Diblock copolymer microdomain morphology

It is well known that block copolymers and graft copolymers composed of incompatible sequences form the self-assemblies (the microphase separations). These morphologies of the microphase separation are governed by Molau s law [1] in the solid state. Nowadays, not only the three basic morphologies but also novel morphologies, such as ordered bicontinuous double diamond structure, are reported [2-6]. The applications of the microphase separation are also investigated [7-12]. As one of the applications of the microphase separation of AB diblock copolymers, it is possible to synthesize coreshell type polymer microspheres upon crosslinking the spherical microdomains [13-16]. 

Laser ablation of polymer films has been extensively investigated, both for application to their surface modification and thin-film deposition and for elucidation of the mechanism [15]. Dopant-induced laser ablation of polymer films has also been investigated [16]. In this technique ablation is induced by excitation not of the target polymer film itself but of a small amount of the photosensitizer doped in the polymer film. When dye molecules are doped site-selectively into the nanoscale microdomain structures of diblock copolymer films, dopant-induced laser ablation is expected to create a change in the morphology of nanoscale structures on the polymer surface. 

As aforementioned, diblock copolymer films have a wide variety of nanosized microphase separation structures such as spheres, cylinders, and lamellae. As described in the above subsection, photofunctional chromophores were able to be doped site-selectively into the nanoscale microdomain structures of the diblock copolymer films, resulting in nanoscale surface morphological change of the doped films. The further modification of the nanostructures is useful for obtaining new functional materials. Hence, in order to create further surface morphological change of the nanoscale microdomain structures, dopant-induced laser ablation is applied to the site-selectively doped diblock polymer films. 

The best-known and simplest class of block copolymers are linear diblock copolymers (AB). Being composed of two immiscible blocks, A and B, they can adopt the following equilibrium microphase morphologies, basically as a function of composition spheres (S), cylinders (C or Hex), double gyroid (G or Gyr), lamellae (L or Lam), cf. Fig. 1 and the inverse structures. With the exception of the double gyroid, all morphologies are ideally characterized by a constant mean curvature of the interface between the different microdomains. 

Recently, significant advances have been made in controlling the micro domain orientation in diblock copolymer films [10,11,270-284]. When the copolymer is placed between two solid interfaces, the morphology responds strongly to the deviation of the film thickness from the integer number of the layers [271-274]. By adjusting the chemical structure of the interfaces so that both blocks interact with them equally, perpendicular orientation of the microdomains was... 

The self-organization of block copolymers constitutes a versatile means of producing ordered periodic structures with phase-separated microdomain sizes on the order of tens of nanometers. The morphology of microdomains formed by diblock copolymers in the bulk has been intensively researched and is by now a relatively well-imderstood area [74,75]. 

Fig. 5.12 Schematic of the surface-ordering process in a diblock copolymer. The top diagram shows the dibiock copolymer in a phase mixed state. This is not accessible for PS/PMMA co-polymers via solvent-casting processes. The center diagram corresponds to a microphase-separated morphology where the periodic lamellar microdomains are randomly oriented in the specimen. After annealing for 24 h at 170 °C, the copolymer exhibits a lamellae morphology oriented parallel to the surface as shown in the bottom picture. Reprinted with permission from ref. [96]...

Theoretical approximations and morphology predictions were recently carried out for miktoarm star terpolymers of the ABC type. The literature concerning theoretical predictions for this complex architeaure is rather limited, as the synthesis of such materials leading to morphologically three-phase stmaures has been developed rather recently. The behavior of miktoarm star terpolymers was simulated using the Monte Carlo calculation method. This approach was already used for the microdomain structural behavior of diblock copolymers of the AB type, and the consideration that needed to be taken into account for the calculations was the addition of the C chain at the common junction point of the A... 

Politakos, N. Ntoukas, E. Averopoulos, A. Krikorian, V. Pate, B. D. Thomas, E. L. Hfll, R. M., Strongly Segregated Cubic Microdomain Morphology Consistent with the Double Gyroid Phase in High Molecular Weight Diblock Copolymers of Polystyrene and Poly(dimethylsiloxane). J. Polym. Sci., PartB Polym. Phys. 2009,47,2419-2427. 

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