Synthesis of poly(methyl methacrylate–methallyl alcohol) via controllable partial hydrogenation of poly(methyl methacrylate) towards high pulse energy storage capacitor application
Methallyl alcohol has never been reported to be homo-polymerized or copolymerized directly with other monomers. In this manuscript, we report the first synthesis of poly(methyl methacrylate–methallyl alcohol) (P(MMA–MAA)) copolymers via an indirect polymerization process involving the partial hydrogenation of PMMA. The copolymers with varied monomer molar ratios have been carefully characterized with nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA) and dynamic mechanical analysis (DMA). The introduction of –OH groups leads to the formation of H-bonds among –OH and ester groups, which is responsible for the enhanced glass transition temperature and Young's modulus. As a result, the permittivity of P(MMA–MAA) is increased at low MAA content and reduced quickly as more MAA introduced. The breakdown strength (Eb) of P(MMA–MAA)s is improved significantly from about 400 MV m−1 of PMMA to over 550 MV m−1 of P(MMA–MAA) bearing 19 mol% MAA units. The highest discharged energy density (Ue) is observed as 13 J cm−3 at 550 MV m−1 electric field which is 2–3 times larger than BOPP and 50% higher than that of PMMA. Most interestingly, energy loss (Ul) is well maintained at about 8%@550 MV m−1, which is rather close to biaxially oriented polypropylene (BOPP). The promising energy storage capability and excellent energy discharging efficiency of the P(MMA–MAA) copolymer could finally meet the desperate need in high pulse energy storage capacitors. Constructing strong H-bonds in glassy dipolar polymers might offer a great option for designing and fabricating polymeric dielectrics with high Ue and low Ul.