Refractive index detectors number-average molecular

The determination of the molecular weight of nanoparticles is performed by gel permeation chromatography (GPC). The experimental setup consists of a high performance liquid chromatography system with a size exclusion column and a refractive index detector. The nanoparticles are usually freeze-dried and dissolved in tetrahydrofuran for analysis on the system. Poly(styrene) or poly(methylmethacrylate) standards are used to calibrate the column, to enable the determination of number average molecular weight (Mn), as in... 

The molecular weight and its distribution of prepolymers were determined in THF by gel permeation chromatography (Waters Associates). Four different pore size columns (10, 10, 10 and 10 A i -Styrogels) and a refractive index detector were used. The instrument was calibrated with polyisoprene samples which were prepared similarly in this laboratory and whose number-average molecular weights were determined with a vapor phase osmometer (Wescan, Model 232 A) in toluene at 50 C. 

Instrumentation. Number (MJ and weight (M ) average molecular weights were determined by gel phase chromatography (GPC) using tetrahydrofuran at a flow rate of 1.0 ml/min on a Waters system calibrated witii polystyrene standards and equipped with a refractive index detector. C and H NMR were determined on a Bmcker WM 360 MHz NMR spectrometer and infrared spectra on a Nicolet FTIR-20 spectrometer. 

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