Amphiphilic Microgels Research Articles

COMPUTER SIMULATION OF BIPHASIC CATALYTIC PROCESS IN PRESENCE OF POLYMER MICROGELS

Dissipative particle dynamics were used for the first time to simulate the reaction of biphasic catalysis with microgels adsorbed at the phase boundary with catalytic groups. It is shown that the rate of the catalytic process increases with the degree of deformation of the polymer network, which depends on the amount of the crosslinker and the solubility of the polymer in both phases. In this case, the highest rate of catalysis was observed for the microgel soluble in both phases due to an increase in its porosity (compared to amphiphilic microgels) and the “water–microgel–oil” contact area with a simultaneous decrease in the time for reagents to reach the catalytic groups due to the flattening of the microgel. The results obtained can be useful for increasing the efficiency of a wide range of catalytic reactions of the considered type through the use of network macromolecules.

Effect of Characteristics of Polymer Microgel Catalysts on the Efficiency of Interfacial Catalysis

Effect of the architecture and composition of a hydrophilic microgel catalyst on the rate of interfacial catalytic reaction proceeding at the water/oil interface and involving reagents dissolved in opposite phases is studied using dissipative particle dynamics simulations. It is shown that a decrease in the crosslinking density of the microgel, the existence of a cavity in its architecture, an increase in its size, the incorporation the hydrophobic comonomers into a macromolecule, and a rise in the degree of solubility of a network macromolecule in oil contribute to acceleration of the catalytic reaction due to increase of the area of the water–oil–microgel contact and growth of the number of contacts between reagents and catalytic groups. However, in the case of amphiphilic microgels and microgels soluble in both phases, the acceleration of the reaction is restrained by a low rate of reagents diffusion and a rapid reduction in the concentration of reagents in the vicinity of catalytic sites.

Cyclodextrin-Modified Amphiphilic Microgel with Bifunctional Domains for Infected Wound Healing via Photothermal Antibacterial Therapy and Nitric Oxide Release.

Bacterial infections are one of the major contributing factors to human mortality, which can cause secondary damage to the injured area, such as leading to inflammation, tissue death, and even personal death. Herein, we developed a novel cyclodextrin (CD)-modified amphiphilic microgel with a 3D network nanostructure that encapsulates hydrophilic indocyanine green (ICG) as a trigger for photothermal therapy (PTT) and hydrophobic N,N'-disubstituted-butyl-N,N'-dinitro-1,4-benzenediamine (BNN6) as a heat-sensitive nitric oxide (NO) donor (CD@I-B) to cope with bacteria-infected wound therapy. This biocompatible microgel showed excellent broad-spectrum antibacterial capability under near-infrared (NIR) laser irradiation, while the photothermal conversion process promotes the deswelling of the microgel and release of NO, which synergistically accelerates wound healing. The therapy strategy by synergizing NO delivery with PTT promoted the formation of neovascularization and collagen fiber as well as the elimination of inflammation cells, thus facilitating wound healing. Our study further demonstrates the fantastic opportunities of applying high-performance microgels to provide all-in-one sites for treating wound sterilization and healing.

Amphiphilic microgels adsorbed at oil–water interfaces as mixers of two immiscible liquids

Amphiphilic microgels adsorbed at an oil-water interface were studied by means of dissipative particle dynamics (DPD) simulations. The hydrophobic (A) and hydrophilic (B) monomer units in the polymer network are considered to be randomly distributed. Effects of the crosslinking density, interfacial tension between the liquids, their selectivity as solvents towards species A and B, and the degree of incompatibility between the A and B units on the internal microgel structure and distribution of the liquids are considered. The most important predictions are that (i) two immiscible liquids can homogeneously be mixed within the microgels and (ii) the adsorbed microgels contain a high fraction of the liquids (they are swollen at the interface). Simultaneous fulfillment of these two conditions can have a high impact on the design of new and efficient catalytic systems. In particular, such microgels can mix immiscible reactants dissolved in water and oil and trigger chemical reactions in the presence of a catalyst embedded into the microgel.

Fabrication of tailorable pH responsive cationic amphiphilic microgels on a microfluidic device for drug release

ABSTRACTCationic, amphiphilic microgels of differing compositions based on hydrophilic, pH, and thermoresponsive 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and hydrophobic, nonionic n‐butyl acrylate (BuA) are synthesized using a lab‐on‐a‐chip device. Hydrophobic oil‐in‐water (o/w) droplets are generated via a microfluidic platform, with the dispersed (droplet) phase containing the DMAEMA and BuA, alongside the hydrophobic cross‐linker, ethylene glycol dimethacrylate, and a free radical initiator in an organic solvent. Finally, the hydrophobic droplets are photopolymerized via a UV light source as they traverse the microfluidic channel to produce the cationic amphiphilic microgels. This platform enables the rapid, automated, and in situ production of amphiphilic microgels, which do not match the core‐shell structure of conventionally prepared microgels but are instead based on random amphiphilic copolymers of DMAEMA and BuA between the hydrophobic cross‐links. The microgels are characterized in terms of their swelling and encapsulation abilities, which are found to be influenced by both the pH response and the hydrophobic content of the microgels. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 59–66

Biocompatible amphiphilic microgel derived from dextrin and poly(methyl methacrylate) for dual drugs carrier

Biopolymer-dextrin and poly(methyl methacrylate) (PMMA) based biodegradable, biocompatible and amphiphilic crosslinked microgel (c-Dxt/pMMA) has been synthesized for dual drugs (ciprofloxacin and ornidazole) carrier. The morphology, structure and composition of the microgel have been characterized using FTIR and 1H NMR spectroscopy, FESEM, EDAX, DLS and TGA analyses. The swelling study and rheological experiments demonstrate gel characteristics of c-Dxt/pMMA microgel at 37 ± 0.1 °C. The in vitro results of cytotoxicity assays revealed that the crosslinked microgel is non-toxic to human mesenchymal stem cells (hMSCs). The microgels could efficiently encapsulate both ciprofloxacin and ornidazole. Hemocompatibility study implies that the synthesized microgel can be safely used for intravenous administration. The simultaneous loading ability and controlled release of ciprofloxacin and ornidazole from the microgel ascertain the dual drugs carrier features of c-Dxt/pMMA microgel.

Microfluidically fabricated pH-responsive anionic amphiphilic microgels for drug release.

Amphiphilic microgels of different composition based on the hydrophilic, pH-responsive acrylic acid (AA) and the hydrophobic, non-ionic n-butyl acrylate (BuA) were synthesised using a lab-on-a-chip device. Hydrophobic droplets were generated via a microfluidic platform that contained a protected form of AA, BuA, the hydrophobic crosslinker, ethylene glycol dimethacrylate (EGDMA), and a free radical initiator in an organic solvent. These hydrophobic droplets were photopolymerised within the microfluidic channels and subsequently hydrolysed, enabling an integrated platform for the rapid, automated, and in situ production of anionic amphiphilic microgels. The amphiphilic microgels did not feature the conventional core-shell structure but were instead based on random amphiphilic copolymers of AA and BuA and hydrophobic crosslinks. Due to their amphiphilic nature they were able to encapsulate and deliver both hydrophobic and hydrophilic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the surrounding aqueous solution and the hydrophobic content of the microgels.

Surface activity of amphiphilic cationic pH-responsive poly(4-vinylpyridine) microgel at air/water interface

Abstract In this study, we report the relation between the surface activity parameters of soft, pH sensitive microgel particles based on cationic poly(4-vinyl pyridine), p(4-VP) for the first time and corroborate the variation of their chemical structures and their concentrations adsorbed at the air–water interface. In this respect, p(4-VP) particles were quaternized by modifying with alkyl bromides of different chain length. Additionally, hydroxyl, amino and nitrile functional group-containing alkyl bromides were used to quaternize the crosslinked p(4-VP) to determine the effect of hydrophilic and hydrophobic groups on the surface activities of the prepared microgels. The chemical structures of the prepared microgel were characterized by Fourier transform infrared spectrometry (FT-IR). The solution behavior was investigated by surface tension technique, scanning electron microscopy (SEM), dynamic light scattering (DLS), and zeta potential measurements. The results indicate that the microgels can spontaneously assemble into spherical-shaped micelle aggregates, with different critical aggregation concentrations (cac), and hydrodynamic diameters from about 500–1000 nm at pH 4, 7 and 9, depending on the microgel chemical structure. For the first time, p(4-VP) microgels quaternized with hydroxyethyl bromide showed reduction of surface tension of water using amphiphilic microgels from 72.1 to 31.1 mN/m.

Tailoring pH-responsive acrylic acid microgels with hydrophobic crosslinks for drug release.

Amphiphilic microgels based on the hydrophilic acrylic acid (AA) and hydrophobic crosslinks of different compositions were synthesised using a lab-on-a-chip device. The microgels were formed by polymerising hydrophobic droplets. The droplets were generated via a microfluidic platform and contained a protected form of AA, a hydrophobic crosslinker (ethylene glycol dimethacrylate, EGDMA) and a free radical initiator in an organic solvent. Following photopolymerisation and subsequent hydrolysis, AA based microgels of amphiphilic nature were produced and it was demonstrated that they can successfully deliver both hydrophilic as well as hydrophobic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the aqueous solution as well as the crosslinking density and hydrophobic content of the microgels.

Swelling behavior of responsive amphiphilic gels

We study the equilibrium swelling degrees of an amphiphilic microgel which consists of two different types of constituents: hydrophobic (H) and hydrophilic (P) monomers. Using Flory-type theories, scaling arguments, and variational calculations, we investigate the influence of the number of cross links and cross-linking types on the equilibrium swelling behavior. We show that amphiphilic microgels exhibit discrete swelling degrees which are more pronounced than for homopolymer networks as the fraction of hydrophobic components in the gel changes. The heterogeneous cross links between different types of monomers prevent a complete phase separation and stabilize the gel at relatively high fraction of H monomers. Disorder in the arrangement of the monomers as well as the cross-linking positions is treated in the framework of the variational principle. The method developed here is also applied for designed networks which display well-defined conformational transitions. Such macrogels can be used for drug loading or release under specific environments. We provide scaling results for specifically constructed networks that are confirmed by our variational theory.

Infrared Study on Molecular Orientation and Phase Transition in Langmuir−Blodgett Films of an Amphiphilic Microgel Copolymer with the Branching of Octadecyl Groups

Molecular orientation, structure, and phase transition in Langmuir−Blodgett (LB) films of an amphiphilic polymer consisting of a flexible hydrophilic epichlorohydrin−ethylenediamine slightly cross-linking microgel and a number of hydrophobic stearic chains (ES-3) have been studied by infrared (IR) transmission and reflection−absorption (RA) spectroscopy. The infrared study indicates that the LB films of ES-3 possess crystalline, tightly packed methylene chains and extended interchain hydrogen bonds between the amide groups, which connect the alkyl chains with the microgel. A comparison of the band intensities between the transmission and RA spectra suggests that the hydrocarbon chains are highly oriented with a small tilt angle and that N−H and CO bonds of the amide groups and the interchain hydrogen bonds between the N−H and CO bonds are nearly parallel to the surface. It is indicated from infrared spectra of LB films of ES-3 prepared under different surface pressures that the alkyl chains are highly ord...

Molecular orientation and structure in ultrathin films of amphiphilic microgel copolymer with the branching of octadecyl groups studied by infrared spectroscopy

Molecular orientation and structure in ultrathin films of amphiphilic microgel copolymer with the branching of octadecyl groups studied by infrared spectroscopy