Characterization of Linear and 3‐Arm Star Block Copolymers by Liquid Chromatography at Critical Conditions

Abstract

Summary: LCCC for polyMA homopolymers was established in order to analyze the polyMA‐polySt linear and star block copolymers. The validity of the assumption that under the LCCC for polyMA, the polyMA segment in the polyMA‐containing block copolymer is chromatographically “invisible” was verified. It was found that within the scale of investigation ($\overline M _{{\rm n},{\rm polyMA}} \leq 5\;\overline M _{{\rm n},{\rm polySt}}$), the molecular weight and architecture of the polyMA segments had no evident influence on the retention behavior of the polySt‐polyMA block copolymers and the polyMA block in the copolymer was “invisible”. The critical conditions of polyMA were used for quantitative analysis of the polySt block in the linear and 3‐arm star polyMA‐polySt block copolymers, which were synthesized by AGET ATRP in miniemulsion. It was shown that the copolymer had completely different elution peak from its MI. The calculated molecular weights of polySt blocks in the block copolymers were similar to those obtained from normal SEC analysis. Transferring the eluates from the LCCC (the first dimension) column to a SEC column (the second dimension) produced LCCC × SEC two‐dimensional chromatogram, which contained information on both chemical composition and molecular weight of the synthesized copolymers. The combination of these liquid chromatography methods clearly confirmed the high initiation efficiency of the polyMA MIs during the synthesis of block copolymers and the presence of a byproduct formed by radical‐radical coupling. magnified image

Biotin‐, Pyrene‐, and GRGDS‐Functionalized Polymers and Nanogels via ATRP and End Group Modification

“…Gradient polymer elution chromatography (GPEC) is a powerful tool for the characterization and separation of the polymers 66, 81, 87. When the diazide and di‐biotin‐functionalized PSt were analyzed by normal GPC, an apparent decrease in molecular weight was observed, even though the addition of biotin caused by an increase in the apparent molecular weight (Figure 10).…”

Transformation of macromonomers into ring‐opening polymerization macroinitiators: A detailed initiation efficiency study

“…A similar situation occurs—yet vice versa—at the critical conditions of block B. LCCC characterization thus leads to a more detailed visualization of the block building efficiency since the block segment elutes at different retention times. In the literature LCCC as powerful characterization method, especially hyphenated with SEC, has been employed by several research groups for a detailed analysis method of (block) copolymers 22–30. In work related to this study, Roos et al synthesized block copolymers with a poly( n ‐butyl acrylate) (pBA) segment and analyzed them via liquid chromatography at critical conditions 31.…”

Synthesis of 3‐Arm Star Block Copolymers by Combination of “Core‐First” and “Coupling‐Onto” Methods Using ATRP and Click Reactions

“…Since hydroxyl‐terminated PS polymers can be efficiently separated by the GPEC technique based on the number of hydroxyl groups per polymer molecule,38, 40 the analysis of the coupling product between (PS‐N 3 ) 3 and propargyl alcohol can quantitatively determine the distribution of the azido functionality on the 3‐arm PS star polymers. It is worth noting that liquid adsorption chromatography36, 41, 42 is currently the only method to evaluate the distribution of chain‐end functionality of telechelic polymers while the traditional analytical techniques, such as NMR, UV‐vis spectroscopy, can only determine the average functionality per polymer molecule.…”