A controlled synthesis method of alkyl methacrylate block copolymers via living anionic polymerization at ambient temperature

Abstract

A controlled synthesis method of alkyl methacrylate block copolymers such as poly(methyl methacrylate)-b-poly(ethyl methacrylate) (PMMA-b-PEMA), poly(methyl methacrylate)-b-poly(butyl methacrylate) (PMMA-b-PBMA) and poly(ethyl methacrylate)-b-poly(butyl methacrylate) (PEMA-b-PBMA) via living anionic polymerization was innovated with potassium tert-butoxide (t-BuOK) as initiator in tetrahydrofuran(THF) solvent. The sequential anionic copolymerization could be smoothly conducted at 0 °C and the conversion of all monomers reached up to almost 100%. The copolymers were characterized by gel permeation chromatography (GPC), proton nuclear magnetic resonance (¹H-NMR), fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analysis (DMA). It was found that all block copolymers were in a narrow MWD while M_w and weight ratio of each block were coincided with the theoretical values and feed ratio. DMA measurement indicated that all the block copolymers have two glass transition temperatures which have proved the certain microphase separation and the partial compatibility of the blocks. The similar results were achieved after changing feed order or addition amount. Furthermore, the reactivity ratio was also studied and confirmed that reactivity ratio of MMA was the largest among alkyl methacrylate. Based on these results, the anionic block copolymerization containing polar alkyl methacrylate monomers at a commercial scale starts to become possible.