Directive Monomers

Polymerization of t-butyl methacrylate initiated by lithium compounds in toluene yields 100% isotactic polymers 64,65), and significantly, of a nearly uniform molecular-weight, while the isotactic polymethyl methacrylate formed under these conditions has a bimodal distribution. Significantly, the propagation of the lithium pairs of the t-Bu ester carbanion, is faster in toluene than in THF. In hydrocarbon solvents the monomers seem to interact strongly with the Li+ cations in the transition state of the addition, while the conventional direct monomer interaction with carbanions, that requires partial dissociation of ion-pair in the transition state of propagation, governs the addition in ethereal solvents. 

The observation of Tsuji et al. 148) concerned with copolymerization of 1- or 2-phenyl butadiene with styrene or butadiene illustrates again the importance of the distinction between the classic, direct monomer addition to the carbanion, and the addition involving coordination with Li4. The living polymer of 1- or 2-phenyl butadiene initiated by sec-butyl lithium forms a block polymer on subsequent addition of styrene or butadiene provided that the reaction proceeds in toluene. However, these block polymers are not formed when the reaction takes place in THF. The relatively unreactive anions derived from phenyl butadienes do not add styrene or butadiene, while the addition eventually takes place in hydrocarbons on coordination of the monomers with Li4. The addition through the coordination route is more facile than the classic one. 

The major species in most cationic polymerization systems are covalent, including halides and esters. There has been considerable controversy as to whether covalent species undergo propagation by direct monomer insertion into a covalent bond or only through ionization to... 

Comparison of Copolymers via Sequential and Direct Monomer Addition... 

The use of acrylic acid not only led to a functionalization of nanoparticles, but also was important as a structure-directing monomer for the formation of nanocapsules. In this case, the hydrophilic groups of the acrylic acid [30] or methacrylic acid [31] resulted in the formation of a nanocapsule structure, instead of Janus-like or even separate nanoparticles. The copolymerization of the functional n-methylol acrylamide with vinyl acetate was found to follow (in batch miniemulsion) the Mayo-Lewis equation, despite huge differences in the solubility of the monomers in the aqueous continuous phase [32]. A functionality of fluori-nated particles could be easily introduced by copolymerizing fluoroalkylacrylates with protonated monomers, such as acrylic acid and methacryloxyethyltrimethyl ammonium chloride [33]. 

Reaction b), the direct monomer reduction may be realized at zinc, whidt has the highest hydrogen overpotential, but it is unlike to take place at Fe electrodes before reduction. 

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