Polymerization by addition

Nylon 6, 11, and 12. This class of polymers is polymerized by addition reactions of ring compounds that contain both acid and amine groups on the monomer. 

Photoinduced free radical graft copolymerization onto a polymer surface can be accomplished by several different techniques. The simplest method is to expose the polymer surface (P-RH) to UV light in the presence of a vinyl monomer (M). Alkyl radicals formed, e.g. due to main chain scission or other reactions at the polymer surface can then initiate graft polymerization by addition of monomer (Scheme 1). Homopolymer is also initiated (HRM-). 

Most commercially available silicone elastomers, and especially those which polymerize by addition-cure, do not, or weakly, adhere to most surfaces. Adhesion promoters known as surface primers are available and are often used to adhere the silicone to the protected... 

There are two different ways for carrying out polyreactions in a solvent. When both the monomer and the resulting polymer are soluble in the solvent, one speaks of a homogeneous solution polymerization on the other hand, if the polymer precipitates during the course of the reaction, it is called precipitation polymerization. By addition of a solvent, different effects are obtained Basically, the viscosity of the reaction mixture is decreased in comparison to a bulk polyreaction this facilitates heat transfer, mass transport, and handling. 

Solutions are gently mixed according to Table 2.9 in the indicated order and filled up with ddH20. Start the polymerization by addition of Soln. F and pour the mixture immediately into the gel cassette. When the appropriate height is reached, cover the liquid with water or n-butanol to get a smooth surface. Prepare the stacking gel as short as possible before starting the electrophoresis to avoid a decrease of the pH jump between stacking and separation gel by diffusion. 

For the case of polymerization by addition across single double bonds in each monomer, Z may be written as... 

Nucleophilic attack of carbanions on silicon in silacyclobutane rings results in breaking of the Si-C bond in the ring leading to the recovery of the carbanionic center. Disilacyclobutane 38 was polymerized by addition of alkyllithium as initiator in tetrahydrofuran (THF) at — 78 °G in the presence of hexamethylphosphoramide (HMPA) acting as an activator (Equation 14) <2000MI805>. 

Table 2-2 lists the common names and structures of a few chain-growth polymers. For each of these the common name of the homopolymer and its repeat unit are also shown. Two examples of copolymers are also provided. The subscripts m and n indicate only the total number of repeat units of each monomer not the arrangement in the copolymer. In other words, these are presumed to be random, not block, copolymers. All of the monomers in Table 2, a and b, polymerize by addition to a carbon-carbon double bond by a chain-growth mechanism. 

A large section of the polymer industry involves the production of macromolecules from ethylene or substituted ethylenes. As discussed previously, ethylene molecules polymerize by addition after the double bond has been broken by some initiator ... 

The mechanism of initiation is based on an examination of reaction products in an early stage of the polymerization. After short-stopping the polymerization by addition of sodium methoxide/methanol solution, the main product subsequently identified by gas chromatography was C2H5OCH2CH2OCH2OCH3. The rate of polymerization is presumed to follow the standard eqn. (6) for an equilibrium polymerization without termination and with rapid initiation. It is acknowledged that there is an induction period (presumably due to reaction of catalyst with adventitious water, since rigorous drying reduced the induction time to only... 

Methyl vinyl ketone, CHjCCH=CH2, can be polymerized by addition polymerization. The addition reaction involves only the C=C bond. Write the structural formula of a four-unit segment of this polymer. 

Polystyrene formed under these conditions has a narrower range of molecular weights than provided by other methods. Initiation of polymerization by addition of... 

Analogous to the initiation of anionic polymerization by addition of nucleophiles to alkenes, cationic polymerization can be initiated by the addition of electrophiles. The alkenes that respond well to cationic polymerization are those that form relatively stable carbocations when protonated. Of these, the one used most often is 2-methylpropene, better known in polymer chemistry by its common name isobutylene. 

Describe and illustrate by chemical equations the initiation mechanism in a homogeneous polymerization by addition of an butyllithium to an olefin in a nonpolar solvent. What is the effect of heteroatoms, such as oxygen present in the monomers Illustrate. 

Such radicals are incapable of initiating polymerizations by additions to the double bonds, but react selectively with growing radicals to form reversibly covalent species [265]. In addition, the reactions of growing radicals with dormant species occur via degenerative transfer ... 

Polyvinylidene Chloride (PVDC). Polyvinylidene chloride (PVDC) is similar to PVC except that two chlorine atoms are present on one of the carbon groups. Like PVC, PVDC is also polymerized by addition polymerization methods. Both emulsion and suspension polymerization methods are used. The reaction is shown below in Fig. 2.42. The emulsion polymers are either used directly as a latex or dried for use in coatings or melt processing. 

It is clear, however, that too much oxidation will favour disproportionation in the normal Pt(2+) and Pt(4+) compounds, the latter tending to negative octahedral coordination. The same occurs in the reversible solutions. But at least in the case of the dioxalato complex, there are deeply colored polymeric species at high concentrations, as can be shown by osmotic, conductivity, pH, and spectral measurements. The equilibrium is shifted towards polymerization by addition of H -ions, while protons are generated by the depolymerization process, according to the overall equation... 

Polymerization by addition. A reaction characterized by the stoichiometric combination of residues from one or several monomers each containing at least one unsaturated (i.e., double or triple) chemical bond in their molecules such as is found in hydrocarbons like the alkenes and alkynes. The overall chemical reaction can be sketched as follows ... 

Polybutadiene Microstructure. Butadiene polymerizes by addition. Having two double bonds, it forms a variety of polymer structures. One of these, known as the vinyl or 1,2-type, results from addition across just one of the double bonds (eq. 3). 

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