Poly chain-growth syntheses

The chain-growth condensation polymerization leading to aromatic polyether can be applied to the synthesis of a well-defined poly(ether sul-fone) by the condensation polymerization of 25, which is different from other monomers for chain-growth condensation polymerization in that the nucleophilic site and electrophilic site are on each benzene ring connected with an electron-withdrawing group, a sulfonyl group (Scheme 94). In the polymerization of 25 in the presence of an initiator and 18-crown-6 in sulfolane at... 

Step-growth polymerization, 22, 24-25, 23, 84-86, 86,90-92,114-115, 261 compared with chain-growth polymerization, 88-89, 88-89 interfacial polymerization, 91-92 laboratory activities on synthesis of nylon, 228-230 synthesis of polyesters in the melt, 231-233 synthesis of polyurethane foam, 234-237 molar mass and, 86, 86 polycondensation of poly ethylene terephthalate), 90-91 polymers produced by, 86 types of monomers for, 90 Stereochemistry, 28, 37-39,41-42, 70 tacticity, 103-105 Stereoisomers, 41 Stereoregularity, 70 Stiffness, 142, 261 Strain, 142-143, 261 Strength... 

Throughout this chapter, the examples of polymerizations in compressed CO2 have been primarily for chain growth polymerization processes. However, step-growth methods represent an area of new interest for SCFs. Initial experiments in this area include the synthesis of aromatic polyesters such as poly(ethylene terephthalate) (PET) in SCCO2 as illustrated in Scheme 4.5-9 [144]. An advan-... 

The synthesis and the modification techniques concerning PES have been reviewed by Kricheldorf. Poly(ethersulfone)s can be obtained either by a conventional step-growth polycondensation, or by a chain-growth polycondensation, which is in fact a living polycondensation. ... 

Perhaps the first indication of chain-growth polymerization was realized in the synthesis of poly(phenylene sulfide) using p-halothiophenol salts. For certain monomers, it was realized that the pol5mier chain end groups were more reactive than the monomers. Later, in the polycondensation of chlorophenylsulfonyl phenoxide, an increased reactivity of the polymer end group was detected. The reaction scheme is shown in Figure 7.2. The polymeric end group reacts ca. 20 times faster than the monomer. 

T. Yokozawa, T. Taniguchi, Y. Suzuki, and A. Yokoyama. Chain-growth polycondensation of monomer consisting of two aromatic rings Synthesis of well-defined poly(ether sulfone) from 4-fluoro-4 -hydroxydiphenyl sulf-one. J. Polym. ScL, Part A Polym. Chem., 40 3460-3464, 2002. 

Yokozawa T, Taniguchi T, Suzuki Y, Yokoyama A. Chain-growth polyconden sation of monomer consisting of two aromatic rings synthesis of well-defined poly (ether sulfone) from 4-fluoro-4 -hydrox ydiphenyl sulfone. J Polym Sci Part A Polym Chem 2002 40 3460-4. 

Scheme 8 Synthesis of highly branched poly(methylmethacrylate)s via RAFT-mediated AB + A2B2 chain growth.

Alcaligenes eutrophus has been used for industrial production of poly(hydroxyaIkanoate)s (PHAs). PHA is prepared from acetyl CoA in three steps and the last step is the chain growth polymerization of hydroxyalkanoate CoA esters catalyzed by PHA polymerase, yielding PHA of high molecular weight, which has heen in vitro examined, leading to synthesis of PHAs with well-defined structure. This synthetic process obeys the biosynthetic pathways (see Poly(3-H DROXYALKANOATES)). 

Since Yokozawa and coworkers published in 2007 the first example of chain-growth Suzuki-Miyaura polymerization for the synthesis of poly(9,9-dioctyl-2,7-fluorene) using PhPd[P Bu3]Br as an initiator [90], different methods have been developed for synthesizing Jt-conjugated polymers with specific architectures. IPr-Pd-PEPPSI complex was found to mediate hving, chain-growth homo- and... 

Marvel s Precursor. Marvel s precursor concept for the synthesis of poly(p-phenylene) dates back to the late 1950s (Fig. 11). The route is characterized, however, by several problems such as low molecular weight, poor regiochemical control, lack of stereochemical control, and poor control of the final aromatization process. This strategy nevertheless contains all the important features also found in more modern approaches to precursor polymers for poly(p-phenylene) the use of a cyclohexadiene monomer, its chain-growth polymerization to furnish the precursor polymer, and the precursor s subsequent aromatization to poly(p-phenylene) [316, 317]. 

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