Styrenes, controlled/living anionic polymerization

Novel sulfonated and carboxylated ionomers having "blocky" structures were synthesized via two completely different methods. Sulfonated ionomers were prepared by a fairly complex emulsion copolymerization of n-butyl acrylate and sulfonated styrene (Na or K salt) using a water soluble initiator system. Carboxylated ionomers were obtained by the hydrolysis of styrene-isobutyl-methacrylate block copolymers which have been produced by carefully controlled living anionic polymerization. Characterization of these materials showed the formation of novel ionomeric structures with dramatic improvements in the modulus-temperature behavior and also, in some cases, the stress-strain properties. However no change was observed in the glass transition temperature (DSC) of the ionomers when compared with their non-ionic counterparts, which is a strong indication of the formation of blocky structures. 

Controlled/Living Anionic Polymerization of Styrenes in Polar Solvent Using Flow Microreactor Systems [145]... 

PS macromonomers have been efficiently applied to the synthesis of well-defined polymer hybrids with controlled length of grafts. They are, in general, prepared via living anionic polymerization of styrene monomers and their treatment with vinyl compounds, such as -allyl, -undecenyl, and styryl compounds. 

In a similar manner, Yoshida and Osagawa [436] synthesized poly(s-caprolactone) with 2,2,6,6-tetramethylpiperdine-l-oxyl (TEMPO) at one end by anionic polymerization of caprolactone using an aluminum tri(4-oxy-TEMPO) initiator. The TEMPO-supported polycaprolactone behaved as a polymeric counter radical for a controlled/ living radical polymerization of styrene to form block copolymers [436]. 

Ramakrishnan, A., and Dhamodharan, R. (2000). A novel and simple method of preparation of poly(styrene-b-2-vinylpyridine) block copolymer of narrow molecular weight distribution living anionic polymerization followed by mechanism transfer to controlled/iivingc radical polymerization (ATRP). J. Macromol. ScL, Pure Appl. Chem., A37(6) 621-631. 

The synthesis of block copolymers of controlled structures is most conventionally accomplished through the use of living anionic polymerization. One can easily imagine, however, desirable block copolymers derived from monomers which are inert to anionic polymerization conditions, or which do not share any common mode of polymerization. In a recent series of papers (24-34), Richards and coworkers have addressed this problem in a general way, and have developed methods which convert one kind of active center into another. Within the context of cyclic ether polymerizations, Richards has focused on the preparation of block copolymers of styrene and tetrahydrofuran (THF) several methods of accomplishing this copolymerization are described in the following paragraphs. 

For carbon-based vinyl monomers, controlled polymerization has been traditionally achieved by ionic mechanisms [174]. The living anionic polymerizations of styrene and methyl methacrylate are quite common, resulting in preservation of the polymer functionality. However, alike the inorganic analogues the ionic polymerization mechanism is limited to a rather narrow class of monomers, under conditions of the most stringent purity. Therefore, the aim to develop a controlled free radical... 

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