Addition polymerization ring-opening

Since polycondensations of aa -t- b monomers have a much longer history, their description and discussion will be presented first. Syntheses of hb polymers from abn monomers will be discussed in Chap. 11. To avoid misunderstandings, it should be emphasized that the text of both Chaps. 10 and 11, is limited to true polycondensation processes. Synthses of hb polymers based on addition-polymerizations, ring-opening polymerizations, or stepwise construction of dendrimers are not considered. 

Block copolymer—These copolymers are built of chemically dissimilar terminally connected segments. Block copolymers are generally prepared by sequential anionic addition or ring opening or step growth polymerization. 

In step growth polymerization, initially dimer formation takes place due to condensation, addition or ring opening etc., e.g. 

In addition to the alkenyldioxolanes, 4-methylenedioxolane (87) and dioxoles (88) and (89) can be utilized to produce heterocyclic polymers containing this ring system. In a comparative study on the cationic polymerization of these monomers (79MI11105) it was found that the order of reactivity is (87) > (88) > (89). In these polymerizations, ring-opening reactions were found to the extent of 35% and 9%, respectively, for monomers (89) and (88) in addition to the normal 1,2-addition mode. 

The resulting substituted norbomenes can be interesting as monomers for addition or ring-opening polymerization reactions. 

Random copolymers have grown to be the most versatile, economical, and easily synthesized types of copolymers. A wide variety of free-radical, ionic-addition, and ring-opening polymerization techniques, as well as many step-growth reactions, are employed. 

Iv) Substitution. The skeleton of an oligomeric or polymeric system is constructed by condensation, addition or ring-opening techniques, but variations in side-group structure must generally be introduced by substitutive methods ... 

Okoroanyanwu, T. Shimokawa, J.D. Byers, and C.G. WiUson, AUcyclic pol3Tners for 193 nm resist applications synthesis and characterization, Chem. Mater. 10(11), 3319 3327 (1998) U. Okoroanyanwu, J.D. Byers, T. Shimokawa, and C.G. Willson, AUcyclic pol3uners for 193 nm resist appUcations Uthographic evaluation, Chem. Mater. 10(11), 3328 3333 (1998) U. Okoroanyanwu, T. Shimokawa, J.D. Byers, and C.G. Willson, Pd(II) catalyzed addition and ring opening metathesis polymerization of aUcyclic monomers routes to new matrix resins for... 

As disciissed in Chapter 1, under a scheme proposed by Carothers, polymers are classified as addition or condensation polymers depending on the type of polymerization reaction involved in their synthesis. This classification scheme, however, does not permit a complete difierentiation between the two classes of polymers. A more complete but still oversimplified scheme that is still based on the dilTerent polymerization processes places polymers into three classes condensation, addition, and ring-opening polymers. This scheme reflects the stractures of the starting monomers. Probably the most general classification scheme is based on the polymerization mechanism involved in polymer synthesis. Under this scheme, polymerization processes are classified as step-reaction (condensation) or chain-reaction (addition) polymerization. In this chapter, we will discuss the different types of polymers based on the different polymerization mechanisms. 

Several acronyms are used to describe these polymerizations Reversible Addition-Fragmentation Transfer (RAFT), Group transfer polymerization, Ring Opening Metathesis Polymerization (ROMP), Group Transfer polymerization. 

Reaction of bicyclo[3.2.0]hept-2-ene with TiCl4/Et3Al gives undefined products, probably as a result of both addition and ring-opening polymerization [Eq. (73)]. 

Various Ziegler-Natta and ROMP caalysts based on group IV-VIII transition metal salts showed to be very active and selective in the polymerization of both exo-and ew(7o-dicyclopentadiene [151-155]. Thus, binary Ziegler-Natta systems derived from chromium, molybdenum, and tungsten halides associated with organo-aluminum compounds form addition and ring-opened polymers [Eq. (94)]. 

Dimethyleneoctahydronaphthalene has been polymerized by a great variety of Ziegler-Natta and ROMP catalysts based on transition metal salts of titanium, zirconium, vanadium, molybdenum, tungsten, ruthenium, iridium, osmium, platinum or palladium and organometallic compounds [159]. Depending on the catalyst employed, addition or ring-opened polymers were preferentially formed [Eqs. (99) and (100)]. 

A great number of norbornene-like monomers [e.g., m = 1-3, R] and R2 = alkyl and aryl groups, Eqs. (103) and (104)] with or without substituents have been employed in polymerization reactions induced by Ziegler-Natta and ROMP catalysts derived from ruthenium, osmium, iridium, palladium, platinum, molybdenum, and tungsten halides or vanadium and zirconium halides or acetylacetonate associated with organometallic compounds [162, 163]. Both addition and ring-opened polymers have been obtained by this way depending on the catalyst employed [Eqs. (103) and (104)]. 

Control of Addition and Ring-Opening Polymerizations with Metalloporphyrin Catalyst... 

---