The functionality of stimuli-responsive microgels can be tailor-made by manipulating their internal nanostructure induced by the chemical composition and morphology of the polymer network. Microgels with phase-separated domains on a nanoscopic length scale were synthesized by copolymerization of N-vinylcaprolactam (VCL) and amphiphilic-to-hydrophobic 1-vinyl-3-alkylimidazolium (VIM+C n H2n+1) bromides (Br–) of different alkyl chain lengths (n = 12, 14, 16) as comonomers. These quaternized imidazoles provide dual functionality for immobilization of payload by electrostatic and hydrophobic interactions. The morphologies and properties of synthesized poly­(VCL-co-VIM+C n H2n+1Br–) microgels with 10 mol % comonomer were investigated systematically by 1H and 13C high-resolution NMR spectroscopy and relaxometry. Chemical side-selective information about the monomers’ volume-phase transition temperatures, width of transition, and change in transition entropy was reported and correlated to the alkyl chain length of the VIM+C n H2n+1Br– comonomer. 13C NMR spectroscopy reveals the existence of trans and gauche conformers of alkyl chains, which depends on the alkyl chain length and temperature. Morphologies and dynamic contrasts of alkyl chain domains and VCL moieties of poly­(VCL-co-VIM+C n H2n+1Br–) microgels were investigated by 1H transverse magnetization relaxation (T 2-relaxation). Finally, the microgels were successfully applied in the uptake of the hydrophobic dye Nile red, proving their ability to solubilize hydrophobic substances. In addition, the poly­(VCL-co-VIM+C n H2n+1Br–) microgels were utilized in electrostatic interactions, as well as simultaneous addition of hydrophobic and negatively charged payload as a proof of concept for dual functionality. This investigation will allow for a better understanding of the internal nanophase structure of complex poly­(N-vinylcaprolactam) (PVCL)-based microgels comprising pH-independent positive charges, as well as hydrophobic compartments, which have potential application as dual-functional delivery systems.

Poly-N-vinylcaprolactam based microgels with positively charged 1-vinyl-3-methylimidazolium were analyzed by functional group volume phase transitions and morphology. The microgels are antibacterial, due to positive charges in the microgel corona.

Microgels are an emerging class of “ideal” enzyme carriers because of their chemical and process stability, biocompatibility, and high enzyme loading capability. In this work, we synthesized a new type of permanently positively charged poly­(N-vinylcaprolactam) (PVCL) microgel with 1-vinyl-3-methylimidazolium (quaternization of nitrogen by methylation of N-vinylimidazole moieties) as a comonomer (PVCL/VimQ) through precipitation polymerization. The PVCL/VimQ microgels were characterized with respect to their size, charge, swelling degree, and temperature responsiveness in aqueous solutions. P450 monooxygenases are usually challenging to immobilize, and often, high activity losses occur after the immobilization (in the case of P450 BM3 from Bacillus megaterium up to 100% loss of activity). The electrostatic immobilization of P450 BM3 in permanently positively charged PVCL/VimQ microgels was achieved without the loss of catalytic activity at the pH optimum of P450 BM3 (pH 8; ∼9.4 nmol 7-hydroxy-3-carboxy coumarin ethyl ester/min for free and immobilized P450 BM3); the resulting P450-microgel systems were termed P450 MicroGelzymes (P450 μ-Gelzymes). In addition, P450 μ-Gelzymes offer the possibility of reversible ionic strength-triggered release and re-entrapment of the biocatalyst in processes (e.g., for catalyst reuse). Finally, a characterization of the potential of P450 μ-Gelzymes to provide resistance against cosolvents (acetonitrile, dimethyl sulfoxide, and 2-propanol) was performed to evaluate the biocatalytic application potential.

We evaluate recent developments in the design, synthesis, and application of microgels with an amphiphilic polymer network with regard to the structure of their hydrophobic domains.

Herein, the synthesis of amylose‐coated, temperature‐responsive poly(N‐vinylcaprolactam) (VCL)‐based copolymer microgels by enzyme‐catalyzed grafting‐from polymerization with phosphorylase b from rabbit muscle is reported. The phosphorylase is able to recognize the oligosaccharide maltoheptaose as primer and attach glucose units from the monomer glucose‐1‐phosphate to it, thereby forming amylose chains while releasing inorganic phosphate. Therefore, to enable the phosphorylase‐catalyzed grafting‐from polymerization of glucose‐1‐phosphate from the PVCL‐based microgels, the maltoheptaose primer is covalently attached to the microgel in the first synthesis step. This is realized by adding N‐(2‐aminoethyl)methacrylamide (AEMAA) as a comonomer to the PVCL microgel to integrate primary amino groups and subsequent coupling of maltoheptaonolactone. Both the PVCL/AEMAA microgel as well as the obtained microgel–maltoheptaose construct are characterized in detail by dynamic light scattering, electrophoretic mobility measurements, IR spectroscopy, and atomic force microscopy. From the microgel–maltoheptaose construct, the grafting‐from polymerization of glucose‐1‐phosphate is performed by the addition of phosphorylase b. Atomic force microscopy images clearly demonstrate the formation of an amylose shell around the microgels. The developed amylose‐coated microgels open up promising application possibilities, for example, as colloidal scavengers, since amylose helices can serve as host molecules for inclusion of hydrophobic guest molecules.

We investigate the effect of different anions on the temperature-dependent solution properties of poly(N-vinylcaprolactam) microgels carrying alkylated ionic liquid vinylimidazolium moieties synthesized by a pre- and post-functionalization approach.