Polymer Orientation Control

There is no such thing as a pure polymer. All polymers comprise molecules that exhibit chemical and physical distributions of many variables these include molecular weight, branching, steric defects, molecular configuration, preferential chain orientation, and crystallite size and shape. The properties and characteristics that we exploit in polymers are controlled by the overall balance of these distributions. 

The properties of a semicrystalline polymer are controlled by its degree of crystallinity, the alignment of crystallites relative to one another, the number and type of links between the crystallites and amorphous regions, and the overall orientation of molecules within the material. 

The self-assembly of block polymers, in the bulk, thin film and solution states, produces uniformly sized nanostructured patterns that are very useful for nanofabrication. Optimal utilization of these nanoscopic patterns requires complete spatial and orientational control of the microdomains. However, the microdomains in the bulk state normally have grain sizes in the submicron range and have random orientations. In block copolymer thin films, the natural domain orientations are generally not desirable for nanofabrication. In particular, for composition-asymmetric cylindrical thin films, experimental... 

Most of the systems described in Chapter 5 contain small- or medium-sized or multinuclear benzenoid and non-benzenoid arenes. In Chapter 6, Hoger gives an overview over the mastery of the synthesis of macro- and megacycles. He shows different approaches towards shape-persistent macrocycles and carefully examines and discusses selected examples that display the advantages and disadvantages of macrocycle synthesis under kinetic and thermodynamic control. The template approach (both supramolecular and covalent) towards functionalized rings is also discussed and introduces a strong motif of supramolecular chemistry, which is much further developed but in a more polymer-oriented topic, in the next chapter. 

Water-insoluble materials such as hydrophobic polymers can supply hydrophobic interfacial environments. However, molecular assemblies such as micelles and lipid bilayer vesicles are more advantageous, because they supply large surface areas that are in contact with a water phase and more flexible organization. These characteristics are advantageous for substrate incorporation and product release. As explained in Chap. 4, a lipid bilayer provides a more stable hydrophobic environment, while micelles provide more dynamic and less stable assembUes. Structural and orientational control between the... 

Somasundaran P, Xiang Y, Krishnakumar S. Role of conformation and orientation of surfactants and polymers in controlling flocculation and dispersion of aqueous and nonaqueous suspensions. Colloids Surf A 1998, 133, 125-133. 

Mesoscale crystalline morphology, crystallinity, and molecular orientation in these deposited thin films strongly depend on molecular properties [17,18], chemical nature of the solvent, and processing condition, resulting in very different field-effect mobilities [15,23,36]. Specifically, due to heterogeneous surface-induced (epitaxy) crystal growth as a nature of semicrystalline polymers, fine control of substrate properties and solvent evaporation rate tends to yield favorable molecular orientation of these polymers (i.e., edge-on structure with respect to dielectric substrates) in solution-deposited films [24,66]. 

Lauren E.K., Huaping T., Siddharth J., Steven R.L., Jason W.R, and Kacey G.M. Protein bioactivity and polymer orientation is affected by stabilizer incorporation for double-walled microspheres. J Control. Release 141(2) (2010) 168-176. 

Two important modifications have to be mentioned, which permit to control stiffness and tonghness of a pol3rmer material separately polymer orientation and reinforcement through a second phase such as core-shell particles, mineral fillers, or short fibers (see Reinforcement). 

Harris KD, Cuypers R, Scheibe P, Mol GN, Lub J, Bastiaansen CWM, Broer DJ (2005) Molecular orientation control for thermal and UV-diiven polymer MEMS actuators. Smart Sensors, Actuators, and MEMS 11 5836 493-503... 

In order to use liquid crystalline polymers as commercial optical films, it is necessary to achieve both the immobilization of the liquid crystal molecular oriented structure and the orientation control of the liquid crystalline polymer. However, in the 1980s there was no technology that could satisfy both requirements and it was necessary to develop it ourselves. The key phrase at that time was do not be bound by common sense. ... 

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