Synthesis, self-assembling properties, and atom transfer radical polymerization of an alkylated L-phenylalanine-derived monomeric organogel from silica: a new approach to prepare packing materials for high-performance liquid chromatography.
The monomer N'-octadecyl-N(alpha)-(4-vinyl)-benzoyl-L-phenylalanineamide (4) based on L-phenylalanine has been simply but effectively synthesized, and its self-assembling properties have been investigated. FTIR and a variable-temperature (1)H NMR spectroscopic investigation demonstrated that the aggregation of compound 4 in various organic solvents is due to the formation of intermolecular hydrogen bonds among the amide moieties. UV/Vis measurements indicated that the multiple pi-pi interactions of the phenyl groups also contribute to the self-assembly. As was observed by (13)C cross-polarization magic-angle spinning (CP/MAS) NMR and variable-temperature (1)H NMR measurements, the ordered alkyl chains also played an important role in the molecular aggregation by van der Waals interactions. Compound 4 was polymerized by surface-initiated atom transfer radical polymerization from porous silica gel to prepare a packing material for HPLC. The results of thermogravimetric analysis showed that a relatively large amount of polymer was grafted onto the silica surface. The organic phase on silica was in a noncrystalline solid form in which the long alkyl chain exists in a less-ordered gauche conformation. Analysis of chromatographic performance for polyaromatic hydrocarbon samples showed higher selectivity than conventional reversed-phase HPLC packing materials.
Rahman
M Mizanur
MM
Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto 860-8555, Japan.
Czaun
Miklós
M
Takafuji
Makoto
M
Ihara
Hirotaka
H
D000478:Alkylation; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation* / Q000379:methods; D005782:Gels; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013818:Thermogravimetry
D005782:Gels; C527857:N'-octadecyl-N(alpha)-(4-vinyl)-benzoyl-L-phenylalanineamide; D011108:Polymers; D010649:Phenylalanine; C020457:phenylalanine amide; D012822:Silicon Dioxide