Poly chain extension

These iniferter sites containing an N-H group can be easily transformed into the corresponding thiol which leads to disulfide by oxidative coupling and can form chelation with metal ions (Eq. 47) [171,172]. Poly(St) prepared for polymerization with 44 and 45 was applied to the chain-extension reaction by the S-S bond or chelation bond formations. 

Polymerization reactions were carried out via a prepolymer formation followed by chain extension. One equivalent of poly(tetramethylene oxide) [number-average molecular weight (Mn) = 1400g/mol] was injected slowly by a syringe pump into a... 

The trans-poly-1,4-butadiene isomer is a harder and less soluble rigid crystalline polymer than the cis isomer. As shown by the skeletal structures for the trans isomer (Figure 1.11), chain extensions on opposite sides of the double bonds allow good fitting of adjacent polymer chains, and this, results in a rigid structure. In contrast, the os-poly-1,4-butadiene isomeric polymer units do not permit such interlocking of alternate units. Even so, chain... 

A further extension to the trisazo dyes on the principle of series coupling D—>Mr M2— M3— K offers no advantages, because the intermediate isolation that is frequently necessary leads to yield losses, and a chain extension is therefore ruled out on economic grounds. This is also reflected in the number of poly-azo dyes listed in the Colour Index [5], Although 78 tetrakisazo dyes with eleven different synthesis principles are listed, only 14 dyes with five and more azo groups are mentioned, two of which are specified with eight azo groups. 

Diols are predominantly used for chain extensions to give a product with only urea bonds. The progress is similar to the formation of the poly(urea-urethane), but with only urethane bonds. See Figure 2.32. 

Keywords. Monomers from renewable resources, Polymers from renewable resources, 1,3-Propanediol, Succinic acid, Lactones, Cyclohexanedimethanol, Polyethyleneglycol, Chain-extension, Poly(ester-urethane)s, Poly(ester-carbonate)s... 

As an additional component, various thermoplastic polymers can be used. As a binder for copper clad laminates, a solution of solid epoxide resin (Epikote 1001), BPA/DC prepolymer, Zn acetate and poly(phenylene sulfide) was used [83], Other binders for reinforced plastics contain polysulfone. Such compositions consist of liquid BPA/ECH epoxide resin, BPA/DC prepolymer, polysulfone and bis(4-hydro-xyphenyl)sulfone [85]. Bis(4-aminophenyl)sulfone can be also added [86]. In such systems the bisphenol reacts with the epoxide resin as a chain extension agent, whereas the diamine crosslinks the diepoxide. The Tg values are close to 200 °C. They can be increased a little, if the BPA/ECH epoxide resin is replaced by the tetra-epoxide A,A,A, A -tetrakis(2,3-epoxypropyl)diaminodiphenylmethane [87]. 

In the polyurethane industry, the polymeric glycols are prepared by anionic polymerization of epoxides such as ethylene oxide and propylene oxide. Poly(tetra-methylene glycol), which was prepared by polymerization of tetrahydrofuran, was subjected to chain extension by reaction with diisocyanate (polyurethane formation) and with dimethyl terephthalate (polyester by alcoholysis). 

Samples. Linear polurethane block copolymers with hard segments composed of 2,4- or 2,6-TDI, and 1,4-butanediol, BD, and either 1040 or 2060 molecular weight poly (tetramethylene oxide), PTMO, soft segments were supplied through the courtesy of N. S. Schneider of the Army Materials and Mechanics Research Center, Watertown, MA. These polymers were prepared by a two-step process, first an endcapping of the PTMO with a 5% molar excess of TDI, followed by chain extension... 

The domains found after the chain extension components at the C-termini of fungal NR-PKS are highly varied. These components include putative Claisen-cyclase/thiolesterases (CLC/ TE), C-methyl transferases (C-MeT), reductases (R), and additional ACP domains. Recent work indicates that these processing components act after chain assembly to modify either a poly-keto or a cyclized intermediate. 

The low molecular weight poly sulphides have found somewhat greater use. Of general structure HS—R—SH and with molecular weights of approximately 1000 they will react with the epoxy group to cause chain extension but not cross-linking. The normal hardeners must therefore be employed in the usual amounts... 

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