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Wednesday, 18 September 2019
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Raw materials & technologies, Raw materials, Coatings binders

Developing a modified emulsion polymerisation method

Thursday, 13 November 2014

Researchers studied the emulsion polymerisation of methyl methacrylate (MMA) in the presence of azobisisobutyronitril (AIBN) as initiator.

A modified emulsion polymerisation method was developed for the synthesis of PMMA nanolatexes. Source: Kaay Ranson/Fotolia

A modified emulsion polymerisation method was developed for the synthesis of PMMA nanolatexes. Source: Kaay Ranson/Fotolia

By a combined use of oil-soluble initiators and the semi-continuous monomer feeding, a modified emulsion polymerisation method was developed for the synthesis of poly(methyl methacrylate) (PMMA) nanolatexes at high monomer concentrations. The influences of various parameters on the polymerisation were studied, including the monomer feeding rate, the surfactant concentration, the initiator amount, and the monomer concentration. Narrowly-distributed PMMA nanolatex particles with smaller sizes can be prepared by slowing down the monomer feeding rate, modestly increasing the surfactant concentration, or decreasing the monomer concentration.

PMMA nanolatex particles remain stable

The molecular weight of PMMA nanolatex particles increases with the monomer feeding rate and the monomer concentration. Most importantly, PMMA nanoparticles with a z-average hydrodynamic diameter of 77nm, a polydispersity index of 0.07, and a number-average molecular weight of 3.96 × 106g mol-1 was fabricated at a monomer concentration as high as 315mg mL-1 and a surfactant concentration as low as 1.67 mg mL-1. The surface coverage ratio of the nanolatex particles is decreased down to a surprising low value of 0.084. This can be attributed to the slow polymerisation rate of the modified emulsion polymerisation as well as the interactions between the polar ester groups of PMMA and water.

The study is published in: European Polymer Journal, in press.

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