Amphiphiles domain morphology

In most instances, ROMP is utilized to arrange monomer blocks sequentially into distinct amphiphilic domains in order to create a polymer capable of self-assembly. In this way, one can vary the hydrophobic tail length and hydrophilic head size in order to create a wide range of morphologies. Shunmugam and coworkers [84] have shown that homopolymers comprised of only one type of... 

Block copolymers of PDMS are amphiphiles and behave as surfactants. At low concentrations they accumulate at the surface, at intermediate concentrations they may form micelles, and at high concentrations and in the bulk they segregate into domains of one block in a continuum of the other. Thus one would expect the surface composition and morphology to be quite different from that in the bulk. 

Figure 25 Assembly of DNA-brush copolymers into micelles with spherical or cylindrical morphologies. Amphiphile structures are represented as cones for each respective motphology, with the hydrophobic domain highlighted in red. TEM images of (a) 25-nm spherical micelles assembled from initial DNA-brush copolymers (b) cylindrical morphology formed following DNAzyme addition to spheres (c) spherical micelles (green) formed after the addition of hi to cylinders. Reproduced with permission from Chien, M.-P. Rush, A. M. Thompson, M. P. etal. Angew. Chem. Int. Ed. 2010,49, 5076-5080. 2...

The strongest variation of the film morphology, however, could be achieved by cospreading diyne surfactants with other amphiphiles. Already small amounts of additives as low as 0.1 to 1 mole percent reduced the average domain sizes considerably . 

Here, the distinct domains of the resulting hybrid polymer are responsible for the self-assembly of the material. It should be noted that there are several other approaches to nanomaterials via ROMP, including the synthesis of dispersed latex nanoparticles, [29-34] hybrid nanoparticles via scaffolded initiation [35-39], and nanoparticles encapsulated in polymer matrices [40,41]. Amphiphilic micellar nanoparticles are by far the most prevalent systems in the literature relevant to a discussion of ROMP in nanoparticle synthesis, particularly those fully characterized in terms of particle formation and morphological characterization of the resulting polymer aggregates. Amphiphilic copolymers synthesized by ROMP that are not studied in this manner [42-45] or those nanoscale architectures involving only covalent interactions [46, 47] are not discussed here. 

We have clearly demonstrated the different aggregate structures of isomeric phenols-formaldehyde monolayers by BAM and SMM. The synthetic amphiphilic phenols of structural isomers, o-, m- and / -HP, showed characteristic monolayer properties on the aq. formaldehyde subphase. The aggregate patterns are supposed to give a clue to understand the microscopic morphology of the commercially important phenolic resins. The micron-sized domains observed by SMM can be related to the surface or interior morphology of the bulk phenolic... 

Controlling the spontaneous formation of ordered domains in soft materials such as block copolymers [189] may lead to the development of stimuli-responsive materials for applications such as actuators [190] and photonics [191] due to the reversible nature of order formation. However, the stimuli that are typically used to control the morphology of block copolymers are e.g., temperature, pressure, solvent type and concentration... Pioneering work by Abbott and co-workers used the chemical oxidation approach to control the self-assembly of small-molecule amphiphiles containing ferrocene [192]. Rabin and co-workers have shown that the introduction of dissociated charges on one of the blocks of a diblock copolymer leads to stabilization of the disordered phase [193]. They also quantified the increase in x at the order-disorder transition (ODT), xodt, due to the entropic contribution of the dissociated counterions. The Flory-Huggins parameter,x, that is used to quantify interactions between polymer chains is assumed to be proportional to the difference in the polarizibility of the blocks [194]. The polarizibility of polyferrocenyldimethylsilane, which is larger than that of either polystyrene or polyisoprene [195], must increase upon oxidation due to the presence of the NO ions. 

Self-assembly and morphology of block copolymers depend on their architecture and composition [3]. Several equilibrium phases like lamellae, gyroid, hexagonal-packed cylinders, and body-centered cubic phases were observed in melts. In thin films, microphase separation resulted in formation of lamellae, stripes, and circular domains. Various types of micellar structures and arrangements were seen in dilute solutions [4], These phase behaviors were dictated by Flory-Huggins interaction parameter (/), copolymer degree of polymerization N), and composition (/) in melts and thin films. In addition to these parameters, amphiphilicity was the most important property of block copolymers enabling them to self-assemble into various stmctures in dilute solutions [3]. 

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