Synthesis and characterization of poly(2-ethylhexyl methacrylate) copolymers containing pendant, self-complementary multiple-hydrogen-bonding sites

The synthesis and characterization of copolymers containing 2-ethylhexyl methacrylate and a quadruple-hydrogen-bonding site, 2-ureido-4[1H]-pyrimidone methacrylate (UPyMA), are described. An analogous dimeric hydrogen-bond- containing copolymer based on 2-ethylhexyl methacrylate and methacrylic acid (PEHMA-co-MAA) was also synthesized for comparative purposes. The glass-transition temperatures of the poly(2-ethylhexyl methacrylate-co-2-ureido- 4[1H]-pyrimidone methacrylate) (PEHMA-co-UPyMA) series increased linearly with increasing UPyMA content. Creep compliance measurements as a function of temperature indicated a decrease in the creep compliance with increasing UPyMA content over the range of 1-10 mol % UPyMA. Melt rheological analysis also showed an increase and lengthening of the plateau modulus as a function of frequency with increasing UPyMA content, as well as increasing complex viscosity as a function of temperature. The analogous PEHMA-co-MAA copolymer, which contained 11 mol % methacrylic acid, showed, in the melt rheological analysis, behavior similar to that of the PEHMA-co-UPyMA copolymer containing only 1 mol % UPyMA units. The multiple-hydrogen-bond-containing copolymers were successfully analyzed with time-temperature superposition for the construction of master curves.