Tunable Hydrophilicity of Poly(ethyl lactate acrylate-co-acrylic acid)
Four copolymers of poly(ethyl lactate acrylate-co-acrylic acid) were prepared by the solution polymerization technique by varying the comonomer content from 0.2 to 0.8 mole percent. The copolymers were characterized by FT-IR, 1H-NMR and proton decoupled 13C-NMR spectroscopic techniques. The reactivity ratio of ethyl lactate acrylate (ELA) and acrylic acid (AA) was calculated using the Fineman-Ross method and the values were found to be 0.101 and 0.186, respectively, indicating the formation of an alternating copolymer. From the wide-angle X-ray diffraction studies (WAXD), the average molecular interchain spacing (
) was calculated from the 2 value of amorphous halo at about 20°. The values varied from 5.20 to 5.64 Å and increased with an increase in the ELA content. The water absorption of copolymers followed
Fickian absorption. Depending upon the copolymer composition, relative humidity and time, the water absorption of copolymers can be tuned to a wide range from 3 to 35% (w/w). The Tg of copolymers decreased from 106 to –27.4°C with an increase in the ELA content. The copolymers
were thermally stable up to 150°C and thereafter exhibited three-step thermal degradation in nitrogen atmosphere. The thermal stability of polymers can be explained on the basis of value.
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