Continuous Kinetic Sampling of Flow Polymerizations via Inline UV-Vis Spectroscopy.

Gapless monitoring of polymerization reactions is of paramount interest for academia and the polymer industry, allowing for efficient reaction screening and precise tailoring of the polymeric products. Herein, UV-visible spectroscopy (UV-vis) is employed as an operando measurement technique in continuous flow polymerization with ex situ calibration, to calculate monomer conversions with unprecedented resolution of only 10 s. A mathematical model based on volume contraction is provided for the first time, which yields monomer conversions from the absorption in the visible region for theoretically any homopolymerization. This model is validated for different monomers, solvents, and concentrations in a photoiniferter reversible addition-fragmentation chain transfer polymerization, proving the versatility of the presented setup. Notably, an ultralow measurement volume of merely a few hundred nanoliters is enough to ensure high accuracy.

An eco-friendly pathway to thermosensitive micellar nanoobjects via photoRAFT PISA: the full guide to poly(N-acryloylpyrrolidin)-block-polystyrene diblock copolymers.

Spherical macromolecular assemblies, so-called latexes, consisting of polystyrene (PS) resemble a relevant class of synthetic polymers used for a plethora of applications ranging from coatings or lubricants to biomedical applications. Their synthesis is usually tailored to the respective application where emulsifiers, radical initiators, or other additives still play a major role in achieving the desired properties. Herein, we demonstrate an alternative based on the photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) of Poly(N-acryloylpyrrolidin)-block-polystyrene (PAPy-b-PS). This approach yields monodisperse nanospheres with tunable sizes based on an aqueous formulation with only two ingredients. These nanospheres are additionally thermosensitive, meaning that they change their hydrodynamic diameter linearly with the temperature in a broad range between 10 °C and 70 °C. Combined with the eco-friendly synthesis in pure water at 40 °C, the herein presented route constitutes an unprecedented pathway to thermosensitive diblock copolymer aggregates in short reaction times without any additives.

Ultrafast PhotoRAFT Block Copolymerization of Isoprene and Styrene Facilitated through Continuous-Flow Operation.

Polymers made from isoprene and styrene resemble an important class of synthetic macromolecules found in a wide range of everyday commodity products. Their synthesis is usually limited to radical emulsion or anionic polymerization. Herein, we report on ultrafast photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization of isoprene and styrene in a continuous-flow microreactor. The cooperative action of a high photoinitiation efficiency and use of elevated temperatures considerably reduces the reaction times to less than half an hour to give high monomer conversions, allowing for the first time polyisoprene to be yielded from controlled radical polymerization in high definition and reasonable reaction times. High chain-end fidelities are maintained and block copolymers were prepared including a polystyrene-block-polyisoprene-block-polystyrene (PS-b-PI-b-PS) triblock copolymer.