PMMA Shell Research Articles

Interfacial blending in co-axially electrospun polymer core-shell fibers and their interaction with cells via focal adhesion point analysis

Electrospun polymer scaffolds have gained prominence in biomedical applications, including tissue engineering, drug delivery, and wound dressings, due to their customizable properties. As the interplay between cells and materials assumes fundamental significance in biomaterials research, understanding the relationship between fiber properties and cell behaviour is imperative. Nevertheless, altering fiber properties introduces complexity by intertwining mechanical and surface chemistry effects, challenging the differentiation of their individual impacts on cell behaviour. Core-shell fibers present an appealing solution, enabling the control of mechanical properties of scaffolds, flexibility in material and drug selection, efficient encapsulation, strong protection of bioactive drugs against harsh environments, and controlled, prolonged drug release. This study addresses a key challenge in core-shell fiber design related to the blending effect between core and shell polymers. Two types of fibers, PMMA and core-shell PC-PMMA, were electrospun, and thorough analyses confirmed the desired core-shell structure in PC-PMMA fibers. Surface chemistry analysis revealed PC diffusion to the PMMA shell of the core-shell fiber during electrospinning, subsequently prompting an investigation of the fiber’s surface potential. Conducting cellular studies on osteoblasts by super-resolution confocal microscopy provided insights into the direct influence of interfacial polymer blending and, consequently, altered fiber surface and mechanical properties on cell focal adhesion points, bridging the gap between material attributes and cell responses in core-shell fibers.

Micro-encapsulation of a low-melting-point alloy phase change material and its application in electronic thermal management

The application of liquid metal (LM) with high thermal conductivity in electronic thermal management is an emerging hotspot, but leakage of LM can cause environmental pollution and lead to corrosion of electronic equipment, thereby affecting the safety of its operation. Moreover, large temperature fluctuation will be caused for the limited thermal storage capacity of LM. To solve the above problems, it is urgent to develop LM-based microcapsules with high thermal conductivity and high thermal storage capacity. Herein, a novel micro-encapsulated phase change material (MEPCM) with an internal void, composed of liquid metal Sn–Bi–In core and PMMA shell, was firstly fabricated via liquid phase micro-encapsulation method. The results showed that microcapsules maintained good morphology and efficient thermal storage capacity (246.46 J cm−3) after 300 thermal cycles, 97.12% of that before the cycle (253.77 J cm−3). Subsequently, the MEPCM-based composite was prepared by mixing MEPCM into thermal gel. The enthalpy of 50 wt% MEPCM composite was 126.72 J cm−3, and the thermal conductivity of it was 3.23 W m−1·K−1, while that of thermal gel was 0.98 W m−1·K−1. Then the 50 wt% MEPCM-based composite was applied for LED chip, and the temperature of chip was 71.1 °C, 11.2 °C lower than that of thermal gel. Therefore, MEPCM-based composites with high thermal conductivity and thermal storage capacity are considerably potential for electronic thermal management.

A micromechanical damage-healing model for encapsulation-based self-healing polymer composites under tensile loading

In this study, a novel micromechanics-based damage model is proposed for the damage evolution of a two-component microencapsulated-based self-healing polymer composite. In this way, a representative volume element (RVE) including an epoxy matrix with randomly distributed poly(methyl methacrylate) (PMMA) microcapsules is modeled in DigimatTM software and analyzed in Abaqus®. A new technique is developed to investigate the progressive damage by pre-inserted cohesive elements along all element boundaries of the epoxy matrix, PMMA shell, and capsule-matrix interfaces with the bilinear traction–separation law. Moreover, the impact of interface bonding strength, interface fracture energy, and PMMA microcapsules volume fraction on the load-carrying capacity of the RVEs under uniaxial tension loading was studied. The results indicated that the tensile strength of the self-healing polymer composite increased as the interfacial strength and fracture energy increased from 10 to 60 MPa and 100 to 1000 J/m2, respectively. Furthermore, the higher volume fraction of 5% PMMA microcapsules results in a lower load-carrying capacity of self-healing polymer composite with a strength of 4.9 N. A similar trend of Young’s modulus was observed for microcapsule-loaded epoxy composite compared to the pristine epoxy matrix. The micromechanical model has proper accuracy in predicting the tension behavior of self-healing composite in comparison to experimental results. Finally, two healing strategies are considered for the damaged RVE.

A new type of carbonate hydroxyapatite nanoparticles made from PMMA and oyster shells: evaluation of structure, morphology and biocompatible properties

A new type of carbonate hydroxyapatite nanoparticles made from PMMA and oyster shells: evaluation of structure, morphology and biocompatible properties

A low-temperature digital microfluidic system used for protein-protein interaction detection.

The occurrence, development and prediction of various biological processes and diseases are inseparable from the protein-protein interaction (PPI), so it is extremely meaningful to perfect PPI networks. However, shortcomings of traditional detection methods, such as protein degradation, long detection time, complex operation, poor automation and high cost, restrict the rapid development of PPI networks. Here, a low-temperature digital microfluidic (LTDMF) system-based PPI detection box (LTDMF-PPI-Box) was developed to achieve rapid, lossless and efficient PPI detection. It consists of a PMMA shell, LTDMF-PPI and an integrated temperature control system. LTDMF reduces the PPI detection time from tens of hours to 1.5 hours by programmatically controlling the movement of droplets. Moreover, an integrated thermoelectric cooler (TEC) ensures an operating temperature of 4 °C, resulting in a protein protection up to 90%. The interaction between RILP protein and Rab26 protein which has a close connection to insulin secretion was demonstrated as a prototype to illustrate the feasibility of the LTDMF-PPI-Box. LTDMF with automation characteristics is capable of meeting the requirement of high-throughput screening of interacting proteins; therefore, the LTDMF-PPI-Box is expected to accelerate the establishment of the PPI network in the future.

Testing the encapsulation of phase change materials using supercritical emulsion extraction

Continuous supercritical CO2 emulsion extraction (SEE-C) technology is proposed for the first time to test the encapsulation of two fatty acids: Stearic acid and isopropyl myristate, to be used as model Phase Change Materials (PCM) in a PMMA shell. Spherical microcapsules with smooth surface and a mean diameter between 163-431 nm have been produced. Encapsulation efficiencies larger than those in the literature and up to a max of 91 % were measured. Therefore, supercritical PCM encapsulation can open new perspectives in thermal energy storage application.

Preparation and characterization of phase change material microcapsules with modified halloysite nanotube for controlling temperature in the building

Microencapsulated phase change material (mPCM) with effective heat transfer and flame retardant is highly desirable given today’s increasing energy demand. In this article, the halloysite nanotube (D-HNT) was modified by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and then inserted into the mPCM (D-H-mPCM) successfully. The transmission electron microscope, X-ray photoelectron spectroscopy and FT-IR results showed that the DOPO is grafted in both interior and exterior walls of halloysite nanotube (HNT), and the D-HNT is successfully inserted into mPCM. According to thermogravimetric analysis tests, D-H-mPCM was the best thermally stable sample among other mPCM for the existence of HNT and DOPO. The differential scanning calorimetry tests showed that the latent heat of D-H-mPCM was 113.52 J/g, and the D-HNT embedded in the mPCM greatly contributes to the heat transfer of the PMMA shell. To detect the flame retardancy and temperature control performance of mPCM samples, D-H-mPCM was incorporated into epoxy resin (EP-D-H-mPCM). The data of the cone calorimeter test suggested the EP-D-H-mPCM exhibited the lowest peak of heat release rate (pHRR) and total heat release (THR) of 572.65 kW/m2 and 93.95 MJ/m2 respectively. Finally, the small room model test and infrared thermal imager test showed the application of D-H-mPCM in EP can regulate indoor temperature and moderate temperature fluctuation. This work provides a new methodology to improve both thermal conductivity and flame retardancy of mPCM.

Effects of the methyl methacrylate addition, polymerization temperature and time on the MBG@PMMA core-shell structure and its application as addition in electrospun composite fiber bioscaffold

Mesoporous bioactive glass (MBG) possesses a high specific surface area and excellent biocompatibility making it a promising biomaterial. In the present study, poly(methyl methacrylate) (PMMA) was coated on MBG to obtain a MBG@PMMA core-shell structure to further expand the potential applications of MBG. Changes in the MMA to MBG ratio, polymerization temperature and time were investigated to determine their effects on the core-shell structure. The as-prepared core-shell powders were evaluated using scanning electron microscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy to determine the optimal core-shell structure for electrospinning application. Electrospun composite fiber scaffolds prepared by adding MBG with or without an optimized PMMA shell were examined through microstructural observation, mechanical testing, Raman spectroscopy, and in vitro bioactivity evaluation. Experimental results showed that optimized MBG@PMMA core-shell powder was prepared using MMA: MBG = 3: 1, with polymerization at 70 °C for 4 h. The spherical core-shell powder exhibited a relatively smooth surface and the flake- or cotton-like shell structure was beneficial to electrospinning. Electrospun composite fiber scaffold prepared using MBG@PMMA powder exhibited superior mechanical performance and excellent biocompatibility compared to its shell-less MBG counterpart.

A nano-compression model to characterize the elastic properties of core–shell structured microspheres

Nano-compression is a convenient approach for investigating the elastic modulus of microcapsule shells by compressing a core–shell structured microsphere between two parallel plates in nanoscale. A nano-compression model was developed through energy minimization, which avoids determining the complicated load distribution at interface. The total potential energy of microcapsule includes the work done by compression load and the strain energy of shell and core. By minimizing the total potential energy, the correlation among the compression load, the compression displacement, and the elastic and geometric parameters of microcapsules was derived. With this model, the shell elastic modulus then can be evaluated by fitting the loading responses of microcapsules. To validate the proposed model, nano-compression tests were conducted on PMMA microcapsules. The elastic moduli for PMMA shells evaluated by the nano-compression model agree well with the reference value with a maximum relative error of -12.12%. The elastic moduli of the PMMA shells determined by the nano-compression model were then used in finite element simulations to predict the compression load–displacement curves, which show good agreement with those measured in experiments with a relative error within ±9.64%.

Fabrication of a sugar-immobilized fluorescent PMMA shell on a Ni core particle via soap-free emulsion polymerization.

Sugar chain immobilized polymer particles having both magnetic and fluorescent properties can be expected to be useful in a wide variety of biomedical applications such as the detection, separation, and purification of proteins, viruses, or bacteria, because sugar chains specifically adsorb them. Since high magnetic responsiveness is required for such applications, we attempted to fabricate core-shell particles consisting of a submicron-sized magnetic core and a thin polymer shell (nano- to dozens of nanometers thick) that incorporates a fluorescent dye, with sugar molecules immobilized on the surface. Soap-free emulsion polymerization using methyl methacrylate (MMA) monomer and potassium persulfate (KPS) initiator in the presence of aminopropyltrimethoxysilane-treated Ni particles, octyl-β-D-glucopyranoside (octyl-glc), and rhodamine B (RhB) produced a glucose-immobilized fluorescent PMMA thin shell on a Ni particle (Ni/PMMA/RhB/octyl-glc). Electrostatic interaction was used both to incorporate RhB into the PMMA shell and to coat the Ni core with the PMMA-RhB shell. Glucose was immobilized on the PMMA shell by embedding a hydrophobic octyl group derived from octyl-glc in the PMMA matrix, and the resulting sugar-immobilized PMMA shell was able to adsorb protein (concanavalin A; a protein that specifically adsorbs glucose). The resulting Ni/PMMA/RhB/octyl-glc particles were well-dispersed in water, detected by highly sensitive fluorescence techniques, and could be collected by a magnet within 10 sec. They are expected to be applied to detect biological substances such as various proteins and viruses by changing the glucose moiety of the particle surface to other functional glycans.Graphical Supplementary informationThe online version contains supplementary material available at 10.1007/s00396-022-04945-7.

The flame retardant and thermal conductivity properties of high thermal conductivity expandable graphite microcapsule filled natural rubber composites

The flammable feature limits the application of natural rubber in building fields. Although expandable graphite (EG) microcapsule has good compatibility with natural rubber (NR), the organic wall material of microcapsule has the disadvantage of low thermal conductivity and increases the risk of combustion of NR. In this study, EG microcapsule was prepared via in-situ polymerization (BN-PMEG) whilst its organic shell with high compatibility and thermal conductivity was developed by boron nitride (BN)-doped. The composite structure and thermal performances were analyzed via scanning electron microscope test (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG). Following this, the cone calorimeter test, limiting oxygen index test, vertical burning test, time to ignition test, tensile strength and fracture test were used to describe the fire behavior and mechanical properties. The results indicate that the BN is embedded in the PMMA shell and the diameter of BN-PMEG is 20–50 μm. According to the mechanical property and thermal conductivity test, BN-PMEG have better compatibility with NR than expansible graphite and increases the thermal conductivity of NR composites. Our work provides a new choice for designing and applying rubber composite materials in buildings.

Spherical indentation model for evaluating the elastic properties of the shell of microsphere with core-shell structure

The indentation of a microcapsule with a spherical indenter is an effective technique to evaluate the elastic properties of microcapsule shells. The spherical indentation of a microcapsule could be modelled as a microsphere with core–shell structure indented by a rigid sphere. Based on the assumption that the deformed pattern of microcapsule is axisymmetric at small indentation displacement, the deformed profile of shell was divided into five regions according to curvature change. The strain energy of shell was then obtained by adding the bending and membrane strain energy of each region together. The strain energy of core is mainly caused by the volume change of core. The microcapsule was treated as a system and its total potential energy is the sum of the strain energy of shell and core minus the work done by external load. Applying the minimum total potential principle, a spherical indentation model that establishes the relationship among the indentation load, the indentation displacement, and the elastic properties and geometric parameters of microcapsules was proposed. Experiments were carried out on PMMA microcapsules with different dimensions to validate the newly proposed spherical indentation model. The average value of elastic moduli obtained by conventional nanoindentation tests on bulk PMMA and the cross-section of PMMA shell was regarded as the nominal value. The average elastic modulus of PMMA shells determined by the proposed model shows a good agreement with the nominal value. Finally, finite element simulations combined with the proposed model were used to predict the indentation behaviors of microcapsules with different dimensions.

Effect of agitation speed on microencapsulation of healing agent in PMMA shell and study on the mechanical properties of epoxy/PMMA microcapsules

In this study, the effect of agitation speed as a key process parameter on the morphology and particle size of epoxy-Poly (methyl methacrylate) (PMMA) microcapsules was investigated. Thus, a new interpretation is presented to relate between the microcapsule size to rotational speed so as to predict the particle size at different agitation speeds from the initial capsule size. The PMMA shell capsules containing EC 157 epoxy and hardener as healing materials were fabricated through the internal phase separation method. The process was performed at 600 and 1000 rpm mechanical mixing rates. Scanning electron microscopy (SEM) revealed the formation of spherical microcapsules with smooth surfaces. According to static light scattering (SLS) results, the average diameter size of the epoxy/PMMA capsules at two mixing rates were 7.49 and 5.11

Fracture Strength of Interim CAD/CAM and Conventional Partial Fixed Dental Prostheses

AbstractPurpose To compare the fracture strength of three‐unit provisional partial fixed dental prostheses (FDPs) fabricated by an indirect‐direct technique from poly(methylmethacrylate) (PMMA) through digital and conventional workflows, and FDPs fabricated by a direct technique using Bisacryl (BisA) and externally reinforced BisA.Materials and Methods Forty partially edentulous typodonts with a missing mandibular left first molar and standard preparations on mandibular left second premolar and molar were used to fabricate three‐unit provisional FDPs. Two materials and two techniques were used to fabricate a total of forty provisional FDPs: (1) BisA; (2) BisA reinforced with glass fiber strips [BisA‐GFR]; (3) conventionally fabricated PMMA shell relined with PMMA [C‐PMMA]; (4) CAD/CAM fabricated PMMA shell relined with PMMA [CAD/CAM‐PMMA]. Provisional FDPs were then luted onto the preparations using a temporary cement. Specimens were mounted onto a chewing simulator; 20,000 cycles of 70 N forces were applied under 25°C distilled water. Specimens were then loaded to fracture using a universal testing machine (The Dillion Quantrol TC2i; Mecmesin) with a crosshead speed of 2 mm/min. One‐way ANOVA, followed by Tukey post hoc test, was used to assess the effect of production technique on the fracture strength of the provisional FPDs (α = 0.5).Results Mean fracture strengths recorded for the CAD/CAM‐PMMA, C‐PMMA, BisA, and BisA‐GFR groups were 520 N, 448 N, 245 N, and 169 N, respectively. PMMA groups had significantly (p < 0.0001; F = 24.40) higher fracture strength compared to Bisacryl groups.Conclusion When high occlusal forces are expected, provisional FDPs fabricated with PMMA using the indirect‐direct technique are recommended, irrespective of CAD/CAM or conventional workflow.

Dual Microcapsulation of an Environmentally‐Friendly‐Based Reactive Multifunctional Acrylated Epoxy Resin and Thiol by Internal Phase Separation Technique for Self‐healing Applications

In this research, the microcapsules were individually prepared via internal phase separation technique using reactive bio-based acrylated epoxidized soybean oil, AESO, and trimethylolpropane tris(3-mercaptopropionate), TMPMP as healing and curing agents respectively in PMMA shell for self-healing intentions. The desired variables used were the ratio of the shell/core, the type of surfactant (ionic and polymeric) and PMMA molecular weights. FTIR confirmed very fast crosslinking reaction between reactive epoxy and acrylate functional groups in AESO and thiol groups in TMPMP, which is very important for self-healing purposes. Furthermore, FTIR and thermal characterization results confirmed the encapsulation of both the resin and the curing agent components in two different core–shell microcapsules. The surface morphology of microcapsules obtained changed from dimpled and holed to plain for AESO and TMPMP respectively suggesting that it depends strongly on the nature of the core, type of surfactant and the ratio of shell/core. The produced core–shell microcapsules had a mean diameter of 7.9–169.7 µm and 9.9–64.1 µm for AESO/PMMA and TMPMP/PMMA, respectively. With changing the percentage of shell revealed that increasing the PMMA dosage in both surfactants causes a decrease in the size of TMPMP-filled microcapsules.

Preparation of Self-healing Additives for Concrete via Miniemulsion Polymerization: Formulation and Production Challenges

Concrete structures undergo internal damage; this usually starts at the atomic level with defects that then grow and form cracks, which can propagate through the material. Here, a method of preparation of poly(methyl methacrylate) (PMMA) nanocapsules adhesive system via miniemulsion polymerization technique is reported, where MMA + DMA (resin + accelerator) and BPO (hardener) components are separately encapsulated by PMMA shells. The crack-healing potential of these nanocapsules was then investigated by embedding them into the mortar matrix. The prepared PMMA core–shell self-healing nanostructures survived the mixing and hardening processes, and the hardened mortar alkaline environment. The stress fields associated with propagating cracks (load‐induced cracking) broke the brittle/weak inert shell of these core–shell structures, resulted in releasing the healing agents to bridge the nascent and early-stage fractures (< 10 µm) in a short time. Long-term healing was achieved through the formation of polymorph calcite crystals in the presence of moisture and CO2, which improved the durability of mortar by filling the gaps. Formulation design (addition of chemical admixtures) and process parameters (blade design and mixing speed) were found to directly impact the uniform distribution of nanocapsules, the survival rate of nanocapsules, and the overall strength of the hardened concrete. The stepwise approach to formulate and fabricate a novel high-strength self-healing concrete system unlocks unique opportunities to design nanomaterials that safeguard the integrity of concrete structures.

Effect of different molecular architectured POSS-fluoropolymers on their self-assembled hydrophobic coatings

A total of 1/2/4/6-armed molecular architectured polyhedral oligomeric silsesquioxane (POSS) fluoropolymers were synthesized via atom transfer radical polymerization (ATRP) by linear (L), dicephalus (D), four-arm (T), and six-arm (S) initiators initiating same content of methyl methacrylate (MMA), methacrylate POSS (MA-POSS), and dodecafluoroheptyl methacrylate (DFHM). The obtained L/D/T/S-(PMMA-b-PMAPOSS-b-PDFHM)1/2/4/6 had increased molecular weight with arm increase. Driven by the stereo-hindrance and curvature effects of segments in tetrahydrofuran (THF), they assembled into the decreased spherical core-shell micelles (250–100 nm) with arm increase as PMA-POSS/PDFHM core and PMMA shell. Because of easy surface migration of fluorine-containing groups in small micelles, the casted film by S-(PMMA-b-PMAPOSS-b-PDFHM)6 performed the fluorine-rich (46.44%) and rough (5.41 nm) surface, and therefore with the hydrophobic (112°) and low water adsorption surface (1522 ng/cm2). Also, POSS-fluoropolymers obtained the enhanced thermostability with arm increase. It is believed that this research will provide a bright view for design and application of POSS-fluoropolymers.

Snake Tracks in Polymer Land: Wavy Polymer Structures via Selective Solvent Vapor Annealing.

Wavy patterns are interesting geometric patterns and commonly seen in nature, such as serpentine streams or snake tracks in the sand. Although many efforts have been devoted to fabricating artificial wavy structures, it remains a great challenge to obtain wavy structures with controllable curvatures and desired functional properties. Here, we present an unprecedented approach to generate wavy polymer structures by annealing electrospun core-shell fibers on polymer films. Polystyrene (PS)/poly(methyl methacrylate) (PMMA) core-shell fibers, produced via the viscosity-induced phase separation in the electrospinning process, are annealed on PMMA films using vapors of acetic acid, a selective solvent for PMMA but not for PS. After the swollen PMMA chains of the PMMA shells are shed, the revealed PS cores start to buckle, driven by the elastic force from the strain release, forming the wavy structures. The degrees of the buckling, measured by the curvatures and the amplitudes of the wavy structures, are controlled by the annealing times. Furthermore, fluorescent properties are selectively introduced to the wavy structures using pyrene solutions or pyrene-containing vapors, demonstrating the potential application as fluorescent wavy materials.

Microcompression Method for Determining the Size-Dependent Elastic Properties of PMMA Microcapsules Containing n-Octadecane.

Accurate evaluation of the shell elastic modulus of microcapsules is of great significance to understanding their performance during production, processing, and applications. In this work, microcompression was employed to investigate the elastic behaviors of a single microcapsule. It was modeled as a microsphere with a core-shell structure compressed between two rigid plates. Based on the assumption that the contact pressure between the microsphere and plates obeys parabolic distribution, a microcompression method derived from the Reissner's theory and the modified Hertz contact theory was established to evaluate the shell elastic modulus. Applications were carried out on poly(methylmethacrylate) (PMMA) microcapsules containing n-octadecane. The average elastic modulus of PMMA shells measured by the proposed microcompression method agrees well with that of the bulk PMMA sample. Furthermore, the elastic modulus of PMMA shells was found to have size dependence on the diameter of the microcapsules. Finally, finite element models combined with the newly proposed method were constructed to accurately predict the microcompression behaviors of microcapsules with different sizes.

Fabrication and characterization of nanoencapsulated epoxy resin/crosslinked PMMA shells with in situ polymerization via phase inversion emulsion (PIE) method

ABSTRACTEncapsulated epoxy resin healing agents with poly(methyl methacrylate (PMMA) as a thermoplastic polymeric shell are suffered from leakage of the core after a while. This problem leads to loss of their performance and its ability in self‐healing systems. One way to stop or reduce the leakage of the core is crosslinking the PMMA shell. In this study, nanoencapsulation of epoxy healing agent with crosslinked PMMA as shell was carried out by in situ polymerization via phase inversion emulsion method. Ethylene glycol dimethacrylate was employed as crosslinking agent. Nonionic (SPAN 60) and ionic (sodium dodecyl sulfate) surfactants were used for competitive adsorption and phase inversion in emulsion system. Chemical structures, morphologies, and thermal properties of nanocapsules were characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis, respectively. SEM investigations showed that nanocapsules had a particle size of less than 100 nm with a narrow particle size distribution. Efficiency of nanoencapsulation was equal to 83.5%. And synthesized nanocapsules had at least 37% core contents. Nanocapsules with crosslinked shell were able to maintain liquid core up to 18 weeks, while, noncrosslinked shell lost core content after 14 weeks. It seems that low crosslink density has no effect on capsule durability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48793.