Block diblock copolymer

Comparison of SCF predictions [37] (solid lines) and scaling predictions [3 ] (dolled lines) for the adsorption of an A and B block diblock copolymer as a function of the fraction of A monomers (n, see text N = 500, adsorption energy = 2 kT). (a) Resulting grafting density (per monomer length ( ) squared), (b) Brush height in monomer chain lengths. 

Annis B K, Noid D W, Sumpter B G, Reffner J R and Wunderlich B 1992 Application of atomic force microscopy (AFM) to a block copolymer and an extended chain polyethylene Makromol. Chem., Rapid. Commun. 13 169 Annis B K, Schwark D W, Reffner J R, Thomas E L and Wunderlich B 1992 Determination of surface morphology of diblock copolymers of styrene and butadiene by atomic force microscopy Makromol. Chem. 193 2589... 

Block copolymers are closer to blends of homopolymers in properties, but without the latter s tendency to undergo phase separation. As a matter of fact, diblock copolymers can be used as surfactants to bind immiscible homopolymer blends together and thus improve their mechanical properties. Block copolymers are generally prepared by sequential addition of monomers to living polymers, rather than by depending on the improbable rjr2 > 1 criterion in monomers. 

ABA and ) n block polymers exhibit higher melt viscosities than do AB diblock copolymers with similar molecular weights. The former two... 

The main results of this miero-mechanical model in the quasi-static regime have been compared with experimental results obtained by placing polystyrene (PS)-polyvinyl pyridine (PVP) diblock copolymers with a short PVP block between PS and PVP homopolymers. The fracture toughness was found to increase linearly with E from that of the bare PS/PVP interface, while the slope of the line increased with the degree of polymerization of the block being pulled out. If the data for the different copolymers were plotted as AG vs. (where... 

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]. 

As previously described, all microspheres discussed in this chapter were synthesized from AB type diblock copolymers. Precursor block copolymers, poly(styrene-b-4-vinyl pyridine) (P[S-b-4VP]) diblock copolymers, were synthesized using the additional anionic polymerization technique [13]. The basic properties of the block copolymers were determined elsewhere [24,25] and are listed... 

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. 

AB diblock copolymers in the presence of a selective surface can form an adsorbed layer, which is a planar form of aggregation or self-assembly. This is very useful in the manipulation of the surface properties of solid surfaces, especially those that are employed in liquid media. Several situations have been studied both theoretically and experimentally, among them the case of a selective surface but a nonselective solvent [75] which results in swelling of both the anchor and the buoy layers. However, we concentrate on the situation most closely related to the micelle conditions just discussed, namely, adsorption from a selective solvent. Our theoretical discussion is adapted and abbreviated from that of Marques et al. [76], who considered many features not discussed here. They began their analysis from the grand canonical free energy of a block copolymer layer in equilibrium with a reservoir containing soluble block copolymer at chemical potential peK. They also considered the possible effects of micellization in solution on the adsorption process [61]. We assume in this presentation that the anchor layer is in a solvent-free, melt state above Tg. The anchor layer is assumed to be thin and smooth, with a sharp interface between it and the solvent swollen buoy layer. 

Vinyl copolymers contain mers from two or more vinyl monomers. Most common are random copolymers that are formed when the monomers polymerize simultaneously. They can be made by most polymerization mechanisms. Block copolymers are formed by reacting one monomer to completion and then replacing it with a different monomer that continues to add to the same polymer chain. The polymerization of a diblock copolymer stops at this point. Triblock and multiblock polymers continue the polymerization with additional monomer depletion and replenishment steps. The polymer chain must retain its ability to grow throughout the process. This is possible for a few polymerization mechanisms that give living polymers. 

Kennedy J.P. and Shim J.S., Star-block polymers having multiple polyisobutylene containing diblock copolymers arm radiating from a siloxane core and a method of synthesis thereof. Disclosure 318, US Patent, Notice of Allowance, 2001. 

LeiblerL., Theory of microphase separation in block copolymers. Macromolecules, 13, 1602, 1980. Eoerster S., Khandpur A.K., Zhao J., Bates E.S., Hamley I.W., Ryan A.J., and Bras W. Complex phase behavior of polyisoprene-polystyrene diblock copolymers near the order-disorder transition. Macromolecules, 21, 6922, 1994. 

The living nature of PCL obtained in the presence of Zn(OAl-(OPri)2)2 has been used to prepare both di- and triblock copolymers of e-caprolactone and lactic acid (42,43). Treatment of the initial living PCL with dilactide afforded a PCL-PLA diblock with M /Mn = 1.12, with each block length determined by the proportions of the reactants, i.e., the ratio of [monomer]/[Zn]. While the living diblock copolymer continued to initiate dilactide polymerization, it failed to initiate e-caprolactone polymerization. To obtain a PCL-PLA-PCL triblock, it was necessary to treat the living PCL-PLA-OAIR2 intermediate with ethylene oxide, then activate the hydroxy-terminated PCL-PLA-(OCH2CH2)nOH with a modified Teyssie catalyst (Fig. 5). 

In 2000, the first example of ELP diblock copolymers for reversible stimulus-responsive self-assembly of nanoparticles was reported and their potential use in controlled delivery and release was suggested [87]. Later, these type of diblock copolypeptides were also covalently crossUnked through disulfide bond formation after self-assembly into micellar nanoparticles. In addition, the encapsulation of l-anilinonaphthalene-8-sulfonic acid, a hydrophobic fluorescent dye that fluoresces in hydrophobic enviromnent, was used to investigate the capacity of the micelle for hydrophobic drugs [88]. Fujita et al. replaced the hydrophilic ELP block by a polyaspartic acid chain (D ). They created a set of block copolymers with varying... 

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