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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
Author(s) -
Rahman M. Mizanur,
Czaun Miklós,
Takafuji Makoto,
Ihara Hirotaka
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701302
Subject(s) - monomer , atom transfer radical polymerization , polymerization , alkylation , polymer chemistry , chemistry , chemical engineering , materials science , organic chemistry , polymer , catalysis , engineering
Abstract The monomer N ′‐octadecyl‐ N α ‐(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 π–π 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.