Study On Synthesis Of Polycarboxylic Acid Macromonomer And Properties Of Polymer Microspheres

In this paper, bulk atom transfer radical polymerization (ATRP) of tert- butylmethacrylate (tBMA) was studied.P-chloromethylstyrene (CMSt) was selected as an initiator, 2, 2'-bipyridyl(bpy) or N,N,N′,N″,N″-Penta-methyldiethylenetriamine (PMDETA) as a ligand, with CuCl as catalyst. Poly(tert-butyl methacrylate) with a halogen atom end group St-PtBMA was synthesized by bulk ATRP at 80 oC. It was found that ligand could clearly affect polymerization rate of tBMA monomer based on measurement of molecular weight of St-PtBMA under different ligand systems by using gel permeation chromatography (GPC). The polymerization regulations under different system were compared. The number average molecular weight (Mn) of St-PtBMA could be controlled in a range from 2×103 to 1.8×104 g/mol by varying the ratio of monomer to initiator (1: 25, 1: 50, 1: 100 and 1: 150), and distribution of molecular weight (Mw/Mn) kept lower than 1.31. The 1H-NMR chemical shifts in parts per million (ppm) were recorded from 0.00 ppm using tetramethylsilane as an internal reference. It was found that obtained PtBMA had a specific structure.Then hydrophilic poly(methacrylic acid) macromonomer (St-PMAA) was obtained through hydrolysis of St-PtBMA in CH2Cl2 in the presence of trifluoroacetic acid (TFA).Further more, poly(methacrylic acid) (St-PMAA) macromonomer was selected as reaction stabilizer to prepare St-PMAA grafted polystyrene (PSt) microspheres (PSt-g-PMAA). The morphology and particle size of the microspheres were studied by using scanning electron microscopy (SEM) and Zetasizer Nano instruments. The effects of polymerization reaction parameters such as media polarity, concentration of St-PMAA macromonomer and polymerization temperature on the particle size of the PSt-g-PMAA microspheres were investigated. It was shown that the average size of the forming microspheres ranges from 340 to 1200nm by varying those experimental parameters. The PMAA chain on the surface of PSt-g-PMAA microspheres was determined based on the results of Zeta data. Therefore, this kind of graft copolymer microspheres will be expected to get some applications in drug carriers and protein adsorption/separation for its pH response.