Liquid crystalline polymers as stationary phases: IV. Chemical bonding and immobilization of the polymer on silica characterization by solid-state nuclear magnetic resonance spectroscopy

• Published in: Journal of Chromatography A Vol. 922; no. 1; pp. 37 - 50
• Main Authors: Gritti, F, Terrien, I, Menu, S, Dufourc, E.J, Félix, G, Achard, M.-F, Hardouin, F
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 13-07-2001; Elsevier
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Crystallization; Exact sciences and technology; Liquid crystalline polymers; Magnetic Resonance Spectroscopy - methods; Other chromatographic methods; Polycyclic Compounds - isolation & purification; Polymers - chemistry; Silicon Dioxide - chemistry; Immobilization; Chemical bonding; Liquid crystalline polymers; Stationary phases, LC; Performance evaluation; Hydrocarbon; Carotene; Cross polarization; HPLC chromatography; Hydrosilylation; NMR spectrometry; Polycyclic aromatic compound; Experimental study; Magic angle; Characterization; Solid state; Silicon 29; Efficiency; Liquid crystal polymers; Fullerenes; Silica gel; Carotenoid; Siloxane polymer; Carbon 13; Bonded stationary phase; Modified material; Ultraviolet visible spectrometry
• ISSN: 0021-9673
• DOI: 10.1016/S0021-9673(01)00886-X

Chemical bonding reaction and immobilization through low energy radiation (heating) have been investigated to fix a side-chain liquid crystalline polymer (SC-LCP) on silica particles in order to use the resulting modified silica in normal-phase HPLC. Highly stable chromatographic stationary phases are observed under excellent polymer solvent flow conditions (THF) for both methods and better column efficiencies are also exhibited towards PAHs’ separation compared to the classical coated stationary phase. The characterization of these new stationary phases and the rationale for improved column stability have been investigated by solid state
13C and
29Si CP/MAS NMR spectroscopy. It is clearly shown that the chemical bonding is achieved by the classical hydrosilylation reaction between PHMS chains and vinyl modified silica. The bonded polymer is likely a copolymer than a homopolymer. The immobilization of the SC-LCP by heating results in the breaking of Si–O–Si bonds of the polysiloxane chain after the attack of the silica surface silanols. Applications to fullerenes and carotenes separation of these bonded stationary phases are compared to the separation power of a classical monomeric C
18 stationary phase in NP-HPLC as
n-hexane–toluene or methyl-tertiobutyl ether–methanol mixtures.