Ming Gong,Daijun Zhang,Jiayang Zhang,Jun Li,Xiangbao Chen
Vinyl polymerization is an important path for in-situ polymerization of thermoplastic resins. BPO (Benzoyl peroxide) and DMT (dimethyl-p-toluidine) were chosen to initiate the radical polymerization of MMA (methyl methacrylate) in this work. Optimization of initiator concentration was studied through reaction rate of polymerization progress and properties of PMMA (polymethyl methacrylate). At first, the catalytic of DMT in MMA polymerization was studied through polymerization experiments and rheological experiments. Results showed that DMT could catalyze more than one molecular BPO in the whole reaction period. It can catalyze the decomposition of BPO after being connected to PMMA chains. Second, the BPO: DMT ratio was set to 2:1 to study the ideal content by comparing the mechanical properties of PMMA. Results showed that with the increase of initiator contents, Tg, molecular weight, and residual monomer were all declining. Meanwhile, the mechanical properties of PMMA matrix first increased and then decreased. This phenomenon was analyzed by 1H-NMR and SEM. And the optimal BPO-DMT concentration was 1.0 mol%–0.5 mol%.
The Schiff base condensation reaction was adopted to synthesize a series of pyridine-based quinoxaline ligands ( L1, L2, L3, L4 ) using 2-acetylpyridine and 1,2-phenylenediamine aromatic amines with different substituents of –OCH 3 , –F, -Cl, -Br. Then, four symmetrical dinuclear metal complexes ( 1–4 ) were obtained by coordination reaction of the synthesized ligands with CoCl 2 ·6H 2 O, and six unexpectedly systematic and novel solvent-involved asymmetric mononuclear metal complexes ( 1A-4A, 3B, 4B ) were obtained during single crystals cultivating by solvent diffusion method. The microscopic composition of the complexes were proved by a series of characterizations such as elemental analysis, IR and UV–vis. At the same time, by improving the single crystal culture technology, full crystal sample of compounds was obtained and X-ray single crystal diffraction showed a rare single crystal to single crystal structure transition (SCSC) phenomenon in this study. Furthermore, the catalytic properties of the complexes for MMA polymerization was explored, it was found that the catalytic activity of complexes 1–4 containing different types of substituents on pyridyl quinoxaline ligand was in the order of 1 < 2 < 3 < 4 , indicating that the complex with an electron-withdrawing substituent showed the higher activity than that of electron-donating substituent. Complexes 1A-4A, 3B and 4B showed higher catalytic activity in MMA polymerization than 1–4 , which confirmed that the catalytic activity of mononuclear complexes were generally higher than that of binuclear complexes.
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