Preparation of Addition or Chain-Growth Polymers

Carothers, in 1929, classified synthetic polymers into two classes, according to the method of their preparation, i.e., condensation polymers and addition polymers. In polycondensation, or step-growth polymerization, polymers are obtained by reaction between two polyfunctional molecules and elimination of a small molecule, for example water. Typical condensation polymers are shown in Figure 2. Addition (or chain reaction) polymers are formed from unsaturated monomers in a chain reaction. Examples of addition polymers are shown in Figure 2. 

Synthetic polymers can be classified as either chain-growth polymen or step-growth polymers. Chain-growth polymers are prepared by chain-reaction polymerization of vinyl monomers in the presence of a radical, an anion, or a cation initiator. Radical polymerization is sometimes used, but alkenes such as 2-methylpropene that have electron-donating substituents on the double bond polymerize easily by a cationic route through carbocation intermediates. Similarly, monomers such as methyl -cyanoacrylate that have electron-withdrawing substituents on the double bond polymerize by an anionic, conjugate addition pathway. 

Synthetic polymers can be divided into two major classes, depending on their method of preparation. Chain-growth polymers, also known as addition polymers, are made by chain reactions—the addition of monomers to the end of a growing chain. The end of the chain is reactive because it is a radical, a cation, or an anion. Polystyrene—used for disposable food containers, insulation, and toothbrush handles, among other things—is an example of a chain-growth polymer. Polystyrene is pumped full of air to produce the material known as Styrofoam . 

Synthetic Methods. Water-soluble copolymers are prepared by step-growth or chain-growth mechanisms. Linear or branched systems may be formed from single monomers or from multiple monomers. Distribution of monomers, along the backbone or side chain, can be controlled in a number of ways. In nearly all cases, sequence selection is obtained by carefully controlling monomer reactivity, concentration, addition order, and reaction conditions. Most chain-growth, water-soluble polymers are prepared by classical free radical pol5unerization techniques. 

Typical acrylic resins are high MW polymers or copolymers of acrylate and/or methacrylate monomers prepared by radical-initiated chain-growth polymerization (see Figure 2.28). In addition to the (meth) acrylate monomers, other functional (meth)acrylate monomers as well as non-acrylate monomers (typically vinyl monomers) are frequently used in preparation of commercial acrylic copolymer resins to impart reactive functionality or special properties or for lower cost. Some examples of these monomers are shown in Figure 2.29. 

The first step for the core-first stars is the synthesis of multifunctional initiators. Since it is difficult to prepare initiators that tolerate the conditions of ionic polymerization, mostly the initiators are designed for controlled radical polymerization. Calixarenes [39, 58-61], sugars (glucose, saccharose, or cyclodextrins) [62-68], and silsesquioxane NPs [28, 69] have been employed as cores for various star polymers. For the growth of the arms, mostly controlled radical polymerizations were used. There are only very rare cases of stars made from nitroxide-mediated radical polymerization (NMRP) [70] or reversible addition-fragmentation chain transfer (RAFT) techniques [71,72], In the RAFT technique one has to differentiate between approaches where the chain transfer agent is attached by its R- or Z-function. ATRP is the most frequently used technique to build various star polymers [27, 28],... 

Nylon 11 is a polyamide used as fishing line and is prepared by heating 11-aminoundecanoic acid [H2N(CH2)ioC02H]. What is the repeating unit of nylon 11 Is it a condensation or an addition polymer Chain-growth or step-growth ... 

Furfural and HMF are readily prepared from various catalytic biomass conversion processes. Both furfural and HMF can be readily converted to a large variety of monomers for polymerizations by chain-growth and/or condensation mechanisms. As the transformation of furfural and HMF to fine chemicals or monomers for polymers has been well documented by several comprehensive reviews [107-113, 130, 131], this chapter has mainly focused on the bio-based furan polymers with self-healing ability through thermally reversible Diels-Alder reactions, which is a recently exploited prosperous research area. In addition, the furan-based DA reaction has also been used in the thermoreversible nonlinear polymerization and dendrimer chemistry. 

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