Hydrogen bonding interactions, crystallization, and surface hydrophobicity in nanostructured epoxy/block copolymer blends

Hydrogen bonding interactions, phase behavior, crystallization, and surface hydrophobicity in nanostructured blend of bisphenol A-type epoxy resin (ER), for example, diglycidyl ether of bisphenol A (DGEBA) and poly(ε- caprolactone)block-poly(dimethyl siloxane) - block- poly (ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, transmission electron microscopy, small-angle X-ray scattering, and contact angle measurements. The PCL-PDMS-PCL triblock copolymer consisted of two epoxy-miscible PCL blocks and an epoxy-immiscible PDMS block. The cured ER/PCL-PDMS-PCL blends showed compositiondependent nanostructures from spherical and worm-like microdomains to lamellar morphology. FTIR study revealed the existence of hydrogen bonding interactions between the PCL blocks and the cured epoxy, which was responsible for their miscibility. The overall crystallization rate of the PCL blocks in the blend decreased remarkably with increasing ER content, whereas the melting point was slightly depressed in the blends. The surface hydrophobicity of the cured ER increased upon addition of the block copolymer, whereas the surface free energy (γ_s) values decreased with increasing block copolymer concentration. The hydrophilicity of the epoxy could be reduced through blending with the PCL-PDMS-PCL block copolymer that contained a hydrophobic PDMS block.