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This work focuses on the pH‐triggered disassembly of supramacromolecular microgels, which are composed of the temperature‐responsive poly(N‐vinylcaprolactam) (PVCL) and the natural polyphenol tannic acid (TA). A systematic investigation of the microgel formation demonstrates that a retarded addition of tannic acid during semi‐batch precipitation polymerization influences the yield, chemical composition, and properties of the microgels to a great extent. Microgel properties, such as size, deformability, and chemical stability, can be easily tuned by varying the ratio between both building blocks PVCL and TA. Finally, the pH‐triggered disassembly of supramacromolecular microgels at different pH and temperatures demonstrates that their chemical structure can precisely control the degradation profile. Temperatures lower than the volume phase transition temperature (VPTT) of PVCL (T < 32 °C) and a pH > 10 result in a complete disassembly of the microgels into PVCL chains and TA due to the destruction of the hydrogen bonds responsible for the formation of a colloidal microgel. Interestingly, at temperatures above VPTT, the microgels keep their integrity due to enhanced hydrophobic interactions between the polymer chains of the microgel and are no longer affected by pH changes. [ABSTRACT FROM AUTHOR]

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions. [ABSTRACT FROM AUTHOR]

Reversible addition–fragmentationchain transfer (RAFT) copolymerizations of methacrylic acid N-hydroxysuccinimide ester and cyclic N-vinylamide derivatives (N-vinylpyrrolidone, N-vinylpiperidone, and N-vinylcaprolactam)were successfully performed with methyl 2-(ethoxycarbonothioylthio)propanoateas chain transfer agent (CTA). Effects of different reaction parameters,such as solvent type, temperature, and CTA-to-initiator (C/I) ratio,were studied to optimize the polymerization conditions in order toobtain copolymers with variable chemical composition, controlled molecularweight, and narrow polydispersity index (PDI). The solvent type hasa high impact on the polymerization reaction, and a high C/I ratiodecreases polydispersity as well as conversion. Increased steric hindrancethrough an enlarged lactam ring offsets the monomer reactivity. Thecontrolled character of RAFT polymerization was evidenced by the lowPDI of the copolymers and a linear relationship between conversionand molecular weight. Biohybrid nanogels were synthesized by directcoupling between reactive copolymers and enhanced green fluorescentprotein (EGFP) or cellulase (CelA2_M2) at room temperature in a water-in-oilemulsion. The EGFP-conjugated nanogels were fluorescent, while theCelA2_M2 encapsulated in nanogels retained its catalytic activity,as demonstrated by the hydrolysis of 4-methylumbelliferyl-β-d-cellobioside. [ABSTRACT FROM AUTHOR]

Rücktitelbild: Synthesis of Polyampholyte Janus-like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization (Angew. Die Mischzeit der zwei Lösungen wachsender Mikrogel-Vorläufer bestimmt die Morphologie der Polyampholyt-Mikrogele. Janus-artige Mikrogele, Molekulare Modellierung, Polyampholyte, Responsive Materialien, Selbstassemblierung. [Extracted from the article]

Particle size distribution and in particular the mean particle size are key properties of microgels, which are determined by synthesis conditions. To describe particle growth and particle size distribution over the progress of synthesis of poly( N -vinylcaprolactam)-based microgels, a pseudo-bulk model for precipitation copolymerization with cross-linking is formulated. The model is fitted and compared to experimental data from reaction calorimetry and dynamic light scattering, showing good agreement with polymerization progress, final particle size, and narrow particle size distribution. Predictions of particle growth and reaction progress for different experimental setups are compared to the corresponding experimental data, demonstrating the predictive capability and limitations of the model. The comparison to reaction calorimetry measurements shows the strength in the prediction of the overall polymerization progress. The results for the prediction of the particle radii reveal significant deviations and highlight the demand for further investigation, including additional data., Competing Interests: The authors declare no competing financial interest., (Copyright © 2019 American Chemical Society.)