Regioselective ring-opening polymerization

A series of lanthanide metallocene catalysts are active in the regioselective ring-opening polymerization of strained f .vo-rnethylcnecycloalkanes to yield f . v>-mcthylene-functionalizcd polyethylenes.9 a Methylenecyclobutane affords the polymer [-CH2CH2C112C( =CH2)-] under the catalytic action of [ 1,2-... 

Most cationic ring-opening polymerizations are highly regioselective with the formation of head-to-tail structures, although varying amounts of head-to-head and tail-to-tail structures are found in some systems [Dreyfuss and Dreyfuss, 1987]. 

The stereochemistry of ring-opening polymerizations has been studied for epoxides, episul-fides, lactones, cycloalkenes (Sec. 8-6a), and other cyclic monomers [Pasquon et al., 1989 Tsuruta and Kawakami, 1989]. Epoxides have been studied more than any other type of monomer. A chiral cyclic monomer such as propylene oxide is capable of yielding stereoregular polymers. Polymerization of either of the two pure enantiomers yields the isotactic polymer when the reaction proceeds in a regioselective manner with bond cleavage at bond 1. 

H. Kamitakahara and F. Nakatsubo, Substituent effect on ring-opening polymerization of regioselectively acylated 1,4-anhydro-a-D-glucopyranose derivatives, Macromolecules, 29 (1996) 1119-1122. 

Ethyl glucoside as a multifunctional initiator for enzyme-catalyzed regioselective lactone ring-opening polymerization. J. Am. Chem. Soc.,... 

Cationic ring-opening polymerization of a bicyclic acetal monomer was a possible method to synthesize cellulose [29]. A polysaccharide of DP 20 was obtained however, a regioselective ring-opening did not take place. The major component was a tetrahydrofuran-ring unit and not a six-membered glucopyranose unit. 

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