Search results for "Gee"
showing 10 items of 639 documents
Triggering a transient organo-gelation system in a chemically active solvent
2021
A transient organo-gelation system with spatiotemporal dynamic properties is described. Here, the solvent actively controls a complex set of equilibria that underpin the dynamic assembly event. The observed metastability is due to the in situ formation of a secondary solvent, acting as an antagonist against the primary solvent of the organogel. peerReviewed
Multinuclear and Solid State NMR of Gels
2020
Over the past six decades, nuclear magnetic resonance spectroscopy has been an integral part of synthetic organic and organometallic chemistry, as well as biochemistry. Beyond solution state experiments, increasing developments have opened new avenues to study materials in their solid state. Between two extremes (i.e., solution and solid), there exist several other forms of materials, especially soft materials such as gels and liquid crystals. Traditionally gels have been studied using solution state NMR spectroscopic methods. However, the viscosity of complex viscoelastic fluids such as gels affects the molecular tumbling, which in turn affects the chemical shift anisotropy and dipolar and…
Gelation and gel properties of two- and three-component pyrene based low molecular weight organogelators
2011
The research described in this thesis covers the synthesis, characterization and the study of the gelation ability of fteen pyrene based low molecular weight organogelators (LMOGs). The gelation and gel properties were investigated by rheometry, scanning electron microscopy, di erential scanning calorimetry, UV-Vis and uorescence spectroscopy. The pyrene based LMOGs form complexes with 2,4,7-trinitro uorenone (TNF) and self-assemble non-covalently through - stacking, donor-acceptor and van der Waals interactions to form thermoreversible gels, which remain stable at least for two years. The strongest gels were obtained in primary alcohols whereas the poor solubility of TNF restricted gelatio…
Multivalent N-donor ligands for the construction of coordination polymers and coordination polymer gels
2018
This work describes the synthesis and characterisation of several multivalent N-donor ligands and their coordination compounds and the use of these ligands in the construction of coordination polymers and coordination polymer gels. The project can be divided into two parts. The first part of the research is focused on the coordination chemistry of ring-substituted biimidazoles in acidic media. The dependence of the formation of ion pairs and zwitterionic, especially zinc and copper containing coordination compounds on the pH of the reaction medium and ring-substituents of the ligand were examined. The second part of the study deals with the preparation of Ag, Zn and Cu coordination polymers…
The Effect of the Side Chain on Gelation Properties of Bile Acid Alkyl Amides
2021
Abstract Six bile acid alkyl amide derivatives were studied with respect to their gelation properties. The derivatives were composed of three different bile acids with hexyl or cyclohexyl side chains. The gelation behaviour of all six compounds were studied for 36 solvents with varying polarities. Gelation was observed mainly in aromatic solvents, which is characteristic for bile‐acid‐based low molecular weight gelators. Out of 108 bile acid‐solvent combinations, a total of 44 gel systems were formed, 28 of which from lithocholic acid derivatives, only two from deoxycholic acid derivatives, and 14 from cholic acid derivatives. The majority of the gel systems were formed from bile acids with…
Nanoscale probing of the supramolecular assembly in a two‐component gel by near‐field infrared spectroscopy
2023
The design of soft biomaterials requires a deep understanding of molecular self-assembly. We introduce here a nanoscale infrared (IR) spectroscopy study of a two-component supramolecular gel to assess the system´s heterogeneity and supramolecular assembly. In contrast to far-field IR spectroscopy, near-field IR spectroscopy revealed differences in the secondary structures of the gelator molecules and non-covalent interactions at three distinct nano-locations of the gel network. A β-sheet arrangement is dominant in single and parallel fibres with a small proportion of an α-helix present, while the molecular assembly derives from strong hydrogen bonding. However, at the crossing point of two …
Diversity at the nanoscale : laser-oxidation of single-layer graphene affects Fmoc-phenylalanine surface-mediated self-assembly
2023
We report the effects of a laser-oxidized single layer graphene (SLG) surface on the self-assembly of amphiphilic gelator N-fluorenylmethoxycarbonyl-L-phenylalanine (Fmoc-Phe) towards an gel–SLG interface. Laser oxidation modulates the levels of hydrophobicity/hydrophilicity on the SLG surface. Atomic force, scanning electron, helium ion and scattering scanning nearfield optical microscopies (AFM, SEM, HIM, s-SNOM) were employed to assess the effects of surface properties on the secondary and tertiary organization of the formed Fmoc-Phe fibres at the SLG–gel interface. S-SNOM shows sheet-like secondary structures on both hydrophobic/hydrophilic areas of SLG and helical or disordered structu…
Rapid Self-Healing and Thixotropic Organogelation of Amphiphilic Oleanolic Acid–Spermine Conjugates
2021
Natural and abundant plant triterpenoids are attractive starting materials for the synthesis of conformationally rigid and chiral building blocks for functional soft materials. Here, we report the rational design of three oleanolic acid–triazole–spermine conjugates, containing either one or two spermine units in the target molecules, using the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. The resulting amphiphile-like molecules 2 and 3, bearing just one spermine unit in the respective molecules, self-assemble into highly entangled fibrous networks leading to gelation at a concentration as low as 0.5% in alcoholic solvents. Using step-strain rheological measurements, we show ra…
Kemiallisten ja fysikaalisten ärsykkeiden vaikutus supramolekulaaristen geelien muodostumiseen ja geelin rakenteeseen
2016
Tutkielman kirjallisessa osassa perehdyttiin siihen, kuinka kemialliset ja fysikaaliset tekijät vaikuttavat geelin muodostukseen ja siihen, kuinka näillä ärsykkeillä voidaan vaikuttaa geelin rakenteeseen, ominaisuuksiin tai olomuotoon. Kokeellisessa osassa tutkittiin kuinka jäähtymisprofiilin vaikutusta geelinmuodostuksen nopeuteen ja geelin rakenteeseen. Kokeissa käytettiin gelaattorina koolihapon ja L-metioniinimetyyliesterin amidia, joka liuotettiin ultraäänikäsittelyn ja lämmityksen avulla eri liuottimiin, jotka olivat o-ksyleeni, tolueeni, bentseeni ja tert-butyylibentseeni. Pääasiallisena tutkinnan kohteina olivat tolueenin, bentseenin ja tert-butyylibentseenin ja gelaattorin muodosta…
Probing the self-assembly and anti-glioblastoma efficacy of a cinnamoyl-capped dipeptide hydrogelator
2022
Herein, we introduce the first diphenylalanine dipeptide hydrogelator capped with the cinnamoyl functional group (Cin-L-F-L-F). We evaluate the effects of the cinnamoyl moiety on molecular self-assembly events and resultant physical properties of the hydrogel formed. In addition, we report our preliminary results of this dipeptide's cytotoxicity against glioblastoma (GBM) cancer cells. peerReviewed