Other Miscellaneous Polymerization Reactions

Another interesting research in the area of catalysis is developing catalytic processes which could be controlled by external switches. Organometallic complexes capable of reversible processes are the first candidate for this purpose. Oxidation-reduction is one of these reversible processes which could be extensively modulating reactivity and selectivity of the catalyst through the redox control of the supporting ligand in a metal complex. 

Broderick and co-workers developed one of such alkoxide based catalysts for LA ROP reaction by using ferrocene derivatives, 31-32 [35]. They showed that by using yttrium t-butoxide, LA ROP reaction could be proceeded with 31 but clogged with 32. Consequently, they designed a catalytic system that stopped by addition of FcBAr and resumed by addition of CoCp. Nevertheless, if the metal alkoxide changed to indium phenoxide, this effect will be reversed. 

All polymers discussed in this section have unimodal molecular weight distribution, which implied single-component catalytic systems. Also in most cases the polymer chain molecular weights were lower than estimation, which showed the presence of exchange and/or backbiting processes. This could be the reason of macrocycle detection in some cases. 

Ihere are also some reports on the use of metal alkoxides (vanadium [39, 40], titanium [15, 41, 42], zirconium [15, 43], hafnium [15], and niobium [44]) as pre-catalyst along with organometalllc alumimun com-poimds (chlorodiethyl [39], chlorodimethyl [40], triethyl [41], tri-isobutyl [42] and tri-octyl [42], methylaluminoxane [ 15,43,44]) in olefin (ethylene [15,39-44], propylene [15], 1-hexene [39]) polymerization. The role(s) of metal alkoxides was (were) not studied precisely in these reports and so will not discuss more in this section. 

---

Dimerization and polymerization reactions Other miscellaneous photochemical reactions... 

Other miscellaneous compounds that have been used as inhibitors are sulfur and certain sulfur compounds (qv), picryUiydrazyl derivatives, carbon black, and a number of soluble transition-metal salts (151). Both inhibition and acceleration have been reported for styrene polymerized in the presence of oxygen. The complexity of this system has been clearly demonstrated (152). The key reaction is the alternating copolymerization of styrene with oxygen to produce a polyperoxide, which at above 100°C decomposes to initiating alkoxy radicals. Therefore, depending on the temperature, oxygen can inhibit or accelerate the rate of polymerization. 

OTHER COMMENTS used as a gasoline additive for automotive, aviation and farm equipment used in solvent extraction processes, as a general laboratory solvent, and as a medium solvent for polymerization reactions used in the synthesis of amyl chlorides for intermediates in manufacture of paint, lacquer solvents, hydraulic fluids, paint removers, and miscellaneous petrochemicals used in the synthesis of polychlorocyclopentanes as intermediates in manufacture of fire-resistant polyester resins and paints, dye intermediates, and plasticizers use as a heat-exchange medium, a component of lighter fluids and blow-torch fuel, and in the manufacture of polystyrene beads for styrofoam production. 

Miscellaneous Reactions. Epoxy compounds yield chlorosubstituted carbonates (45). The reaction of chloroformates with hydrogen peroxide or metal peroxides results in the formation of peroxydicarbonates that are used as free-radical initiators of polymerization of vinyl chloride, ethylene, and other unsaturated monomers (46,47). 

Miscellaneous Routes. Polyamides have been prepared by other reactions, including addition of amines to activated double bonds, polymerization of isocyanates, reaction of formaldehyde with dinitriles, reaction of dicarboxylic acids with dllsocyanates, reaction of carbon suboxide with diamines, and reaction of diazlactones with diamines. These reactions are reviewed in Reference 4. 

The four major methods of preparation of poly(alkylene sulfides) involves the polymerization of episulfides (thiiranes), addition of dithiols to olefins, reactions of dithiols with carbonyl compounds, and reaction of dithiols with dihalides and these will be discussed in this section. Other methods will be mentioned in Section 5 (Miscellaneous Preparations). 

---