The scope of this Perspective is to highlight innovative contributions in the synthesis of well-defined complex macromolecular architectures and to emphasize the importance of these materials to polymer physical chemistry, physics, theory, and applications. In addition, this Perspective tries to enlighten the past and show possible pathways for the future. Among the plethora of polymerization methods, we briefly report the impact of the truly living and controlled/ living polymerization techniques focusing mainly on anionic polymerization, the mother of all living and controlled/living polymerizations. Through anionic polymerization well-defined model polymers with complex macromolecular architectures having the highest molecular weight, structural and compositional homogeneity can be achieved. The synthesized structures include star, comb/graft, cyclic, branched and hyberbranched, dendritic, and multiblock multicomponent polymers. In our opinion, in addition to the work needed on the synthesis, properties, and application of copolymers with more than three chemically different blocks and complex architecture, the polymer chemists in the future should follow closer the approaches Nature, the perfect chemist, uses to make functional complex macromolecular structures by noncovalent chemistry. Moreover, development of new analytical methods for the characterization/purification of polymers with complex macromolecular architectures is essential for the synthesis and properties study of this family of polymeric materials.

Thin film morphologies of a 75.5 kg/mol polystyrene-block-polydimethylsiloxane (PS-b-PDMS) diblock copolymer subject to solvent vapor annealing are described. The PS-b-PDMS has a double-gyroid morphology in bulk, but as a thin film the morphology can form spheres, cylinders, perforated lamellae, or gyroids, depending on the film thickness, its commensurability with the microdomain period, and the ratio of toluene:heptane vapors used for the solvent annealing process. The morphologies are described by self-consistent field theory simulations. Thin film structures with excellent long-range order were produced, which are promising for nanopatterning applications.

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A universal block copolymer pattern transfer method was demonstrated to produce Co nanostructures consisting of arrays of lines or dots from a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) diblock copolymer. Three processes were used: liftoff, a damascene process, and ion beam etching using a hard mask of tungsten, including a sacrificial poly(methyl methacrylate) layer under the PS-b-PDMS for the etch and liftoff processes. The ion beam etch process produced the most uniform magnetic arrays. A structural and magnetic comparison in terms of uniformity, edge roughness and switching field distribution has been reported.

A combined experimental and self-consistent-field theoretical (SCFT) investigation of the phase behavior of poly(stryrene- b-dimethylsiloxane- b-styrene) (PS- b-PDMS- b-PS, or SDS32) thin films during solvent vapor annealing is presented. The morphology of the triblock copolymer is described as a function of the as-cast film thickness and the ratio of two different solvent vapors, toluene and heptane. SDS32 formed terraced bilayer morphologies even when the film thickness was much lower than the commensurate thickness. The morphology transitioned between bilayer cylinders, bilayer perforated lamellae, and bilayer lamellae, including mixed structures such as a perforated lamella on top of a layer of in-plane cylinders, as the heptane fraction during solvent annealing increased. SCFT modeling showed the same morphological trends as a function of the block volume fraction. In comparison with diblock PS- b-PDMS with the same molecular weight, the SDS32 offers a simple route to produce a diversity of well-ordered bilayer structures with smaller feature sizes, including the formation of bilayer perforated lamellae over a large process window.

We report a combined directing effect of the simultaneously applied graphoepitaxy and electric field on the self-assembly of cylinder forming polystyrene-b-poly­(dimethylsiloxane) block copolymer in thin films. A correlation length of up to 20 μm of uniaxial ordered striped patterns is an order of magnitude greater than that produced by either graphoepitaxy or electric field alignment alone and is achieved at reduced annealing times. The angle between the electric field direction and the topographic guides as well as the dimensions of the trenches affected both the quality of the ordering and the direction of the orientation of cylindrical domains: parallel or perpendicular to the topographic features. We quantified the interplay between the electric field and the geometry of the topographic structures by constructing the phase diagram of microdomain orientation. This combined approach allows the fabrication of highly ordered block copolymer structures using macroscopically prepatterned photolithographic substrates.

Supramolecular block copolymers ( PS-DAT- sb -PI-Thy ) were synthesized via noncovalent hydrogen bonding between well-defined thymine end-functionalized polyisoprene ( PI-Thy ) and diaminotriazine (DAT) end-functionalized polystyrene ( PS-DAT ). Three covalently linked block copolymers were also synthesized for comparison with the noncovalent supramolecular block copolymers. The complementary DAT/Thy interaction resulted in the microphase separation of the supramolecular block copolymer system. Detailed characterization of all functionalized homopolymers and block copolymers was carried out via proton nuclear magnetic resonance ( 1 H NMR) spectroscopy, gel permeation chromatography, matrix-assisted laser desorption/ionization-time of flight mass spectrometry, and differential scanning calorimetry. The self-assembly process of supramolecular block copolymers was evidenced by transmission electron microscopy. Small-angle X-ray scattering was also performed to study the microphase separation of supramolecular and covalently linked block copolymers. Comparison of microphase separation images of supramolecular block copolymers and the corresponding covalently linked analogues reveals differences in d -spacing and microdomain shape.

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