The influence of hydrophilic and hydrophobic domains on water wettability of 2‐hydroxyethyl methacrylate‐styrene copolymers

Cooligomers and ABA-type block copolymers composed of a hydrophilic monomer, 2-hydroxyethyl methacrylate (HEMA), and a hydrophobic monomer, styrene, were synthesized to study the relation between their microstructure and hydrophilic and hydrophobic functions. Films of cooligomers and ABA-type block copolymers were cast from DMF solutions at 40°C. The wettability, which was determined from the contact angle with water, increased considerably when HEMA mole fraction reached around 0.8 in the cooligomer system and around 0.9 in the ABA-type block copolymer system. The microstructures of the copolymer films were observed by electron microscopy using the osmium tetroxide fixation technique. The morphologic change in the domain structure was observed at an HEMA mole fraction of about 0.8 in the cooligomer system and about 0.9 in the ABA-type block copolymer system. It is suggested that hydrophilic and hydrophobic functions are largely influenced by the state of aggregation of each segment, that is, the size and geometry of the hydrophilic and hydrophobic domains.