List of Diblock Copolymers

Appendix B List of Diblock Copolymers Table B.l (continued)... 

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... 

Table 1 lists some of the homopolymers and diblock copolymers which have been employed in our experimental investigations (1-8). Particular emphasis has been placed on blends containing 1,4 polybutadiene (1,4B). In one case, 1,4B was blended with various amounts of 1,2 polybutadiene (1,2B) and the corresponding 1,2B/1,4B diblock copolymer. A second major set of samples was constructed from various combinations of 1,4B and cis 1,4 polyisoprene (1,41) and 1, 41/1,4B diblock copolymers. A large number of ternary blends were studied, the preponderence of which contained either 25%, 50% or 75% (by weight) of a selected diblock copolymer, the remainder of the blend being comprised of one or both of the corresponding homopolymers. Homopolymer blends (0% diblock) and the pure copolymers (100% diblock) were also studied in detail. 

In the following discussion, block copolymers will be simply designated by the acronym A-B for a diblock copolymer, A-B-A for a triblock copolymer with two identical outer blocks, A-B-C for an ABC triblock copolymer, etc. A complete list of abbreviations for the A, B, and C polymer blocks is given in the Abbreviations and Symbols section. 

The designed set of 2-oxazoline monomers that was used for the synthesis of the triblock copolymers (MeOx, EtOx, PheOx, and NonOx) yielded polymers of different polarity [91], P(MeOx) and P(EtOx) are hydrophilic, whereas P(PheOx) and P(NonOx) are hydrophobic. All possible combinations of these four different monomers would result in 64 different structures. However, all polymers that would have two times the same block after each other were excluded since they do represent diblock copolymers. Additionally, some structures, which have NonOx as the first block and EtOx or MeOx as the second block, were excluded due to extensive side reactions. Consequently, 30 different triblock copolymers were synthesized, and they are listed in Table 13 with their corresponding structural characterization. 

Figure 13.3 Dependence of the apparent X parameter on inverse temperature, extracted from fits of the Fredrickson-Helfand fluctuation theory to neutron scattering data for the polystyrenc-polyisoprene diblock copolymers listed. The reference volume v is 1.503 x 10 cm. Note that for most of the samples, a linear relationship between / and 1/ T is observed, consistent with Eq. (13-1). The apparent x values for highly asymmetric diblocks are higher than those for more symmetric ones. (Reprinted with permission from Lin et al., Macromolecules 27 7769. Copyright 1994, American Chemical Society.)-------------...

One way to achieve compatibilization involves physical processes such as shear mixing and thermal history, which modify domain size and shape. The second way is the use of physical additives to increase attraction between molecules and phases. The third method is reactive processing, which is used to change the chemical structure of one or more of the components in the blend and thus increase their attraction to each other. Table 1.5 contains a list of compatibilizers used in the formulation of polyolefin blends. As can be seen from Table 1.5, most of the compatibilizers used in the formulation of polyolefin blends contain compounds such as maleic anhydride, acrylic and methacrylic acid, glycidyl methacrylate, and diblock and triblock copolymers involving styrene, ethylene, and butadiene. 

Microphase separation does occur at shorter block lengths when the two blocks are highly immiscible, such as with hydrocarbon and fluorocarbon blocks. For example, all of the diblock copolymers of (perfluorooctyl)ethyl vinyl ether and n-[(4 -cyanophenyl-4"-phenoxy)alkyl] vinyl ethers (PRf-PCNVE ) or 2-[(4 -biphe-nyloxy)ethyl]vinyl ether (PRf-PbiPHVE2) listed in Table 16 exhibit the phases characteristic of both of the corresponding homo-... 

To make matters even worse, the vacuum ovens used before installing the minioven were falsely calibrated and had a temperature offset of 10 and 15 C. Combined, these circumstances made initial experiments poorly reproducible. Nonetheless, almost five dozen of the synthesized diblock copolymers were identified to form double-gyroids. They are listed in Table4.3. The complete list of all studied copolymers together with their theoretical PLA volume fraction and the adopted... 

Our intentions with these block copolymers were to develop a microphase separated matrix, and differential scanning thermal analysis of the P[MG8-4VP] diblock copolymers indeed showed the presence of two glass transition temperatures indicating microphase separation. The thermal transitions for the block copolymers are listed in Table 4. Depending on the block copolymer composition, a soft (oxyethylene) phase glass transition temperature (Tg) is observed between -60 and -45°C and a hard (4-vinylpyridine) phase between 135 and 143 C. The slight lowering of the of the hard phase relative to the 150°C of pure poly(4-vinylpyridine) is due to internal plasticization of the hard phase by the short... 

Poly(L-lactide)- -poly(e-caprolactone) (PLLA-fe-PCL) diblock copolymers were synthesized by controlled/ living sequential block copolymerization as initiated by aluminum trialkoxides in toluene solution. These procedures were reported in detail previously [50,98]. Table 11.6 lists the molecular weight characterization data obtained by size exclusion chromatography (SEC) and by NMR. The diblock nomenclature we have used denotes the PLEA block as L and the PCL block as C, the subscripts indicate the approximate composition in wt% and the superscripts the approximate number average molecular weight of the entire block copolymer in kg/mol. 

Another important aspect of adding homopolymer to a block copolymer is the ability to change morphology (without synthesis of additional polymers). Furthermore, morphologies that are absent for neat diblocks such as bicontin-uous cubic double diamond or hexagonal-perforated layer phases have been predicted in blends with homopolymers [183], although not yet observed. Transitions in morphology induced by addition of homopolymer are reviewed elsewhere [1], where a list of experimental studies on these systems can also be found. 

Block copolymer thin films have heen used as stmctme-direrting agents to pattern many different inorganic materials. Several reviews have created a comprehensive list of the resulting patterned materials and their applications. " While many different patterned inorganic materials have been formed, they have been created using only a few approaches to patterning. First, seleaive removal of one block of a self-assembled diblock... 

We investigated the morphologies of blends of well-ordered core-shell type microsphere with AB diblock copolymers, which form lamellar or spherical microdomains in a matrix [45,46]. The poly(S-Z>-4VP) with lamellar morphology or poly(S-Z>-4VP), poly(S-Z>-2VP), and poly(S- -I) with spherical morphology, synthesized by anionic polymerization, were chosen as the blend materials. The results are listed in Table 7. The P4VP core-PS shell microsphere SV500-M used in this work easily forms an ordered structure on its own. Some characteristics of the microsphere SV500-V are shown in Table 8. 

Three homopolymers and one diblock copolymer were used. A barefoot resin of high-density polyethylene (HOPE 3000) was supplied by Petromont. Polypropylene PP PD702 was supplied by Eased, while polystyrene PS 615APR was supplied by the Dow Chemical Company. SEE CAP4741, a 1,4-hydrogenated styrene-ethylene-butylene diblock copolymer, was supplied by Shell. The materials characteristics are listed in Table 1. 

Critical micelle concentrations for a range of PEO-PBO, PBO-PEO (here the block order reflects the synthesis sequence), PEO-PBO-PEO, PBO-PEO-PBO and cyclo-PBO-PEO ring copolymers are listed by Booth et al. (1997). Polymerization of PEO second (PBO-PEO diblock) leads to a broader PEO block length distribution, which in turn leads to a difference, for example, in surface tension (this is illustrated for PE04iPB08 and PB08PE041 by Booth et al. 

To take a closer look at the area per molecule in the condensed phase of the diblock monolayers, the x-axis of Fig. 4.14a is expanded and shown in Fig. 4.14c. The extrapolated value of the area per molecule and the theoretically expected value for the area are listed in Table 4.5. To calculate the theoretically expected area for the hybrid block copolymers in the condensed phase, it is assumed that the stearate end groups are extended into the air perpendicular to the air-water interface as shown schematically in Fig. 4.14d. This assumption is based on the behavior of pure stearic acid, which forms ordered monolayers with the alkyl chains oriented perpendicular to the air-water interface. The area per molecule for stearic acid with this orientation is 20 A2, [113] Here, the theoretically expected area was calculated by multiplying the area per stearate molecule (20 A2) with the number of stearate groups present at the ends of the dendrimer block. PEO(2k)-S having no dendrimer block but a single... 

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