Polylactide is a biodegradable versatile material based on annually renewable resources and thus CO2‐neutral in its lifecycle. Until now, tin(II)octanoate [Sn(Oct2)] was used as catalyst for the industrial ring‐opening polymerization of lactide in spite of its cytotoxicity. On the way towards a sustainable catalyst, three iron(II) hybrid guanidine complexes were investigated concerning their molecular structure and applied to the ring‐opening polymerization of lactide. The complexes could polymerize unpurified technical‐grade rac‐lactide as well as recrystallized l‐lactide to long‐chain polylactide in bulk with monomer/initiator ratios of more than 5000:1 in a controlled manner following the coordination–insertion mechanism. For the first time, a biocompatible complex has surpassed Sn(Oct)2 in its polymerization activity under industrially relevant conditions.

Four non-toxic, highly active and robust complexes have been used in the ring opening polymerisation of non-purifed lactide to substitute Sn(Oct)2.

Functional microgels with tailored structure and specific properties are required for medical and technical applications, thus motivating model-based optimization of their fabrication processes. An important step in the creation of accurate models is parameter estimation. We present a methodology for a parameter identifiability analysis, which approximates the feasible parameter set as a box by solving a series of constrained dynamic optimization problems. The method is applied to the synthesis of microgels based on two monomers, N-vinylcaprolactam and N-isopropylacrylamide, and the cross-linker N,N-methylenebis(acrylamide). The results show that kinetic parameters corresponding to the reaction of the monomers are identifiable as are a subset of the kinetic parameters involving the cross-linker. The reaction kinetics of the cross-linking are faster in comparison to the main polymerization reaction for N-vinylcaprolactam; this allows for an improved understanding of the occurring reaction phenomena. The reaction kinetics of the cross-linking are not identifiable for N-isopropylacrylamide for the given experimental setup; model-based experimental design for parameter precision might enable their identification. The results also indicate potential for model simplification and allow us to make suggestions toward the enhancement of Raman spectroscopy measurements.

Polylactide (PLA) is a high potential bioplastic that can replace oil‐based plastics in a number of applications. To date, in spite of its known toxicity, a tin catalyst is used on industrial scale which should be replaced by a benign catalyst in the long run. Germanium is known to be unharmful while having similar properties as tin. Only few germylene catalysts are known so far and none has shown the potential for industrial application. We herein present Ge complexes in combination with zinc and copper, which show amazingly high polymerization activities for lactide in bulk at 150 °C. By systematical variation of the complex structure, proven by single‐crystal XRD and DFT calculations, structure–property relationships are found regarding the polymerization activity. Even in the presence of zinc and copper, germanium acts as the active site for polymerizing probably through the coordination–insertion mechanism to high molar mass polymers.

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Functionalized microgels are typically based on structured copolymers, whose synthesis necessitates knowledge of interactions between different monomer units. This contribution presents in‐line Raman and turbidity monitoring of copolymer microgels based on monomers N‐vinylcaprolactam (VCL) and N‐isopropylacrylamide (NIPAM). During reaction, in‐line Raman spectra are evaluated via multivariate indirect hard modeling (IHM) regression, utilizing pure component models based on parameterized peak functions. To account for variation in Raman baseline intensity, the linear IHM baseline is replaced by a curved baseline, resulting in calibration R² above 0.98 and root‐mean‐squared errors of cross‐validation below 0.12 wt%. Spectra taken in‐line during microgel syntheses reveal NIPAM to react slower than VCL in homopolymerization, but faster than VCL in copolymerization. This effect can be used for synthesis of functional microgels, that is, with tunable volume phase transition temperature. This effect is not visible from turbidity measurements, demonstrating the advantage of in‐line Raman monitoring of chemical components in polymerization processes.

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