Polymer synthesis chemical polymerization

Template-free techniques have been extensively studied for the fabrication of conducting polymer nanomaterials fabrication. Compared with hard and soft template methods, these methodologies provide a facile and practical route to produce pure, uniform, and high quality nanofibers. Template-free methods encompass various methods such as electrochemical synthesis, chemical polymerization, aqueous/organic interfacial polymerization, radi-olytic synthesis, and dispersion polymerization. 

P. Soudan, P. Lucas, H.A. Ho, D. Jobin, L. Breau and D. Belanger, Synthesis, chemical polymerization and electrochemical properties of low bandgap conducting polymers for use in supercapacitors, J. Mater. Chem., 11, 773-782 (2001). 

Ouchi, M., Terashima, T, and Sawamoto, M. (2009) Transition metal-catalyzed living radical polymerization toward perfection in catalysis and precision polymer synthesis. Chemical Reviews, 109,4963. 

New elastic polymeric materials (resistance to higher stroke or air) can be obtained by using physical modification methods, but using this method, two phases (PS and rubber) in the mixture were formed. Small rubber particles spread as a PS layer and, after awhile, the relationship between the layers decreases and rubber particles gather in the upper layer of the materials. This can be the cause of the loss of resistance of the materials. These material disadvantages have stimulated the polymer synthesis to increase the PS resistance to higher physico-mechanical properties, such as higher temperature and stroke for the chemical modification of PS with various functional modifiers. 

Conditions that are important to all chemical reactions such as stoichiometry and reactant purity become critical in polymer synthesis. In step growth polymerization, a 2% measuring and/or impurity error cuts the degree of polymerization or the molecular weight in half. In chain growth polymerization, the presence of a small amount of impurity that can react with the growing chain can kill the polymerization. 

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

The use of porphyrinic ligands in polymeric systems allows their unique physio-chemical features to be integrated into two (2D)- or three-dimensional (3D) structures. As such, porphyrin or pc macrocycles have been extensively used to prepare polymers, usually via a radical polymerization reaction (85,86) and more recently via iterative Diels-Alder reactions (87-89). The resulting polymers have interesting materials and biological applications. For example, certain pc-based polymers have higher intrinsic conductivities and better catalytic activity than their parent monomers (90-92). The first example of a /jz-based polymer was reported in 1999 by Montalban et al. (36). These polymers were prepared by a ROMP of a norbor-nadiene substituted pz (Scheme 7, 34). This pz was the first example of polymerization of a porphyrinic macrocycle by a ROMP reaction, and it represents a new general route for the synthesis of polymeric porphyrinic-type macrocycles. 

A line of research that has aroused much interest in recent years is the study of head-to-head, tail-to-tail polymers (96-98). Their direct synthesis has little likelihood of being successffil as head-to-tail sequences usually predominate in vinyl polymerization. One possibility for their preparation is through the chemical modification of suitable preformed polymers. In the case of the head-to-head, tail-to-tail polypropylene, different stereoisomeric forms have been isolated, depending on the method of preparation. In the general scheme, the precursor is an unsaturated polymer obtained by polymerization of the disubsti-tuted butadiene (2,3-dimethylbutadiene or 2,4-hexadiene) then, by chemical or catalytic reduction, this polymer is converted into the desired polypropylene, whose stmcture can then be examined by NMR spectra. Head-to-head, tail-to-... 

Carbon dioxide is a widely available, inexpensive, and renewable resource. Hence, its utilization as a source of chemical carbon or as a solvent in chemical synthesis can lead to less of an impact on the environment than alternative processes. The preparation of aliphatic polycarbonates via the coupling of epoxides or oxetanes with CO2 illustrates processes where carbon dioxide can serve in both capacities, i.e., as a monomer and as a solvent. The reactions represented in (1) and (2) are two of the most well-studied instances of using carbon dioxide in chemical synthesis of polymeric materials, and represent environmentally benign routes to these biodegradable polymers. We and others have comprehensively reviewed this important area of chemistry fairly recently. Nevertheless, because of the intense interest and activity in this discipline, regular updates are warranted. 

Star polymers of chemically different arms are usually called miktoarm stars. Although there are several individual methods for the synthesis of miktoarm stars four general methodologies have been developed. Three of them are based on anionic polymerization and the fourth on cationic polymerization. In all of them the use of appropriate linking agents is necessary. 

It is clear that Tgxp is a function of curing conversion or molecular weight (for linear polymers) at adiff. One can observe a noticeable difference between T xp and T for such processes of polymer synthesis as polyaddition or condensation polymerization reactions. It is especially important for polymers with high T . For many heat-resistant polymers, T is higher than the temperature limit of their chemical decomposition. We can never reach natural T for these polymers. For such polymers, one really measures only Tgxp, the value of which depends on the reaction conditions. For structure-glass transition temperature correlations of networks, T is the most important quantity. 

Electrochemical polymerization is preferred to chemical polymerization, especially if the polymeric product is intended to be used as a polymer film electrode, thin layer sensor, in microtechnology etc., because the potential control is a precondition of the production of good-quality material and the polymer film is formed at the desirable spot that serves as an anode during the synthesis. 

N-Benzyl and iV-alkoxy pyridinium salts are suitable thermal and photochemical initiators for cationic polymerization, respectively. Attractive features of these salts are the concept of latency, easy synthetic procedures, their chemical stability and ease of handling owing to their low hygroscopicity. Besides their use as initiators, the applications of these salts in polymer synthesis are of interest. As shown in this article, a wide range of block and graft copolymer built from monomers with different chemical natures are accessible through their latency. 

Cationic polymerizations are presently overshadowed by other methods of polymer synthesis. The main reason is the extraordinary complexity of the chemical processes in cationic polymerizations, and the consequent difficulty in controlling technological problems. Some monomers cannot, however, be polymerized in any other way. This is a sufficient reason for studying the generation and reactions of carbocations (and also carboxonium and oxonium ions),... 

The discovery that doped forms of polypyrroles conduct electrical current has spurred a great deal of synthetic activity related to polypyrroles [216-218], Reviews are available on various aspects of the synthesis and properties of polypyrroles [219,220]. In addition, summaries of important aspects of polypyrroles are included in several reviews on electrically conducting polymers [221-226]. Polypyrrole has been synthesized by chemical polymerization in solution [227-231], chemical vapor deposition (CVD) [232,233], and electrochemical polymerization [234-240]. The polymer structure consists primarily of units derived from the coupling of the pyrrole monomer at the 2,5-positions [Eq. (84)]. However, up to a third of the pyrrole rings in electrochemically prepared polypyrrole are not coupled in this manner [241]. 

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