Compositional Characterization of AES Blends by Size-Exclusion and Precipitation−Redissolution Liquid Chromatography

Abstract

Chemical composition characterization of blends formed by styrene−acrylonitrile (SAN), ethylene−propylenediene (EPDM) and EPDM-g-SAN copolymer molecules has been performed with size-exclusion chromatography with DRI and UV detectors. With proper detector calibration reliable average composition results were obtained, whereas it has been found that the composition distributions calculated from the chromatogram fractions are affected by large experimental errors. The blend components were successfully separated with precipitation−redissolution liquid chromatography, and an evaporative light scattering detector was found suitable for eliminating baseline drifts in the chromatograms, due to the eluent gradients which had to be employed. The application of evaporative detectors for quantitative measurements, however, appears questionable.

Caraterização composicional do AES - um copolímero de enxertia de poli(estireno-co-acrilonitrila) em poli(etileno-co-propileno-co-dieno)

“…Pesquisas levaram ao terpolímero poli(etileno-co-propileno-co-dieno), EPDM, que apresenta maior resistência à temperatura, à oxidação, à luz, ao oxigênio, ao ozônio e à radiação ultravioleta em comparação com o polibutadieno [4,6,10,11] . Esta substituição gerou o AES, que pode ser obtido por copolimerização radicalar de estireno e acrilonitrila em presença de poli(etileno-copropileno-co-dieno), EPDM [9,12] . Neste processo, ocorre a copolimerização do estireno e da acrilonitrila, formando o SAN, que encontra-se tanto na forma livre como enxertada no EPDM, sendo que uma parte das cadeias de EPDM também permanece livres de SAN [12] .…”

“…Esta substituição gerou o AES, que pode ser obtido por copolimerização radicalar de estireno e acrilonitrila em presença de poli(etileno-copropileno-co-dieno), EPDM [9,12] . Neste processo, ocorre a copolimerização do estireno e da acrilonitrila, formando o SAN, que encontra-se tanto na forma livre como enxertada no EPDM, sendo que uma parte das cadeias de EPDM também permanece livres de SAN [12] . Neste sistema, o copolímero de enxertia atua como um compatibilizante entre as fases imiscíveis de EPDM e de SAN.…”

Microstructural characterization of aromatic copolyesters made by step reactions, by gradient polymer elution chromatography

“…That is why we prefer the generally applicable term Gradient Polymer Elution Chromatography (GPEC) [37][38][39][40][41][42][43] rather than High-Performance Precipitation Liquid Chromatography (HPPLC) 12,18 or Liquid Adsorption Chromatography, 15,16 which refer only to a part of the separation mechanism. It must be emphasized here, that although the combination of SEC with multiple detection such as ultraviolet (UV) and differential refractive index (DRI) detection or with infrared spectroscopy is often used for the detection of polymer inhomogenities, 34,44 this kind of analysis is not capable of providing the CCD. Although useful, such analysis only gives an impression of the average chemical composition as a function of molar mass, saying nothing about the broadness of a CCD and being unable to discriminate between the difference between a polymer blend or a copolymer, which easily leads to misinterpretation.…”

Microstructural characterization of aromatic copolyesters made by step reactions, by gradient polymer elution chromatography

“…For the determination of the CCD, especially gradient HPLC has been shown to be a versatile technique. After first being applied by Teramachi7 the technique has been used by a (still rather limited) number of workers for the structural investigation of statistical copolymers3, 7–25 and, to a lesser extent, of block copolymers26, 27 and graft copolymers 28–34. A combination of at least two solvents is used, one of which is a chromatographically strong displacer and the amount of which is gradually increased in time.…”

“…That is why we prefer the generally applicable term Gradient Polymer Elution Chromatography (GPEC)37–43 rather than High‐Performance Precipitation Liquid Chromatography (HPPLC)12, 18 or Liquid Adsorption Chromatography,15, 16 which refer only to a part of the separation mechanism. It must be emphasized here, that although the combination of SEC with multiple detection such as ultraviolet (UV) and differential refractive index (DRI) detection or with infrared spectroscopy is often used for the detection of polymer inhomogenities,34, 44 this kind of analysis is not capable of providing the CCD. Although useful, such analysis only gives an impression of the average chemical composition as a function of molar mass, saying nothing about the broadness of a CCD and being unable to discriminate between the difference between a polymer blend or a copolymer, which easily leads to misinterpretation 33, 46…”