Imidazolium ionic liquids as fracture toughening agents in DGEBA-TETA epoxy resin

Although epoxy resins are used in a broad variety of applications due to their good mechanical and thermal properties, their low fracture toughness is a limitation, exhibiting brittle behavior. This study explored the potential use of imidazolium ionic liquids (IL) as toughening agents for epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) with triethylenetetramine (TETA) as curing agent. Fracture toughness was evaluated for DGEBA-TETA epoxy resins with eleven imidazolium IL and the best results were found for the IL with the chloride anion and the shortest N-alkyl side chain, C4MImCl. The use of 1.0 phr of C4MImCl lead to the reduction of the crosslink density of the post-cured resin, resulting in the increase of 25.5% in stress intensity factor and 8.2% in tensile strength with no significant loss in other mechanical properties

Epoxy-based composites reinforced with imidazolium ionic liquid-treated aramid pulp

Two types of physisorbed imidazolium ionic liquids (IL), 1-n-butyl-3-methylimidazolium chloride (C4MImCl) or 1-n-butyl-3-methylimidazolium acetate (C4MImAc), were used for the surface treatment of polyaramid pulp (AP), aiming to enhance the interaction with an epoxy matrix. The treatments promoted a greater defibrillation of AP, which was most likely due to an interference of IL in the hydrogen bonding network of polyaramid. Composites of AP/epoxy (0.2, 0.4 or 0.6 parts per hundred of resin (phr)) were prepared, and those with 0.4 phr of IL-treated AP presented enhanced mechanical properties, compared to the neat or the untreated AP com-posites. Better homogeneity and stronger bonding between AP and the epoxy matrix were also observed, especially in the case of AP treated with C4MImCl. Moreover, the AP surface treatment increased the glass transition temperature and the storage moduli in both glassy and rubbery regions. The fracture toughness improvement of the composites was also achieved with the addition of the IL-treated AP

Imidazolium ionic liquids as compatibilizer agents for microcrystalline cellulose/epoxy composites

Four imidazolium-based ionic liquids (IL; 1-butyl-3-methylimidazolium chloride, 1-carboxymethyl3-methylimidazolium chloride, 1,3-dicarboxymethylimidazolium chloride and 1-(2-hydroxyethyl)- 3-methylimidazolium chloride) were tested as compatibilizers of microcrystalline cellulose (MCC). Subsequently, ethanolic IL solutions were prepared; MCC was mixed, and the mixtures were left to evaporate the ethanol at ambient conditions. These modified MCC were characterized and applied as reinforcements (5.0 and 10 phr) in an epoxy resin aiming to manufacture biobased composites with enhanced performances. The IL did not significantly modify the morphological and structural characteristics of such reinforcements. Regarding the thermal stability, the slight increase was associated with the MCC-IL affinity. The IL-modified MCC-epoxy composites presented improved mechanical responses, such as flexural strength (≈22.5%) and toughness behavior (≈18.6%), compared with pure epoxy. Such improvement was also obtained for the viscoelastic response, where the storage modulus at the glassy state depended on the MCC amount and IL type. These differences were associated with stronger hydrogen bonding between IL and epoxy hardener or the IL with MCC, causing a “bridging” effect between MCC and epoxy matrix

Avaliação in vitro do potencial antifúngico de sais imidazólicos frente a Candida albicans

Aim: This study aims to evaluate the antifungal potential of imidazolium salts (IS) against Candida albicans. Material and methods: Antifungal evaluation of the IS was performed using the disk diffusion test, using a strain of Candida albicans (ATCC 90028). Five different IS were synthesized and tested in the present study: 1,8-bis(methylimidazolium-1-yl) octane bromide (MImC8MImBr2), 1,12-bis(methylimidazolium-1-yl) dodecane methanesulfonate (MImC12MIm(MeS)2), 1-n-hexadecyl-2,3-dimethylimidazolium chloride (C16DMImCl), 1,10-bis(methylimidazolium-1-yl) decane methanesulfonate (MImC10MIm(MeS)2) e 1,10-bis(methylimidazolium-1-yl) decane bromide (MImC10MImBr2). Cetylpyridinium chloride (C16PyrCl) was used as a reference substance. Chlorhexidine (C34H54Cl2N10O14) and saline (NaCl 0,9%) solutions were positive and negative controls, respectively. Results: Among the tested IS, MImC12MIm(MeS)2, MImC10MIm(MeS)2 and MImC10MImBr2 showed the following values for inhibition halos: 28,00 mm, 20,50 mm and 18,75 mm, respectively. These values were similar or superior than those found for the positive control (14.87 mm) and reference (0 mm) substances. Discussion: IS can be a promising alternative to antifungal conventional therapies, as exemplified in previous studies. However, further in vitro and in vivo studies are needed to assess the antifungal potential of these compounds against Candida-mixed biofilms. Conclusion: Based on these results, there are three in vitro promising antifungal potential against Candida albicans IS tested in this study.Objetivo: O objetivo deste estudo foi avaliar o potencial antifúngico de um conjunto de sais imidazólicos (SI) frente a Candida albicans. Materiais e métodos: A avaliação antifúngica dos SI foi realizada por meio do teste de difusão em ágar, utilizando uma cepa de Candida albicans (ATCC 90028). Cinco diferentes SI foram sintetizados e testados no presente estudo: brometo de 1,8-bis(metilimidazólio-1-il) octano (MImC8MImBr2), metanossulfonato de 1,12-bis(metilimidazólio-1-il) dodecano (MImC12MIm(MeS)2), cloreto de 1-n-hexadecil-2,3-dimetilimidazólio (C16DMImCl), metanossulfonato de 1,10-bis(metilimidazólio-1-il) decano (MImC10MIm(MeS)2) e brometo de 1,10-bis(metilimidazólio-1-il) decano (MImC10MImBr2). O cloreto de cetilpiridíneo (C16PyrCl) foi utilizado como composto de referência e as soluções de digluconato de clorexidina (C34H54Cl2N10O14) e salina (NaCl 0,9%) foram utilizadas como controles positivo e negativo, respectivamente. Resultados: Dentre os SI testados, MImC12MIm(MeS)2, MImC10MIm(MeS)2 e MImC10MImBr2 apresentaram os seguintes valores para os halos de inibição formados: 28,00 mm, 20,50 mm e 18,75 mm, respectivamente. Esses valores foram similares ou superiores inclusive aos encontrados para o controle positivo (14,87 mm) e o composto de referência (0 mm). Discussão: Os SI podem apresentar uma alternativa promissora às terapias com antifúngicos convencionais, concordando com estudos prévios. Entretanto, mais estudos in vitro e in vivo são necessários para avaliar o potencial antifúngico destes compostos frente a biofilmes multiespécies de C. albicans. Conclusão: Baseado nestes resultados, três dos SI testados apresentam atividade antifúngica in vitro promissora frente à Candida albicans

Imidazolium salts as an alternative for anti-Leishmania drugs: Oxidative and immunomodulatory activities

In this study we explored the previously established leishmanicidal activity of a complementary set of 24 imidazolium salts (IS), 1-hexadecylimidazole (C16Im) and 1-hexadecylpyridinium chloride (C16PyrCl) against Leishmania (Leishmania) amazonensis and Leishmania (Leishmania) infantum chagasi. Promastigotes of L. amazonensis and L. infantum chagasi were incubated with 0.1 to 100 μM of the compounds and eight of them demonstrated leishmanicidal activity after 48 h – C10MImMeS (IC50L. amazonensis = 11.6), C16MImPF6(IC50L. amazonensis = 6.9), C16MImBr (IC50L. amazonensis = 6), C16M2ImCl (IC50L. amazonensis = 4.1), C16M4ImCl (IC50L. amazonensis = 1.8), (C10)2MImCl (IC50L. amazonensis = 1.9), C16Im (IC50L. amazonensis = 14.6), and C16PyrCl (IC50L. amazonensis = 4).The effect of IS on reactive oxygen species production, mitochondrial membrane potential, membrane integrity and morphological alterations of promastigotes was determined, as well as on L. amazonensis-infected macrophages. Their cytotoxicity against macrophages and human erythrocytes was also evaluated. The IS C10MImMeS, C16MImPF6, C16MImBr, C16M2ImCl, C16M4ImCl and (C10)2MImCl, and the compounds C16Im and C16PyrCl killed and inhibited the growth of promastigote forms of L. amazonensis and L. infantum chagasi in a concentration-dependent manner, contributing to a better understanding of the structure-activity relationship of IS against Leishmania. These IS induced ROS production, mitochondrial dysfunction, membrane disruption and morphological alterations in infective forms of L. amazonensis and killed intracellular amastigote forms in very low concentrations (IC50 amastigotes ≤ 0.3), being potential drug candidates against L. amazonensis