Phase structure in blends of poly(ethylene glycol) and poly(styrene-co-methacrylic acid)

Phase structures in blends of poly(ethylene glycol) (PEG) and poly(styrene-co-methacrylic acid) (P(S-co-MAA)) with several contents of methacrylic acid units are investigated by using both optical microscopy and field emission type scanning electron microscopy (FE-SEM). It is found that phase-separated domains are diminished with increasing MAA content in PEG/P(S-co-MAA) blends. Further, in the blends in which the ratio of MAA/-CH2CH2O- is larger than 0.2 (mol/mol), macroscopic phase structures disappeared despite the presence of two T-g's meaning separation into two phases in differential scanning calorimetry (DSC) measurements. In PEG/P(S-co-MAA) blends in which MAA/-CH(2)CH(2)OEnDash- > 0.2 (mol/mol), phase-separated structures like interpenetrating networks are found by FE-SEM observations.