Aqueous (co) Polymerization Of MMA And Styrene By Ti And Zr Cyclopentadinyl Complexes

Transitional Ziegler-Natta catalyst and metallocene catalysts as the presentation of titanium and zirconium metallocene compounds usually produce the polymerization in organic solvent because of their extreme oxophilicity. However, aqueous polymerizations in the synthesis of high polymer material can not only reduce the cost but also be environmentally friendly. A large number of reports have appeared on the development of late transition metal catalytic systems capable of polymerization in aqueous medium as their stability, while they are found to afford only low molecular weight polymers because of the ease of 3 -hydride elimination. In contrast, early transition metal catalysts like those of titanium and zirconium metallocene compounds which have cyclopentadiene or its derivatives in the ligands reduce Lewis acidity or their oxophilicity to a certain extent are expected to be used as polymerization catalysts in aqueous medium.In this paper, mono-metallocene complexes of titanium and zirconium and dinuclear metallocene complexes were first successfully used in homopolymerization and copolymerization of MMA and styrene in aqueous medium. The effects of the polymerization conditions such as temperature, time, mole ratio of [monomer]/[catalyst], the volume of water on catalytic behaviors were investigated in detail. The results showed as follow:1. Under the polymerization condition (55℃,15 h, V_H2O = 10 ml, C[SDS]= 0.02 mol/L, n(CpTiCl₃)/n(MMA) = 1:100) of CpTiCl₃ catalytic system, the conversion of MMA reached 91.65%, M_w of PMMA is 78×10⁴, molecular weight distribution of PMMA is 4.39, the syndiotactic content of PMMA is 56%. While 65℃, M_w of PMMA reached 221×10⁴. Under the polymerization condition (55℃,15 h, V_H2O = 10 ml, C[SDS]= 0.02 mol/L, n(CpTiCl₃)/Ai(St) = 1:100) of CpTiCl₃ catalytic system, the conversion of styrene reached 27%, M_w of PS is 106×10⁴, molecular weight distribution of PS is 3.35.2. Under the polymerization condition (55℃,15 h, V_H2O = 10 ml, C[SDS]= 0.02mol/L, n(CpZrCl₃·DME)/n(MMA) = 1:100) of CpZrCl₃·DME catalytic system, the conversion of MMA reached 60.2%, M_w of PMMA is 158×10⁴, molecular weight distribution of PMMA is 3.16. Increasing the volume of SDS (n(SDS)=0.4×10^-3mol), the conversion of MMA reached 74%. Under the polymerization condition (55℃,15 h, V_H2O = 40 ml, C[SDS]= 0.02 mol/L, n(CpTiCl₃)/n(St) = 1:100) of CpZrCl₃·DME catalytic system, the conversion of styrene reached 71.3%, M_η of PS is 189 ×10⁴.3. Under the polymerization condition (55℃,15 h, V_H2O= 20 ml, C[SDS]= 0.02 mol/L, n(CpTiCl₃)/n(MMA+St) = 1:100, feed ratio, n(MMA)/n(St)=1:1) of CpTiCl₃ catalytic system, copolymer composition is 1:1.03, molecular weight distribution of copolymer is 3.45.