Applications of the critical phenomena concept in liquid chromatography for functionally type separation of macromolecules

Effect of Block Copolymer Chain Architecture on Chromatographic Retention

“…This is realized if the visible block is more interactive with the stationary phase than the invisible block. Since the elution condition needs to be fixed at the critical condition for the block made invisible , the application is limited to rather short visible block lengths (or end-group analysis) due to the exponential dependence of the retention on the chain length (Martin's rule). − The other method is to elute the block copolymers in the size exclusion regime (eluting before the injection solvent peak) if the visible block is less interactive with the stationary phase. The majority of the LCCC applications to the characterization of block copolymers have been made in this mode, and the molecular weight distribution of the block of interest is determined by the standard calibration method commonly used in SEC. ,− …”

Characterization of Polystyrene-b-polyisoprene Diblock Copolymers by Liquid Chromatography at the Chromatographic Critical Condition

“…At this condition the retention of the homopolymer would become independent of molecular weight. The study on this interesting feature was started in the 1970s, , which has been supported by a number of experimental studies ,− although there remains some controversy as to whether such a precise coelution condition indeed exists. , Furthermore, other anomalies such as limited recovery for high molecular weight polymers as well as peak broadening and/or splitting have been reported at the critical condition. , Nevertheless, the critical condition has been successfully employed for the chromatographic separation of the components in polymer blends , and for the separation of polymers with respect to the terminal functional group. ,,− This technique is variously termed: liquid chromatography at the critical condition (LCCC), liquid chromatography at the point of exclusion−adsorption transition (LC-PEAT), or liquid chromatography at the critical adsorption point (LC-CAP). Another interesting application of the technique is the characterization of block copolymers. ,− The application is based on the assumption that a block at the critical condition is chromatographically “invisible”, and the retention of the block copolymer is supposed to be governed solely by the other blocks in the block copolymer.…”

“…This is realized if the block is more interactive with the stationary phase than the “invisible” block. Since the elution condition needs to be fixed at the critical condition for the block made “invisible”, the applications are limited to end group analysis or to rather short block lengths, due to the exponential dependence of the retention on the chain length. ,,,− The other separation mode is to elute the block copolymers in the size exclusion regime (eluting before the system peak) in terms of the block length of the block(s) to be analyzed if the “visible” block is less interactive with the stationary phase. Most of the LCCC applications to the characterization of block copolymers have been made in the latter mode, and the determination of the molecular weight distribution of the block of interest has been made using the standard calibration method commonly used in size exclusion chromatography. ,− For example, Zimina et al used the standard calibration method to examine the PS fraction of polystyrene/poly(methyl methacrylate) diblock copolymers (PS- b -PMMA) under the critical condition of PMMA .…”

“…8,14 Nevertheless, the critical condition has been successfully employed for the chromatographic separation of the components in polymer blends 15,16 and for the separation of polymers with respect to the terminal functional group. 6,11,[17][18][19] This technique is variously termed: liquid chromatography at the critical condition (LCCC), liquid chromatography at the point of exclusionadsorption transition (LC-PEAT), or liquid chromatography at the critical adsorption point (LC-CAP). Another interesting application of the technique is the characterization of block copolymers.…”

Chromatographic Analysis of Structural Elements of Molecular Polyimide Brushes with Polymethacrylate Side Chains

“…[15,[24][25][26][27][28][29][30][31][32] These issues are the best documented from both experimental and theoretical viewpoints by Evreinov, Entelis et al [24][25][26] In papers by Gorbunov et al, [30,31] the theory of liquid chromatography for linear and cyclic mono-and bifunctional macromolecules was developed. [15,[24][25][26][27][28][29][30][31][32] The fact that the retention of macromolecules is independent on their molecular weight under [21] and polarity index Р' [22] ). [33,34] Cleaved PMMA sc and PTBMA sc isolated after a complete alkaline hydrolysis of the backbone of PI-g-PMMA and PI-g-PTBMA polyimide brushes are presumably linear macromolecules with two functional polar groups at both ends, these functional groups being adsorption-active unlike middle monomer units with side ester moieties.…”