Journal
POLYMERS
Volume 12, Issue 11, Pages -Publisher
MDPI
DOI: 10.3390/polym12112747
Keywords
ultrahigh molecular weight; PMMA; Pd nanoparticles; organic halides; mechanism
Categories
Funding
- National Natural Science Foundation of China [21174133]
- Zhejiang Natural Science Foundation for Distinguished Young Scholars [LR12B04002]
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A facile and versatile approach for the synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) at mild conditions was developed. Certain organic halides combined with a catalytical amount of palladium nanoparticles (Pd NPs) were found to be very effective in initiating polymerizations of methyl methacrylate (MMA), methyl acrylate, vinyl acetate and other vinyl monomers. An ultrahigh molecular weight PMMA with a number-average molecular weight of 4.65 x 10(6) Da and a weight-average molecular weight of 8.08 x 10(6) Da was synthesized at 70 degrees C using 2-bromoisobutyric acid ethyl ester (EBiB) as an initiator in the presence of catalytical amount (10.1 ppm) of Pd NPs. A kinetic investigation found that the orders of polymerization with respect to EBiB, Pd NP and MMA were 0.23, 0.50, and 0.58, respectively. Proton nuclear magnetic resonance (H-1 NMR) combined with matrix-assisted laser desorption ionization time of flight mass spectroscopy (MALDI-TOF) and gel permeation chromatography (GPC) were used to prove that the macromolecular chain had an end-group of EBiB residue. The electron spin resonance (ESR), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) results reveal that the reaction of EBiB with Pd NPs caused a bromo atom (Br) transfer from EBiB to Pd NPs and resulted in the generation of EBiB residue radical to initiate the polymerization of MMA and the formation of (PdBr2)-Br-II on the surface of Pd nanoparticles.
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