Proton-Conducting Properties of Acid-Doped Poly(glycidyl methacrylate)-1,2,4-Triazole Systems

Study of Proton Transport in Diethylmethylammonium Poly[4-styrenesulfonyl(trifluoromethylsulfonyl)imide]-Based Composite Membranes with Triflic Acid and Diethylmethylamine-Rich Compositions

The study highlights the effect of acid- and base-rich conditions on the proton dynamics of diethylmethylammonium poly[4-styrenesulfonyl(trifluoromethylsulfonyl)imide, [DEMA][PSTFSI], a polymerized protic ionic liquid designed as a polymer electrolyte for nonhumidified polymer electrolyte membrane fuel cells. Different proportions of triflic acid (HTf) and diethylmethylamine (DEMA) were added to the pristine polymer. The thermal analysis of the mixtures revealed that the addition of the base increases the glassy/amorphous nature of the polymer; however, HTf plasticizes the polymer and lowers the T_g value, so that it falls outside of the differential scanning calorimetry-studied temperature range. 50 mol % doping of the HTf contents increases the conductivity upto 0.952 mS cm^-1, and 50 mol % DEMA mixture has a conductivity of 0.169 mS cm^-1 at 100 °C. Vogel-Tamman-Fulcher fitting of the ionic conductivities of the doped systems suggested that the ionic conductivities are completely decoupled from segmental motion of the polymer. A combination of Fourier transform infrared and static NMR studies demonstrated that HTf-added polymer composites show conduction via Grotthuss and vehicular mechanisms, while DEMA-added polymer composites show predominantly a Grotthuss mechanism by developing the aggregates of proton and added base.

Impact of N-Substituent and pKa of Azole Rings on Fuel Cell Performance and Phosphoric Acid Loss

The influence of N-substituent and pK_a of azole rings has been investigated for the performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Imidazole, benzimidazole, and triazole groups were functionalized on the side chains of poly(phenylene oxide), respectively. Each azole group is categorized by their N-substituent into two types: unsubstituted and methyl-substituted azoles. The membranes with methyl-substituted azoles showed higher phosphoric acid (PA) doping levels with an average increase of 20% compared to those with unsubstituted azoles in the full-doped states. However, unsubstituted azoles more effectively improved the proton conductivity and the membrane with unsubstituted imidazole (IMPPO-H) showed a high anhydrous proton conductivity of 153 mS/cm at 150 °C. In contrast, the membranes with methyl-substituted azoles showed a higher PA retention with an average increase of 81% compared to those with unsubstituted azoles. The higher PA retention of methyl-substituted azoles also led to the higher fuel cell performance with the maximum increase of 95% in the power density. It was also revealed that higher pK_a of azoles enhanced the PA retention and the fuel cell performance. Based on the experimental results of PA retention and density functional theory calculations, the PA loss mechanism was also proposed.

Synthesis and Characterization of Novel Azole Functionalized Poly(glycidyl methacrylate)s for Antibacterial and Anticandidal Activity

BACKGROUND

Presently, rise in the infectious diseases and subsequent development of drug resistance, is a global threat to human health. However, much efforts are being made by scientists, to develop novel antimicrobials, and also to improve the efficacy of available drugs, in order to combat the lifethreatening infections.

OBJECTIVE

Synthesis and characterization of azole functional polymer systems for antimicrobial applications.

MATERIALS AND METHODS

Poly(glycidyl methacrylate) (PGMA), was produced by free radical polymerization of the monomer, glycidyl methacrylate (GMA). Different azole functional PGMAs were produced, through chemical modification with imidazole (Im), 1H-1,2,4-triazole (Tri) and 3-amino-1,2,4-triazole (ATri), to get PGMA-Imi, PGMA-Tri and PGMA-ATri, respectively. The structure was confirmed by Fourier transform infrared spectroscopy (FT-IR), thermal properties were investigated by Thermogravimetric Analysis (TGA), and surface morphology was studied by scanning electron microscopy (SEM). Newly synthesized derivatives were further explored, for their antibacterial and anticandidal activities.

RESULTS

All the three synthesized and characterized derivatives, displayed a significant activity against the tested microorganisms. The minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC), recorded against Staphylococcus aureus (S. aureus), was 0.5 &1mg/ml for PGMA-Imi, followed by PGMA-ATri & PGMA-Tri, respectively, followed by E. coli with, 1 & 2 mg/ml, 4 & 8 mg/ml, 4& 8 mg/ml, respectively, whereas the maximum MIC & MFC was recorded against C. albicans i.e., 8 & 16 mg/ml, 4 & 8 mg/ml ,4 & 8 mg/ml for PGMA-ATri, PGMA-Tri, PGMA-Imi, respectively.

CONCLUSION

In the present work, we report on the state-of-the-art, azole functional polymer systems for antimicrobial applications. These findings suggest that the synthesized azole functional polymer films have antimicrobial properties, which could be potential candidates for coating applications in the biomedical and wastewater treatment field.

Delivery of Conjugated Silicon Dioxide Nanoparticles Show Strong Anti-Proliferative Activities

Conjugation of different molecules is a promising approach to enhance the drug delivery and treatment. In the present study, here, we have synthesized silica oxide (SiO₂) nanoparticles conjugated with (3-Glycidyloxypropyl) trimethoxysilane (3GPS) and further reacted with 1,2,4-triazole (Tri), 3-aminotriazole (ATri), 5-aminetetrazole (Atet), imidazole (Imi). The structure, size, and morphology of nanocomposite materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) methods. These nanocomposite materials were tested on human colorectal carcinoma cells (HCT-116) to examine their anti-cancer capabilities by using MTT assay and morphometric analysis. Our results revealed that nanocomposite materials decreased cancer cell viability and cell proliferation and caused cell death in a concentration-dependent manner. Our findings demonstrate that SiO₂-conjugated nanocomposite materials possess strong anti-cancer capabilities and hold a great potential for the colon cancer treatments.

A polyelectrolyte-containing copolymer with a gas-switchable lower critical solution temperature-type phase transition

A polyelectrolyte-containing copolymer with a CO₂/N₂-switchable cloud point, resulting from the gas-induced alternation of hydrophilicity, was prepared.

Remarkable enhancement of ambient-air electrical conductivity of the perylenediimide π-stacks isolated in the flexible films of a hydrogen-bonded polymer

N,N′-di(2-(trimethylammoniumiodide)ethylene) perylenediimide (TAIPDI), forming extensive π-stacks through the strong π–π interactions of large π-planes, was isolated in the hydrogen-bonding milieu of polyvinyl alcohol (PVA) from aqueous solutions.

Proton exchange membrane developed from novel blends of polybenzimidazole and poly(vinyl-1,2,4-triazole)

In continuation (J. Phys. Chem. B2008, 112, 5305; J. Colloid Interface Sci. 2010, 351, 374) of our quest for proton exchange membrane (PEM) developed from polybenzimidazole (PBI) blends, novel polymer blend membranes of PBI and poly(1-vinyl-1,2,4-triazole) (PVT) were prepared using a solution blending method. The aim of the work was to investigate the effect of the blend composition on the properties, e.g., thermo-mechanical stability, swelling, and proton conductivity of the blend membranes. The presence of specific interactions between the two polymers in the blends were observed by studying the samples using varieties of spectroscopic techniques. Blends prepared in all possible compositions were studied using a differential scanning calorimetry (DSC) and exhibited a single T(g) value, which lies between the T(g) value of the neat polymers. The presence of a single composition-dependent T(g) value indicated that the blend is a miscible blend. The N-H···N interactions between the two polymers were found to be the driving force for the miscibility. Thermal stability up to 300 °C of the blend membranes, obtained from thermogravimetric analysis, ensured their suitability as PEMs for high-temperature fuel cells. The proton conductivity of the blend membranes have improved significantly, compared to neat PBI, because of the presence of triazole moiety, which acts as a proton facilitator in the conduction process. The blend membranes showed a considerably lower increase in thickness and swelling ratio than that of PBI after doping with phosphoric acid (PA). We found that the porous morphology of the blend membranes caused the loading of a larger amount of PA and, consequently, higher proton conduction with lower activation energy, compared to neat PBI.

Applications of high-resolution 1H solid-state NMR

This article reviews the large increase in applications of high-resolution (1)H magic-angle spinning (MAS) solid-state NMR, in particular two-dimensional heteronuclear and homonuclear (double-quantum and spin-diffusion NOESY-like exchange) experiments, in the last five years. These applications benefit from faster MAS frequencies (up to 80 kHz), higher magnetic fields (up to 1 GHz) and pulse sequence developments (e.g., homonuclear decoupling sequences applicable under moderate and fast MAS). (1)H solid-state NMR techniques are shown to provide unique structural insight for a diverse range of systems including pharmaceuticals, self-assembled supramolecular structures and silica-based inorganic-organic materials, such as microporous and mesoporous materials and heterogeneous organometallic catalysts, for which single-crystal diffraction structures cannot be obtained. The power of NMR crystallography approaches that combine experiment with first-principles calculations of NMR parameters (notably using the GIPAW approach) are demonstrated, e.g., to yield quantitative insight into hydrogen-bonding and aromatic CH-π interactions, as well as to generate trial three-dimensional packing arrangements. It is shown how temperature-dependent changes in the (1)H chemical shift, linewidth and DQ-filtered signal intensity can be analysed to determine the thermodynamics and kinetics of molecular level processes, such as the making and breaking of hydrogen bonds, with particular application to proton-conducting materials. Other applications to polymers and biopolymers, inorganic compounds and bioinorganic systems, paramagnetic compounds and proteins are presented. The potential of new technological advances such as DNP methods and new microcoil designs is described.

New proton conducting materials for technical applications: what can we learn from solid state NMR studies?

Many novel proton conducting materials are based on complex hydrogen bonding networks of amphoteric hydrogen bonded moieties. Solid state NMR provides unique methods to study the properties of such network and specific proton conduction mechanisms in detail. In particular 1H solid state NMR techniques under fast magic angle spinning are powerful tools in this area. Site specific studies of the dynamic behavior via variable temperature 1H MAS measurements provide insight in the thermodynamics of the hydrogen bonding as well as activation energies for the proton transfer between the amphoteric sites. On macroscopic length scales, pulsed field gradient NMR experiments are able to determine the proton mobility and the contribution of different conduction mechanisms. In this article, aspects of recent solid state NMR studies in the field are reviewed and typical experimental methods as well as their possible outcome are discussed.

Anhydrous Poly(2,5-benzimidazole)–Poly(vinylphosphonic Acid) Acid–Base Polymer Blends: a Detailed Solid-State NMR Investigation

The present study aims at understanding the molecular structure and dynamics of the acidic polymer poly(vinylphosphonic acid) (PVPA) blended with the basic polymer poly(2,5-benzimidazole) (ABPBI) under anhydrous conditions. The extent of the acid–base complexation is probed at different mixing ratios. Advanced 1H, 13C, and 31P solid-state NMR methods are used to investigate the structural features in these systems. In addition, molecular dynamics is studied by variable-temperature 1H magic angle spinning and one-dimensional double-quantum NMR methods. Many different types of hydrogen-bonding are identified in the acid–base complexes. Addition of the acidic PVPA to the basic ABPBI changes the molecular packing arrangements of the ABPBI moieties with hydrogen-bond formation as the driving force. The complex with a 1:1 mixing ratio has the lowest activation energy for proton mobility, and at the same time contains the most structured hydrogen-bonded protons. The results show that molecular-level mixing is achieved for the complexes.