Abstract

Urethane macromonomers (UMs) having different urethane chain lengths (X) were synthesized by the reaction of an isocyanate-terminated prepolymer with 2-hydroxy ethyl methacrylate (HEMA) and isopropanol. The existence and the structural identification of the UMs were verified by FTIR, ¹H NMR and ¹³C NMR spectroscopy. Various percentages of the respective UMs (0-40 wt % acrylate monomers) were then incorporated into methyl methacrylate (MMA) and n-butyl methacrylate (n-BMA) backbones via solution free-radical copolymerization. The resulting methyl methacrylate-g-urethane and n-butyl methacrylate-g-urethane copolymers were characterized by GPC, ¹H NMR, ¹³C NMR, FTIR, TGA and DMA. Phase separation between the urethane segment and the acrylate segment in the graft copolymerization products was investigated by DMA and TEM. DMA results showed that in most graft copolymer products the two respective component parts of PMMA-g-urethane or n-PBMA-g-urethane were compatible as only one T_g was observed. Two glass transitions, at temperatures of 22 and 76 ^oC, corresponding to the n-PBMA and urethane moieties, were observed when the chain length of the UMs was increased from X=4 to X=32. Microphase separation was also evident in TEM measurement.

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