Determination Of Chemical Composition Distribution Research Articles

Determination of Chemical Composition Distribution and Molecular Weight Distribution of Poly(2-(perfluoroalkyl)ethyl acrylate-co-alkyl acrylate) by High Performance Liquid Chromatography and Size Exclusion Chromatography

The molecular weight distribution (MWD) of poly(2-(perfluoroalkyl)ethyl acrylate-co-alkyl acrylate) can be determined by size exclusion chromatography (SEC) using an appropriate mobile phase such as a mixture of HCFC225 and THF; however, the chemical composition distribution (CCD) of the copolymer has not been elucidated. We developed an HPLC method for determining the CCD by using a silica-based column modified by polyfluorinated groups, a devised mobile phase gradient system, and an evaporative light scattering detector. In this system, polymers having perfluoroalkyl units are retained on the column through interaction between fluorinated groups and elute at longer retention times. It has become apparent that the copolymer has a broad and characteristic CCD of three components, consisting of fluorinated and non-fluorinated forms and their copolymer. Two-dimensional development of MWD and CCD of the copolymer, called cross-fractionation, is also examined and discussed.

Determination of chemical composition distribution of poly(methyl methacrylate)- graft-polystyrene prepared from ω- p-vinylbenzyl polystyrene macromonomer by adsorption high-performance liquid chromatography

Chemical composition distributions (CCDs) of poly(methyl methacrylate)- graft-polystyrene samples with different compositions and conversions synthesized from methyl methacrylate and ω-vinylbenzyl polystyrene macromonomer were determined by high-performance liquid chromatography using both reversed-phase and normal-phase adsorption modes. The good agreement between CCDs obtained by both modes showed that the molecular-weight effect on the CCDs is negligible. All samples have broad CCDs. As the macromonomer content increases, the CCD becomes sharper. These results are in accordance with the theoretical predictions. As the conversion increases at the same feed composition, the CCD becomes broader towards the low-macromonomer-content side, which is in contrast to the CCDs of the samples obtained previously from ω-methacryloyl polystyrene macromonomer

Composition distribution separation of methyl methacrylate-methacrylic acid copolymers by normal-phase gradient elution high-performance liquid chromatography

The characterization of copolymers requires the determination of chemical composition distribution in addition to molecular mass ( M) distribution. Techniques commonly applied to copolymer analysis provide either average bulk composition or a convolution of M and composition distributions. The application of gradient elution adsorption chromatography, under appropriate conditions, allows the separation of copolymers based solely upon their chemical composition in a M-independent mode. Separation independent of M requires the elimination of size-exclusion effects with the porous adsorbent and the minimization of precipitation contributions. For separation over a wide copolymer composition range, the relative contributions of adsorption and precipitation retention mechanisms change with solvent composition. Under gradient elution conditions where adsorption retention dominates, composition fractionation can be combined with subsequent size-exclusion chromatography to provide a complete composition/ M map of the copolymer.

Determination of chemical composition distribution of poly(methyl methacrylate)-graft-polystyrene by adsorption high-performance liquid chromatography

Three poly(methylmethacrylate)-graft-polystyrene samples of different compositions at low conversions and four samples obtained at different conversions from the same monomer feed compositions were separated and analyzed by HPLC using reversed-phase combination of an octadecyl-modified silica gel column and a linear gradient of THF and acetonitrile. The samples were eluted from components of high MMA content to components of low MMA content. The chromatograms were converted to chemical composition distributions using three samples of different compositions as standards by the optimization method

Determination of chemical composition distribution of styrene-methyl methacrylate copolymers by reversed-phase high-performance liquid chromatography

Preparation de copolymeres de composition et de masse moleculaire differentes. Utilisation d'un melange CH 2 Cl 2 -CH 3 (n) pour eluant et d'un gel de polystyrene comme phase stationnaire. Etude de l'influence de la masse moleculaire des copolymeres sur la separation: elargissement des pics par diminution de la masse moleculaire. Temps de retention augmentant avec la teneur en styrene

Determination of chemical composition distribution of styrene—methyl methacrylate copolymers by reversed-phase high-performance liquid chromatography

Determination of chemical composition distribution of styrene—methyl methacrylate copolymers by reversed-phase high-performance liquid chromatography

Determination of Chemical Composition Distribution in a High-Conversion Copolymer of Styrene and Methyl Acrylate by Cross Fractionation

The chemical composition distribution (CCD) of a high-conversion copolymer of styrene and methyl acrylate was determined by cross fractionation and compared with theoretical CCD. Two systems of chloroform–cyclohexane and 2-hydroxyethyl methyl ether–methanol were found to be appropriate for the cross fractionation of the copolymer. It was shown that CCD, determined by cross fractionation, is in fairly good agreement with the value calculated from the classical theory of copolymerization. What is called the gel-effect appears to be negligible in CCD.