Amine Density Research Articles

Surface functionalization of silica particles for their efficient fluorescence and stereo selective modification

Abstract Optimization of reaction conditions between surface silanols of silica particles and 3-aminopropyltriethoxysilane is performed. A reasonably good surface coverage by amino groups is achieved by adjustment of solvent polarity, temperature and reaction time. The best results are obtained for the ratio of toluene/ethanol 9:1 (v/v) and 5 h of reaction time at 50 °C, which can be further improved increasing the surface amine density from 0.62 to 0.87 groups/nm 2 under dry silanization conditions. The availability of surface amino groups for further coupling is verified by decoration of anisotropically modified (Janus) particles with gold nanoparticles and by reaction with a fluorescent dye Rhodamine B isothiocyanate. The duration of coupling with the dye is crucial for efficient dye incorporation and particle fluorescence. The emission intensity of the dyed particles declines if the reaction is conducted for more than 24 h because of the degradation of the particle-dye adduct.

Influence of amine-modified poly(vinyl alcohol)s on vibrating-membrane nebulizer performance and lung toxicity

A suitable aerosol droplet size and formulation output rate is essential for the therapy of lung diseases under application of nebulizers. The current study investigated the potential of amine-modified poly(vinyl alcohol)s as excipients for inhalation delivery.A change of conductivity (effective at <0.1mg/ml) and viscosity (effective at >0.1mg/ml) of samples that were supplemented with charge-modified polymers had a significant influence on the generated droplet size (shift from ~8 to ~4μm) and formulation throughput rate (shift from ~0.2 to ~1.0g/min), where polymers with a higher amine density (and molecular weight) showed an elevated activity. Biocompatibility assessment of polymers in A549 cells and an isolated lung model resulted in cell lysis and lung edema formation dependent on the type (degree of amine substitution) and dose of polymer applied.Suitable compositions and concentrations of amine-modified poly(vinyl alcohol)s were identified with respect to an optimized nebulizer performance and acceptable biocompatibility. Charge-modified polymers represent novel excipients with potential to improve inhalation therapy.

Impact of solvents and surfactants on the self-assembly of nanostructured amine functionalized silica spheres for CO2 capture

Macroscopic SiO2 spheres with a homogeneous amine distribution were synthesized by a one-step emulsion based synthesis approach in a flow column reactor. The CO2 adsorption capacity of the nano-structured amine-functionalized silica spheres was studied in absence and presence of H2O. The structural properties were adjusted by varying solvents and surfactants during the synthesis and, at constant amine loadings, were found to be the main factor for influencing the CO2 sorption capacities. Under water-free conditions CO2 is bound to the amino groups via the formation of carbamates, which require two neighboring amino groups to adsorb one CO2 molecule. At constant amine concentrations sorbents with lower surface area allow to establish a higher amine density on the surface, which enhances the CO2 uptake capacities under dry conditions. In presence of H2O the CO2 adsorption changes to 1:1 stoichiometry due to stabilization of carbamates by protonation of H2O and formation of further species such as bicarbonates, which should in principle double the adsorption capacities. Low concentrations of physisorbed H2O (0.3mmol/g) did not impair the adsorption capacity of the adsorbents for CO2, while at higher water uptakes (0.6 and 1.1mmol/g) the CO2 uptake is reduced, which could be attributed to capillary condensation of H2O or formation of bulky reaction products blocking inner pores and access to active sites.

Role of Amine Functionality for CO2 Chemisorption on Silica.

The mechanism of CO2 adsorption on primary, secondary, and bibasic aminosilanes synthetically functionalized in porous SiO2 was qualitatively and quantitatively investigated by a combination of IR spectroscopy, thermogravimetry, and quantum mechanical modeling. The mode of CO2 adsorption depends particularly on the nature of the amine group and the spacing between the aminosilanes. Primary amines bonded CO2 preferentially through the formation of intermolecular ammonium carbamates, whereas CO2 was predominantly stabilized as carbamic acid, when interacting with secondary amines. Ammonium carbamate formation requires the transfer of the carbamic acid proton to a second primary amine group to form the ammonium ion and hence two (primary) amine groups are required to bind one CO2 molecule. The higher base strength of secondary amines enables the stabilization of carbamic acid, which is thereby hindered to interact further with nearby amine functions, because their association with Si-OH groups (either protonation or hydrogen bonding) does not allow further stabilization of carbamic acid as carbamate. Steric hindrance of the formation of intermolecular ammonium carbamates leads to higher uptake capacities for secondary amines functionalized in porous SiO2 at higher amine densities. In aminosilanes possessing a primary and a secondary amine group, the secondary amine group tends to be protonated by Si-OH groups and therefore does not substantially interact with CO2.

Polyethyleneimine-Based Nanocarriers for Gene Delivery.

There is a tremendous progress in the design and synthesis of nano-scaled, non-viral carriers in the previous two decades. The nanodelivery systems can significantly improve biopharmaceutical features, pharmacokinetic properties and therapeutic efficacy of entrapped drugs. Branched polyethylenimine (PEI) is a cationic polymer that contains primary, secondary and tertiary amino groups. Such type of water-soluble polymer having high density of amines is one of the most promising cationic vectors for gene delivery. Hence, constructing nanocarriers that contain PEI have attracted much research effort in gene therapy because of the synergy effects of PEI molecules for their efficient transfection and the multi-functionality of nanoparticles in delivery. In this review, we focus on the recent development on the design and synthesis of four types of PEI-based nanocarriers: 1) PEI-based polymeric micelles systems; 2) PEI-based polymeric nanoparticle system; 3) PEI/silica nanoparticle systems; and 4) PEI/metal nanoparticle systems. Their in vitro gene transfaction and in vivo gene therapy will be also discussed. Results from these studies have demonstrated that PEI-based nanocarriers are promising delivery systems because of their efficient gene transfection, negligible toxicity, capability to co-deliver nucleic acids and chemotherapy drugs, ease of modification with the targeting molecules, and good responsiveness to external stimulus.

Predicting normal densities of amines using quantitative structure-property relationship (QSPR)

This paper reports on a quantitative structure–property relationship (QSPR) approach applied to predict the normal density of amines. A heuristic method was applied to a dataset of experimental densities measured for more than 140 amines extracted from the literature. Statistical processing was performed to find the best correlations. The resulting model was validated successfully based on an external test set. The QSPR analysis showed the importance of intrinsic density, obtained by dividing molecular weight by calculated molecular volume. Further improvement of the model’s predictive ability was achieved by introducing descriptors quantifying the influence of intermolecular volume. It has been shown that a simple correlation equation is sufficient to predict the density of amines with satisfactory accuracy. The equation requires only three descriptors: intrinsic density, overall or summation solute hydrogen bond acidity and a sum of intrinsic state values, each of which can be easily calculated using the Simplified Molecular Input Line Entry System Specification (SMILES). The equation provided may be applied to determine the density of amines or their derivatives which are unavailable or unknown.

Investigating the Dispersion Behavior in Solvents, Biocompatibility, and Use as Support for Highly Efficient Metal Catalysts of Exfoliated Graphitic Carbon Nitride.

The liquid-phase exfoliation of graphitic carbon nitride (g-C3N4) to afford colloidal dispersions of two-dimensional flakes constitutes an attractive route to facilitate the processing and implementation of this novel material toward different technological applications, but quantitative knowledge about its dispersibility in solvents is lacking. Here, we investigate the dispersion behavior of exfoliated g-C3N4 in a wide range of solvents and evaluate the obtained results on the basis of solvent surface energy and Hildebrand/Hansen solubility parameters. Estimates of the three Hansen parameters for exfoliated g-C3N4 from the experimentally derived data yielded δD ≈ 17.8 MPa(1/2), δP ≈ 10.8 MPa(1/2), and δH ≈ 15.4 MPa(1/2). The relatively high δH value suggested that, contrary to the case of other two-dimensional materials (e.g., graphene or transition metal dichalcogenides), hydrogen-bonding plays a substantial role in the efficient interaction, and thus dispersibility, of exfoliated g-C3N4 with solvents. Such an outcome was attributed to a high density of primary and/or secondary amines in the material, the presence of which was associated with incomplete condensation of the structure. Furthermore, cell proliferation tests carried out on thin films of exfoliated g-C3N4 using murine fibroblasts suggested that this material is highly biocompatible and noncytotoxic. Finally, the exfoliated g-C3N4 flakes were used as supports in the synthesis of Pd nanoparticles, and the resulting hybrids exhibited an exceptional catalytic activity in the reduction of nitroarenes.

Effect of Amine Surface Density on CO2 Adsorption Behaviors of Amine-Functionalized Polystyrene

Abstract Ethylenediamine was grafted onto a polystyrene surface to study the relationship between amine density and amine efficiency. Amine-tethered polystyrene was synthesized in two steps: (1) chloromethylation and (2) amination. The products were characterized by argentometry, N2 physisorption, thermogravimetric analysis, X-ray diffraction, and FT-IR spectroscopy. The amine efficiency declined drastically when the amine density was less than 1 amine molecule per nm2, because formation of ammonium carbamate is difficult under such conditions. A double-functionalization method was introduced to improve the CO2 uptake and amine efficiency of the amine-grafted sorbent by impregnating more amino groups into the porous structure. The combination of grafted and mobile amino groups led to a synergic effect, resulting in a CO2 uptake of up to 20.2 wt % at 30 °C and 1 bar CO2. It was concluded that double-functionalization with tetraethylenepentamine was advantageous for enhancing the amine efficiency, whereas double-functionalization with polyethyleneimine was advantageous for enhancing the cyclic stability of the sorbent.

Improved mechanical properties of polylactide nanocomposites-reinforced with cellulose nanofibrils through interfacial engineering via amine-functionalization

One of the main factors responsible for the mechanical and physical properties of nanocomposites is the effectiveness of the interfacial region to transfer loads and mechanical vibrations between the nano-reinforcements and the matrix. Surface functionalization has been the preferred approach to engineer the interfaces in polymer nanocomposites in order to maximize their potential in structural and functional applications. In this study, amine-functionalized cellulose nanofibrils (mCNF-G1) were synthesized via silylation of the hydroxyl groups on the CNF surface using 3-aminopropyltrimethoxysilane (APTMS). To further increase the amine density (mCNF-G2), dendritic polyamidoamine (PAMAM) was grafted onto mCNF-G1 by the Michael addition of methacrylate onto mCNF-G1, followed by the transamidation of the ester groups of methacrylate using ethylenediamine. Compared to native CNF-reinforced, poly(l-lactide) (PLLA) nanocomposites, amine-functionalized CNF exhibited significantly improved dispersion and interfacial properties within the PLLA matrix due to the grafting of PLLA chains via aminolysis. It is also a more effective nucleating agent, with 15% mCNF-G1 leading to a crystallinity of 32.5%, compared to 0.1 and 8.7% for neat PLLA and native CNF-reinforced composites. We have demonstrated that APTMS-functionalized CNF (mCNF-G1) significantly improved the tensile strength compared to native CNF, with 10% mCNF-G1 being the most effective (i.e., >100% increase in tensile strength). However, we also found that excessive amines on the CNF surface (i.e., mCNF-G2) resulted in decreased tensile strength and modulus due to PLLA degradation via aminolysis. These results demonstrate the potential of optimized amine-functionalized CNF for future renewable material applications.

Applications of Dendrimer-Based Nano-Architectures in Lithium-Air and Lithium-Sulfur Batteries

Dendritic branched polymers, particularly the well studied, most commonly synthesized and commercially available polyamidoamine (PAMAM) dendrimers have a high degree of surface functionalities, high surface-area, large molecular weights, and ample well-defined interior space. PAMAM dendrimers are particularly attractive candidates as templates for the synthesis of catalyst metal nanoparticles due to a high density of interior tertiary amines, which are able to complex with metal ions and variable surface groups to tailor their solubility. These remarkable physico-chemical properties of dendrimers enable them to be applied in next-generation energy storage technologies. Amongst all sustainable rechargeable Li-batteries, Li-air (Li-O2) and Li-sulfur (Li-S) batteries are the most promising with very high theoretical specific energy densities (11,140 Wh/kg and 2,600 Wh/kg respectively). However, several fundamental issues hinder their commercialization; for example, slow kinetics of the oxygen evolution reaction (OER) during charging results in low round-trip efficiency of the Li-O2 battery. High voltage required during the OER process leads to degradation of non-aqueous electrolytes and carbon-based air electrodes resulting in rapid capacity fade and further increasing the discharge-charge voltage. In Li-S batteries, the charge/discharge reaction creates highly soluble polysulfide intermediates in electrolytes, causing irreversible loss of active sulfur and low cycling efficiency. Furthermore, most research focus has been on improving the cycle life of the batteries by using thin electrodes (<2 mg/cm2 of active sulfur loading). However, for practical applications, it is imperative to validate the different approaches on fabricating electrodes at a relevant scale. Here, we will discuss a fundamental understanding of branched polymers as advanced energy storage materials expanding their applications to sustainable high-energy density storage and conversion systems such as those mentioned above. We have recently showed that PAMAM dendrimers can be used as hosts to encapsulate monodispersed ruthenium oxide (RuO2) nanoparticles, and employed as catalysts in the air electrode for Li-O2 batteries. The dendrimers stabilized the RuO2 nanoparticles while ensuring the availability of the entire nanoparticle surface for catalysis, thus reducing the amount of noble metal catalysts used in these systems by almost ten times than the state-of-the-art, without sacrificing their catalytic efficiency. We will further discuss the formation of highly catalytically efficient sub-nanometer clusters of Ru atoms using dendrimers as templates, i.e. dendrimer-based superatoms, in organic solvents. Additionally, we also explored the application of chemically modified PAMAM dendrimers with high electronic conductivity in Li-S batteries. These modified dendrimers showed a better cycling stability compared with hyperbranched polymers used as cathode materials. While challenges exist in the properties of the cathode materials themselves, the binder in the electrode is also critical in bonding the active materials together as well as maintaining a good electrical contact with the current collector. We have been able to obtain high loading (> 4 mg/cm2) of active sulfur using dendrimer-based functional binders with various surface functionalities. Here, we will discuss the structure-function relationships of dendrimer-based binders and cathode materials in enhancing the performance of high areal capacity Li-S batteries. Detailed characterizations of these novel nano-architectures will be discussed to understand how their structure and chemistry influence the electrochemical performance of the aforementioned energy systems. By using novel dendrimer chemistry and assembly, our research provides new clues to embody the nanoscale properties of soft and porous dendritic nanostructures for improving the state‐of‐the‐art of sustainable, high energy density battery technology applications.

1,3,5-Triazine-pentaethylenehexamine polymer for the adsorption of palladium (II) from chloride-containing solutions

A triazine-hexamine (TAPEHA) polymer demonstrating high acid-resistance, good affinity to noble metals, and a high density of amine and triazine functional groups has been designed and synthesized. The obtained polymer was used as an adsorbent for the recovery of palladium (II) ions from chloride-containing solutions. Effects of pH, pCl, contact time, initial Pd(II) concentration, and temperature on adsorption were investigated and optimized by batch adsorption experiments. The pseudo second-order kinetic equation provides the best correlation for the process. While five isotherms were used, the nonlinear resolution of the Langmuir isotherm equation has been found to provide the closest fit to the equilibrium data. The monolayer adsorption capacity which is highest among literature is 517.2mg/g. All thermodynamic parameters suggest that Pd(II) adsorption onto TAPEHA particles is a spontaneous, physisorptive, and exothermic process. The formation of TAPEHA and Pd-adsorbed TAPEHA has been characterized by FE-SEM, EDAX, XRD, and FTIR instrumentations. Adsorption of the negatively charged chloropalladium (II) species mostly takes place via ligand exchange mechanism. Ease of synthesis and low cost, coupled with highly efficient and rapid removal of Pd(II) ions, make TAPEHA an attractive adsorbent.

Plasma Parameter Aspects in the Fabrication of Stable Amine Functionalized Plasma Polymer Films

Amine containing plasma polymer films are of interest due to their ability to bind biomolecules either covalently or electrostatically. One issue with generating such plasma polymers is the need to generate sufficient amine density on the surface to enable binding, while simultaneously maintaining the chemical, physical stability of the surface in aqueous media. Here we investigate the relationship between plasma parameters, film stability for two commonly used monomers, allylamine AA, ethylenediamine EDA. Plasma polymer films from AA, EDA were produced at radio frequency RF powers between 2 and 20 W at a constant monomer flowrate. Deposition rate, ion flux, ion energy, plasma phase mass spectrometry were used to investigate the plasma‐surface interactions. Film stability was assessed by comparing X‐ray photoelectron spectroscopy XPS, atomic force microscopy AFM measurements before, after washing in phosphate buffered saline PBS. The results show that films generated from EDA plasmas are generally unstable in aqueous media, while films generated from AA plasmas exhibit higher stability, particularly those deposited at high RF power. The chemical, physical stability of the films is then related to the mechanisms of deposition, the energy density provided to the surface during film growth.

Systematic adjustment of charge densities and size of polyglycerol amines reduces cytotoxic effects and enhances cellular uptake.

Excessive cationic charge density of polyplexes during cellular uptake is still a major hurdle in the field of non-viral gene delivery. The most efficient cationic vectors such as polyethylene imine (PEI) or polyamidoamine (PAMAM) can be highly toxic and may induce strong side effects due to their high cationic charge densities. Alternatives like polyethylene glycol (PEG) are used to 'shield' these charges and thus to reduce the cytotoxic effects known for PEI/PEG-core-shell architectures. In this study, we compared the ability of hyperbranched polyglycerol amines (hPG amines) with different amine densities and molecular weights as non-viral cationic vectors for DNA delivery. By adjusting the hydroxyl to amine group ratio on varying molecular weights, we were able to perform a systematic study on the cytotoxic effects caused by the effective charge density in correlation to size. We could demonstrate that carriers with moderate charge density have a higher potential for effective DNA delivery as compared to high/low charged ones independent of their size, but the final efficiency can be optimized by the molecular weight. We analyzed the physicochemical properties and cellular uptake capacity as well as the cytotoxicity and transfection efficiency of these new vector systems.

Optimized effective charge density and size of polyglycerol amines leads to strong knockdown efficacy in vivo.

RNA interference (RNAi)-based therapy extends the range of "druggable" targets beyond existing pharmacological drugs and enables the development of new treatment strategies for various diseases. A prerequisite are non-viral polyvalent gene delivery vectors capable for safe and effective siRNA delivery to cells in vivo allowing a broad clinical application. We synthesized hyperbranched polyglycerol amines (hPG amines) which varied in their charge density, multiplicity (absolute frequency of amine groups) and core size to successfully develop potent and safe siRNA transfer vectors. The characterization of hyperbranched polyglycerol amines with an invariable core size (8 kDa) but different amine loading revealed a correlation between the effective charge density and the transfection efficacy without impacting the cell viability in vitro. However, this correlation was not seen in tumor bearing mice in vivo treated with 8 kDa hPG amine-siRNA complexes. Improving the effective charge density and the multiplicity of amine functionalities by increasing the molecular weight (43 kDa) revealed comparable transfection efficacy in vitro but less toxic side effects after systemic administration in vivo compared to the respective hPG amine (8 kDa). In addition, in vivo delivery of 43 kDa hPG amine-siRNA-polyplexes in tumors resulted in a highly specific and significant knockdown effect. These findings demonstrate that hyperbranched polyglycerol amines with a balanced effective charge density, multiplicity and core size are promising gene delivery vectors for siRNA therapy which enable to address so far "undruggable" targets due to high tolerability and effective siRNA delivery.

NH2-rich polymer/graphene oxide use as a novel adsorbent for removal of Cu(II) from aqueous solution

Graphene oxide nanosheets (GO) were dispersed and crosslinked with a water soluble polymer, namely poly(allylamine hydrochloride) (PAH) with high amine density, to prepared a novel PAH-GO composite, which was used for removing Cu(II) ions from aqueous solutions. The physico-chemical properties of PAH-GO composites were investigated by transmission electron microscopy, thermogravimetric analysis, etc. Adsorption experiments indicated that adsorption process was strongly dependent on pH and temperature, however weakly dependent on ionic strength. The maximum adsorption capacity was about 349.03mg/g higher than that of currently reported. Competitive adsorption studies for the ternary system suggested that the adsorption of PAH-GO composite for Cu(II) ions was much preferable to Cd(II) and Ni(II) ions. Thermodynamic parameters suggested that adsorptions were endothermic and spontaneous processes. The Langmuir adsorption isotherm was applicable fit adsorption process, and adsorption kinetic process could be described by the pseudo-second-order model. Adsorption–desorption results showed that the reusability of PAH-GO composite was encouraging. Based on the results obtained, we conclude that PAH-GO composite can be an effective and potential adsorbent for removing Cu(II) ions from an aqueous solution.

Fabrication of porous resins via solubility differences for adsorption of cadmium (II)

By exploiting the different solubilities of triphenylphosphine in water, resins and organic solvents, porous melamine–formaldehyde (pMF) and porous urea–formaldehyde (pUF) resin materials could be successfully fabricated and used for adsorption of cadmium (II) (Cd(II)) cations. The obtained pMF and pUF materials had specific surface areas of 77.5 m2 g−1 and 79.0 m2 g−1, respectively, and were able to be recycled and reused to greatly reduce raw material consumption. Due to their porous structures and high amine density, the prepared materials exhibited high removal efficiencies (94%, pMF; 90%, pUF) and adsorption capacities (3.33 mg g−1, pMF; 3.12 mg g−1, pUF) of Cd(II). The effect of pH, adsorption time, ion concentration, amount of adsorbent and interfering ions on Cd(II) adsorption, and adsorption thermodynamics and kinetics were investigated. The results showed that the adsorption behaviors of Cd(II) on pMF and pUF followed Langmuir and pseudo-second-order kinetic models. Furthermore, the pMF and pUF showed efficient removal of Pb(II) (90.29%, pMF; 91.32%, pUF), Cu(II) (71.47%, pMF; 83.28%, pUF) and Cr(III) (92.28%, pMF; 88.69%, pUF), while the recycled pMF and pUF showed high removal efficiencies of 88.36% (Cd(II), pMF) and 88.04% (Cd(II), pUF) even after five cycles. Their high removal efficiencies and adsorption capacities, simple and convenient synthesis, and affordability make pMF and pUF especially competitive in the arena of heavy metal ions remediation.

Important roles of enthalpic and entropic contributions to CO2 capture from simulated flue gas and ambient air using mesoporous silica grafted amines.

The measurement of isosteric heats of adsorption of silica supported amine materials in the low pressure range (0-0.1 bar) is critical for understanding the interactions between CO2 and amine sites at low coverage and hence to the development of efficient amine adsorbents for CO2 capture from flue gas and ambient air. Heats of adsorption for an array of silica-supported amine materials are experimentally measured at low coverage using a Calvet calorimeter equipped with a customized dosing manifold. In a series of 3-aminopropyl-functionalized silica materials, higher amine densities resulted in higher isosteric heats of adsorption, clearly showing that the density/proximity of amine sites can influence the amine efficiency of adsorbents. In a series of materials with fixed amine loading but different amine types, strongly basic primary and secondary amine materials are shown to have essentially identical heats of adsorption near 90 kJ/mol. However, the adsorption uptakes vary substantially as a function of CO2 partial pressure for different primary and secondary amines, demonstrating that entropic contributions to adsorption may play a key role in adsorption at secondary amine sites, making adsorption at these sites less efficient at the low coverages that are important to the direct capture of CO2 from ambient air. Thus, while primary amines are confirmed to be the most effective amine types for CO2 capture from ambient air, this is not due to enhanced enthalpic contributions associated with primary amines over secondary amines, but may be due to unfavorable entropic factors associated with organization of the second alkyl chain on the secondary amine during CO2 adsorption. Given this hypothesis, favorable entropic factors may be the main reason primary amine based adsorbents are more effective under air capture conditions.

Oligospermines and Nucleic Acid Interaction: A Structure Property Relationship Study.

A variety of delivery vehicles use spermine as a polycationic component to form complexes with nucleic acids. Thus, we investigated the influence of molecular architecture, amine density, and molecular weight of oligospermines on its binding to nucleic acids. We report the synthesis of mono, bis, and tetraspermines with linear, cyclic, dendritic, and quatrefoil architecture. The effect of molecular weight was more pronounced in linear oligospermines than their cyclic counterparts. Oligospermines with similar amine density but different molecular architectures exhibited different binding profiles. Among all oligospermines evaluated, dendritic tetraspermine exhibited the highest binding affinity. Atomistic molecular dynamics simulations also indicated higher affinity for dendritic tetraspermine to siRNA than its linear counterpart suggesting the importance of spermine geometry in binding to nucleic acids. Importantly, dendritic tetraspermine was less toxic than linear tetraspermine, suggesting its potential in nucleic acid delivery.

Applications of Dendrimer-Based Nano-Architectures in Li-Air and Li-Sulfur Batteries

Dendritic branched polymers, particularly the well studied, most commonly synthesized and commercially available polyamidoamine (PAMAM) dendrimers have a high degree of surface functionalities, high surface-area, large molecular weights, and ample well-defined interior space. Additionally, due to their high porosities, high room temperature ionic conductivities of their lithium (Li) salts, and good chemical and thermal stabilities, they may provide improved properties as potential electrode materials and polymer electrolytes. PAMAM dendrimers are particularly attractive candidates as templates for the synthesis of catalyst metal nanoparticles due to a high density of interior tertiary amines, which are able to complex with metal ions and variable surface groups to tailor their solubility. These remarkable physico-chemical properties of dendrimers enable them to be applied in next-generation energy storage technologies.Amongst all sustainable rechargeable Li-batteries, Li-air (Li-O2) and Li-sulfur (Li-S) batteries are the most promising with very high specific energy densities (11,140 Wh/kg and 2,600 Wh/kg respectively). However, several fundamental issues hinder their commercialization. Oxidation of the insoluble, poorly conducting Li2O2 discharge products during charging, slow kinetics of the oxygen reduction reaction during discharge, and the oxygen evolution reaction (OER) during charging resulting in low round-trip efficiency of the battery, high voltage required during the OER process leading to degradation of non-aqueous electrolytes and carbon-based air electrodes resulting in rapid capacity fade and further increasing the discharge-charge voltage hysteresis in the battery are some of the critical challenges with the Li-O2 battery. In Li-S batteries, the charge/discharge reaction creates highly soluble polysulfide intermediates in electrolytes, causing irreversible loss of active sulfur and low cycling efficiency. Furthermore, the battery’s cycle life and safety can be greatly improved by replacing liquid electrolytes with gel or solid polymer electrolytes.Here, we will discuss a fundamental understanding of branched polymers as advanced energy storage materials expanding their applications to sustainable high-energy density storage and conversion systems such as those mentioned above. Specifically, dendrimer-encapsulated ruthenium nanoparticles (DEN-Ru) were used as catalysts in Li-O2 batteries for the first time. The DEN-Ru significantly improves the cycling stability of Li-O2 batteries with carbon black electrodes and decreases the charging potential even at low catalyst loading. Furthermore, the potential of using DEN-Ru as a standalone cathode material for Li-O2 batteries also will be discussed.Additionally, we also explored the application of chemically modified PAMAM dendrimers with electronic conductivity in Li-S batteries. These modified dendrimers showed a better cycling stability compared with hyperbranched polymers used as cathode materials.We will also discuss the potential of ionically conducting dendrimers as electrolyte systems. Detailed characterizations of these novel nano-architectures will be discussed to understand how their structure and chemistry influence the electrochemical performance of the aforementioned energy systems. It is anticipated that by using novel dendrimer chemistry and assembly, our research will lead to the development of energy materials that embody the nanoscale properties of soft and porous dendritic nanostructures and provide innovative solutions for improving the state‐of‐the‐art of sustainable, high energy density applications.

In situ infrared study of the effect of amine density on the nature of adsorbed CO2 on amine-functionalized solid sorbents.

In situ Fourier transform infrared spectroscopy was used to determine the nature of adsorbed CO2 on class I (amine-impregnated) and class II (amine-grafted) sorbents with different amine densities. Adsorbed CO2 on amine sorbents exists in the form of carbamate-ammonium ion pairs, carbamate-ammonium zwitterions, and carbamic acid. The adsorbed CO2 on high-amine density sorbents showed that the formation of ammonium ions correlates with the suppression of CH stretching intensities. An HCl probing technique was used to resolve the characteristic infrared bands of ammonium ions, clarifying that the band observed around 1498 cm(-1) is a combination of the deformation vibration of ammonium ion (NH3(+)) at 1508 and 1469 cm(-1) and the deformation vibration of NH in carbamate (NHCOO(-)) at 1480 cm(-1). Carbamate and carbamic acid on sorbents with low amine density desorbed at a rate faster than those on sorbents with high amine density after switching the flow from CO2 to Ar at 55 °C. Evaluation of the desorption temperature profiles showed that the temperature required to achieve the maximal desorption of CO2 (Tmax.des) increases with amine density. The adsorbed CO2 on sorbents with high amine density is stabilized via hydrogen bonding interactions with adjacent amine sites. These sorbents require higher temperature to desorb CO2 than those with low amine density.