Towards microphase separation in epoxy systems containing PEO/PPO/PEO block copolymers by controlling cure conditions and molar ratios between blocks. Part 2. Structural characterization

The influence of addition of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO–PPO–PEO) copolymers on final morphologies of modified epoxy matrices has been investigated as a function of PEO:PPO molar ratio and cure conditions by comparison with the cured epoxy blends only containing poly(ethylene oxide) (PEO) or poly(propylene oxide) (PPO) homopolymers. Atomic force microscopy (AFM) has been used to characterize structural features of blends. Whilst diglycidyl ether of bisphenol-A (DGEBA)/4,4’-diaminodiphenylmethane (DDM)/PPO system macrophase separates, the interactions between PEO and cured epoxy are responsible for miscibility of DGEBA/DDM/PEO system. Depending on PEO:PPO molar ratio, micro- or macrophase separated morphologies have been obtained for block copolymer modified epoxy matrices. Moreover, the influence of both copolymer content and cure temperature on final morphologies has also been investigated by both experimental and theoretical analysis.