PHASE MORPHOLOGY IN BLOCK-COPOLYMER SYSTEMS

Microphase separation in block copolymer systems forms well-defined, p eriodic structure on the sub-micron length scale. This structure arise s from the system striving to satisfy the delicate balance of minimizi ng the area of contact between incompatible chain segments and maximiz ing the conformational entropy of the macromolecules. Candidate geomet ries satisfying these constraints possess intermaterial dividing surfa ces (IMDS) of constant mean curvature. These include triply periodic, bicontinuous structures related to minimal surfaces. These structures, recently observed in microphase-separated block copolymer systems, al so arise in phase-separated surfactant-water systems, indicating the t wo phenomena may be driven by similar physical mechanisms. A complete description of block copolymer phase morphology requires characterizat ion of the long-range ordered single grain microdomain structure, the defect structures within grains, and the microstructure of the boundar y region between grains. The type of structure observed is sensitive t o the architecture, chemical composition, and molecular mass of the co polymers. Thermodynamic treatments using a geometrical description of the IMDS provide a means for probing the physics of phase morphology i n block copolymers.