Effect Of Hydrophobic Moieties Research Articles

Effect of Hydrophobic Moieties on the Assembly of Silica Particles into Colloidal Crystals

To boost the implementation of colloidal crystals (CCs) in separation science, the effects of the most common chromatographic reversed phases, that is, butyl and octadecyl, on the assembly of silica particles into CCs and on the optical properties of CCs are investigated. Interestingly, particle surface modification can cause phase separation during sedimentation because the assembly is highly sensitive to minute changes in surface characteristics. Solvent-induced surface charge generation through acid-base interactions of acidic residual silanol groups with the solvent is enough to promote colloidal crystallization of modified silica particles. In addition, solvation forces at small interparticle distances are also involved in colloidal assembly. The characterization of CCs formed during sedimentation or via evaporative assembly revealed that C4 particles can form CCs more easily than C18 particles because of their low hydrophobicity; the latter can only form CCs in tetrahydrofuran when C18 chains with a high bonding density have extra hydroxyl side groups. These groups can only be hydrolyzed from trifunctional octadecyl silane but not from a monofunctional one. Moreover, after evaporative assembly, CCs formed from particles with different surface moieties exhibit different lattice spacings because their surface hydrophobicity and chemical heterogeneity can modulate interparticle interactions during the two main stages of assembly: the wet stage of crystal growth and the late stage of nano dewetting (evaporation of interparticle solvent bridges). Finally, short, alkyl-modified CCs were effectively assembled inside silica capillaries with a 100 μm inner diameter, laying the foundation for future chromatographic separation using capillary columns.

Effect of hydrophobic moiety on the gelation behavior of pyridyl boronic acid-derived amphiphiles: application in entrapment and release of vitamin B12

Low molecular weight organic gelators (LMOGs) have received great attention for their tremendous applications in multiple fields in the past few decades. Therefore, nowadays, synthesis of new type of LMOGs is a demanding field of research. In this work, the effect of hydrophobic moiety on gelation behavior of three synthesized pyridyl boronic acid-derived amphiphiles named sodium, 2-decylpyridine-5-boronate (SDPB), sodium, 2-oxydecylpyridine-5-boronate (SODPB) and sodium, 2-oxydodecylpyridine-5-boronate (SODDPB) has been investigated. The results confirmed that these amphiphiles are good gelators in common organic solvents in the presence of 60 μl of buffer solution and the gelation capability diminished in case of oxygen atom present in the alkyl chain. Further distortion of gelation process was observed with increase of chain length in oxy-alkyl chain. Rheological measurements established that the gel emulsion of SDPB is most stable towards external forces with highest elasticity value. XRD study was performed to analyze the orientation of the alkyl chain in the 3D network structure in the gel emulsions. The morphological changes with respect to concentration were investigated by FE-SEM study of the gel emulsions. The prepared gel emulsions with these amphiphiles are capable to entrap and release the biomolecule vitamin B12 at room temperature keeping the structure and activity unchanged which is indicative that the amphiphiles can be successfully utilized in pharmaceutical industries as drug delivery vehicles.

Effect of Hydrophobic Moieties in Water-Soluble Polymers on Physical Exfoliation of Graphene

Graphene is a fascinating material with unique properties, such as high mechanical strength and excellent electronic and thermal conductivities, as well as many other beneficial properties. Despite much recent effort, the facile synthesis and colloidal stabilization of graphene in aqueous solutions remains central to both academic research and practical applications. Here, we provide an in-depth insight into how the hydrophobic moieties of polymers affect the physical exfoliation of graphite into graphenes in aqueous solution. Four different polymers with graphene-like moieties, such as phenyl- and pyrenyl-functionalized side chains, were synthesized on the basis of the two water-soluble polymers poly(vinyl alcohol) (PVA) and dextran. Simply, sonication of graphite with the polymers in an aqueous solution produced stable graphene dispersions even after centrifugation. The ability of the polymers to exfoliate graphene sheets from the graphite was systematically investigated. Notably, 10 wt % phenyl-PVA led...