Copolymers polycondensation reaction

They also synthesized polymeric iniferters containing the disulfide moiety in the main chain [149,150]. As shown in Eq. (30),polyphosphonamide,which was prepared by the polycondensation reaction of phenyl phosphoric dichloride with piperadine, was allowed to react with carbon disulfide in the presence of triethylamine, followed by oxidative coupling to yield the polymeric iniferter 32. These polymeric iniferters were used for the synthesis of block copolymers with St or MMA, with the composition and block lengths controlled by the ratio of the concentration of the polymeric iniferter to the monomer or by conversion. The block copolymers of polyphosphonamide with poly(St) or poly(MMA) were found to have improved flame resistance characteristics. 

The formation of copolymer by polycondensation reaction was proved by IR analysis. The spectra show absorption band at 1470, 1640, 2990, and 3100 cm-1 characteristic of—C—O—NH— groups, at 3300 cm-1 for imine groups and at 920 cm-1 for primary amine groups. From the point of view of chemical composition, the polycondensation products are composed by a fraction insoluble in... 

Free radical initiators or active hydrogen compounds such as amines or alcohols are not very effective initiators for the polymerization of lactones. Polyesters of low molecular weight are produced by these techniques. For example, copolymerization of various lactones in the presence of water at 200 °C proceeded via a hydrolysis followed by the polycondensation reaction of the hydroxy acid, giving low molecular weight products [67-69]. Low molecular weight (=10,000) tri-block copolymer (CL-b-EO-b-CL) has been prepared from e-CL and poly(ethylene glycol) (Mn=10 3) by carrying out the polymerization at 165 °C for several hours in the absence of catalysts [70]. 

The polycondensation reaction between telechelic hydride and telechelic methoxy siloxane in the presence of very low levels of B(CgFj)3 has been described. The compromise between large polymer content and reasonable molar masses is found by tailoring the addition rate and excess content of L H reagent. Rubinsztajn et al. showed that with silphenylene-co-PDMS copolymers, the reaction was completed... 

All-p-phenylene oxadiazole/N-methyl hydrazide copolymers have yielded high performance fibers with tenacities of 18-21 gpd and moduli above 300 gpd through an unconventional polycondensation reaction of terephthalic acid, dimethyl terephthalate and hydrazine sulfate in fuming sulfuric acid and subsequent "reaction spinning" into aqueous acid. 

In Table 10 we have gathered different 1,2-disubstituted tetraphenylethanes reported in the literature to get telechelic polymers. We can remark that few studies were undertaken in the area of telechelic polymers hence, despite a one-step reaction to get a telechelic structure, the main interest attributed to initer systems concerns the ability to restart a block copolymerization. The number of publications concerning the synthesis of diblock copolymers may prove this assumption. Under certain polymerization conditions, the chain ends, comprising the last monomer unit and the primary radical formed from the intiator, may split up into new radicals able to reinitiate further polymerization of a second monomer, leading to block copolymers. This is certainly the reason why 1,2-disubstituted tetraphenylethane does not present such interesting condensable functions (X in Scheme 10) for polycondensation reactions (Table 10). 

Other polycondensation reactions which lead to finely dispersed polymers in liquid polyethers are the polycondensation reactions of urea and melamine with aqueous formaldehyde [92-95]. The reaction medium is usually polyether polyols, PO homopolymers or PO-EO copolymers (random or block copolymers), with MW of 3000-5000 daltons. During the polycondensation reaction, the aminoplast polymer precipitates, being insoluble in polyether and water (water from formaldehyde solution and reaction water), is eliminated by vacuum distillation. A variant of this reaction is to develop the polycondensation in water, and water containing the aminoplast polymer (as a viscous solution) is added to a polyether polyol, under vacuum, and at high temperature (100-130 °C), water being continuously eliminated from the reaction medium. The aminoplast insoluble polymer precipitates in the form of fine particles. 

Si-H terminated PDMS was prepared by termination of the living polymer with dimethylchlorosilane. A hydrosilylation reaction was performed between the Sill terminated PDMS and the product of the reaction between 4-bromo butene-1 and 4,4 -dinitro-2-hydroxybiphenyl to produce the dinitrobiphenyl-terminated PDMS. The subsequent reduction gave the macromonomer [111]. These macromonomers were used for the preparation of graft copolymers via polycondensation reaction with other comonomers (Scheme 38). 

When atriazine unit is a component of a PPS copolymer, a highly refractive and transparent compound emerges [73]. The polymer can be prepared by a polycondensation reaction from 4,4 -thiobis(benzenethiol) and 2,4-dichloro-6-methylthio-1,3,5-triazine. 

A PAES block copolymer was synthesized from a fluoride-terminated oligomer with methyl side groups and a hydroxyl-terminated oligomer by an aromatic nucleophilic substitution polycondensation reaction [86]. Afterwards the methyl side groups were brominated and converted into quaternary ammonium groups. The copolymer can be used for ultrafiltration membranes for protein separation. 

An interesting example of block copolymers is work by de Ruijter et al. [348], who prepared a series of block copolymers that contain rigid liquid crystal forming blocks of poly(p-phenylene terephthalamide) and flexible blocks of hexamethylene adipamide. The polymers have been prepared in a one-pot procedure by a low-temperature polycondensation reaction in A-methyl-2-pyrrolidone. 

Tetsuka and co-workers [15] showed that the of copolymers prepared by two-step polycondensation reactions of adipate, butane-1,4-diamine and linear diol homopolyesters were higher than those of polyesters consisting of the same ester units, and tended to increase with an increase in amide content of copolymers produced from adipate, butane-1,4-diol, and butane-1,4-diamine had especially high thermal stabilities compared to polytetramethylene adipate. They had of more than 200 °C. 

Characteristic examples concerning the S5mthesis of macromonomers prepared hy polycondensation reactions and the subsequent formation of graft copolymers are given in Table 5. 

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