Poly(methyl methacrylate) and glycidyl-functionalized poly(methyl methacrylate) nano-size latex particles via differential microemulsion polymerization

Abstract

The differential microemulsion polymerization technique was used to synthesize nanoparticles of glycidyl-functionalized poly(methyl methacrylate), PMMA, via a two-step process, by which the amount of sodium dodecyl sulfate (SDS) surfactant required was 1/217 of the monomer amount by weight and the surfactant/water ratio could be as low as to 1/600. The first step was to synthesize the core PMMA nanoparticles having high molecular weight of 10[superscript 6] g mol[superscript -1] using the AIBN oil soluble initiator at 70 [degrees Celsius] for 90 min by drop-wise addition of the monomer. The high molecular weight PMMA latex nanoparticles (~ 20 nm in size) have a rich syndiotactic configuration (53-57 % rr triads). The rate of polymerization increased with an increase in the concentration of the SDS surfactant. The maximum conversion of polymerization was observed at a polymerization time of 3600 s. The nearly constant value of PDI over the whole range of the polymerization time could be attributed to the significance of particle nucleation occurring via a heterogeneous nucleation mechanism. The high molecular weight PMMA nanoparticles have spherical shape with a T[subscript g] of about 125 [degrees Celsius]. The second step was to add glycidyl methacrylate in the PMMA latex via a similar manner to obtain the glycidyl-functionalized PMMA nanoparticles. A core/shell structure of the glycidyl-functionalized PMMA latex nanoparticles observed are composed of a high molecular weight PMMA core with the random copolymer of poly[(methyl methacrylate)-ran-(glycidyl methacrylate)] as a shell layer on the surface. Particle sizes of about 50 nm were achieved and the molecular weight of glycidyl-functionalized PMMA was in the range of about 1x10[superscript 6] to 3x10[superscript 6] g mol[superscript -1]. Approximately 1-2 wt% of glycidyl functional groups were determined using a titration method. The low content detected was due to precipitation and a drying effect. The glycidyl-functionalized PMMA has two regions of T[subscript g] at 90 [degrees Celsius] and 125 [degrees Celsius], which were referred to as poly[(methyl methacrylate)-ran-(glycidyl methacrylate)] and PMMA, respectively. It is very interesting to note that the polymerization conversion reaches a maximum, within a short reaction time in the presence of less surfactant and without the need of a co-surfactant along with a high monomer-to-water ratio.