Nonionic Block Copolymer Research Articles

Nonionic Block Copolymer Coacervates

Liquid–liquid phase separation of macromolecules is an important process in many biological and synthetic systems. The process results in the formation of coacervates that act as membraneless compa...

Copper-doped Ordered Mesoporous Bioactive Glass: A Promising Multifunctional Platform for Bone Tissue Engineering †.

The design and development of biomaterials with multifunctional properties is highly attractive in the context of bone tissue engineering due to the potential of providing multiple therapies and, thus, better treatment of diseases. In order to tackle this challenge, copper-doped silicate mesoporous bioactive glasses (MBGs) were synthesized via a sol-gel route coupled with an evaporation-induced self-assembly process by using a non-ionic block co-polymer as a structure directing agent. The structure and textural properties of calcined materials were investigated by X-ray powder diffraction, scanning-transmission electron microscopy and nitrogen adsorption-desorption measurements. In vitro bioactivity was assessed by immersion tests in simulated body fluid (SBF). Preliminary antibacterial tests using Staphylococcus aureus were also carried out. Copper-doped glasses revealed an ordered arrangement of mesopores (diameter around 5 nm) and exhibited apatite-forming ability in SBF along with promising antibacterial properties. These results suggest the potential suitability of copper-doped MBG powder for use as a multifunctional biomaterial to promote bone regeneration (bioactivity) and prevent/combat microbial infection at the implantation site, thereby promoting tissue healing.

Nonionic Amphiphilic Linear Dendritic Block Copolymers. Solvent-Induced Self-Assembly and Morphology Tuning

In this article, we report the solution self-assembly of a series of amphiphilic linear–dendritic block copolymers (LDBCs), which are composed of hydrophilic dendritic poly(ether-ester), PEE, blocks based on 2,2-bis(hydroxymethyl)propionic acid and hydrophobic linear poly(styrene), PSt, blocks. The investigated LDBCs have narrow dispersity with three PEE generations (1–3) and a broad range of PSt molecular masses and are produced by dendron-initiated atom transfer radical polymerization of styrene followed by deprotection of the peripheral dendron hydroxyl groups. The solution self-assembly of the copolymers is performed by slowly adding water to the polymer solution in tetrahydrofuran (THF) as the common solvent for both blocks of the copolymers. The morphologies of the supramolecular assemblies are preserved either by diluting their dispersion by excess of water or by THF evaporation. It is found that the micellar morphology (sphere, wormlike, and/or vesicle) depends on the hydrophilic block fraction (F...

Simvastatin-loaded nanotubular mesoporous bioactive glass scaffolds for bone tissue engineering

Abstract Nanofibrous scaffolds with drug delivery functions are highly demanded in promoting tissue regeneration. Herein, we report a novel type of three-dimensional (3D) mesoporous bioactive glass (MBG) scaffolds. Such MBG scaffolds are consisted of 3D MBG nanotubes with highly ordered mesopores. The MBG nanotubes were prepared by template-assisted sol-gel procedure using bacterial cellulose (BC) as template and the mesopores were obtained using nonionic block copolymer (P123) as structure-directing agent. To improve bone regeneration capability, we loaded the nanotubular MBG scaffolds with simvastatin (SIM), as a representative small molecule, rather than commonly used growth factors which are large-sized, expensive, and fragile and may lead to serious side effects. By seeding human bone marrow stromal cells (hBMSCs) on the SIM-loaded nanotubular MBG scaffolds, the biocompatibility and bone regeneration were assessed by observing cell morphology, measuring cell viability and osteogenic-related gene expression. We found that SIM was successfully loaded into the nanotubular MBG scaffolds with a high loading efficiency of approximately 50%, and the nanotubular MBG scaffolds exhibited a sustained release of SIM. More importantly, the SIM-loaded nanotubular MBG scaffolds exhibited improved proliferation, ALP activity and osteogenic-related gene expression of hBMSCs over the bare MBG scaffold. We believe that the SIM-loaded nanotubular MBG scaffolds have great potential application in bone tissue regeneration.

Bioactive glass nanotube scaffold with well-ordered mesoporous structure for improved bioactivity and controlled drug delivery

In this study, a novel mesoporous bioactive glass nanotube (MBGN) scaffold has been fabricated via template-assisted sol-gel method using bacterial cellulose (BC) as template and nonionic block copolymer (P123) as pore-directing agent. The scaffold was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption analysis. Furthermore, simvastatin was used to evaluate the loading efficiency and release kinetics of the scaffold. The obtained scaffold displays nanofiber-like morphology, ordered mesopores on the tube walls, and interconnected three-dimensional (3D) network structure that completely replicates the BC template. In addition, it shows dual pore sizes (16.2 and 3.3 nm), large specific surface area (537.2 m2 g−1) and pore volume (1.429 cm3 g−1). More importantly, the scaffold possesses excellent apatite-forming ability and sustainable drug release as compared to the counterpart scaffold without mesopores. This unique scaffold can be considered a promising candidate for drug delivery and bone tissue regeneration.

Thermodynamics, Microstructures, and Solubilization of Block Copolymer Micelles by Density Functional Theory

Block copolymer micelle is one of the most versatile self-assembled structures with applications in drug delivery, cosmetic products, and micellar-enhanced ultrafiltration. The key to design an effective block copolymer to form micelles is to understand how molecular architecture affects critical micelle concentrations, micellar dimensions, and partitioning of solute into the micelle. In this work, we studied micelles from nonionic block copolymers using interfacial statistical associating fluid theory a density functional theory, which explicitly includes block copolymer-water hydrogen bonding and water-water hydrogen bonding. We are able to predict and explain how micellar thermodynamic properties depend on polymer chain architecture. Dimension and aggregation of micelles are investigated for block copolymers with different hyrophobes and hydrophiles. The effects of temperature and pressure on micelle stability are also captured by the theory. The enhanced solubility of hydrophobic substance in water by micelle loading is demonstrated, and predicted solute distribution answers the question about the locus of benzene in micelles from a theoretical perspective.

Preparation of stable dispersion of graphene using copolymers: dispersity and aromaticity analysis

ABSTRACTIn this study, effectiveness of non-ionic block copolymers such as Lugalvan BNO12 and Triton X series (Triton X100 & Triton X405) has been reported for graphene dispersion in aqueous solutions. Stability of the aqueous graphene dispersions is investigated using UV–visible spectroscopy, Rheological, and Conductivity studies. Adsorption isotherms are constructed to determine the amount of polymers adsorbed on the surface of graphene by the spectroscopic analysis. Lugalvan BNO12 has been found to be adsorbed in higher amounts on the graphene surface compared to the Triton X series polymers. Thermogravimetric analysis (TGA) and Fourier Transform Infrared (FTIR) Spectroscopy investigations indicated grafting of polymers chains to the graphene surfaces. The dispersions prepared with optimum concentrations (as determined from adsorption isotherms) of polymers have shown lower viscosity and conductivity values. Lugalvan BNO12 has been found to be a better stabilizer for graphene than the Triton X series dispersants because the former contains two aromatic rings in its structure that acts as an anchoring group and helps in the stabilization of graphene dispersion in comparison to the single aromatic group in the Triton X series. The experimental results reported have shown that the aromaticity of polymeric dispersants plays significant role in the aqueous graphene dispersions. The non-ionic block copolymers that assisted dispersed graphene are potential candidates for the fabrication of various devices such as sensors, batteries, and supercapacitors applications.

Interactions of Pluronic F127 in Rhodamine B Dye and Effects of Inorganic Cations through Fluorescence Data

Non-ionic surfactant block copolymer of polypropylene glycol flanked by two blocks of polyethylene glycol known as pluronic. Pluronic F127 or poloxamer 407 is used to improve the solubility and enhance the bioavilability of many drugs. The interactions of pluronic F127 was studied in Rhodamine B dye and effects of inorganic cations through fluorescence data were observed. Fluorescence quenching were studied by series cations of salts viz CdSO4, MnSO4, ZnSO4, FeSO4, CuSO4 in the above system. Cu2+ was found to be extremely efficient quencher, Cd2+ and Fe2+ were moderate quenchers. Apart from fluorescence, lifetime, DLS, and SEM were used as characterization for the above study.

Effect of surfactant concentration on textural characteristics and biomineralization behavior of mesoporous bioactive glasses

We report mesoporous bioactive glasses (MBGs) with different pore architecture synthesized using the supramolecular chemical approach using acid assisted sol-gel method followed by evaporation induced self-assembly (EISA) process. The surfactant of non-ionic block co-polymer used in the present work act as structure directing agent (SDA) with varying amount, which brings different textural properties. As prepared glasses possess wormhole-like mesostructure with different textural characteristics and it varies with surfactant concentrations. The pristine MBGs have been characterized by various analytical techniques before and after immersing in simulated body fluid (SBF). The textural properties show non-monotonous variations with varying the surfactant concentrations. We have quantified the various structural species present in the glass sample by using local structural probe such as nuclear magnetic resonance technique. Invitro studies on the MBGs revealed the influence of textural characteristics on the formation of nano-crystalline hydroxycarbonated apatite (HCA) layer. The biodegradability is largely related to the pore architecture and it affects the biocompatibility as well as bone formation. In-vitro studies reveals that there are serious negative effects that have been observed in the case of larger pore sized samples due to rapid degradation. We found that MBG with pore sizes of few nano meters exhibit favorable biocompatibility in vitro behavior and found to be promising candidate in the field of biomaterials including tissue regeneration and drug storage.

DNA-Coated Functional Oil Droplets.

Many industrial soft materials include oil-in-water (O/W) emulsions at the core of their formulations. By using tuneable interface stabilizing agents, such emulsions can self-assemble into complex structures. DNA has been used for decades as a thermoresponsive, highly specific binding agent between hard and, recently, soft colloids. Up until now, emulsion droplets functionalized with DNA had relatively low coating densities and were expensive to scale up. Here, a general O/W DNA-coating method using functional nonionic amphiphilic block copolymers, both diblock and triblock, is presented. The hydrophilic poly(ethylene glycol) ends of the surfactants are functionalized with azides, allowing for efficient, dense, and controlled coupling of dibenzocyclooctane-functionalized DNA to the polymers through a strain-promoted alkyne-azide click reaction. The protocol is readily scalable due to the triblock's commercial availability. Different production methods (ultrasonication, microfluidics, and membrane emulsification) are used with different oils (hexadecane and silicone oil) to produce functional droplets in various size ranges (submicron, ∼20 and >50 μm), showcasing the generality of the protocol. Thermoreversible submicron emulsion gels, hierarchical "raspberry" droplets, and controlled droplet release from a flat DNA-coated surface are demonstrated. The emulsion stability and polydispersity is evaluated using dynamic light scattering and optical microscopy. The generality and simplicity of the method opens up new applications in soft matter, biotechnological research, and industrial advances.

Demonstration of a Novel Charge-Free Reverse Wormlike Micelle System.

We demonstrate a novel charge-free reverse wormlike micelle (RWLM) consisting of a ternary mixture of a nonionic amphiphilic block copolymer, fatty acid alkyl ester oil, and water under ambient conditions. Nonionic amphiphile tetra-[poly(oxyethylene)-poly(oxybutylene)]pentaerythrityl ether (TEBPE) self-assembled into spheroid-type micelles in nonaqueous media isopropyl myristate (IPM) with viscosity comparable to that of IPM. The addition of water increases viscosity only slightly up to a certain concentration of water and then drastically, demonstrating the sphere-to-wormlike micelle transition as confirmed by small-angle X-ray scattering. Further increase in water decreases the viscosity after attaining a maximum value. The zero shear viscosity (η0) of the 10 wt % TEBPE/IPM system reached the maximum at 2.6 wt % water and ca. 56 Pa·s, which is ∼fivefold higher than that of water. Dynamic rheological measurements on the highly viscous solutions confirmed the viscoelastic behavior and could be described by the Maxwell model. Conductivity, measured in the presence of a conductive probe, 1-ethyl-3-methylimidazolium tetrafluoroborate, was found to be higher for viscous samples compared to the nonviscous samples, suggesting the static percolation caused by the RWLM formation. Decrease in η0 and conductivity beyond a maximum suggests the shortening of reverse micelles. A similar behavior has been observed in other fatty acid alkyl ester oils of different alkyl chain lengths. Note that most of the RWLM systems previously reported are based on phosphatidylcholine (PC). Formulation and structure-properties related to non-PC-based RWLMs have been rarely explored. Non-PC-based RWLMs using chemically stable and low-cost synthetic molecules can be applied not only in pharmaceuticals and cosmetics but also in a wide range of applications including drag reduction agents for nonaqueous fluids and as a template for nanomaterial synthesis.

Synthesis, characterization and in vitro bioactivity of mesoporous copper silicate bioactive glasses

In this study, 68SiO2–23CaO–4P2O5–CuO bioglasses with and without surfactant (nonionic block copolymer, EO20PO70EO20 P123) for producing multifunctional scaffold were synthesized by sol-gel method. The resulting dried sol underwent an evaporation-induced self-assembly (EISA) process at 40°C. TG-DTA (thermogravimetric-differential thermal analysis) was completed to obtain the optimized temperature for calcination of the prepared powder. The dried gel was calcined at 650°C for 2h to obtain the final bioglasses. Then, the composition and phase structure, morphology, surface area and mesoporous structure were evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analyses. In addition, the biological behavior (bioactivity, biocompatibility and antibacterial properties) of the powder was examined for their applicability in medical science. The results demonstrated that the synthesized bioglass powder formed mesoporous structure with nano-sized morphology and high surface area, and also suitable biological characteristics. The P123 (the nonionic block copolymer EO20PO70EO20) surfactant was responsible for improving homogeneous mesoporous structures and biological characteristics for the template bioglass. In addition, the use of copper in the glass structure did not inhibit its anti-bacterial properties and resulted in a low risk toxic bioglass. Finally, this synthesized bioactive glass could have the potential capability for bone defects treatment in tissue engineering due to their versatile attributes.

Increase in the length of poly(ethylene oxide) blocks in amphiphilic copolymers facilitates their cellular uptake

ABSTRACTAmphiphilic nonionic block copolymers induce different biological effects on living cells. In particular, the hydrophobic members of the Pluronics family suppress drug efflux systems in multidrug‐resistant cells, whereas hydrophilic Pluronics support cell viability. However, the relationship between the copolymer structure and its binding to cells is still unclear. Using a tritium‐labeling approach, we analyzed interactions of nine Pluronics and three diblock copolymers with human and murine cells in vitro and revealed that the binding efficiency of the copolymers increased in line with the length of their poly(ethylene oxide) (PEO) blocks. In contrast, partitioning of the same polymers into artificial lipid bilayers determined by Isothermal Titration Calorimetry (ITC) decreased with increasing length of the PEO block. The opposite influence of hydrophilic blocks on the copolymer affinity to living cells and artificial lipid bilayers implied the binding of long PEO blocks to the hydrophilic moieties of cellular membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45492.

In Situ Gold Nanoparticle Gradient Formation in a 3D Meso- and Macroporous Polymer Matrix.

Herein, the development and characterization of a 3D gradient structure of gold nanoparticles is described. The gradient of gold nanoparticles is made in situ in a macroporous nonionic block copolymer hydrogel matrix, through gold ion diffusion control. The polymer provides a matrix for diffusion of gold ions, acts as a template for controlling nanoparticle growth, and facilitates the in situ reduction of gold ions to gold nanoparticles. A clear gradient in gold nanoparticles is observed across the 3D space of the polymer matrix using scanning electron microscopy, fluorescence microscopy, atomic force microscopy, and thermogravimetric analysis. The particle gradient is further functionalized with both hydrophobic and hydrophilic groups via thiol-gold linkage to demonstrate the ability to form gradients with different chemical functionalities. Using additive manufacturing, the polymer can also be printed as a porous network with possible applications for 3D cell culturing in, e.g., biomaterials research.

Metal‐containing ionic liquid‐based, uncharged–charged diblock copolymers that form ordered, phase‐separated microstructures and reversibly coordinate small protic molecules

Metal‐containing ionic liquid‐based, uncharged–charged diblock copolymers that form ordered, phase‐separated microstructures and reversibly coordinate small protic molecules

PEGylated Nanoemulsions for Oral Delivery: Role of the Inner Core on the Final Fate of the Formulation.

Since the past decade, there has been growing interest to grant nanoparticles with diffusion properties across mucosae. In this sense, the nonionic block copolymer Pluronic F127 (PF127) has emerged as a promising coating agent to formulate mucus-penetrating particles. In the journey to find efficient coating agents, researchers have focused more on the effect of the coating agent architecture rather than on the role of the physicochemical properties of the nanoparticle used as the substrate. The current knowledge about mucodiffusive particles is in general based on model-like nanoparticles, such as polystyrene or poly(lactic-co-glycolic) acid nanoparticles, but there is a lack of information about the potential of PF127 on other colloidal systems. This work aims to shed some light on this issue by selecting three oils, palm (solid), coconut (semisolid), and wheat germ (liquid), with different physicochemical properties to formulate PF127-coated nanoemulsions. The obtained nanoemulsions were characterized, and their colloidal stability was tested. Their diffusion capacity was determined by particle tracking after challenging the nanoemulsions across an intestinal porcine mucus layer. In accordance with the evidence of model-like nanoparticles, our results state that PF127 allows mucodiffusion, but its effectiveness as a coating agent clearly depends on the physicochemical properties of the nanostructure core over which PF127 is placed. Among other physicochemical properties, the results certainly showed that the hydrophobic character of the nanostructure core emerges as a critical factor in the formulation of successful PF127 coatings.

Triblock copolymer-assisted synthesis of hierarchical ZIF-67 in the presence of 1,3,5-trimenthylbenzene

A hierarchically porous ZIF-67 was successfully synthesized by using non-ionic block copolymers P123 as a supramolecular templating surfactant and 1,3,5-trimethylbenzene (TMB) as a swelling agent. It was noted that TMB was an effective swelling agent to expand the pore size. Pore size distribution analyses reveal that the as-synthesized hierarchical ZIF-67 has a typical trimodal pore size distribution showing simultaneous micro-, meso- and macropore channel systems. Due to the effect of TMB and P123, the diameter of ZIF-67 nanoparticles was about twice of that synthesized with P123 only and larger pores were formed among the enlarged nanoparticles. This strategy is expected to be a facile and efficient method for the preparation of hierarchical ZIF-67.

Amphiphilic Ferrocene-Containing PEG Block Copolymers as Micellar Nanocarriers and Smart Surfactants.

An important and usually the only function of most surfactants in heterophase systems is stabilizing one phase in another, for example, droplets or particles in water. Surfactants with additional chemical or physical handles are promising in controlling the colloidal properties by external stimuli. The redox stimulus is an attractive feature; however, to date only a few ionic redox-responsive surfactants have been reported. Herein, the first nonionic and noncytotoxic ferrocene-containing block copolymers are prepared, carrying a hydrophilic poly(ethylene glycol) (PEG) chain and multiple ferrocenes in the hydrophobic segment. These amphiphiles were studied as redox-sensitive surfactants that destabilize particles as obtained in miniemulsion polymerization. Because of the nonionic nature of such PEG-based copolymers, they can stabilize nanoparticles even after the addition of ions, whereas particles stabilized with ionic surfactants would be destabilized by the addition of salt. The redox-active surfactants were prepared by the anionic ring-opening polymerization of ferrocenyl glycidyl ether, with PEG monomethyl ether as the macroinitiator. The resultant block copolymers with molecular weights (Mn) between 3600 and 8600 g mol-1 and narrow molecular weight distributions (Mw/Mn = 1.04-1.10) were investigated via 1H nuclear magnetic resonance and diffusion ordered spectroscopy, size exclusion chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Furthermore, the block copolymers were used as building blocks for redox-responsive micelles and as redox-responsive surfactants in radical polymerization in miniemulsion to stabilize model polystyrene nanoparticles. Oxidation of iron to the ferrocenium species converted the amphiphilic block copolymers into double hydrophilic macromolecules, which led to the destabilization of the nanoparticles. This destabilization of nanoparticle dispersions may be useful for the formation of coatings and the recovery of surfactants.

Low-index, smooth Al_2O_3 films by aqueous solution process

We describe low-index porous alumina thin films deposited from aqueous solutions containing flat-Al13 clusters and the nonionic block copolymer Pluronic F127. The films exhibit surface roughness as low as 0.5 nm, a characteristic useful for the fabrication of multilayer optical devices. We have investigated the chemical, optical, and structural properties of the films and their formation by Fourier transform infrared spectroscopy, temperature programmed desorption, spectroscopic ellipsometry, transmission electron microscopy, atomic force microscopy, and X-ray diffraction. By varying the Pluronic F127 concentration, film porosities can be tuned to produce refractive indexes between n = 1.26 and 1.54 (λ = 550 nm).

Facile synthesis of MgO and Ni-MgO nanostructures with enhanced adsorption of methyl blue dye

Nanostructured Magnesium oxide (MgO) was prepared by a simple method using a non-ionic block copolymer as surfactant. Ni was introduced to MgO to improve surface properties. The effect of Ni loading on the MgO crystalline structure, surface morphology and magnetic properties was observed by powder X-ray diffraction, field-emission scanning electron microscopy and a vibrating sample magnetometer, respectively. Textural properties of produced samples were investigated by nitrogen adsorption–desorption isotherms and the Brunauer–Emmett–Teller method. The as-prepared samples were employed as an adsorbent for the removal of Methyl blue (MeB) dye. The adsorption isotherms were studied using the Langmuir model. The results show a high adsorptive behavior for relatively high concentrated MeB with a maximum adsorption capacity of 367mgg–1 indicating the enhanced adsorption performance of our produced structures. A mechanism for adsorption of MeB molecules on the prepared MgO is proposed.