Microdomains phase separation

Halogenonitroaromatic compound, 295 Hard-block domain structure, 218-219 Hard-block microdomain, 215 Hard-block/soft-block phase separation, 220... 

Examples of these formulations are systems based on a difunctional LC epoxy monomer (diglycidyl ether of 4-4 -dihydroxy-Q -methylstilbene), cured with methylene dianiline (Ortiz et al., 1997). The generation of liquid-crystalline microdomains (smectic or nematic) in the final material required their phase-separation before polymerization or at low conversions. This could be controlled through the initial cure temperature. Values of GIc, (kJm-2) were 0.68 (isotropic), 0.75 (nematic), and 1.62 (smectic). The large improvement produced by the smectic microdomains was attributed to an extensive plastic deformation. 

In our experiments, the quench from a swollen to a glassy state has been achieved within tens of seconds, and has been shown not to alter the phase separation in a swollen state[49]. Figure 17 compares surface structures in SB41 films that have been exposed to a relative vapor pressure p/po of 72% and of 80%. With an increase of the solvent concentration, the in-plane order of the microdomains... 

Figures 4A and 4B are the ultra-thin cross-sections of OsOi+-stained two-stage (styrene//styrene-butadiene) and (styrene-butadiene/ /styrene) latex particles at the stage ratio of 50/50 (LS-10 and LS-11), respectively. Latex samples were mixed with a polymerizable monomer mix of butyl and methyl methacrylates, cured, and microtomed for examination. Figure 4A shows particle cross-sections much smaller than the actual particle size of LS-10. It appears that since the embedding monomer solution was a solvent for polystyrene, the continuous polystyrene phase was dissolved and small S/B copolymer microdomains were left behind. This is further evidence that the second-stage S-B copolymers phase-separated as microdomains within the first-stage polystyrene phase, as shown in Figures 1A and 1A. Figure 4B shows somewhat swollen and deformed particle cross-sections, suggesting that the first-stage cross-linked S-B copolymers were a continuous phase. Indeed, the former (LS-10) behaved like a hard latex, but the latter (LS-11) behaved like a soft latex.

As an alternative to surface energy matching, electrical poling can be used to orient the microdomains.32 33 One of the advantages of this method is that the thickness of the film can be thicker, and the substrate can be varied.34 When the block copolymer is allowed to phase separate on an electrode surface, the porous film can be filled via electroplating, leading to the formation of nanowires ( 15 nm in diameter) in a polymer matrix.35... 

As the specific properties of block copolymers are related to the formation of microdomains, the present review will deal with the shape, size, and arrangements of microdomains in block copolymer systems. The phenomenon of phase separation and of microdomains formation is not restricted to dry copolymers, but is also a characteristic feature of their concentrated solutions, where mesophases are observed11, and, therefore, we shall generally consider systems copolymer/solvent and treat dry copolymers as their limiting case. 

Ionomers consist of statistical copolymers of a non-polar monomer, such as ethylene, with (usually) a small proportion of ioniz-able units, like methacrylic acid. Ethylene-co-methacrylic acid copolymers (-5% methacrylic acid) are used to make cut-proof golf balls (see Fascinating Polymers opposite). The protons on the carboxylic acid groups are exchanged with metal ions to form salts. These ionic species phase-separate into microdomains or clusters which act as crosslinks, or, more accurately, junction zones (Figure 6-4). (We discuss interactions in a little more detail in Chapter 8.)... 

Finally, it should be mentioned that the temperature profile may indicate the po.ssible existence of heterogeneities or microdomains. Raman spectra have shown such phase separations in bilayers prepared with DHPC7DPPC mixtures and in lipids containing highly unsaturated sn2-acyl and completely saturated snl-acyl, such as POPC, PARC, and PDPC (Litman et al., 1991). 

The possibility of employing block copolymers as materials that might possess desirable properties was originally considered by Mark In the first period the effort in preparing block copolymers was directed to radical polymerization and it was only in 1956 that Szwarc obtained well-defined block copolymers by anionic polymerization . In block copolymers, the incompatibility between polymeric chains becomes an advantage a phase separation of the blocks occurs leading to the formation of microdomains which are responsible for the ecific properties of block copolymers. For instance, the presence in a molecule of an elastomeric block linked by its ends to thermoplastic blocks generates a polymer in which reversible physical multifunctional cross-links allow the behaviour of conventional vulcanized elastomers at room temperature, but the material remains easily moldable at elevated temperature just as normal thermoplastic resins ° ... 

As distinct from sohd supports such as gold or silver, mercury imparts lateral mobihty to hpid monolayers directly self-assembled on its surface, because of its liquid state. This is demonstrated by rapid spontaneous phase separation, with microdomain formation, in a hpid mixture monolayer self-assembled on top of a DPTL thiolipid monolayer tethered to a mercury microelectrode [30]. The presence of microdomains was directly verified from the images of the distal hpid monolayer obtained using two-photon fluorescence lifetime imaging microscopy. 

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