Divalent Samarium Soft With The Catalytic Lactone Open Ring Polymerization Of Star Polymer Synthesis

Aliphatic polyesters are excellent materials with biodegradability and biocompatality. There is a continuous development of new catalysrs for the ring-opening polymerization of aliphatic polyesters particularly of polylactones due to their importance for medical applications and as plastic modifiers. In this thesis, three rare earth initiators, Sm(PPri2)2, Sm(PPh2)2 containing 1,1,1,1-tetra(2-bromoiso butyryloxymethyl)methane, Sm(PPh2)2 containing 1,1,1,1',1'-,1 hexa(2-bromoiso butyryloxymehtyl)dimethyl ether, have been studied to polymerize -caprolactone(CL) at mild condition. The polymerization feature and mechanism are discussed in details using Sm(PPh2)2 as initiator. Both the structure of linear and star-shaped polymers were characterized by !H NMR, LALLS, GPCSm(PPri2)2 was firstly studied in the polymerization of e-caprolactone. It was highly active to initiated the polymerization of E-caprolactone. Effects of temperature, polymerization time, the concentrations of monomers and initiators, the polarity of solvent on polymerization were studied. High monomer conversion(100%) and high molecular weight(M =11.74 104) polymers were obtained under following condition([CL]/[Sm]=800, VC1/VTHF=1/3, polymerized for 90min at 4 in THF). The polymerization of E-caprolactone initiating by Sm(PPh22)2 was proceeded with "coordination-insertion mechanism", which was studied by the means of ]H NMR and UV-Vis.The catalyst of Sm(PPh2)2/Sml2 and 1,1,1,1-tetra(2-bromoisobutyryloxymethyl) methane was firstly studied in the polymerization of e-caprolactone.. It was found that the polymerizatio. High molecular weight (Mn,=11.74 104) polymers were obtained under following condition([CL]/[Sm] =1000, [CL]=1.67 mol/1. polymerized for 6h at room temperature catalyzed by Sm(PPri2)2 and 1,1,1,1-tetra(2-bromoisobutyryloxymethyl) methane). The polymers has tetra-arms confirmed by 1H NMR, GPC and LALLS. The Mark-Houwink equation of the solution of tetra-armed polymers: K=2.50 10-4, =0.49.The catalyst of Sm(PPh2)2/Sml2 and 1,1,1,1 ',1 ', 1'-hexa(2-bromoisobutyryloxymehtyl)dimethyl ether was firstly studied in the polymerization of e-caprolactone. High monomer conversion(99.5%) and high molecular weight(Mw=6.66 104, Mw/Mn=l .72) polymer was obtained under following condition([CL]/[Sm]=1300, [CL]=1 42 mol/1, polymerized for 6h at room temperature in THF catalyzed by Sm(PPh2)2 and l,l,lj',l',r-hexa(2-bromoisobutyryloxymehtyl) dimethyl aether). The structure of ploymers was studied by 'H NMR.