Microphase segregation

Weakly segregated systems, Todt > Tc < Tg with hard confinement. In this case, the crystallization of the semicrystalline block can overwhelm the microphase segregation of the MD structures even though the amorphous block is glassy at the crystallization temperature, because of the weak segregation strength [19]. 

Fig. 21. Microphase segregation and axial contraction of molecular brushes [82]...

A compound that has two immiscible hydrophilic and hydrophobic parts within the same molecule is called an amphiphilic molecule (as mentioned earlier). Many amphiphilic molecules show lyotropic liquid-crystalline phase sequences, depending on the volume balances between the hydrophilic part and the hydrophobic part. These structures are formed through the microphase segregation of two incompatible components on a nanometer scale. Hand soap is an everyday example of a lyotropic liquid crystal (80% soap + 20% water). 

Fig. 58. a A height SFM micrograph of polymethymethacrylate brushes adsorbed on mica from a dilute solution in chloroform [581].b Magnified image of single molecules which exhibit a caterpillar shape. The axial modulations of the diameter have been explained by microphase segregation of the side chains into pinned clusters upon evaporation of the solvent [589]... 

Block copolymers containing crystallizable blocks have been studied not only as alternative TPEs with improved properties but also as novel nanos-tructured materials with much more intricate architectures compared to those produced by the simple amorphous blocks. Since the interplay of crystallization and microphase segregation of crystalline/amorphous block copolymers greatly influences the final equilibrium ordered states, and results in a diverse morphological complexity, there has been a continued high level of interest in the synthesis and characterization of these materials. 

One effective approach in increasing the fire resistance of polyurethane (PU) is to incorporate PDMS into its structure.28 Microphase-segregated PU block copolymers containing hydroxyl-terminated silicone as the soft segment have been synthesized. The enhanced siliconated surface of the block copolymer has been confirmed by ESCA and x-ray analyses. 

Figure 25.7 Schematic illustration of the microphase-segregated layered structure for the mixtures of hydroxyl-terminated mesogenic compounds 13 and 15 with ionic liquid 16.

Phase segregation affects the dependence of the viscosity growth on the applied stress of shear rate [88], It is possible to see Such an effect is seen experimentally in a sufficiently extended part of flow ability after a microphase segregation i.e. the ratio ijt is relatively small, for example, in curing melamine-formaldehyde resins in solution [87], However, the case of tp/t close to unity, this effect may not always be revealed due to experimental difficulties. 

Rgure 8.5 Representative polymer-polymer phase behaviour with different molecular architectures. Microphase separation (a) results when thermodynamically incompatible linear homopolymers are mixed. The covalent bond between blocks in a diblock copolymer leads to microphase segregation (c). A mixed architecture of linear homopolymers and the corresponding diblock copolymer produces a surfactant-like stabilized intermediate-scale phase separation (b). 

It is well known that the connection of oligo(alkylene ether) chains into a calamitic rigid rod at the terminals destabilizes the thermotropic meso-phases [8]. However, mesomorphic properties can be obtained by molecules with extended rigid rod segments as a result of the microphase segregation between the polar flexible oligo(alkylene oxide) ethers and rigid rod seg-... 

Carbohydrates are natural compounds which have hydroxyl groups capable of hydrogen bonding. Amphiphilic sugars with long alkyl chains form layered or columnar mesomorphic structures due to microphase segregation, as shown in Fig. 1 (Type A-I-c) [17-20, 149-153]. Alkylglucosides are representative... 

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