length scales. The model identifies how spatial ordering at multiple length scales emerges due to competing interactions between the system components, e.g., molecules of different sizes and different chemical properties. As an example of single and multiple length scale assembly, we map out a generic phase diagram for a solution with two solute species differing in their mutual and solvent interactions. We further connect the phase diagram to a molecular system via molecular simulations of a block-copolymer system that has a transition from regular single-core polymer particles to multicore aggregates that exhibit multiple structural length scales. The findings provide guidelines to understanding the length scales rising spontaneously in biological self-assembly but also open venues to the development and engineering of biomolecular and polymeric functional materials and pharmaceutical formulations.Received 20 January 2021Accepted 25 March 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.L022008Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasClassical statistical mechanicsClusteringPhase diagramsSelf-assemblyThermodynamicsCondensed Matter, Materials & Applied PhysicsStatistical PhysicsPolymers & Soft Matter

Design and evaluation of novel MOF-polymer core-shell composite as mixed-mode stationary phase for high performance liquid chromatography.

A general method was developed for preparing ametal-organic framework-polymer composite coated silica core-shell stationary phase. Silica microspheres were comodified with metal-organic framework and polyvinylpyrrolidone rather than the in situ method of silica modification by original metal-organic framework particles. Metal-organic framework particles and polyvinylpyrrolidone on silica surface were beneficial to suppress silanol activity and enhance composite material tolerance, as well as increasing the water compatibility of the original metal-organic framework-based stationary phases. The stationary phase exhibited superior hydrophilic and hydrophobic performance in terms of separation for various analytes including seven alkaloids, six sulfonamides, five antibiotics, and five polycyclic aromatic hydrocarbons. Moreover, the composite material also showed excellent stability with the relative standard deviation of the retention time of 0.4 to 0.7%. The separation performance with real samplesproved that the column has good practical application potential. In summary, the poposed method provides a general way for preparing metal-organic framework-polymer composite material and changed the current status of original metal-organic framework particles modified silica as a single mode chromatographic stationary phase.

Numerical Simulation of a Core-Shell Polymer Strand in Material Extrusion Additive Manufacturing.

Material extrusion additive manufacturing (ME-AM) techniques have been recently introduced for core–shell polymer manufacturing. Using ME-AM for core–shell manufacturing offers improved mechanical properties and dimensional accuracy over conventional 3D-printed polymer. Operating parameters play an important role in forming the overall quality of the 3D-printed manufactured products. Here we use numerical simulations within the framework of computation fluid dynamics (CFD) to identify the best combination of operating parameters for the 3D printing of a core–shell polymer strand. The objectives of these CFD simulations are to find strands with an ultimate volume fraction of core polymer. At the same time, complete encapsulations are obtained for the core polymer inside the shell one. In this model, the deposition flow is controlled by three dimensionless parameters: (i) the diameter ratio of core material to the nozzle, ; (ii) the normalised gap between the extruder and the build plate, ; (iii) the velocity ratio of the moving build plate to the average velocity inside the nozzle, . Numerical results of the deposited strands’ cross-sections demonstrate the effects of controlling parameters on the encapsulation of the core material inside the shell and the shape and size of the strand. Overall we find that the best operating parameters are a diameter ratio of , a normalised gap of , and a velocity ratio of .