Copolymers of 4-adamantylphenyl methacrylate derivatives with methyl methacrylate and styrene

Three 4-(1-adamantyl)phenyl methacrylate monomers were synthesized from 4-(1-adamantyl)phenol derivatives which were obtained by Friedel-Crafts alkylation of phenol, 2-methylphenol and 2,6-dimethylphenol with 1-bromoadamantane. Characterization of the monomers by IR, ¹H and ¹³C NMR, GC and elemental analysis confirmed structures and purities. Copolymers of these new monomers with styrene were synthesized using free radical techniques. One series of 4-(1-adamantyl)phenyl methacrylate was also prepared with methyl methacrylate (MMA). Copolymer compositions were evaluated by ¹H and ¹³C solution NMR, and with FTIR. Reactivity ratios were estimated to have values of r₁ = 0.22 and r₂ = 1.51 for styrene and 4-(1-adamantyl)phenyl methacrylate copolymers; r₁ = 0.31 and r₂ = 2.44 for styrene and 2-methyl-4-(1-adamantyl)phenyl methacrylate; and r₁ = 0.97 and r₂ = 0 for styrene and 4-(1-adamantyl)-2,6-dimethylphenyl methacrylate copolymers (J Polym Sci A 3 (1965) 369-87, J Macromol Sci Rev C4 (1970) 281). All homo- and copolymers were characterized using DSC and TGA to determine copolymer composition effects on T_g and thermal stability. The estimated T_g for the homopolymer of 4-(1-adamantyl) phenyl methacrylate was 253°C and the onset of decomposition was 250°C in nitrogen. The homopolymer of 2-methyl-4-(1-adamantyl) phenyl methacrylate had a T_g of 250°C which was at the onset of decomposition in nitrogen. The homopolymer of 4-(1-adamantyl)-2,6-dimethylphenyl methacrylate could not be obtained by free-radical polymerization. 4-(Adamantyl)phenyl methacrylate was incorporated into styrene copolymers at 1-30 mol% and gave T_g increases of ca. 5-60°C over that of polystyrene, respectively. Incorporation of this monomer into MMA copolymers (0.75-35 mol%) resulted in T_g increases of ca. 6-70°C over that of poly(methyl methacylate).