Self-assembly and thermal behavior of amphiphilic di-block copolymers of poly(methyl methacrylate)-block-poly(ethylene oxide) (PMMA-b-PEO)

Two amphiphilic di-block copolymers with composition of PMMA(118)-b-PEO45 and PMMA(25)-b-PEO45 have been synthesized and characterized by NMR and FTIR spectroscopies. The critical micelle concentration (CMC) of synthesized copolymers in toluene has been determined. The variation in CMC of both polymers was recorded under the influence of temperature. Interestingly, it was found that CMC decreases with increase in the polymethyl methacrylate (PMMA) chain length and increase in temperature. A decrease in Gibbs free of micellization (Delta G(mic)) energy was found in the range of (- 17.3 to - 20.4), and increase in the entropy of micellization was observed in the range of (26.4 to 29.4) mol(-1) at temperature in the range from 293 to 323 K with 10 K increment, while enthalpy is independent of temperature. From thermal analysis, it was concluded that degradation temperature slightly increases as the PMMA length increases. This is probably due to difficult diffusion of thermal energy across the entangled chains of PMMA.