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Modified data handling for rapid low‐field nuclear magnetic resonance characterization of lyotropic liquid crystal composites
Author(s) -
Nadakatti Suresh M.
Publication year - 1999
Publication title -
journal of surfactants and detergents
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.349
H-Index - 48
eISSN - 1558-9293
pISSN - 1097-3958
DOI - 10.1007/s11743-999-0100-9
Subject(s) - chemistry , composite number , phase (matter) , characterization (materials science) , spectrometer , composite material , liquid crystal , isotropy , lyotropic liquid crystal , analytical chemistry (journal) , materials science , chromatography , optics , nanotechnology , optoelectronics , organic chemistry , physics
Abstract A refined nuclear magnetic resonance (NMR) technique was developed to determine the relative volumetric proportions of various phases present in lyotropic liquid crystal (LLC) composites such as soap/detergent bars. Conventionally, the FID (free induction decay, referred to hereafter as Method 1) technique is used for analysis of these systems. This technique is suitable only for composites containing a high concentration of solids and liquid crystals. Method 1 gives erroneous results for composites with a high proportion (>10%) of isotropic liquid phase ( L 1 ). The procedure currently practiced (Method 2) for analyzing systems containing >10% L 1 entails a considerable amount of experimental and analysis time and involves subjectivity in data analysis. Typically, the phase characterization of the composite using conventional low‐field NMR techniques takes more than 1 h. Furthermore, the hardware and data acquisition features of currently available conventional low‐field NMR spectrometers are inadequate for accurate estimation of relative phase volumes in LLC composites. We developed a modified data‐handling technique (FID—Carr‐Purcell‐Meiboom‐Gill technique, or FIDCPMG technique) which enabled rapid phase characterization of LLC composites and minimized subjectivity while analyzing the data. The standard design of a conventional low‐field NMR spectrometer was upgraded by incorporating a high‐power transmitter and a fast digitizer. The phase composition of four model LLC composites (with L 1 percentages varying from 7 to 90%) was determined using FIDCPMG technique and was compared with results from conventional techniques. Phase composition of the LLC composite could be determined in less than 5 min.