Diblock copolymer schematic

The long sequences of A and B units of a block copolymer can be arranged in several different ways. A diblock copolymer, schematically represented as... 

Micellar structure has been a subject of much discussion [104]. Early proposals for spherical [159] and lamellar [160] micelles may both have merit. A schematic of a spherical micelle and a unilamellar vesicle is shown in Fig. Xni-11. In addition to the most common spherical micelles, scattering and microscopy experiments have shown the existence of rodlike [161, 162], disklike [163], threadlike [132] and even quadmple-helix [164] structures. Lattice models (see Fig. XIII-12) by Leermakers and Scheutjens have confirmed and characterized the properties of spherical and membrane like micelles [165]. Similar analyses exist for micelles formed by diblock copolymers in a selective solvent [166]. Other shapes proposed include ellipsoidal [167] and a sphere-to-cylinder transition [168]. Fluorescence depolarization and NMR studies both point to a rather fluid micellar core consistent with the disorder implied by Fig. Xm-12. 

The chain arrangement of this morphology was schematically proposed as in Fig. 10. The cell of the microsphere has a hexagonal surface, and the AB diblock copolymers form a bilayer between the microspheres. From this schematic arrangement, the optimal blend ratio of the AB block copolymer in this system was calculated as 0.46. This value was very close to the blend ratio of the AB type block copolymer 0.5 at which the blend showed the hexagonal packed honeycomb-like structure. 

Figure 2. Schematic three-dimensional plot showing various planes of AB polymer/polymer composition. From left to right homopolymer blends blends containing 50 weight percent diblock copolymer diblock copolymers. 

Finally, we have designed and synthesized a series of block copolymer surfactants for C02 applications. It was anticipated that these materials would self-assemble in a C02 continuous phase to form micelles with a C02-phobic core and a C02-philic corona. For example, fluorocarbon-hydrocarbon block copolymers of PFOA and PS were synthesized utilizing controlled free radical methods [104]. Small angle neutron scattering studies have demonstrated that block copolymers of this type do indeed self-assemble in solution to form multimolecular micelles [117]. Figure 5 depicts a schematic representation of the micelles formed by these amphiphilic diblock copolymers in C02. Another block copolymer which has proven useful in the stabilization of colloidal particles is the siloxane based stabilizer PS-fr-PDMS [118,119]. Chemical... 

Fig. i Schematic representation of chain conformation in micelles from a linear PEO-PBO diblock copolymers, b linear PEO-PBO-PEO triblock copolymers, c linear PBO-PEO-PBO triblock copolymers and d cyclic PEO-PBO diblock copolymers... 

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])...

Figure 8.14 Schematic diagram of the interconversion between diblock copolymer and star-like nanogel throngh the radical crossover reaction of alkoxyamine units [44],...

A number of researchers have used surface energy libraries to examine the self-assembly of block copolymer species in thin films. It is well known that substrate-block interactions can govern the orientation, wetting symmetry and even the pattern motif of self-assembled domains in block copolymer films [29]. A simple illustration of these effects in diblock copolymer films is shown schematically in Fig. 6. However, for most block copolymer systems the exact surface energy conditions needed to control these effects are unknown, and for many applications of self-assembly (e.g., nanolithography) such control is essential. 

Figure 6 Schematic representation of the problems that can be encountered during the synthesis of a zwitterionic diblock copolymer by aqueous ATRP. I represents the initiator fragment and represents the block junction...

Doi et al.ll2> have concluded that the diblock copolymer is formed via the transformation of living polypropylene and (3) to radical end (7), as schematically represented by reaction (45). 

A well-defined diblock copolymer of propylene and tetrahydrofuran (THF) was synthesized on the basis of the transformation of living polypropylene end (3) to cationic end (9) which initiates the living polymerization of THF, as schematically represented by reaction (46)104). 

Fig.23. Schematic illustration of wetting geometries expected for ultra-thin films of diblock copolymers a - parallel lamellae, b - surface (pinned) micelles, c - perpendicular lamellae. L corresponds to the equilibrium period of the lamellar morphology...

Figure 27 Schematic illustrations of lamellar morphologies for AB diblock copolymers under flat and curved confinements. The concentric cylinder barrel structure under curved confinement corresponds to the parallel lamellar structure under flat confinement (left). The sector column structure corresponds to the vertical lamellar structure (right).

Fig. 10. Schematic phase diagram of a semi-infinite block copolymer melt for the special case of a perfectly neutral surface (Hj=0). Variables chosen are the surface interaction enhancement parameter (-a) and the temperature T rescaled by chain length (assuming X l/T the ordinate hence is proportional to %c/%). While according to the Leibler [197] mean-field theory a symmetric diblock copolymer transforms from the disordered phase (DIS) at Tcb oc n in a second-order transition to the lamellar phase (LAM), according to the theory of Fredrickson and Helfand [210] the transition is of first-order and depressed by a relative amount of order N 1/3. In the second-order case, the surface orders before the bulk at a transition temperature T (oc l / ) as soon as a is negative [216], and the enhancement...

Fig. 12. Schematic variation of the order parameter profile /(z) of a symmetric (f=l/2) diblock copolymer melt as a function of the distance z from a wall situated at z=0. It is assumed that the wall attracts preferentially species A. Case (a) refers to the case % %v where non-linear effects are still negligible, correlation length and wavelength X are then of the same order of magnitude, and it is also assumed that the surface "field" Hj is so weak that at the surface it only induces an order parameter 0.2 n if mb is the order parameter amplitude that appears for %=%t at the first-order transition in the bulk. Case (b) refers to a case where % is only slightly smaller than %t, such that an ordered "wetting layer" of thickness 1 [Eq. (76)] much larger than the interfacial thickness which is of the same order as [Eq. (74)] is stabilized by the wall, while the bulk is still disordered. The envelope (denoted as m(z) in the figure) of the order parameter profile is then essentially identical to an interfacial profile between the coexisting ordered phase at T=Tt for (zl). The quantitative form of this profile [234] is shown in Fig. 13. From Binder [6]...

Fig. I Schematic representations of the morphologies obtained for diblock copolymer melts. Reprinted with permission from Khandpur et al. [12]. Copyright 1995 American Chemical Society...

Fig. 5 Schematic representation of AB diblock copolymer micelles in a selective solvent of the A block, Rc core radius, L shell (corona) thickness. Adapted from Riess [29]. Copyright 2003, with permission from Elsevier...

Fig. 19 Schematic representation of block-arm star copolymer of type (PS- -P2VP) (PS) and (PS) (P2VP) heteroarm star diblock copolymer complexed with DBSA. In the drawing n = 4, Reprinted with permission from [135,136]. 2005 and 2006 American Chemical Society...

Fig. 11 a Schematic illustration and b chemical structure of the diblock copolymer, c Illustration of the morphology changes with temperature increases from top to bottom represent three temperature regions below 100 °C, 100-150 °C, and above 150 °C. d TEM image of diblock film at room temperature, (e) SAXS intensity curves during heating at 2 °C/min. Reprinted with permission from [84]... 

Figure 4.22 Schematic drawings of various block copolymers. These long-chain molecules synthetic molecules consist of chemically distinct poiymeric "biocks" (denoted by lines of (Afferent thicknesses in the figure), chemically grafl. (Left to right ) Linear diblock copolymer molecule (AB) linear triblock (ABC) star copolymer brush copolymer. If the blocks are mutually immiscible, under suitable conditions die molecules spontaneously dump together forming an array of mesophases.

Fig. 2. Schematic of connecting chains at an interface, a diblock copolymers, b end-grafted chains, c triblock copolymers, d multiply grafted chain, and e random copolymer...

Fig. 35. a Surface analysis after fracture of the interface between PS and PVP reinforced with a 510-540 dPS-b-PVP diblock copolymer showing the fraction of deuterium on the PS side ( ) and on the PVP side (O). b Schematic of the crack path in the block copolymer lamella. Data from [33]... 

Fig.2 (a) Schematic diagram of potential between the opposing polyelectrolyte brushes (b) expulsion of one layer of micelles at higher diblock copolymer concentrations... 

Fig, 33.a Schematic illustration of N-mer brush layer created by diblock copolymers A-N attached selectively to the interface by their anchor moiety A. Copolymers in the brush layer are in equilibrium with free diblocks incorporated in the bulk region of the sample abundant in homopolymer P. b The form of the diblock volume fraction vs depth ( )(z) profile used in theoretical model, c Potential U(z) affecting the anchor moiety A and driving the diblock segregation... 

Fig. 25 Transmission electron micrographs (TEM) of a ternary nanocomposite of PS-poly(ethyl propylene) (PEP) diblock copolymer with two types of nanoparticle-Ugand systems AuR]- and SiO2R2-ftmctionalized (R i, R2 are alkyl groups) nanoparticles of total volume fraction 0.02. The former appear along the interface of the lamellar microdomains, whereas the latter reside in the center of PEP microphases. Schematically, the nanoparticle distribution is shown in the inset. Taken from [308]...

Fig. 12 Schematic illustration of the formation of vesicles from PAMPA-b-PNIPAM diblock copolymers and their subsequent ionic cross-linking. Li Y, Lokitz BS, McCormick CL (2006) Angew Chem Int Ed 45 5792. Copyright Wiley. Reproduced with permission [121]...

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