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

Abstract

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°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°C, and above 95% at 60°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°C, and the conversions were all above 99%. The GPC and 1H 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°C and 60°C, respectively, which deviated from –2°C and 105°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.

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

“…As our previous study 27,28 showed, t-BuOK was capable of initiation for anionic polymerization of alkyl methacrylate at ambient temperature. For convincing this synthesis method, another homopolymerization of MMA, EMA and BMA was conducted and the results were as Table 1 showed.…”

“…Obviously, for the existence of association state in t-BuOK solution, the initiator efficiency was not close to 100% but at a stable number of approximately 43% at this situation, which has been discussed in our previous work. 27,28 This consequence would provide a possibility of a controlled method for block copolymers of alkyl methacrylate.…”