Vinyl monomers categories

Synthetic polymers are classified by their method of synthesis as either chain-growth or step-growth. The categories ate somewhat imprecise but nevertheless provide a useful distinction. Chain-growth polymers are produced by chain-reaction polymerization in which an initiator adds to a carbon-carbon double bond of an unsaturated substrate (a vinyl monomer) to yield a reactive inter-... 

To the first category belong the homo- and copolymerization of macromonomers. For this purpose, macromolecules with only one polymerizable end group are needed. Such macromonomers are made, for example, by anionic polymerization where the reactive chain end is modified with a reactive vinyl monomer. Also methacrylic acid esters of long-chain aliphatic alcohols or monofunctional polyethylene oxides or polytetrahydrofurane belong to the class of macromonomers. 

Although copper reagents, hahdes and triflates, are widely used in atom-transfer polymerization reactions (ATRP) [63], these processes do not fall under the category of Lewis acid-mediated reactions. Sherrington and co-workers have shown that a vinyl monomer coordinated to a chiral copper Lewis acid (122) undergoes stereoselective polymerization (Sch. 29) [64]. A chiral block-copolymer 124 was prepared under radical conditions. 

Selection of an inhibitor must therefore be made carefully while keeping in mind these characteristics. Several phenolic compounds may have the right profile in each inhibitor category and not effecting the quality and cost of monomer production. Amongst other things, this explains the success of phenolic inhibitors in the vinyl monomer industry. 

Yet another class of niche surface-active agents includes higher molecular weight polymers based on acrylate or maleate esters, vinyl pyrolidone, and other vinyl monomers that contain, or can be modified with hydrophilic head groups. There are numerous chapters dedicated to polymeric surfactants and polymer surfactant interactions that enhance smfactant efficiency.The use of surface-active polymers across all categories is increasing as these materials are customized and optimized to deliver enhanced product performance at very low levels. 

While not strictly considered emulsions, two other systems may be classified in this category, both of which comprise very small particles of silicone fluids in aqueous dispersions. The first method of preparing these microdroplets involves in situ polymerization of a water-soluble vinyl monomer or mixtures of said monomer and acryl comonomers. The silicone fluids are first dispersed into microdroplets in the water phase by means of high-speed agitation and then the vinyl monomers or cationic polymers are added at elevated temperatures in the presence of free-radical catalysts. The resulting aqueous polymer matrix contains stable, discreet microdroplets of the silicone fluids. The second method utilized to prepare such a fine dispersion is very-high-pressure injection of silicone into the aqueous phase. These microdroplets have been referred to as nanoparticles, but they are actually nanometer-sized fluid droplets as opposed to nanometer-sized sihcone resin particles, which are referred to by the same term (86). Both of the systems described above have been claimed to readily deposit onto hair and skin, and to increase ease of formulation (87,88). 

Monomers Several general categories of vinyl monomers are suitable for anionic polymerizations. These include aromatic monomers (2-vinylpyridine, styrene), conjugated dienes (butadiene, isoprene), and alkyl methacrylates. In the case of vinyl monomers, adjacent substituents that stabilize an anion are most suitable for anionic polymerizations. Examples include substituents found in styrene, butadiene, isoprene, alkyl methacrylates, or cyano acrylate which stabilize propagating anions by electronic effects. 

The above described results demonstrate that, given a suitably strong interaction between the propagating carbocation and its counteranion, a broad range of vinyl monomers yield polymers with bimodal MWD. AD these polymers have been formed by 0X0 acids and iodine as initiators the formation of polymers with a bimodal MWD is one of the important characteristics of the polymerizations by non-MX initiators. It should therefore be reasonable and useful to classify cationic initiators into two categories, MX and non-MX types, according to the structure of the counteranions... 

The monomer pair, acrylonitrile—methyl acrylate, is close to being an ideal monomer pair. Both monomers are similar in resonance, polarity, and steric characteristics. The acrylonitrile radical shows approximately equal reactivity with both monomers, and the methyl acrylate radical shows only a slight preference for reacting with acrylonitrile monomer. Many acrylonitrile monomer pairs fall into the nonideal category, eg, acrylonitrile—vinyl acetate. This is an example of a nonideality sometimes referred to as kinetic incompatibiUty. A third type of monomer pair is that which shows an alternating tendency. 

For ambient or low temperature application, thermoplastic polymers can be used. Low cost monomers that have been used in this category include ethylene, ethylene-S02, vinyl acetate, methyl methacrylate, styrene, styrene-acrylonitrile, and chlorostyrene. Others awaiting test are vinyl chloride, vinylidene chloride, and terf-butylstyrene. These monomers are limited for use at temperatures below / 100°C because of their softening points. 

Some of the most important linear or chain polymers belong to the category of homopolymers, for example, polyethylene, polyvinylchloride, and polypropylene (see Table 2.1) where the vinyl-type monomer (see Figure 2.34) with different side groups, R, is repeated [8,195],... 

We have broadly classified monomers polymerisable by a cationic mechanism into four main categories, viz. (i) aliphatic mono-olefins (of which isobutene is the most studied) (ii) aliphatic dienes (cyclopentadiene being the best-known member) (iii) aromatic olefins (with styrene as the most important) (iv) monomers in which the vinyl group is attached to an electrodonating atom (vinyl ethers, N-vinylcarbazole, etc.). Within each category, the ease of initiation for the most representative monomers follows approximately the order given below ... 

The chemist classifies polymers in several ways. There are thermosetting plastics such as Bakelite and melamine and the much larger category of thermoplastic materials, which can be molded, blown, and formed after polymerization. There are the arbitrary distinctions made among plastics, elastomers, and fibers. And there are the two broad categories formed by the polymerization reaction itself (1) addition polymers (e.g., vinyl polymerizations), in which a double bond of a monomer is transformed into a single bond between monomers, (2) condensation poly-... 

Closely related to the ionic polymerization of heterocyclic monomers is, what we can call, pseudoionic polymerization (or sometimes, perhaps, cryptoionic). We use the preffix pseudo- in the same meaning as it was first used in the vinyl cationic polymerization. It means that propagation actually proceeds on the covalent species that could have been in equilibrium with their ionic counterparts. Several systems falling to this category have recently been described for both anionic and cationic polymerization of heterocyclics. In the anionic processes derivatives of Zn or A1 alkyls or alcoholates are believed to function this way. However, for none of these systems the absence of ionic contribution was shown. Two catalytic systems are of particular interest, namely the -Zn-O-AK systems (20) and>Al-alkyl modified by bulky porphyrin derivatives (21). Both are discussed in this volume and both have been clearly shown to produce living systems. The former with e-caprolactone and the latter... 

Examples of monomers in this category include alkyl vinyl ketones and vinyl bromide both of which dissociate when irradiated with ultraviolet light by the following reactions ... 

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