The block copolymer shuffle in size exclusion chromatography: the intrinsic problem with using elugrams to determine chain extension success

Philipps, Kai; Junkers, Thomas; Michels, Jasper J.

doi:10.1039/d1py00210d

Cited by 48 publications

(57 citation statements)

References 70 publications

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“…As mentioned previously, the THF GPC traces of the (PNVCL-SH) 6 star polymers generated in dichloromethane (see Figure 1b) were always shifted to longer retention times compared with the main peak of the starting polymer, probably due to the strong interaction of the thiol fragment with the column [24]. As it can be seen, the GPC curve was unimodal, symmetrical and not skewed, although wider as compared to the starting polymer.…”

Section: Aminolysis Of Linear and Star Pnvcl Polymers Containing Xanthate End-groups And Their Transformation Into Polymers Containing Thsupporting

confidence: 70%

Effective End-Group Modification of Star-Shaped PNVCL from Xanthate to Trithiocarbonate Avoiding Chemical Crosslinking

2021

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In this study, six-arm star-shaped poly(N-vinylcaprolactam) (PNVCL) polymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization were subjected to aminolysis reaction using hexylamine. Chemically crosslinked gels or highly end-functionalized star polymers can be obtained depending mainly on the type of solvent used during the transformation of the RAFT functional group. An increase in the viscosity of the solution was observed when the aminolysis was carried out in THF. In contrast, when the reaction was conducted in dichloromethane, chain-end thiol (PNVCL)6 star polymers could be obtained. Moreover, when purified (PNVCL-SH)6 star polymers are in contact with THF, the gelation occurs in just a few minutes, with an obvious increase in viscosity, to form physical gels that become chemically crosslinked gels after 12 h. Interestingly, when purified (PNVCL-SH)6 star polymers were stirred in distilled water, even at high aqueous solution concentration (40 mg/mL), there was no increase in the viscosity or gelation, and no evident gels were observed. The analysis of the hydrodynamic diameter (Dh) by dynamic light scattering (DLS) did not detect quantifiable change even after 4 days of stirring in water. On the other hand, the thiol groups in the (PNVCL-SH)6 star polymers were easily transformed into trithiocarbonate groups by addition of CS2 followed by benzyl bromide as demonstrated by UV-Vis spectroscopical analysis and GPC. After the modification, the (PNVCL)6 star polymers exhibit an intense yellow color typical of the absorption band of trithiocarbonate group at 308 nm. To further demonstrate the highly effective new trithiocarbonate end-functionality, the PNVCL polymers were successfully chain extended with N-isopropylacrylamide (NIPAM) to form six-arm star-shaped PNIPAM-b-PNVCL block copolymers. Moreover, the terminal thiol end-functionality in the (PNVCL-SH)6 star polymers was linked via disulfide bond formation to l-cysteine to further demonstrate its reactivity. Zeta potential analysis shows the pH-responsive behavior of these star polymers due to l-cysteine end-functionalization. By this using methodology and properly selecting the solvent, various environment-sensitive star polymers with different end-groups could be easily accessible.

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Section: Aminolysis Of Linear and Star Pnvcl Polymers Containing Xanthate End-groups And Their Transformation Into Polymers Containing Thsupporting

confidence: 70%

Effective End-Group Modification of Star-Shaped PNVCL from Xanthate to Trithiocarbonate Avoiding Chemical Crosslinking

2021

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“…This initial shift towards lower apparent molecular weights has to be overcome by growing the polystyrene chain by a given amount of units before the measured "net" trace is shifted in the expected direction with respect to the original macroCTA. Indeed, an analogous situation is described for highly incompatible block copolymer systems in the previously cited work, 52 where the elution time initially increases as the block copolymer is formed.…”

Section: Figure S3mentioning

confidence: 54%

“…This unusual behavior is likely a consequence of the diblock structure. Problematic SEC characterization of block copolymers has been recently outlined, 52 stressing the aspects such as rod-coil architecture and strong block-block and block-column interactions as exacerbating this issue. In the case of Et 3 N-AMPS-block-St copolymers, the extreme difference in polarities of the blocks and the difference in block rigidities are factors that could cause such behavior.…”

Section: Figure S3mentioning

confidence: 99%

Direct synthesis via RAFT of amphiphilic diblock polyelectrolytes facilitated by the use of a polymerizable ionic liquid as a monomer

Guzik

Raffa

2021

Polym. Chem.

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“…For example, stiff, rod-like conjugated polymers (e.g., poly(3-hexylthiophene)) have different elution behavior relative to coiled flexible polymers like polystyrene, which is a typical SEC standard. 21 Junkers et al 22 have documented cases of anomalous SEC elution of block copolymers arising from not only rod-coil morphologies, 23 but also different block solubilities in the mobile phase (e.g., polyfluorinated side chains), 24 selfassembly via hydrogen-bonding, 25 and interactions with the stationary phase. 26 PBN2VN is chemically similar to polystyrene with respect to a flexible backbone and similar solubility properties, suggesting that SEC relative to PS standards should be a reasonable method for S1 for complete data set molecular weight characterization.…”

Section: Role Of Toluenementioning

confidence: 99%

Chain transfer to solvent in BN 2‐vinylnaphthalene radical polymerization

Klausen

2021

Journal of Polymer Science

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The synthesis of vinyl alcohol copolymers is limited due to the poor radical reactivity of vinyl acetate (VAc), the traditional precursor to polyvinyl alcohol (PVA). Main group monomers such as BN 2‐vinylnaphthalene (BN2VN) have attracted attention as alternatives to VAc to form side chain hydroxyls via oxidation, but outstanding questions of molecular weight control remain. Herein we report systematic investigation of solvent, temperature, and initiator concentration as factors influencing BN2VN degree of polymerization. We find increased chain transfer to toluene, hypothesized to arise from differences in radical stabilization and reactivity by aromatic and BN aromatic rings. As a result of these combined efforts, high molecular weight (Mw ~ 105 g mol−1) BN2VN homopolymers and BN2VN‐styrene copolymers were obtained.

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The block copolymer shuffle in size exclusion chromatography: the intrinsic problem with using elugrams to determine chain extension success

Abstract: Size exclusion chromatography (SEC) based on direct homopolymer calibration is the preferred method for molecular weight determination in macromolecular synthesis. However, using the same method and calibration in block copolymer...

Cited by 48 publications

References 70 publications

Effective End-Group Modification of Star-Shaped PNVCL from Xanthate to Trithiocarbonate Avoiding Chemical Crosslinking

Effective End-Group Modification of Star-Shaped PNVCL from Xanthate to Trithiocarbonate Avoiding Chemical Crosslinking

Direct synthesis via RAFT of amphiphilic diblock polyelectrolytes facilitated by the use of a polymerizable ionic liquid as a monomer

Chain transfer to solvent in BN 2‐vinylnaphthalene radical polymerization

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