Summary: In previous papers, a novel melt process was reported for the preparation of colloidal crystals exhibiting the crystalline structure of opals. Latex spheres with a hard, crosslinked core and a grafted-on elastomeric shell flow at elevated temperatures under uniaxial compression much like other polymer melts. However, the spheres start crystallizing at the plates of the press, whereupon the crystalline order grows, layer by layer, into the flowing melt. In this report, the domain order of opal disks thus obtained is discussed, together with the phenomena of light reflection. The pattern of light reflected from the (220) plane of the fcc lattice reveals that, during compression, this lattice is oriented macroscopically by the radial melt flow so that each radial sector of the opal disk forms a crystalline monodomain.
Film of latex spheres with colloidal crystalline order prepared by melt compression of PS/PMMAcsPEA core-shell latex spheres.