Functional initiators peroxides

Peroxide decomposers—These function by reacting with the initiating peroxides to form nonradical products. Presumably mercaptans, thiophenols, and other organic sulfin compounds function in this way [19]. It has been suggested that zinc dialkyldithiocarbamates function as peroxide decomposers, thus giving mbber compounds good initial oxidative stability. 

Figure 6 Phenol removal from a synthetic waste and a foundry waste as a function of HRP dose with and without the presence of 100 mg/L PEG. [Initial phenol] = 3.5 mM (330 mg/L as phenol), [initial peroxide] = 4.9 mM. (Adapted from Ref. 24.)... 

Initiating radicals are formed either from polymers used for functionalization or are generated from initiators. Peroxides and hydroperoxides and AIBN are used as initiators in NR, SBR, NBR or EPDM functionalization [236, 243, 245]. 

Boutevin [2], in his review on Telechelic oligomers by radical reactions developed the categories of functional initiators, i.e., diazoic compounds, hydrogen peroxide, and oxygenated substances. He examined the different reactivities and combinations of such initiators with monomers in order to synthesize telechelic oligomers. Boutevin [2] also summarized the monomers able to totally recombine or to avoid termination by disproportionation. He showed a quantitative amount of recombination only for styrene, acrylates, dienes, and acrylonitrile [31-33]. 

H-C— C-(3-(Mj-0-C—C—H ClCHj—C—0-(m) j-0-C—CHjCI Fig. 3. structure of telechelics obtained by functional benzoyl peroxide initiators. 

The effects of the medium upon the dissociations and efficiencies of typical initiators have been reviewed with some discussion of poly functional initiators. Solvation effects have been considered for azoisobutyronitrile. The rate of decomposition of the azonitrile in dimethylformamide/glycerol mixtures depends upon the composition, but because of inhomogeneities resulting from limited solubility of the initiator and not because of effects such as differences between the viscosities of the various systems. The solubilities of typical peroxides over a range of pressures and. temperatures have been measured to assess problems that might arise from crystallization of initiators at high pressures. ... 

Materials that promote the decomposition of organic hydroperoxide to form stable products rather than chain-initiating free radicals are known as peroxide decomposers. Amongst the materials that function in this way may be included a number of mercaptans, sulphonic acids, zinc dialkylthiophosphate and zinc dimethyldithiocarbamate. There is also evidence that some of the phenol and aryl amine chain-breaking antioxidants may function in addition by this mechanism. In saturated hydrocarbon polymers diauryl thiodipropionate has achieved a preeminent position as a peroxide decomposer. 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

It is interesting to study the polymerization of functional monomer containing an amino group, so-called polymerizable amine by peroxide initiator, which could be anticipated to cause less pulpal irritation and toxic... 

The use of ring substituted diacyl peroxides has also been reported.204 Both the aryl and aroyloxy ends possess the desired functionality. Other initiators used in this context include peroxides (eg. hydrogen peroxide). 

The multifunctional initiators may be di- and tri-, azo- or peroxy-compounds of defined structure (c.g. 20256) or they may be polymeric azo- or peroxy-compounds where the radical generating functions may be present as side chains 57 or as part of the polymer backbone."58"261 Thus, amphiphilic block copolymers were synthesized using the polymeric initiator 21 formed from the reaction between an a,to-diol and AIBN (Scheme 7.22).26 Some further examples of multifunctional initiators were mentioned in Section 3.3.3.2. It is also possible to produce less well-defined multifunctional initiators containing peroxide functionality from a polymer substrate by autoxidalion or by ozonolysis.-0... 

An alternative to the direct use of peroxides in monomer grafting is to first functionalize the polymer with initiator or transfer agent functionality. 

Functional alkoxyamines used as initiators for NMP include 283-287. The functional alkoxyamines can be formed in situ by use of a functional azo compound or peroxide. NMP has been shown to be compatible with hydroxy, epoxy, amide and tertiary amine groups in the initiator. Carboxylic acid groups can cause problems but may be tolerated in some circumstances.106... 

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