Rod-coil block copolymers

In recent years the number of studies on pol5uner vesicles or polymersomes has strongly increased after first reports hy the groups of Eisenherg (11,12), and Bates and Discher (7,13). Since then, amphiphilic block copolymers, rod-coil polymers (14-16), dendrimers (17), and amphiphilic fullerene derivatives (18) have been reported to form vesicular structures. Vesicles can now be made from various pol5uners, from modified biological to wholly synthetic, from dihlock, triblock,... 

III. Block Copolymers Rod-Coil Main Chain Polymers... 

Rod—coil copolymers are a type of amphiphile that can self-assemble into a variety of ordered nanostructures in a selective solvent.36-37-71 In solvents that selectively dissolve only coil blocks, rod—coil copolymers can form well-defined nanostructures with rod domain consisting of the insoluble block. This results in an increase of the relative volume fraction of the coil segments relative to the rod segments, which gives rise to various supramolecular structures. Particularly, poly(alkylene oxide) as the coil block of rod—coil molecule has additional advantages due to complexation capability with alkali metal cation, which can provide an application potential for solid polyelectrolytes and induce various supramolecular structures.72-75... 

Polystyrene-block-poly(L-lysine), polybutadiene-block-poly(L-lysine) [72], and block copolymers of polystyrene or polybutadiene with poly(carboxybenzoxy-L-lysine) [73] were also synthesized by Gallot and coworkers and evidence for lamellar assembUes were presented. Polysaccharide-block-polypeptide rod-coil systems were obtained by polymerizing the IV-carboxyanhydrides of Y -benzyl-L-glutamate from the asparagine a-amino function of carbohydrate fractions of ovomucoid (a glycoprotein extracted from hen egg white). Lamellar assembUes in concentrated solutions and in... 

Fig. 2. Selected architectures of block copolymers (a) diblock (b) triblock (c) comb copolymer consisting of flexible chains (d) rod-coil diblock copolymer consisting of a rodlike block and a coil-like block (e) hairyrods, i.e., comb-block copolymers consisting of rodlike backbone and coil-like side chains and (f) LC coil with a side-chain liquid crystalline (LC) block and a flexible block. Many other variations have been introduced, such as multiblock copolymers, block copolymers consisting of several rodlike blocks, or star-shaped block copolymers. Comb-coil block copolymers with dense packing of side chains are also denoted as molecular bottle brushes, as is illustrated in (g) by a simulated structure of an isolated molecule dissolved in a solvent. (Courtesy of Mika Saariaho.)...

In addition to graft copolymer attached to the mbber particle surface, the formation of styrene—acrylonitrile copolymer occluded within the mbber particle may occur. The mechanism and extent of occluded polymer formation depends on the manufacturing process. The factors affecting occlusion formation in bulk (77) and emulsion processes (78) have been described. The use of block copolymers of styrene and butadiene in bulk systems can control particle size and give rise to unusual particle morphologies (eg, coil, rod, capsule, cellular) (77). 

Schlaad H, Smarsly B, Losik M (2004) The role of chain-length distribution in the formation of solid-state structures of polypeptide-based rod-coil block copolymers. Macromolecules 37 2210-2214... 

A novel coil-rod-coil triblock copolymer, where the rod block was polyflu-orene, PF, and the coil blocks poly(2-tetrahydropyranyl methacrylate),... 

Another key point is selective chemical functionalization at one or both ends, or inside the chain (see scheme 2).m Thus, thiolo functions can serve as clips to create contact with metal surfaces or particles. Quantitative end functionalization of the rigid-rod on one end is a key step toward rod-coil copolymer synthesis (see scheme 3),131 and such a covalent coupling of incompatible polymer blocks is relevant for supramolecular organization.141... 

Scheme 3. Synthetic routes leading to various rod-coil block copolymers via grafting onto" (16a, 16b, 20) or grafting from" (18) reactions.

Block copolymer micelles in which the core-forming polymer blocks are able to crystallize are relatively similar to rod-coil copolymers. A significant part of these crystalline-core micelles is actually resulting from the self-assembly of rod-coil block copolymers. 

Rod-coil copolymers are good candidates for the formation of rodlike or vesicular structures and can be built from polypeptide-block-containing copolymers, as previously discussed in Sect. 6. 

Lee et al. reported the preparation of nanoporous crystalline sheets of penta-p-phenylene using a (oligomeric) block copolymer with a cleavable juncture approach in 2004 [63]. These so-called rod-coil block copolymers of penta-p-phenylene and PPO can self-assemble to give layered phases that contain sheets of perforated crystalline penta-p-phenylene in which the perforations are filled with PPO [64]. The PPO segment is covalently bound to the... 

Microporous structures form on cast film from rod-coil block copolymer micelles... 

Fig. 9 Schematic representation of three approaches to generate nanoporous and meso-porous materials with block copolymers, a Block copolymer micelle templating for mesoporous inorganic materials. Block copolymer micelles form a hexagonal array. Silicate species then occupy the spaces between the cylinders. The final removal of micelle template leaves hollow cylinders, b Block copolymer matrix for nanoporous materials. Block copolymers form hexagonal cylinder phase in bulk or thin film state. Subsequent crosslinking fixes the matrix hollow channels are generated by removing the minor phase, c Rod-coil block copolymer for microporous materials. Solution-cast micellar films consisted of multilayers of hexagonally ordered arrays of spherical holes. (Adapted from [33])...

Fig. 10 Schematic representation of the nanoreplication processes from block copolymers, a Growth of high-density nanowires from a nanoporous block copolymer thin film. An asymmetric PS-fc-PMMA diblock copolymer was aligned to form vertical PMMA cylinders under an electric field. After removal of the PMMA minor component, a nanoporous film is formed. By electrodeposition, an array of nanowires can be replicated in the porous template (adapted from [43]). b Hexagonally packed array of aluminum caps generated from rod-coil microporous structures. Deposition of aluminum was achieved on the photooxidized area of the rod-coil honeycomb structure (Taken from [35])...

The nanoreplication of functional nanostructures has also been achieved through other block copolymer-templated structures. De Boer et al. [35] applied honeycomb-structured films of rod-coil block copolymer as patterned templates to replicate hexagonally packed arrays of aluminum cups on the substrate surfaces (Fig. 10b). Nguyen et al. [237] embedded semiconducting polymers in the channels of oriented hexagonal nanoporous silica and used this nanoscale architecture to control the energy transfer for potential optoelectronic applications. 

More recently [79], a carboxy-terminated PBZT ([r ] = 4.8 dL/g) was reacted with m-phenoxybenzoic acid via a Friedel Craft procedure in a meth-anesulfonic acid/P2Os mixture. This provided an ABA block copolymer in which the outer blocks (A) are composed of flexible coil polyetherketone (PEK) and a center block (B) which contains the rigid-rod PBZT. Thermomechanical analysis showed that 20 PBZT/80 PEK and 10 PBZT/90 PEK compositions exhibited glass transition temperatures of 157 °C and 135°C respectively. Consolidation studies have not been investigated to date. 

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