Bifunctional polymers

Bifunctional monomeric unit, 149 Bifunctional polymer, 178 Binding mechanism, 3 Bismuth-cadmium alloy (Bi5Cd5), calculation of thermodynamic quantities, 136... 

Peter, K. and Thelakkat, M. (2003) Synthesis and characterization of bifunctional polymers carrying tris (bipyridyl)ruthenium(ll) and triphenylamine units. Macromolecules, 36, 1779-1785. 

The bifunctional polymer 2 (2) that is formed when oligomers of J. are heated with 3,3 , 5,5 -tetramethyl-4,4 -diphenoquinone (a byproduct of the synthesis of 1) reacts with a bifunctional coupling reagent to produce a coupled product... 

A catalyst such as XXXXIV is referred to as a bifunctional polymer catalyst—two different catalyst moieties function simultaneously in the same reaction. 

The third method consists in using a,co-bifunctional polymers of known molecular weight, and in reacting them with adequate plurifunctional reagents17-22. In some cases the a, co-bifunctional precursor polymer is also obtained anionically — this provides for a sharp molecular weight distribution — in other cases it is obtained by other methods. 

Our goal in this work has been the development of a terminally bifunctional liquid rubber. Carboxy-terminated polyisobutylene (CTPIB) approaches a terminally bifunctional polymer. It is made by the ozoniza-tion in the presence of pyridine of a high molecular weight, low unsaturation piperylene-isobutylene copolymer as shown in Reaction 1. 

Telechelic or a,co-bifunctional polymers carry functional groups at both terminals. By varying combinations of initiation and termination reac-... 

If R = R (bifunctional polymers), reaction (119) does not affect the functionality but leads to the broadening of the molecular weight distribution, which is occurring anyway, due to the reversibility of propagation. Thus, several bifunctional polymers of 1,3-dioxolane were prepared and used, for example, to form the networks containing degradable and hydrolyzable polyacetal blocks (cf., Section IV.B). Reaction (119), however, may effectively prohibit the preparation of monofunctional polymers, e.g., macromonomers. Indeed, two recent attempts to prepare macromonomers by cationic polymerization of cyclic acetals led to nearly statistical... 

S—4 shows the pH-rate profile for deacylation. The bifunctional polymers give deddedly hi er (more than one himdied times) deacylation rates. In fact, the rates are greater dian that of acet imidazole (broken line in F 5—4). 

Ref. 14S), and the greatest dauylation rate at pH 8 (0.009—0.013 sec" ) was found with bifunctional polymer catalysts (Elm -HA, PVP -HA and HlA-VIm-AAm) (Section S—3). The acylation rate can be further increased by catalysis at higher pH s and by using substrates with longer alkyl chains. 

Figure 1. Chemical structures of the Class I, II, and III dual mechanism bifunctional polymers.

Kunitake and his coworkers have investigated bifunctional polymer catalysts(29) in micelles(30) and polysoaps.(3L) The bifunctional interaction between a hydroxamate nucleophile and a neighboring imidazole group at the catalytic site is similar to the charge relay system of serine proteases. This interaction leads to remarkably accelerated acylation and deacylation processes. In the hydrophobic environment of cationic micelles, where the reactivity of anionic nucleophiles are remarkably enhanced, the overall catalytic efficiency exceeded even that of a-ch3rmotrypsin at pH 8.(30) Micellar monofunctional catalysts, nonmicellar bifunctional catalysts, and polysoap-bound bifunctional catalysts were less effective. 

The killing technique is extremely useful since it allows us to introduce valuable functional end-groups into macromolecules, giving novel and interesting products. It is even more useful when applied to living polymers with two active end-groups since then bifunctional polymers are formed. ... 

Or by partial destruction of bifunctional polymers in the early stages of reaction by impurities still left in the system... 

However, on addition of styrene or butadiene, a bifunctional polymer was produced. It seems that the second step of the addition is prevented by the lack of stabilization of the di-adduct. On the other hand, the reaction... 

Another attempt at preparing bifunctional polymers in hydrocarbon solvents with lithium counter-ions was reported by Sigwalt et al.440. The following compounds were prepared... 

They react with sec- or t-BuLi and are converted into insoluble dilithiated derivatives which become solubilized on addition of monomers and yield bifunctional polymers and A.B.A. block polymers. Useful dilithio-initiators were reported by Tung475. ... 

Rectangular deck boards, 231 Bethoguard, 457 Bifunctional oligomers, 163 Bifunctional polymers, 163... 

Bifunctional oligomers, 163 Bifunctional polymers, 163 Chloroparafins, 163 Compatibility, effect on, 161 Covalent bonds with wood fiber, 161 Dispersing effect, 174 Fiber dispersion, effect on, 161 Flexural modulus, effect on, 168, 174 Flexural strength, effect on, 168, 174 Flowability, effect on, 161... 

An important consideration in catalyst, reagent or substrate recovery is measuring and verifying how effective such recovery actually is. While we have modeled such recovery using dye-modified polymers, analyses of catalysts typically requires additional analytical work. For example, ICP analysis for residual metal can be used as a quantitative and sensitive assay. Such assays are however more problematic with non-metallic catalysts. In this paper, we show that bifunctional polymers where both a catalyst and a colorimetric label are included in the same polyacrylamide polymer provide a simple way to monitor separability and catalyst recovery for non-metallic polymer-bound catalysts. 

The anionic nucler hiles such as hydroxamate, oximate, and thiolate posses very high nucleophOicity toward phenyl esters. This is also true in polymeric systems. Furdier improvements in reactivi were achieved in (he form of the zwitterionic nucleophile and in micellar environmaits. Since decomposition of the acyl intermediate thus formed can be remadmbly accelerated by introducing imidazole or pyridine groups as the seccmd fimcticHial group, die catalytic effidency of these bifunctional polymers is caasiderably improved compared vrith related monofunc-tional pol)miers (see Table 8—1). 

The largest turnover rate is realized by the proper balance of acylation and deacylation, and found for imidazole-containing miceUes (SA -Im-CTAB), bifunctional miceUes (LImHA-CTAB), a polyethyleneimine derivative(D(10%)-PEI-Im(15%) (Section 6—2), and bifunctional polymers(EIm -HA and PVP -HA) (Section 5—3). It is remarkable that the turnover rate of synthetic catalysts can amount to 10 to 20% of that of a-chjonotrypsin, although it is to be noted that PNPA is never a good substrate for OE-chymotrypsin. Comparable rates are observed for acylation and deacylation, when they are compared separately. 

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