Chemical synthesis, polymers miscibility

Polymer blending has attracted the attention of researchers because polymers with extraordinaiy properties obtained by chemical synthesis are more expensive than existing polymers and blending operations. Furthermore, a wise choice and combination of the polymeric materials in specific amounts may lead to the fabrication of blend materials with desirable properties. There are various numbers of polymers that can be combined to form blends with different physical properties. The characteristics of the polymeric blend are influenced by the nature of the dispersed and dispersion phases, the volume ratio of the phases, the sizes and size distributions of the particles of the dispersed phase and interfacial adhesion. One of the popular questions being addressed regarding the polymer blend is the miscibility between the components. The blends formed can be miscible, partially miscible or fully immiscible. The miscible polymer blend is formed by choosing polymers with compatible chemical structures which are capable of specific interactions. ... 

Further research has continued into the development of drug eluting coronary stents for the treatment of cardiovascular restenosis. Because the miscibility of paclitaxel with SIBS as demonstrated by the previous authors [33] is low as measured by DSC, Sipos et al. [34] have reported on the synthesis of poly (p-tertbutyldimethylsiloxy)styrene (TBDMS)-P-isobutylene (IB)-PTBDMS), which can be hydrolysed to poly(PHOS-P-PIB-P-PHOS) in order to modulate the solubility of PTx in the polymer, which, in turn, affects its release from the polymer. Further chemical modification of the polymer can be undertaken to effect changes in the polarity of the polymer, including acetylation, which gives rise to PAcOS-P-PIB-p-PAcOS. 

Several factors are found responsible for why numerous blend systems are not successful. First, the component polymers are usually not miscible with each other due to thermodynamic constraints, for example, lack of solubility and finite inter-fadal tension. Second, immiscible polymer blend preparation is often affected by kinetic constraints, for example, slower rate of deformation of the dispersed polymer and faster rate of coalescence of the droplets. In turn, these rates are directly influenced by the type of flow field, for example, shear versus extensional, strain history, chemical reactions, for example, grafting reactions at polymer-polymer interfaces or polymerization-induced phase separation, and polymer properties, such as viscosity and interfacial tension. Accordingly, the multidisciplinary efforts to analyze, understand, and design polymer blends with improved properties extend from synthesis and characterization to processing and manufacturing. Such efforts... 

In situ and precursor techniques for polymer synthesis are suitable procedures for a combination with a variation of the chemical structure to enhance miscibility. It is the principal... 

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