Multidimensional analytical protocols for the fractionation and analysis of complex polyolefins

Abstract

Although produced from simple monomers that contain just carbon and hydrogen, polyolefin have complex molecular structures that are characterized by distributions in molar mass, chemical composition, and branching. Accordingly, a variety of advanced analytical techniques are needed for the comprehensive characterization of the molecular heterogeneity of polyolefins. These include different fractionation, spectroscopic, and thermal analysis methods.Very frequently, method couplings such as two-dimensional liquid chromatography or the coupling of crystallization-and column-based techniques are required. This review presents the current state of the art in multidimensional analysis of complex polyolefins. It discusses methods for bulk analysis as well as different analytical and preparative fractionation protocols. For different types of polyolefins it is shown that a preparative fractionation according to chemical composition/branching or molar mass helps to reduce the molecular complexity of the sample. Sample libraries can be obtained that may have narrow distributions regarding one molecular parameter. A detailed investigation of such library samples regarding other (broadly distributed) molecular parameters helps to fully explore the molecular heterogeneity of a complex sample.

Cost‐efficient modeling of distributed molar mass and topological variations in graft copolymer synthesis by upgrading the method of moments

“…Interestingly, in recent years, several promising 2D-LC systems have been introduced as a powerful analytical technique for complex polymers. [15][16][17][18][19] In 2D-LC, the effluents from the first dimension (1st-D) need to be analyzed by the second dimension (2nd-D) following another (ideally orthogonal) separation mode. Here, one separates copolymers by CCs or by MM of the specific monomer sequences (e.g., PB or PS segments in the context of the present work).…”

“…This requires the development of in-depth structural characterization tools. [11][12][13][14][15][16][17][18][19] The development of such in-depth tools for nonlinear polymers is although nontrivial as their synthesis is reckoned as a complicated chemical modification, displaying conspicuous structural heterogeneities. For GC synthesis this is especially the case if one employs industrially relevant free-radical-induced grafting (FRIG).…”

“…[26][27][28][29] Recent decades have witnessed the rapid development of chromatographic techniques for experimentally resolving the distributions of more complex polymers, although on an overall basis less focus has been on grafted and crosslinked (co)polymers. [15][16][17][18][19] Size-exclusion chromatography (SEC) with, in several cases, multidetection is the most widespread mode of liquid chromatography (LC) for polymer analysis, due to its high efficiency and tendency toward universality. 15,18 Two-dimensional LC (2D-LC) is deemed as more comprehensive but selecting the appropriate chromatographic tools as well as suited detection procedures is not always straightforward and sometimes even impossible.…”

“…15,18 Two-dimensional LC (2D-LC) is deemed as more comprehensive but selecting the appropriate chromatographic tools as well as suited detection procedures is not always straightforward and sometimes even impossible. 16,17,19 The quantitative interpretation of LC responses is also critical, as one may need to unbiasedly translate overall LC data into multiple distributions reflecting the true contribution of separate polymer molecular structures. [30][31][32][33] From a theoretical perspective, several analytical functions for GC distributions have been derived by statistical models relying on the grafting probability concept.…”

Thermomechanical Degradation of Polypropylene – Polystyrene Blends During Extrusion‐Based Melt Blending – A First Survey of Shear‐Induced Molecular Architecture Changes

“…This could not be revealed by using one-dimensional analytical techniques like SEC [25] for measuring the molecular weight distribution change during the degradation (MWD), [17,20] or onedimensional temperature elution fractionation (TREF) [26][27][28] or crystallization analysis fractionation (CRYSTAF), [29][30][31][32][33] which exclusively would determine the chain regularity distribution. [34,35] The structure of this communication is outlined as follows: In the materials and experimental methods section the materials used, the melt-blending process applied and the developed separation strategy and degradation analysis in terms of molecular weight distribution and regularity distribution are explained. In the results and discussion section, the gained bivariate distributions are shown for the blend samples having different PP/PS compositions.…”