Abstract:Hydrogel films composed of temperature‐responsive microgel particles (GPs) containing amine groups work as stimuli‐responsive carbon dioxide absorbent with a high capacity of approximately 1.7 mmol g −1. Although the dried films did not show significant absorption, the reversible absorption capacity dramatically increased by adding a small amount of water (1 mL g−1). The absorption capacity was independent of the amount of added water beyond 1 mL g−1, demonstrating that the GP films can readily be used under we… Show more
“…Additional functions, for example, for chemical transformation or sensing applications 10 , 11 , can be added using core–shell particles or by decorating the microgels with inorganic nanoparticles 12 , 13 . Microgels are already used in several applications as viscosity modifiers and lubricants 14 , for CO 2 capturing 15 or 3D bioprinting 16 , as biocompatible additives and delivery vehicles 17 , sensors, or stimuli-responsive color-changing systems 18 , 19 . Fig.…”
Due to their controlled size, sensitivity to external stimuli, and ease-of-use, microgel colloids are unique building blocks for soft materials made by crosslinking polymers on the micrometer scale. Despite the plethora of work published, many questions about their internal structure, interactions, and phase behavior are still open. The reasons for this lack of understanding are the challenges arising from the small size of the microgel particles, complex pairwise interactions, and their solvent permeability. Here we describe pathways toward a complete understanding of microgel colloids based on recent experimental advances in nanoscale characterization, such as super-resolution microscopy, scattering methods, and modeling. T he term "microgel" usually refers to a cross-linked polymer network of colloidal size that is swollen in a good solvent and has a diameter between~100 nm and several micrometers 1-3 (Fig. 1). Colloidal hydrogels are a common subtype where the continuous phase is water. Often, but not always, these networks exhibit conformational changes in response to changes in their environment, such as the solvent composition or temperature 1,4,5. The sensitivity to external stimuli, such as temperature, pH, or solvent conditions, is an essential feature of many microgels, in particular for the most widely studied type of microgels, based on pNIPAM (poly-N-isopropylacrylamide) and its derivatives 1,6 (Fig. 1b). Here, we consider homogeneous suspensions of these particles at different densities from the dilute to the highly packed regime, as well as microgels adsorbed at surfaces. It is also possible to synthesize larger, millimeter-sized, gel particles 7 , or to study two-dimensional assemblies at an interface 8,9. Additional functions, for example, for chemical transformation or sensing applications 10,11 , can be added using core-shell particles or by decorating the microgels with inorganic nanoparticles 12,13. Microgels are already used in several applications as viscosity modifiers and lubricants 14 , for CO 2 capturing 15 or 3D bioprinting 16 , as biocompatible additives and delivery vehicles 17 , sensors, or stimuli-responsive color-changing systems 18,19. Despite their popularity and widespread application, the internal structure of microgels is not well-understood. During the microgel synthesis, the degrees of freedom for the polymer strands are intentionally reduced by forming covalent cross-links between polymer chains. The chemical crosslinking itself is a nonequilibrium process, and it does not necessarily progress uniformly, which may lead to spatial fluctuations, gradients, and heterogeneities in the microgel particle architecture 20. For a complete understanding of a microgel colloid as a material building block or a carrier, it is imperative to know the spatial distribution of polymer and cross-link densities on the nanoscale. Initially, many studies assumed that microgels could be described simply as spherical, homogeneous gel particles, as discussed in ref. 1. Based on this assumption, t...
“…Additional functions, for example, for chemical transformation or sensing applications 10 , 11 , can be added using core–shell particles or by decorating the microgels with inorganic nanoparticles 12 , 13 . Microgels are already used in several applications as viscosity modifiers and lubricants 14 , for CO 2 capturing 15 or 3D bioprinting 16 , as biocompatible additives and delivery vehicles 17 , sensors, or stimuli-responsive color-changing systems 18 , 19 . Fig.…”
Due to their controlled size, sensitivity to external stimuli, and ease-of-use, microgel colloids are unique building blocks for soft materials made by crosslinking polymers on the micrometer scale. Despite the plethora of work published, many questions about their internal structure, interactions, and phase behavior are still open. The reasons for this lack of understanding are the challenges arising from the small size of the microgel particles, complex pairwise interactions, and their solvent permeability. Here we describe pathways toward a complete understanding of microgel colloids based on recent experimental advances in nanoscale characterization, such as super-resolution microscopy, scattering methods, and modeling. T he term "microgel" usually refers to a cross-linked polymer network of colloidal size that is swollen in a good solvent and has a diameter between~100 nm and several micrometers 1-3 (Fig. 1). Colloidal hydrogels are a common subtype where the continuous phase is water. Often, but not always, these networks exhibit conformational changes in response to changes in their environment, such as the solvent composition or temperature 1,4,5. The sensitivity to external stimuli, such as temperature, pH, or solvent conditions, is an essential feature of many microgels, in particular for the most widely studied type of microgels, based on pNIPAM (poly-N-isopropylacrylamide) and its derivatives 1,6 (Fig. 1b). Here, we consider homogeneous suspensions of these particles at different densities from the dilute to the highly packed regime, as well as microgels adsorbed at surfaces. It is also possible to synthesize larger, millimeter-sized, gel particles 7 , or to study two-dimensional assemblies at an interface 8,9. Additional functions, for example, for chemical transformation or sensing applications 10,11 , can be added using core-shell particles or by decorating the microgels with inorganic nanoparticles 12,13. Microgels are already used in several applications as viscosity modifiers and lubricants 14 , for CO 2 capturing 15 or 3D bioprinting 16 , as biocompatible additives and delivery vehicles 17 , sensors, or stimuli-responsive color-changing systems 18,19. Despite their popularity and widespread application, the internal structure of microgels is not well-understood. During the microgel synthesis, the degrees of freedom for the polymer strands are intentionally reduced by forming covalent cross-links between polymer chains. The chemical crosslinking itself is a nonequilibrium process, and it does not necessarily progress uniformly, which may lead to spatial fluctuations, gradients, and heterogeneities in the microgel particle architecture 20. For a complete understanding of a microgel colloid as a material building block or a carrier, it is imperative to know the spatial distribution of polymer and cross-link densities on the nanoscale. Initially, many studies assumed that microgels could be described simply as spherical, homogeneous gel particles, as discussed in ref. 1. Based on this assumption, t...
“…1,2 It is thus imperative to explore viable CO 2 capture and sequestration (CCS) technologies to reduce the release of CO 2 and lower its concentration in the atmosphere. 3,4 Conventional technology for the industrial capture of CO 2 largely relies on employing aqueous amine solutions.…”
For the first time, speciation evolution in aqueous sodium salt of alanine (SSA) solution during both CO 2 absorption and desorption has been investigated via nuclear magnetic resonance (NMR) spectroscopy. Results suggest that amine, carbamate, and bicarbonate are the main species formed in the solvent system. During CO 2 absorption, deprotonated alanine (Ala) reacts with CO 2 first to form carbamate, which subsequently hydrolyzes into bicarbonate. At higher CO 2 loadings (∼0.6 mol/mol of Ala), it appears that bicarbonate is dominant. Interestingly, the carbamate concentration in the SSA solution increases first and then decreases slightly during CO 2 desorption, and the amount of carbamate after CO 2 desorption is more than that at the end of the CO 2 absorption, thus reducing the desorption efficiency. Furthermore, the species distributions have also been compared to those of the commercial monoethanolamine (MEA) absorbent, revealing that the main difference between SSA and MEA systems is the hydrolysis rate of carbamate. Determination of the species formed is a first step to understand the chemistry of the solvent system, which may facilitate developing more efficient and energy-saving solvents for CO 2 capture and sequestration.
“…The entrapped metal nanoparticles act as catalyst while the polymer network used as stabilizing or sheltering agent for these particles in a controlled manner [21]. The beauty of these materials is its smart behavior; that is, we can tune the properties of metal nanoparticles by changing the properties of polymer network with external stimuli before or during the process of reduction, e.g., temperature [22][23][24], pH [25][26][27], ionic strength [28,29]. In current years, many investigators have a great interest in the field of stimulus-responsive composite systems composed of continuous organic and dispersed inorganic phase [30] for different applications, e.g., drug delivery [31][32][33], sensors [34,35], electrical [36], catalysis [37][38][39].…”
In this work, we report the synthesis of composite system pNAC, composed of silver nanoparticles embedded in pure thermo-sensitive crosslinked polymer network of poly(N-isopropylacrylamide-co-acrylamide) (pNA), using as a catalyst for the reduction of methylene blue (MB) dye by sodium borohydride (NaBH 4 ). The pNA was prepared by conventional free radical polymerization technique using sodium dodecyl sulfate as stabilizing agent, followed by in situ reduction of AgNO 3 inside the polymer network by NaBH 4 for the synthesis of composite systems pNACs. The synthesized pNA and pNACs were characterized by FTIR, dynamic light scattering, thermogravimetric analysis, scanning electron microscopy and UV-visible spectroscopy techniques. The materials were found sensitive toward temperature change of the medium. The entrapment ability of pNA toward different amounts of AgNO 3 solution was studied, and effect of metal content on particle size of pNACs was analyzed. The pNACs were applied as a catalyst for the reduction of MB in which they exhibit high catalytic activity and reusability toward the reaction.
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