Self bulk state

The self-assembly of block polymers, in the bulk, thin film and solution states, produces uniformly sized nanostructured patterns that are very useful for nanofabrication. Optimal utilization of these nanoscopic patterns requires complete spatial and orientational control of the microdomains. However, the microdomains in the bulk state normally have grain sizes in the submicron range and have random orientations. In block copolymer thin films, the natural domain orientations are generally not desirable for nanofabrication. In particular, for composition-asymmetric cylindrical thin films, experimental... 

Janus micelles are non-centrosymmetric, surface-compartmentalized nanoparticles, in which a cross-linked core is surrounded by two different corona hemispheres. Their intrinsic amphiphilicity leads to the collapse of one hemisphere in a selective solvent, followed by self-assembly into higher ordered superstructures. Recently, the synthesis of such structures was achieved by crosslinking of the center block of ABC triblock copolymers in the bulk state, using a morphology where the B block forms spheres between lamellae of the A and C blocks [95, 96]. In solution, Janus micelles with polystyrene (PS) and poly(methyl methacrylate) (PMMA) half-coronas around a crosslinked polybutadiene (PB) core aggregate to larger entities with a sharp size distribution, which can be considered as supermicelles (Fig. 20). They coexist with single Janus micelles (unimers) both in THF solution and on silicon and water surfaces [95, 97]. 

Self-Assembly in the Bulk State Two Length-Scale Structures. 137... 

A special case of a miktoarm star copolymer with many arms are so-called Janus Micelles, which are formed by cross-linking the short middle block of a triblock terpolymer in the microphase separated bulk state, in which the center block self-assembles in spherical [ 189,190] or cylindrical domains [191]. By this procedure the two different outer blocks are oriented to the two opposite hemicoronas around the center block domain and subsequent dissolution leads to amphiphilic particles (Figure 14). While spherical Janus Micelles form superstructures in solution, the cylindrically shaped Janus Micelles seem to have a lower tendency of self-aggregation to higher superstructures. 

Figure 16 shows schematically various morphologies observed in micellar solutions of amphiphilic diblock copolymers in a water-oil system. The micelles self-assemble into similar morphologies as they are observed in the bulk state of amorphous diblock copolymers. While in the so-called open micelles single macromolecules can leave the micelle to the solution and vice versa, in the so-called frozen micelles the structure is not dynamic, for example, due to a glass transition temperature of the core above the system s temperature. 

Figure 16.15 TEM images for bulk state morphologies of PS- -PFS (a-c), PFS- -PMMA (d) and PMMA- -PFS-Z -PS-Z -PFS- -PMMA (e-f) (PFS = poly(ferrocenylethylmethylsilane) in (a)-(c) and the dimethyl analog in (d)-(f). ((a)-(c) Reprinted with permission from D.A Rider, K.A. Cavicchi, K.N. Power-Billard et al, Diblock copolymers with amorphous atactic polyferrocenylsilane blocks Synthesis, characterization, and self-assembly of polystyrene-block-poly(ferrocenylethylmethylsilane) in the bulk state, Macromolecules, 38, 6931, 2005. 2005 American Chemical Society, (d) Reprinted with permission from C. Kloninger and M. Rehahn, Bicontinuous gyroidic morphologies in ferrocenyldi-methylsilane-b-methyl methacrylate diblock copolymer blends, Macromolecules, 37, 8319, 2004. 2004 American Chemical Society, (e)-(f) Reproduced with permission from U. Datta and M. Rehahn, Synthesis and self-assembly of styrene-[l]dimethylsilaferrocenophane-methyl methacrylate penta-block copolymers, Molecular Rapid Communications, 2004,25,1615. Wiley-VCH Verlag GmbH Co. KGaA.)...

Gwyther, 1. and Manners, 1. (2009) Diblock copolymers with amorphous, high glass transition temperature, organometallic block synthesis, characterisation and self-assembly of polystyiene-i -poly(ferrocenylisopropyl-methylsilane) in the bulk state. Polymer 50, 5384—5389... 

Rider, D.A., Cavicchi, K.A., Power-BiUard, K.N. et al. (2005) Diblock copolymers with ammphous atactic polyferrocenylsilane blocks synthesis, characterization, and self-assembly of polystyrene-block-poly(ferrocenylethyl-methylsilane) in the bulk state. Macromolecules, 38,6931. 

Recently, the enhanced control of bulk and surface ordering of polypeptides has been employed to drive the processing and self-assembly of conductive rigid segments. Mainly triblock copolymer structures have been studied (see the following section). Manners and Winnik (Wang et al., 2008) synthesized a new type of metaUopolymer-polypeptide block copolymer poly(ferrocenyldimethylsilane)-fc-poly(8-benzyloxycarbonyl-L-lysine) (PFS-( -PZLLys) and studied their self-organization behavior in both the bulk state and in solution. In the bulk state, a cylindrical in-lamellar structure was observed in a compositionally asymmetric sample. Rod-like micelles with a polyferrocenylsilane core formed in a polypeptide selective solvent alone or in the presence of a common solvent. 

Hydrogenated random copolymers of 1.4- and 1.2-butadiene represent another class of crystalline-amorphous materials [10-15,17). Following hydrogenation, the resultant copolyolefin contains ethylene (E) and 1-butene (B) units. These materials can be described as PEB-n where n denotes the mun-ber of ethyl units per 100 backbone carbons. Eor samples where n < 12 the samples will show partial crystallinity at room temperature while for n > 13 the samples are amorphous in the bulk state. The latter PEB copolymers lack self-assembly capacity. An equivalent amorphous segment is derived from polyisoprene. In this case hydrogenation yields the essentially alternating ethylene-propylene copolymer (PEP). This material also contains about 7% isopropyl units that randomly appear between the ethylene-propylene units. 

The size dependence of the elastic modulus was also attributed to the total strain energy of a nanocrystalline [1, 2] that can be decomposed into the strain energy of the bulk Ub) and the surface, Us), i.e., U = Ub + Ug. Minimizing the total strain energy of nanocrystals will deform from the bulk crystal lattice into the self-equilibrium state of crystals. The strain in a self-equilibrium state in nanocrystals can be calculated by dU/Vodsij = 0, in which Vq and sy i,j = 1,2,3) are the volume and the elastic strain, respectively. The size-dependent Y modulus of spherical nanocrystals based on the size-dependent surface free energy was derived as [1],... 

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