Chain-growth polymerization copolymers

The fluid loss control of aqueous, clay-based drilling mud compositions is enhanced by the addition of a hydrolyzed copolymer of acrylamide and an N-vinylamide [402], The copolymer, which is effective over a broad range of molecular weights, contains at least 5 mole-percent of the N-vinylamide units, which are hydrolyzed to N-vinylamine units. The copolymers can be made from various ratios of N-vinylamide and acrylamide by using common radical-initiated chain growth polymerization techniques. 

Polyphosphazene block copolymers were synthesized by these chain-growth polymerization methods. The successive anionic polymerization of N-silylphosphoranimines 19d and 19a at 133 °C yielded the block copolymer with Mw/Mn of 1.4-2.3 (Scheme 80) [278,279]. However, due to the presence of two possible leaving groups in 19d, this approach yielded block copolymers where one of the block segments contained a mixture of side groups. On the other hand, the cationic polymerization of 19b with PCI5 was carried out at ambient temperature, followed by addition of a second phosphoranimine to yield a block copolymer with Mw/Mn of 1.1-1.4, where each block segment had one kind of side chain (Scheme 81) [280]. 

To name a copolymer prepared by chain-growth polymerization, we simply link the names of the two (or more) monomers with co and precede the names with poly. The set of names is usually placed in parentheses to avoid confusion. 

Chain growth polymerizations very often contain a double bond however, cyclic ethers will polymerize in this manner [5], POM (polyoxymethylene) made by the Celanese method shown in Figure 3.6 is an example of a cyclic ether with this method. The Celanese route for the production of polyacetal yields a more stable copolymer product via the reaction of trioxane, a cyclic trimer of formaldehyde, and a cyclic ether (e.g., ethylene oxide or 1,3 dioxalane). 

The data on the chain-growth polymerization of hydrophobe-modified monomers are insufficient to provide a quantitative analysis of the influence of hydrophobe sequence lengths and placement in copolymers on solution properties. The concentration of the hydrophobe-modified monomer in the... 

In a well-controlled radical system, the monomer conversion is first order, molar mass increases linearly with monomer conversion, and the molar mass distribution MJM is below 1.5. In addition, chain end functionalization and subsequent monomer addition allow the preparation of well-controlled polymer architectures, for example, block copolymers and star polymers by a radical mechanism, which had been up to now reserved for ionic chain growth polymerization techniques. 

It can be formed by suspension polymerization. One procedure is to carry out the reaction in an aqueous solution of lithium bromide at -25 °C with magnesium carbonate as the suspending agent. No initiator is added and the reaction takes about 20 hours. Because the reaction is inhibited by hydroquinone and accelerated by ultraviolet light, it is believed to take place by a free-radical mechanism. Whether it is chain-growth polymerization, however, is not certain. A1 1 copolymer is always formed regardless of the composition of the monomer feed, and the copolymerization takes place only at low temperatures. At elevated temperatures, however, cyclic oxazetidines form instead ... 

How do block copolymers form in simultaneous free-radical and ionic chain-growth polymerizations Explain and give examples. 

ROMP is a chain growth polymerization that converts cydic olefins to a polymeric material in the presence of transition metal-based complexes such as Ti, Mo, W, Ta, Re, and Ru complexes (Scheme 54) 12,329-337 powerful polymerization method is broadly applicable for the preparation of well-defined polymers. Therefore, transformation reactions of both polycydic olefins such as norbomene (NB), norbona-diene, and dicyclopentadiene and low-strain cydic olefins induding cydopentene (CP) and cydoheptene allow extension of the range of attainable block copolymers. 

Classification of Polymers Free-Radical Chain-Growth Polymerization Cationic Chain-Growth Polymerization Anionic Chain-Growth Polymerization Stereoregular Polymers Ziegler-Natta Polymerization A WORD ABOUT... Polyacetylene and Conducting Polymers Diene Polymers Natural and Synthetic Rubber Copolymers... 

Most of the polymers we have described so far are homopolymers, polymers made from a single monomer. But the variety and utility of chain-growth polymerization can sometimes be enhanced (as we have just seen with SBR synthetic rubber) by using mrjdures of monomers to give copolymers. Figure 14.2 summarizes some of the ways in which monomers can be arranged in homo- and copolymers. The copolymers depicted are limited to two different monomers (A and B) in principle, of course, the possibilities are unlimited. 

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