Synthesis of Block Copolymers of 2-Ethylhexyl Methacrylate, n-Hexyl Methacrylate and Methyl Methacrylate via Anionic Polymerization at Ambient Temperature

It still remains a concern to break through the bottlenecks of anionic polymerization of polar monomers, such as side reactions, low conversion and low temperature (-78 degrees C). In this work, potassium tert-butoxide (t-BuOK) was chosen to initiate the anionic polymerization of 2-ethylhexyl methacrylate (EHMA) in tetrahydrofuran. The conversions were above 99% at 0 or 30 degrees C, and above 95% at 60 degrees C without side reaction inhibitors. The high conversions implied t-BuOK could suppress the side reactions. A series of block copolymers of EHMA, n-hexyl methacrylate (HMA) and methyl methacrylate (MMA) were further synthesized at 0 degrees C, and the conversions were all above 99%. The GPC and H-1 NMR results confirmed the successful synthesis of the block copolymers. The molecular size of monomer and the state of t-BuOK (free ion pairs or aggregates) remarkably affected the polymerization rates and the molecular structures of the products. The DMA results indicated that the glass transition temperatures of PEHMA or PHMA block and PMMA block were 20 degrees C and 60 degrees C, respectively, which deviated from -2 degrees C and 105 degrees C of homopolymer, respectively, due to the partial compatibility of the blocks. This work explored a route of the anionic polymerization of polar monomers at room temperature.