Separation of minor macromolecular constituents from multicomponent polymer systems by means of liquid chromatography under limiting conditions of enthalpic interactions

Comprehensive Molecular Characterization of Complex Polymer Systems by Sequenced Two-Dimensional Liquid Chromatography. Principle of Operation

“…The concentrations or volumes of sample introduced into the 1-d column in the course of particular injections are so adjusted that the polymer detection of the 2-d column effluent is feasible. The group of methods which well fulfill the above conditions for the first-dimension separation is liquid chromatography under limiting conditions of enthalpic interactions (LC LC). ,− LC LC utilizes the significantly different elution rates of small, pore-permeating solvent molecules and large, partially or fully pore-excluded macromolecules. Appropriately chosen slowly eluting low-molecular-mass substances promote interactions of certain macromolecules in the chromatographic system.…”

“…The most suitable so far tested LC LC approach employs adsorption retention mechanism. It is denoted liquid chromatography under limiting conditions of desorption (LC LCD). ,− In the well-flexible LC LCD arrangement, mobile phase promotes SEC elution of all sample constituents. A narrow zone of adsorption promoting liquid, an adsorli, is injected prior to sample.…”

Separation of Parent Homopolymers from Nonpolar Block Copolymers by Means of Liquid Chromatography under Limiting Conditions of Enthalpic Interactions

“…[3,[15][16][17] The important advantage of LC LCD is its applicability to complex polymer systems, which contain very low, even less than 1% of macromolecular additive. [18] LC LCD proved high efficiency in the practical one-step baseline separation of two to four [17][18][19] component blends of homopolymers, in discrimination of low-solubility polymers, [20] macromolecules according to their tacticity, [21] and, especially, in division of parent homopolymers from the block copolymers containing at least one polar chain. [22][23][24][25][26][27][28][29][30][31] Enthalpic partition (absorption) and solubility (phase separation) retention mechanisms were so far used only tentatively, and the resulting methods are denoted as LC under limiting conditions of unpartition (LC LCU) [32] and LC under limiting conditions of insolubility (LC LCI), [33][34][35] respectively.…”

Liquid Chromatography under Limiting Conditions of Desorption IV. Separation of Macromolecules According to Their Stereoregularity

“…30,31 LC LCD was used in the separation of minor (<1%) macromolecular admixtures from the major constituents of polymer blends including parent homopolymers from the diblock copolymers. [32][33][34] The method was shown to exhibit low dependance from the eluent composition, which provides its increased experimental feasibility. Further, the sample recovery of LC LCD was very high or even complete and the narrow, focused peaks were produced.…”

“…36,37 High selectivity of the LC LCD separations was attained when the difference was relatively large in adsorptivity of unlike polymer chains in model polymer blends and in block copolymers that contained parent homopolymers. [32][33][34] It was of interest to evaluate the LC LCD behavior of such macromolecules that exhibit only a minute difference in their adsorptivity and to attempt extension of the method applicability also to separation of polymers according to their tacticity. The selected highly stereoregular poly(methyl methacrylate)s and poly(ethyl methacrylate)s served as appropriate models.…”