Controlled/Living Radical Polymerization In The Presence Of1,1-Diphenylethylene

A suitable controlled polymerization mechanism of methyl methacrylate (MMA) in the presence of1,1-diphenylethylene (DPE) is presented. The PMMAs with different molecular weight are prepared and the structures of the polymers are characterized by nuclear magnetic resonance (NMR) and electrospray-ionization quadrupolar time-of-flight mass spectrometry (ESI-Q-TOF-MS). The good agreements between the theoretical and the experimental m/z values of PMMA samples acquired by ESI-Q-TOF-MS provide positive evidence to confirm that only one DPE unit is incorporated into the PMMA macromolecule chains. TEMPO is used as a radical scavenger to capture the active free radicals generated by the scission of DPE-containing PMMA polymer. The molecular weight of the DPE-containing PMMA decreased dramatically after reaction with TEMPO, meanwhile, the DPE molecule is split from the DPE-containing PMMA. Based on the current investigations, the controlled polymerization mechanism of MMA in the presence of DPE is proposed. The polymerization of methyl acrylate (MA) and n-Butyl acrylate (BA) in the presence of1,1-diphenylethylene (DPE) were investigated to monitor the impact of different monomer on the structure of DPE-containing polymer. Poly(methyl acrylate)(PMA) and poly(n-butyl acrylate)(PBA) polymers with low molecular weight were synthesized and characterized. According to the results of the1H-NMR spectroscopy, DPE is incorporated into the PMA and PBA polymer chains as diphenyl-substituted structure. The experimental m/z values of PMA and PBA polymers acquired by ESI-Q-TOF-MS was in accordance with these of theoretical m/z values, proving that only one DPE unit was incorporated into the PMA or PBA polymer chains. According to these results, the process of polymerization of MA or BA in the presence of DPE was proposed.The poly(styrene)(PSt) with different molecular weight were prepared, and the resulting polymers were characterized by gel permeation chromatography (GPC) and NMR spectroscopy. The GPC results of PSt polymer were consistent with the molecular weight obtained by1H-NMR, indicating that only one DPE molecule was incorporated into the PSt polymers. However, PSt polymers were difficult to be cationized so that ESI-Q-TOF-MS could not be used to analyze the structure of PSt oligomers. The poly(sodium p-styrene sulfonate) was synthesized in the presence of DPE using ABVN as initiator. The resulting polymers were analyzed by ESI-Q-TOF-MS with negative ion mode. It was found that only one DPE unit rather than DPE-dimer (or semi-quinoid structure) was incorporated into the polymer chains.Poly(methyl methacrylate)-b-poly(styrene)(PMMA-b-PSt) block copolymer was synthesized successfully via seeded emulsion polymerization in the presence of DPE. Firstly, emulsion polymerization of MMA was carried out with KPS as initiator in the presence of DPE, giving a DPE-containing PMMA precursor with the ability of reactivation by simply heating. The emulsion polymerization behavior of MMA in the presence of DPE was investigated. The second monomer styrene (St) was then polymerized in PMMA seed emulsion and block copolymer was successfully obtained. The formation of PMMA-b-PSt block copolymer was confirmed by’H-NMR and gel permeation chromatography (GPC). Dynamic light scattering (DLS) was used to monitor the particle diameters, and proved that the particles grew without secondary nucleation occurring.In this research, poly(methyl methacrylate)-b-poly(tert-butyl acrylate)(PMMA-b-P/BA) block copolymers were prepared by1,1-diphenylethene (DPE) controlled radical polymerization in homogeneous systems. Firstly, monomer methyl methacrylate (MMA), initiator2,2-azobisisoheptonitrile (ABVN) and a control agent DPE were solution polymerized to form the DPE-containing PMMA precursor. Then the second monomer tBA was simply heated in the presence of DPE-containing PMMA precursor used as macroinitiator, and the block copolymer was synthesized successfully. The effects of polymerization temperature and solvent on molecular weight (Mn) and molecular weight distribution (MWD) of polymers throughout the polymerization were investigated. The results showed that, increasing the polymerization temperature raised the reaction rate and the second monomer conversion. The more amounts of solvent reduced the reaction rate and viscosity of the polymerization system, which may allow more activation-deactivation cycles to occur at a given conversion, thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated. The poly(styrene) obtained in the presence of DPE could not induce block polymerization.