Anionic ring opening polymerization activators

The kinetics of anionic ring opening polymerization of caprolactam initiated by iso-phthaloyl-bis-caprolactam and catalyzed by caprolactam-magnesium-bromide satisfactorily fit Malkin s autocatalytic model below 50 percent conversion. The calculated value of the overall apparent activation energy for this system is 30.2kJ/mol versus about 70kJ/mol for Na/hexamethylene-l,6,-bis-carbamidocaprolactam as the initiator/catalyst system. 

These anionic ring opening polymerizations are usually carried out either in bulk or in solution. A host of catalyst types are active. For synthetic references using specific catalysts, the reader is referred to several excellent sources (4,7,31,32). Representative catalysts include hydroxides, alcoholates, phenolates, silanolates, siloxanolates, mercaptides of the alkali metals, organolithium and potassium compounds, and quaternary ammonium and phosphonium bases and their silanolates and siloxanolates. Some physical characteristics of linear oligomers are given in Table 5 (10). 

These results provide yet another example of an anionic ring-opening polymerization, in addition to that of styrene oxide polymerization, which can occur with formation of different active centers under the same reaction conditions. These results are in contradiction to those known until now, and to the general opinion that the anionic polymerization of 6-lactones proceeds by either the opening of alkyl-oxygen bond or an acyl-oxygen bond. 

Much of the recent activities in anionic ring-opening polymerization involve the use of anionic coordination initiators. For these initiators, the metal coordinates with the carbonyl (C=0) oxygen of the monomer, which is followed by cleavage of the acyl-oxygen (CO-0) bond of the monomer and insertion into the metal-oxygen (M-O) bond of the initiator. The experimental evidence for this coordination-insertion mechanism comes from end group analysis of the polymer formed. 

For the preparation of a vinyl-functionalized polysiloxane block by anionic ring-opening polymerization commercially available D4 was used and compared with Ds. Because of the diminished ring strain in D4, the ring-opening reaction needs additional activation compared to that of cyclotrisiloxanes. ... 

Homopolymers, as well as random and block copolymers with PDMS, were created by a combination of polycondensation and anionic ring-opening polymerization. To convert the chlor-opropyl side groups into quaternary ammoniums, the polymer was first treated with lithium bromide to replace the chlorine with bromine. The polymer was dissolved with (3-hydroxypro-pyl)dimethylamine to create the amphiphilic quaternary amine-functionalized polymer. Bactericidal assays of statistical and block copolymers gave MIC values of 6-25 pgmr against E. coli and S. aureus, with somewhat better activity against S. aureus. 

A similar class of siloxane polymers was created with imi-dazolium groups (Cl5). ° Monomer synthesis consisted of combining N-allylimidazole and methyldiethoxysilane at elevated temperature. Homopolymers were created by polycondensation. Polymers with dimethylsiloxane spacers were also created by anionic ring-opening polymerization. Both classes of imidazole polymers were then reacted with n-octyl bromide to create the imidazolium side chains. Bactericidal activities of these polymers were similar to the quaternary ammonium polymers. 

Since the critical step in the anionic ring-opening polymerization of propanesultam is the rapture of the ring of the co-catalyst, N- benzenesulfonylsultam (activated sultam), induced by the attack of the cyclic sulufonamide anion, we treated 7V-toluenesulfonyl camphorsultam with sodium methoxide, potassium -butoxide, and a preformed camphorsultam Na salt and analyzed the products by and NMR. In all the cases the NMR analysis suggested that the sulfonamide ring had been opened by the base. It is not clear at the moment why camphorsultam is reluctant to polymerize. 

They are unstable at these temperatures and cannot be melt spun. Fibers, however, were prepared by dry spinning from hydrocarbon suspensions [49]. Later, it was found that when the anionic ring opening polymerizations of 2-pyrrolidone are activated by CO2 in place of the iV-acyl derivative, the resultant higher molecular weight product has much better heat resistance [54]. This new nylon 4, reportedly, can be melt spun. 

Polyether synthesis From activated or metal-free anionic ring-opening polymerization of epoxides to functionahzation 13PPS845. 

Scheme 5. Schematics of non-activated and activated anionic ring-opening polymerization of caprolactam.

Anionic ring-opening polymerization of POx initiated by partially deprotonated dipropyleneglycol (DPG) in the presence of the phosphonium cation tetrakis[cyclohexyl(methyl) amino jphosphonium as counterion (P Scheme 14) has been reported by Rexin and Miilhaupt. An alcohol/phospho-nium alkoxide mixture (95/5) was utilized to control reactivity, making use of a fast proton exchange reaction between dormant hydroxy compounds and active phosphonium alkoxide ends (Scheme 16). 

The nature and concentration of the initiator play a cmcial role in the nonactivated anionic polymerization, where the growing centers are formed in the slow reaction [46] between the monomer and the lactam anion bringing about the presence of some induction periods. On the other hand, the evaluation of the specific action of a given initiator in the activated lactam polymerization is more complex, since it cannot be taken in consideration apart from the activator used. It is necessary to consider here the dual system initiator/activator. It seems that the activation energy for the anionic ring-opening polymerization of CL is almost independent of the activator used, " whilst it is probably a fimction of the initiator nature. 

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