Main-chain structure, monomer

Main-Chain Structure, Monomer Sequence and Stereosequence... 

Free-radical and anionic polymerizations of TAD-DOL—MA (30) proceed exclusively via a cyclization mechanism, and the obtained polymer seems to have a helical conformation with an excess helicity.92-94 The main chain structure of poly(TADDOL—MA) with cyclized units (poly-30) is different from that of all other polymethacrylates discussed here. Similar monomers have been synthesized and polymerized.95... 

Poly(iV-alllinear poly(isopropylenimine) (PiPI) back in 1974 based on the hydrolysis of poly(2,5-dimethyl-2-oxazoline), prepared by living CROP of the corresponding 2-oxazoline monomer. The PiPI is of interest as it is the simplest PAI with a chiral main-chain structure. Even though this specific example yielded a racemic PiPI, this synthetic procedure also provides access to a PiPI with controlled stereochemistry if... 

The total insolubility and intractability of the wholly aromatic LC homopolyesters and homopolyamides posed serious problems in their processability during the developmental stage. Introduction of disrupters (flexible species, rigid kinks, etc.) into the main chain or copolymerization with disrupter monomers reduces the perfectly arrayed chains structures and lowers their melting. Vectra and Xyder are two of the early LC commercial products [204-207]. 

Among the main molecular structural variables in EPDMs that are stipulated by catalyst systems and that affect the vulcanizate tensile properties we may mention molecular weight (MW) and MWD, degree of unsaturation (LG=C 1) and its distribution in the polymer, composition (C S) and monomer sequence length distribution along molecular chains, and long-chain branching if present. Effect of... 

Cyclopolymerization of Nonconjugated Dienes. Cyclopolymerization is an addition polymerization that leads to introduction of cyclic structures into the main chain of the polymer. Nonconjugated dienes are the most deeply studied monomers for cyclopolymerization and for cyclocopolymerizations with alkene monomers 66 In general, (substituted and unsubstituted) dienes with double bonds that are linked by less than two or more than four atoms cannot undergo efficient cyclization and result in crosslinked materials.12 In fact, efficient cyclopolymerization processes have been described, for instance, for a,oo-dienes like 1,5-hexadiene, 2-methyl-l,5-hexadiene, 1,6-heptadiene, and 1,7-octadiene,67 73 which lead to formation of homopolymers and copolymers containing methylene-1,3-cycloalkane units. 

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