Mixtures Of Copolymers Research Articles

An unconditionally energy stable algorithm for copolymer–homopolymer mixtures

The homopolymer and copolymer mixtures have attracted extensive research in various scientific and engineering fields. A highly efficient, temporally second-order accurate, and unconditionally energy stable scheme for the coupled Cahn–Hilliard system simulating the phase separation in the homopolymer and copolymer mixtures is proposed. To appropriately treat the nonlinear and coupling terms in the coupled Cahn–Hilliard system, an efficient variant of the scalar auxiliary variable (SAV) approach is considered. However, the time-discretized modified energy resulting from the SAV method is usually no longer consistent with the original continuous energy because of the truncation errors during numerical implementations. Therefore, a simple and practical energy relaxation technique is adopted to overcome this shortcoming, and then the time-discretized corrected energy is obtained. The present method has the following merits: (i) In each iteration, all variables are decoupled, and we can solve them step-by-step. Thus, the numerical implementation is efficient; (ii) The time-discretized corrected energy and the original energy are highly consistent; (iii) The unique solvability and energy stability are strictly proved; (iv) Various morphologies of pattern formations of the copolymer–homopolymer mixtures can be well simulated. The accuracy, stability, and consistency of developed scheme are demonstrated by various 2D and 3D numerical experiments.

Poly(2-alkyl-2-oxazoline)s: A polymer platform to sustain the release from tablets with a high drug loading.

Sustaining the release of highly dosed APIs from a matrix tablet is challenging. To address this challenge, this study evaluated the performance of thermoplastic poly (2-alkyl-2-oxazoline)s (PAOx) as matrix excipient to produce sustained-release tablets via three processing routes: (a) hot-melt extrusion (HME) combined with injection molding (IM), (b) HME combined with milling and compression and (c) direct compression (DC). Different PAOx (co-)polymers and polymer mixtures were processed with several active pharmaceutical ingredients having different aqueous solubilities and melting temperatures (metoprolol tartrate (MPT), metformin hydrochloride (MTF) and theophylline anhydrous (THA)). Different PAOx grades were synthesized and purified by the Supramolecular Chemistry Group, and the effect of PAOx grade and processing technique on the in vitro release kinetics was evaluated. Using the hydrophobic poly (2-n-propyl-2-oxazoline) (PnPrOx) as a matrix excipient allowed to sustain the release of different APIs, even at a 70% (w/w) drug load. Whereas complete THA release was not achieved from the PnPrOx matrix over 24 ​h regardless of the processing technique, adding 7.5% w/w of the hydrophilic poly (2-ethyl-2-oxazoline) to the hydrophobic PnPrOx matrix significantly increased THA release, highlighting the relevance of mixing different PAOx grades. In addition, it was demonstrated that the release of THA was similar from co-polymer and polymer mixtures with the same polymer ratios. On the other hand, as the release of MTF from a PnPrOx matrix was fast, the more hydrophobic poly (2-sec-butyl-2-oxazoline) (PsecBuOx) was used to retard MTF release. In addition, a mixture between the hydrophilic PEtOx and the hydrophobic PsecBuOx allowed accurate tuning of the release of MTF formulations. Finally, it was demonstrated that PAOx also showed a high ability to tune the in vivo release. IM tablets containing 70% MTF and 30% PsecBuOx showed a lower in vivo bioavailability compared to IM tablets containing a low PEtOx concentration (7.5%, w/w) in combination with PsecBuOx (22.5%, w/w). Importantly, the in vivo MTF blood level from the sustained release tablets correlated well with the in vitro release profiles. In general, this work demonstrates that PAOx polymers offer a versatile formulation platform to adjust the release rate of different APIs, enabling sustained release from tablets with up to 70% w/w drug loading.

ASD Formation Prior to Material Characterization as Key Parameter for Accurate Measurements and Subsequent Process Simulation for Hot-Melt Extrusion

Process simulation facilitates scale-up of hot-melt extrusion (HME) and enhances proper understanding of the underlying critical process parameters. However, performing numeric simulations requires profound knowledge of the employed materials’ properties. For example, an accurate description of the compounds’ melt rheology is paramount for proper simulations. Hence, sample preparation needs to be optimized to yield results as predictive as possible. To identify the optimal preparation method for small amplitude oscillatory shear (SAOS) rheological measurements, binary mixtures of hydroxypropylmethylcellulose acetate succinate or methacrylic acid ethyl acrylate copolymer (Eudragit L100-55) together with the model drugs celecoxib and ketoconazole were prepared. The physical powder mixtures were introduced into the SAOS as a compressed tablet or a disk prepared via vacuum compression molding (VCM). Simulations with the derived parameters were conducted and compared to lab-scale extrusion trials. VCM was identified as the ideal preparation method resulting in the highest similarity between simulated and experimental values, while simulation based on conventional powder-based methods insufficiently described the HME process.

Novel, linear, decoupled and unconditionally energy stable numerical methods for the coupled Cahn–Hilliard equations

This paper uses a novel numerical approach to approximate the coupled Cahn–Hilliard equations, which are a highly nonlinear system depicting the phase separation of the homopolymer and copolymer mixtures. The new method is named 3S-IEQ, and its construction and calculation are more straightforward than the invariant energy quadratization and scalar auxiliary variable methods. Notably, we only need to solve two linear decoupled constant-coefficient equations at each time step. Numerical simulations are shown

The Modification of Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) by Melt Blending.

Crystalline and noncrystalline poly(3-hyroxybutylate-co-4-hyroxybutylate) (P(3HB-co-4HB)) were melt blended to obtain mixtures of P(3HB-co-4HB) copolymers. The mixtures and P(3HB-co-4HB) copolymers of different 4HB contents were compared to study the effect of 4HB content on the properties of the copolymers and mixtures. P(3HB-co-4HB) copolymer mixtures, having various 4HB content, have been successfully made by melt blending instead of bacterial biosynthesis. In the case of copolymers, they were noncrystalline when the 4HB content was over 16%, while the P(3HB-co-4HB) mixtures at the same 4HB content were crystalline. The mixtures had a higher glass transition temperature, suggesting that their chain mobility is relatively low compared with the copolymer having the same 4HB content. Due to this effect, the mixture is expected to have a higher melt viscosity and a lower loss tangent to exhibit better melt processing properties. The mechanical properties of the mixtures show a similar behavior to the copolymers in that the tensile strength and the modulus decreases and elongation at the break increases with an increase in the 4HB content.

Alternating Gyroid in Block Polymer Blends.

Alternating gyroid is a lower symmetry variant of the double gyroid morphology, where the left-handed and right-handed chiral networks are physically distinct. This structure is of particular interest for photonic applications owing to predictions of a complete photonic band gap subject to the requirement of a large dielectric contrast between the individual networks and sufficient optical matching between one of the networks and the matrix. We provide evidence, via self-consistent field theory (SCFT), that stoichiometric blends of double-gyroid-forming AB and BC diblock copolymers with relatively immiscible A and C blocks should form an alternating gyroid morphology with complementary three-dimensional A and C networks that have a free energy that is nearly degenerate with two phase-separated double gyroid states. Solvent casting offers the potential for trapping this binary mixture of diblock copolymers in this metastable alternating gyroid phase. Theory further predicts that the addition of a minuscule amount (<1%) of ABC triblock terpolymer will open an alternating gyroid stability window in the resulting ternary-phase diagram. The surfactant-like stabilization produced by the triblock is relatively insensitive to its exact composition provided the B-block forms a sufficiently long bridge between the A-rich and C-rich networks. This blending strategy provides significant synthetic and material processing advantages compared to prevailing methods to produce an alternating gyroid phase in block polymers.

Detergent-Free Functionalization of Hybrid Vesicles with Membrane Proteins Using SMALPs.

Hybrid vesicles (HVs) that consist of mixtures of block copolymers and lipids are robust biomimetics of liposomes, providing a valuable building block in bionanotechnology, catalysis, and synthetic biology. However, functionalization of HVs with membrane proteins remains laborious and expensive, creating a significant current challenge in the field. Here, using a new approach of extraction with styrene-maleic acid (SMA), we show that a membrane protein (cytochrome bo3) directly transfers into HVs with an efficiency of 73.9 ± 13.5% without the requirement of detergent, long incubation times, or mechanical disruption. Direct transfer of membrane proteins using this approach was not possible into liposomes, suggesting that HVs are more amenable than liposomes to membrane protein incorporation from a SMA lipid particle system. Finally, we show that this transfer method is not limited to cytochrome bo3 and can also be performed with complex membrane protein mixtures.

Intrinsically Breathable and Flexible NO2 Gas Sensors Produced by Laser Direct Writing of Self-Assembled Block Copolymers.

The surge in air pollution and respiratory diseases across the globe has spurred significant interest in the development of flexible gas sensors prepared by low-cost and scalable fabrication methods. However, the limited breathability in the commonly used substrate materials reduces the exchange of air and moisture to result in irritation and a low level of comfort. This study presents the design and demonstration of a breathable, flexible, and highly sensitive NO2 gas sensor based on the silver (Ag)-decorated laser-induced graphene (LIG) foam. The scalable laser direct writing transforms the self-assembled block copolymer and resin mixture with different mass ratios into highly porous LIG with varying pore sizes. Decoration of Ag nanoparticles on the porous LIG further increases the specific surface area and conductivity to result in a highly sensitive and selective composite to detect nitrogen oxides. The as-fabricated Ag/LIG gas sensor on a flexible polyethylene substrate exhibits a large response of -12‰, a fast response/recovery of 40/291 s, and a low detection limit of a few parts per billion at room temperature. Integrating the Ag/LIG composite on diverse fabric substrates further results in breathable gas sensors and intelligent clothing, which allows permeation of air and moisture to provide long-term practical use with an improved level of comfort.

Synthesis and mechanochemical properties of biobased ABCBA‐type pentablock copolymers comprising poly‐d‐lactide (A), poly‐l‐lactide (B) and poly(1,2‐propylene succinate) (C)

AbstractThe ABCBA pentablock copolymers (p‐d‐l‐PPS) comprising poly(d‐lactide) (PDLA: A), poly(l‐lactide) (PLLA: B) and poly(propylene succinate) (PPS: C) were successfully synthesized by two‐step ring‐opening polymerization (ROP) of d‐ and l‐lactide using a dihydroxy‐terminated PPS as a macro‐initiator. The pentablock copolymers revealed the high stereocomplex (sc) crystallinity, thermal stability and elastomeric property in their solution‐cast films. It was found that the Tg was found to be proportional to the PPS content, whereas the Tm was proportional to their average block length. The thermal resistivity of the copolymer films was found to be as high as 202°C owing to their sc formation. The copolymers also showed improved stereocomplexibility compared to the enantiomeric mixtures of triblock copolymers (PLLA‐PPS‐PLLA and PDLA‐PPS‐PDLA) having similar PLLA and PDLA chain lengths. These pentablock copolymers can afford thermoplastic elastomers or flexible plastic materials having a 100% bio‐based content, showing high heat‐resistive property.

Superparamagnetic Poly(aniline-co-m-phenylenediamine)@Fe3O4 Nanocomposite as an Efficient Heterogeneous Catalyst for the Synthesis of 1H-pyrazolo[1,2-a]pyridazine-5,8-diones & 1H-pyrazolo[1,2-b]phthalazine-5, 10-diones Derivatives.

The use of polymer-based catalysts has increased because of their high potential application as an effective catalyst in organic reactions. They have benefits such as high efficiency and reactivity, simple separation, and safety compared to other heterogeneous catalysts. The objective of the current research is to prepare solid polymer-based catalysts, poly(aniline-co-m-phenylenediamine) (PAmPDA), and its superparamagnetic nanocomposite. Then, the catalytic activity of the resulting superparamagnetic nanocomposite was investigated in the synthesis of 1H-pyrazolo[1,2-b]phetalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives. A series of some 1H-pyrazolo[1,2-b]phetalazine-5,10-diones and 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives was tested for its antibacterial properties against the Staphylococcus aureus and E. coli bacteria. PAmPDA copolymer was synthesized in a 1:2 molar ratio of Ani to mPDA via radical oxidative polymerization at room temperature. Superparamagnetic PAmPDA@Fe3O4nanocompo-site was synthesized from a mixture of Fe(II), Fe(III) solution, and PAmPDA copolymer via the in-situ co-precipitation technique. 1H-pyrazolo[1,2-b]phetalazine-5,10-diones were synthesized via one-pot three-component condensation reaction of Phthalhydrazide, aromatic aldehyde derivatives, and malono-nitrile in the presence of PAmPDA under solvent-free conditions at 80 °C. The synthesis of 1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives was carried out via a one-pot three-component condensa-tion reaction of maleic hydrazide, aromatic aldehyde derivatives, and malononitrile in the presence of PAmPDA under reflux conditions at EtOH/H2O 1:1. The antibacterial activity of some derivatives was tested against Gram-positive and Gram-negative bacteria. First, superparamagnetic PAmPDA@Fe3O4 nanocomposite was synthesized and characterized successfully, and then the resulting nanocatalyst was used for the synthesis of pyrazolo[1,2-b]phthalazine and pyrazolo[1,2-a]pyridazine. We obtained the maximum yield of the desired 1H-pyrazolo[1,2-b]phthalazine-5,10 dione derivatives with 0.05 g of catalyst at 80°C, under solvent free conditions, whereby the reaction was complete within 30 min. A wide range of 1H-pyrazolo[1,2-b]phthalazine-5,10 dione derivatives were synthesized in good to excellent yield. On the other hand, pyrazolo[1,2-a]pyridazine derivative was synthesized successfully in high yield using PAmPDA as a nanocatalyst. The antibacterial activity of some derivatives, according to the data (inhibition zone%), showed good ac-tivity against Staphylococcus aureus and E. coli. In this research, PAmPDA was used for mild preparation of 1H-pyrazolo [1,2-a]pyridazine-5,8-diones & 1H-pyrazolo[1,2-b]phetalazine-5,10-diones derivatives with excellent yields and short reac-tion times. The attractive features of this protocol are simple procedure, cleaner reaction, and the use of recyclable nanocatalyst. Satisfactory yields of products and easy workup make this a useful protocol for the green synthesis of this class of compounds. The antibacterial activity of some derivatives, according to the data (inhibition zone%), showed good activity against Staphylococcus aureus and E. coli.

DEVELOPMENT OF MULTICOMPONENT FIBER BOX WITH IMPROVED FIRE RESISTANCE AND BARRIER PROPERTIES

"One of the main purposes of packaging materials is to protect the packed object from mechanical damage that can happen during transport, storage or handling. Extending the functionality of packaging from just mechanical protection to additional moisture and fire protection would present an added value to packaging materials and would be of high interest in preserving archives and cultural heritage objects. In the present research work, we developed a pH neutral fibre material that provides a moisture barrier, inhibits burning and can be shaped into different packaging designs. A multilayer composite was developed, with the outer layers made from pH neutral acid-free paper, compatible with ISO 9706:2014 (the requirement for permanence) and ISO 11108:2016 (the requirement for permanence and durability). The produced pH neutral papers were coated (on the inside) with 6 different combinations of moisture barrier agents and fire-retardant coatings (containing styrene acrylic copolymer, hydrostatin, sodium silicate + aluminium hydroxide/carbonate and lignin), combined into a multilayer material. The developed materials were analysed in terms of their water vapour transmission rate, Cobb absorption and fire retardancy to simulate worst-case scenarios for archives or cultural heritage sites. The results showed that the material coated with the combination of styrene acrylic copolymer aqueous dispersion and mixtures of sodium silicate and aluminium hydroxide achieved the best performance in terms of moisture/fire resistance and could be successfully converted into packaging products for protecting museum objects. "

Homopolymer and ABC Triblock Copolymer Mixtures for Thermoresponsive Gel Formulations.

Our group has recently invented a novel series of thermoresponsive ABC triblock terpolymers based on oligo(ethylene glycol) methyl ether methacrylate with average Mn 300 g mol−1 (OEGMA300, A unit), n-butyl methacrylate (BuMA, B unit) and di(ethylene glycol) methyl ether methacrylate (DEGMA, C unit) with excellent thermogelling properties. In this study, we investigate how the addition of OEGMA300x homopolymers of varying molar mass (MM) affects the gelation characteristics of the best performing ABC triblock terpolymer. Interestingly, the gelation is not disrupted by the addition of the homopolymers, with the gelation temperature (Tgel) remaining stable at around 30 °C, depending on the MM and content in OEGMA300x homopolymer. Moreover, stronger gels are formed when higher MM OEGMA300x homopolymers are added, presumably due to the homopolymer chains acting as bridges between the micelles formed by the triblock terpolymer, thus, favouring gelation. In summary, novel formulations based on mixtures of triblock copolymer and homopolymers are presented, which can provide a cost-effective alternative for use in biomedical applications, compared to the use of the triblock copolymer only.

Hydrogen bonding mediated self‐assembled structures from block copolymer mixtures to mesoporous materials

AbstractThe self‐assembled structures formed through hydrogen bonding interaction of block copolymers in polymeric materials are interesting materials because of their potential applications in biomedicine, nanopatterning and photonics, taking advantage of their responsive and tunable properties. In this review, we discuss the self‐assembled nanostructures that can be obtained from hydrogen‐bonded diblock copolymer/homopolymer (A‐b‐B/C) and diblock copolymer (A‐b‐B/C‐b‐D) mixtures in the bulk and how these block copolymer mixtures can then be used to synthesize mesoporous silica, phenolic and carbon materials. © 2021 Society of Industrial Chemistry.

Studying the Adsorptive Behavior of Poly(Acrylonitrile-co-Styrene) and Carbon Nanotubes (Nanocomposites) Impregnated with Adsorbent Materials towards Methyl Orange Dye.

In this study, a polymeric (acrylonitrile-co-styrene) P(AN-co-St) composite was impregnated with adsorbents, such as sulfonated and multiwall carbon nanotubes (MWCNTs), to increase the adsorptive characteristics of the nanocomposite upon the removal of methyl orange (MO) dye under different conditions. A novel nanocomposite copolymer mixture of P(AN-co-St) and SP(AN-co-St) was used. MWCNTs were prepared by a low-cost chemical vapor deposition (CVD) process. Variation in MO adsorption onto the three nanocomposites was examined in an aqueous solution via the batch technique with respect to contact time, initial MO concentration, adsorbent dosage, pH, and temperature. The surface of the nanocomposites was characterized by a scanning electron microscope (SEM), particle size distribution (PSD), Fourier transform infrared (FTIR), and Raman analysis. The experimental data showed that the efficiency of P(AN-co-St)/ MWCNT removal increased under the conditions of an acidic pH (3 and 5) with an agitation speed of 140 rpm, a sorbent weight of 0.01 g, and 20 mg of initial dye. The maximum sorption capacities were 121.95, 48.78, and 47.84 mg g−1 for the P(AN-co-St)/ MWCNTs, SP(AN-co-St), and P(AN-co-St) composites, respectively, as assessed by the Langmuir model. Additional isotherm models, such as the Freundlich, Temkin, and Halsey models, were used to examine the experimental data. A pseudo-second-order model was found to be more fitting for describing the sorption.

Distinctive Dielectric Permittivity of Hierarchical Nanostructures with Ordered Nanoparticle Networks Self-Assembled from AB-g-NP/AC Block Copolymer Mixtures.

Directing nanoparticles into ordered organization in polymer matrix to improve macroscopic properties of nanocomposites remains a challenge. Herein, by means of theoretical simulations, we show the high permittivity of hybrid nanostructures designed with mixtures of AB block copolymer-grafted nanoparticles and lamella-forming AC diblock copolymers. The grafted nanoparticles self-assemble into parallel stripes or highly ordered networks in the lamellae of the AC diblock copolymers. The ordered nanoparticle networks, including honeycomb-like and kagomé networks, provide bending and conductive pathways for concentrating electric fields, which results in the improvement of the permittivity. We envisage that this strategy will open a gateway to prepare hierarchically ordered functional nanocomposites with distinctive dielectric properties.

Block-Random Copolymer-Micellization-Mediated Formation of Polymeric Patches on Gold Nanoparticles.

Patchy colloidal nanoparticles are important for a broad range of applications, especially as building blocks for complex and functional structural materials, but the controllable generation of chemical patches on as-synthesized nanoparticles remains a challenge. This article describes a robust strategy for the scalable synthesis of high-quality patchy nanoparticles in high yield and solid content. A simple thermal treatment of a mixture of gold nanoparticles and thiol-terminated block-random copolymers in selected solvents produced a variety of patchy nanoparticles with a controlled morphology and number of polymeric patches (e.g., beanlike patch, one patch, two patches, three patches, multiple patches, and open-configuration patch). We show in experiments and simulations that the dynamic detachment/attachment of copolymers and the exchange of copolymers between the nanoparticle surface and free micelles in the solution-which are dictated by the architecture of copolymers-govern the formation of polymeric patches. This work not only offers an effective approach to patchy nanoparticles but also provides new insights into the phase behaviors of copolymers on nanoscale surfaces.

High and Low-Temperature Performance Evaluation and Microanalysis of SMCSBS Compound-Modified Asphalt.

The mixture of styreneic methyl copolymers (SMCs) normal temperature-modified asphalt and styrene-butadiene styrene block copolymer (SBS)-modified asphalt (SMCSBS) compound-modified asphalt was investigated in this study. The viscosity and temperature properties of compound modified asphalt (SMCSBS) were studied by Brookfield rotary viscosity test. Dynamic shear rheometer (DSR) and bending beam rheometer (BBR) were used to test SMCSBS compound modified asphalt with different SMC additions. Finally, the microstructure and physicochemical properties of SMCSBS were evaluated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), and the modification mechanism of the SMCSBS was studied. The results show that the viscosity of the compound-modified asphalt added with SMC is improved, which is conducive to improving its workability. With the increase of SMC content, the high-temperature performance of the compound modified asphalt firstly increases and then decreases with the increase of SMC content. When the content of SMC is 12%, its high-temperature performance is the best. Compared with SBS-modified asphalt, the SMCSBS has better low-temperature performance, and the creep stiffness S and creep rate m of the SMC with different content are better than that of SBS. Finally, the microcosmic characteristics show that the SMC can give full play to its characteristics and can be uniformly dispersed in SBS modified asphalt. SMC is essentially a surfactant, which can reduce the viscosity and construction temperature by changing the surface tension and surface free energy of asphalt molecules. The curing agent of epoxy resin is slowly cross-linked and cured after contacting with air to form a certain strength, thus improving the road performance of the asphalt mixture.

Several Shapes of Single Crystalline Gold Nanomaterials Prepared in the Surfactant Mixture of CTAB and Pluronics.

Twin structures in gold nanomaterials are destined because they reduce the severe strains in the misfit region of nanostructures. Defect-free single crystalline plasmonic nanomaterials gain interests these days as the integration of plasmonic materials or plasmons into electronic devices and circuits becomes more common. In this study, without subtle experimental adjustments, such as pH or halide additives, several shapes of single crystalline gold nanoparticles (NPs) are prepared in the surfactant mixture of cetyltrimethylammonium bromide (CTAB) and Pluronic triblock copolymers. The synthesized NPs are primarily composed of {100} planes with small numbers of particles possessing a [110] zone axis. Pluronic copolymers with low number average molecular weights (Mn), such as L-31 (Mn ≈ 1100) and L-64 (Mn ≈ 2900), prefer anisotropic nanorods with the aspect ratios of 4.3 and 3.0, respectively, while Pluronics with high Mn values, such as F-68 (Mn ≈ 8400) and F-108 (Mn ≈ 14 600), favor more concentric and isotropic cube-like NPs. Extended micelles are believed to form in Pluronics with low Mn values in which hydrophobic cores are merged with the increase of temperature, while the corona regions that are composed of long tails of PEO prevent the merge of hydrophobic cores, and the growth of the micelles is limited in Pluronic copolymers with high Mn values. The catalytic degradation reactions of methyl orange are conducted, and rather than isotropic particles, gold nanorods exhibit better catalytic performances. More hydrophilic environment and the steric alignment of rigid aromatic structures of methyl orange along the nanorods are thought to contribute to the catalytic activities. Overall, highly confined geometries of the appropriately swollen micellar templates of Pluronics and CTAB, which is not so hydrophobic as for the formation of contracted deswollen templates and for the inhibition of the growth of NPs, and which is not so hydrophilic as for the formation of coarse templates and for the formation of isotropic spheres with varying sizes, are believed as the main factor for the formation of single crystalline gold NPs.

Micellization through complexation of oppositely charged diblock copolymers: Effects of composition, polymer architecture, salt of different valency, and thermoresponsive block

AbstractThe structural and electrical characteristics of polyelectrolyte complex micelles (PCMs) formed by mixing of oppositely charged double hydrophilic copolymers are studied by means of molecular dynamics simulations. In mixtures of linear diblock copolymers we found that the preferential aggregation number Np of PCMs is a universal function of the ratio γ± of the total positive to total negative charges of the mixture. The addition of divalent salts ions induces a secondary micellization. In mixtures of copolymers bearing a common neutral thermoresponsive block, micelles with contracted corona consisting of thermoresponsive blocks and complex polyelectrolyte core are formed at low salt concentration and temperature far away the biphasic regime. At high salt concentration and temperature in the biphasic regime, reversed micelles are obtained. In equimolar mixtures of linear copolymers with miktoarm stars we found that Np of PCMs decreases as the number of charged branches of miktoarm copolymer increases. The shape of micelles progressively changes from spherical to worm‐like with the increase of number of branches of miktoarm copolymers. Our findings are in full agreement with existing experimental and theoretical predictions and provides new and additional insights.

Self-Assembly of Polymer Grafted Nanoparticles within Spherically Confined Diblock Copolymers.

Geometric confinement plays an important role in the generation of interesting microstructures on account of structural frustration and confinement-induced entropy loss. In the present study, self-consistent field calculations have been performed to examine the self-assembly behavior of a mixture of diblock copolymers and polymer grafted nanoparticles within a spherical confinement. The analysis is aimed at obtaining the equilibrium distribution of nanoparticles with a high degree of order. The ordered mesophases of diblock copolymers provide useful templates to achieve ordering of nanoparticles in a selective domain. Self-assembly of nanoparticles within frustrated diblock copolymers is found to be very different from the bulk. A rich variety of equilibrium morphologies are observed depending on the degree of confinement and the extent of particle loading. In addition, the role of particle size and selectivity along with the length and the number of polymer chains grafted onto the surface of nanoparticles are analyzed to understand the self-assembly behavior. The specific interest is to obtain the chiral structures out of achiral block copolymers subjected to spherical confinement. The realization of various captivating microstructures, such as chiral ordering of nanoparticles, is highly essential to produce advanced nanomaterials with superior physical properties.