Two different synthetic pathways give access to the amphiphilic block copolymer poly(ethylene oxide)‐block‐poly(tert‐butoxycarbonylaminomethylacrylate). In the first approach, two end‐functionalized segments are linked via click chemistry; and in the second approach, a poly(ethylene oxide) (PEO) based macroinitiator is chain extended via atom transfer radical polymerization (ATRP). In both cases the linking unit consists of an amide group, which is necessary to effectively deprotect the corresponding polymer precursor without cleavage of both segments. For this, amide‐containing ATRP initiators are employed and successful synthesis by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC) analyses before comparing both pathways is demonstrated. After deprotection, a novel double hydrophilic block copolymer, poly(ethylene oxide)‐block‐poly(dehydroalanine), is obtained, which is investigated using SEC (aqueous and DMSO) and 1H‐NMR spectroscopy. Containing a potentially zwitterionic PDha segment and a high density of both amino and carboxylic groups, pH‐dependent aggregation of the block copolymer is expected and is studied using dynamic light scattering, revealing interesting solution properties. The corresponding polymers are applied in various areas including drug delivery systems or in biomineralization.
We synthesized three different polyzwitterions� poly(N,N-diallyl glutamate) (PDAGA), poly(dehydroalanine) (PDha), and poly(2-(imidazol-1-yl)acrylic acid) (PImAA)�and investigated how their ionization states respond to changes in solution pH. We used molecular simulations to determine how the net charge per monomer and the ionization states of individual acidic and basic groups differ from the ideal (Henderson− Hasselbalch) behavior. To complement the theoretical predictions, we performed potentiometric titrations and zeta-potential measurements of all studied polyzwitterions. By comparing these experiments with theoretical predictions, we could show that molecular simulations can predict and explain the origin of the differences between the effective and bare pK a values of individual titratable groups. Furthermore, we have shown that it is not possible to obtain these effective pK a values directly from the equivalence point recognition criterion (ERC), commonly used in potentiometric titrations. However, the effective pK a values can be reliably obtained by calculating the net charge per monomer from the potentiometric titration curves and validating these results against theoretical predictions. The approach we propose works reliably for polyzwitterions in which the ionization response is dominated by electrostatic interactions, such as PDAGA or PDha; however, it fails if other specific interactions contribute significantly, such as in the case of PImAA.
Star-shaped block copolymers are of interest as versatile and highly functional polymeric building blocks and show interesting solution properties or self-assembly. Herein, we report the synthesis of novel, double hydrophilic...
Correction for ‘Double hydrophilic poly(ethylene glycol)-block-poly(dehydroalanine) four-arm star block copolymers: synthesis and solution behavior’ by Peter J. Mons et al., Polym. Chem., 2022, 13, 4298–4308, https://doi.org/10.1039/D2PY00579D.
A total of 18 governments took turns during the period of Latvian parliamentarianism between 1918 and 1934. In science, the question of a felt loyalty by the Baltic Germans, as an imagined collective, towards the new Latvian state belongs to the more frequently asked discussion. This work focuses on the question of how Baltic German loyalty is perceived in German historiography, ascribed by the activities of their representatives in the national parliament. Their activities are closely related to their minority’s overall relation to the Latvian state and evolved over five parliamentary phases. Those will be reevaluated, under consideration of the perception in German historiography, showing that the respective zeitgeist was crucial to understand the Baltic German attitude towards the Latvian state and to finally answer the question of a felt loyalty.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.