RESUMO
Polystyrene (PS) particles were synthesized in ethanol/water mixture by dispersion polymerization using visible light irradiation, with either a N-heterocyclic carbene borane-based photoinitiating system (PIS) or a disulfide. With the full PIS and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as stabilizer, the size distributions were broad and the amount of PEGMA had a strong impact on the experiment reproducibility. The addition of a base solved the problem, leading to faster polymerizations, narrower size distributions and larger particles. With the disulfide as sole PIS, bigger and narrowly distributed PS particles were again formed. Quantitative conversion was achieved in each system, with particle size ranging between 100 and 350â nm. The use of poly(N-vinylpyrrolidone) as stabilizer led to significantly larger particles, up to 1.2â µm, with narrow size distributions. The production of such large latex particles by photoinitiated polymerizations is unprecedented.
RESUMO
In the development of 3D printing fuels, there is a need for new photoinitiating systems working under mild conditions and/or leading to polymers with new and/or enhanced properties. In this context, we introduce herein N-heterocyclic carbene-borane complexes as reagents for a new type of photo-click reaction, the borane-(meth)acrylate click reaction. Remarkably, the higher bond number of boranes relative to thiols induced an increase of the network density associated with faster polymerization kinetics. Solid-state NMR evidenced the strong participation of the boron centers on the network properties, while DMA and AFM showed that the materials exhibit improved mechanical properties, as well as reduced solvent swelling.
