Evaluation of alternative solvents in common amide coupling reactions : replacement of dichloromethane and N,N-dimethylformamide

A range of alternative solvents have been evaluated within amidation reactions employing common coupling reagents with a view to identifying suitable replacements for dichloromethane and N,N-dimethylformamid

Determining free-radical propagation rate coefficients with high-frequency lasers: current status and future perspectives

Detailed knowledge of the polymerization mechanisms and kinetics of academically and industrially relevant monomers is mandatory for the precision synthesis of tailor‐made polymers. The IUPAC‐recommended pulsed‐laser polymerization–size exclusion chromatography (PLP–SEC) approach is the method of choice for the determination of propagation rate coefficients and the associated Arrhenius parameters for free radical polymerization processes. With regard to specific monomer classes—such as acrylate‐type monomers, which are very important from a materials point of view—high laser frequencies of up to 500 Hz are mandatory to prevent the formation of mid‐chain radicals and the occurrence of chain‐breaking events by chain transfer, if industrially relevant temperatures are to be reached and wide temperature ranges are to be explored (up to 70 °C). Herein the progress and state‐of‐the‐art of high‐frequency PLP–SEC with pulse repetition rates of 500 Hz is reported, with a critical collection of to‐date investigated 500 Hz data as well as future perspectives for the field

Particle Size Control in Miniemulsion Polymerization via Membrane Emulsification

y Miniemulsion polymerization of methyl methacrylate has been conducted employing Shirasu porous glass (SPG) membrane emulsification for the generation of the initial miniemulsion. For the first time, submicron-sized monomer droplets and polymer particles have been prepared using membranes with pore sizes significantly smaller than those previously reported. Membrane pore sizes of diameters 100-400 nm were explored, demonstrating that the final particle size can be conveniently tuned within the diameter range of 250-1600 nm. The choice of radical initiator is crucial: a sufficiently hydrophobic initiator (lauroyl peroxide) is required to minimize the generation of bimodal particle size distributions via secondary nucleation. Given the advantages of low energy consumption, reduced shear stress (compared with conventional high-energy mixing approaches such as ultrasonication), and an easily adjustable particle size via the membrane pore size, membrane emulsification has significant potential for the synthesis of polymeric nanoparticles via miniemulsion polymerization.The authors acknowledge the European Union Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 665501 with the research Foundation Flanders (FWO) (N.Z.)

Visible Light-Mediated Polymerization-Induced Self-Assembly Using Continuous Flow Reactors

We present the synthesis of polymeric nano-particles of targeted morphology in a continuous process via visible light-mediated aqueous RAFT polymerization-induced self-assembly (PISA). A trithiocarbonate-derived poly-(ethylene glycol) (PEG) macroRAFT was activated in the presence of hydroxypropyl methacrylate (HPMA) at 37 degrees C under blue light irradiation (460 nm), leading to the formation of PEG-b-P(HPMA) nanoparticles. The method is attractive in its simplicity-spheres, worms, and vesicles can easily be obtained in a continuous fashion with higher control in comparison to conventional batch procedures. This allows for more accurate production of particle morphologies and scalable synthesis of these nano-objects. The versatility of this process was demonstrated by the in situ encapsulation of an active compound.MCSC-IF-GF [12U1717N

Visible Light-Mediated Polymerization-Induced Self-Assembly Using Continuous Flow Reactors

We present the synthesis of polymeric nanoparticles of targeted morphology in a continuous process via visible light-mediated aqueous RAFT polymerization-induced self-assembly (PISA). A trithiocarbonate-derived poly­(ethylene glycol) (PEG) macroRAFT was activated in the presence of hydroxypropyl methacrylate (HPMA) at 37 °C under blue light irradiation (460 nm), leading to the formation of PEG-<i>b</i>-P­(HPMA) nanoparticles. The method is attractive in its simplicityspheres, worms, and vesicles can easily be obtained in a continuous fashion with higher control in comparison to conventional batch procedures. This allows for more accurate production of particle morphologies and scalable synthesis of these nano-objects. The versatility of this process was demonstrated by the <i>in situ</i> encapsulation of an active compound

Rapid Oxygen Tolerant Aqueous RAFT Photopolymerization in Continuous Flow Reactors

Recently, new controlled polymerization pathways have emerged for the synthesis of functional polymer materials. The use of light, particularly visible light, to generate radicals has shown to be beneficial over thermal induction due to the high control over reaction parameters as well as spatiotemporal control. Although numerous photopolymerizations have been performed in batch, additional initiators or activators are often needed to increase the overall yield, making this process time-consuming and costly; optical path lengths directly correlate with achievable space-time yields. The use of flow reactors is in this case advantageous. In this work, new synthetic protocols are demonstrated for the synthesis of di- and triblock copolymers in tubular reactors via photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Within just 10 min of polymerization time, full monomer conversion was reached for a variety of acrylamides and acrylates, and polymers with molecular weights up to 100000 g mol(-1) and high end-group fidelity were obtained. Changing the flow rates, concentrations, and light intensity allowed alteration of the molecular weights, and several di- and triblock copolymers were synthesized, indicating the high level of control over the polymerization. In addition, multiple flow reactors were coupled to allow the synthesis of triblock copolymers in a reactor cascade process without the need for intermediate purification. The attractiveness of this approach is illustrated by considering that a PDMAA-b-PDMAA-b-PDMAA triblock copolymer with a number-average molecular weight of 3200 g mol(-1) and dispersity of 1.24 could be theoretically obtained at a rate of 300 g/day.MCSC-IF-GF applicant no. 12U1717N. We acknowledge The European Union Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 665501 with the research Foundation Flanders (FWO) (N.Z.)