Self-assembly Behavoir And Photonic Performance Of Diblock Copolymer In Array Confinement

In this dissertation, polymeric self-consistent field theory and strong phasesegregation theory are used to explore the self-assembly behavior of AB diblockcopolymers in2d and3d array confinement. In our work, many novel structures arefound and classified reasonably. In the same time, the effect of array-confinementparameters, structural transformation and the control methods of polymeric structureare investigated.In the2d array confinement, the structures of diblock copolymer in square,rectangular and triangular pillar arrays are studied. Our study found thearray-confinement parameters, i.e., pillar pitch and size significantly influence thestretching of diblock copolymers. By changing the pillar pitch and size, the polymerregion is changed, and thus the phase interface, the direction and number of lamellaeare changeable. Besides the array-confinement parameters, the surface field of pillarsinduces the formation of novel structures. Moreover, in the pillar arrays with differentpillar pitches along the x and y directions, or in rectangular and triangular pillar arrays,the equity between the x and y directions is destroyed, and thus the orientation ofpolymeric structure is controllable. In triangular pillar arrays, four novel types ofcylindrical structures are observed and their photonic performance is tested. We foundthe copolymeric structure enlarges the complete photonic band of the arrayconfinement.In the3d array confinement, we apply a self-consistent field theory of polymersto study the structures of a symmetric diblock copolymer in parallel substrates filledwith square-pillar arrays in which the substrates and pillars exhibit a weak preferencefor one block of the copolymer. Three classes of structures, i.e., lamellae,perpendicular cylinders, and bicontinuous structures, are achieved by varying thepolymer film thickness, the pillar pitch (the distance between two centers of thenearest neighboring pillars), the gap and rotation of the pillars. Because of theconfinement along horizontal directions imposed by the pillar array, eight novel typesof perpendicular lamellar structures and eight novel types of cylindrical structureswith various shapes and distributions occur. In the hybridization states of the paralleland perpendicular lamellar structures, several novel bicontinuous structures such as the double-cylinder network, pseudo-lamellae, and perforated lamellar structure arealso found. By comparing the free energies of the various possible structures, theantisymmetric parallel lamellae are observed to be stable with the larger pillar gap at acertain film thickness. The structural transformations between the alternatingcylindrical structures (alternating cross-shaped, square-shaped, and octagonalperpendicular cylinders) and parallel lamellae with increasing film thickness or pillargap are well explained by the modified strong separation theory. Our results indicatethat array confinement can be an effective method to prepare novel polymericnanopattern structures.