Nucleophilic substitution polymerization

Polymerization via Nucleophilic Substitution Reaction. Halo- and nitro- groups attached to phthahmide groups are strongly activated toward nucleophilic substitution reactions. Thus polyetherimides ate synthesized by the nucleophilic substitution reaction of bishaloimides (59,60) and bisnitroimides (61,62) with anhydrous bisphenol salts in dipolar aptotic solvents. 

Phosphazene polymers are normally made in a two-step process. First, hexachlorocyclotriphosphazene [940-71 -6J, trimer (1), is polymerized in bulk to poly(dichlorophosphazene) [26085-02-9], chloropolymer (2). The chloropolymer is then dissolved and reprecipitated to remove unreacted trimer. After redissolving, nucleophilic substitution on (2) with alkyl or aryloxides provides the desired product (3). 

Ammonium ion, JV-(2-thenyl)-N-benzyldimethyl-Stevens and Sommelet rearrangement, 4, 800 Ammonium salts, diallyldialkyl-polymerization, 1, 293 Ammonium salts, 2-pyrrolylmethyl-nucleophilic substitution abnormal, 4, 244 Sommelet rearrangement, 4, 244 Ammonium salts, trimethyl(l,3,5-triazinyl)-applications, 3, 525 Amobarbital, 3, 150 Amodiaquine, 1, 145 Amolanone applications, 4, 708... 

Other salts, especially fluoride salts, (e.g., KF) can be used to perform nucleophilic substitution. As is well known, halides, and particularly the fluoride anions, are rather powerful Lewis bases and can exert a catalytic effect on aromatic nucleophilic substitutions in dipolar aprotic solvents. Phenols can be alkylated in the presence of KF (or CsF) absorbed on Celite64,65 or Et4NF.66 Taking advantage of this reaction, halophenols and dihalides with bisphenols have been successfully polymerized in sulfolane at 220-280°C by using KF as the base. 

The Ullman reaction has long been known as a method for the synthesis of aromatic ethers by the reaction of a phenol with an aromatic halide in the presence of a copper compound as a catalyst. It is a variation on the nucleophilic substitution reaction since a phenolic salt reacts with the halide. Nonactivated aromatic halides can be used in the synthesis of poly(arylene edier)s, dius providing a way of obtaining structures not available by the conventional nucleophilic route. The ease of halogen displacement was found to be the reverse of that observed for activated nucleophilic substitution reaction, that is, I > Br > Cl F. The polymerizations are conducted in benzophenone with a cuprous chloride-pyridine complex as a catalyst. Bromine compounds are the favored reactants.53,124 127 Poly(arylene ether)s have been prepared by Ullman coupling of bisphenols and... 

Preparation of poly(dichlorophosphazene), (NPCl2)n> a polymeric intermediate from which the great majority of POPs have been prepared by nucleophilic substitution of the highly reactive chlorine atoms with carefully selected organic substituents... 

The problem of the thermally induced polymerization reaction of partially or completely substituted cyclophosphazenes has been considered in the past by several authors [355-357], and more recently by H. R. AUcock [358]. This is because of the ease of synthesizing these substrates, the possibihty of preparing structurally regulated poly(organophosphazenes), and the lack of any additional nucleophilic substitution processes on the poly(organophosphazenes) obtained by the ROP process of fully saturated trimers. 

Moreover it has been shown that PV0CC1 prepared by free-radical polymerization of vinyl chloroformate (V0CC1) is an atactic polymer having a Bernouillian statistical distribution as expected (J[9). In order to extend our studies on the chemical modification of PV0CC1, the stereoselective character of the nucleophilic substitution of the chloroformate units with phenol has been examined by the study of the 13c-NMR spectra of partly modified polymers in the region of the aliphatic methine carbon atoms. The results obtained in this field are presented here. 

Within the past several years, we have examined the synthesis and reactions of several classes of polymers related to PECH. We have adopted three simple approaches to the preparation of polymeric substrates more reactive than PECH toward nucleophilic substitution. We have i). removed the 8-branch point by extension of the side chain, ii). replaced the chloride leaving group by a more reactive bromide and iii). replaced the backbone oxygen atom by a sulfur atom that offers substantial anchimeric assistance to nucleophilic... 

Alkyl methacrylates, hydrolysis of polymeric ester functionality, 259 Aluminum-hydrogen bond, nucleophilic substitution, 264 Amines alkylation, 28 benzyl-group cleavage, 25 Aminomethylation chloromethylated polymers, 19 Deltfpine reaction, 19 Anionic polymerization advantages, 85... 

Polyetherimides (PEI) are polyimides containing sufficient ether as well as other flexibi-lizing structural units to impart melt processability by conventional techniques, such as injection molding and extrusion. The commercially available PEI (trade name Ultem) is the polymer synthesized by nucleophilic aromatic substitution between 1,3-bis(4-nitrophthalimido) benzene and the disodium salt of bisphenol A (Eq. 2-209) [Clagett, 1986]. This is the same reaction as that used to synthesize polyethersulfones and polyetherketones (Eq. 2-206) except that nitrite ion is displaced instead of halide. Polymerization is carried out at 80-130°C in a polar solvent (NMP, DMAC). It is also possible to synthesize the same polymer by using the diamine-dianhydride reaction. Everything being equal (cost and availability of pure reactants), the nucleophilic substitution reaction is probably the preferred route due to the more moderate reaction conditions. 

Several different nucleophilic substitution reactions have been observed in the polymerization of methyl methacrylate. Attack of initiator on monomer converts the active alkyl-lithium to the less active alkoxide initiator (Eq. 5-75). Further, methyl methacrylate (MMA) is converted to isopropenyl alkyl ketone to the extent that this reaction occurs. 

The resulting polymerization is a copolymerization between the two monomers, not a homopolymerization of MMA. More importantly, this results in a slower reaction (and lower polymer molecular weight) since the carbanion derived from the ketone is not as reactive as the carbanion from MMA. Nucleophilic substitution by intramolecular backbiting attack of a... 

A variety of protonic and Lewis acids initiate the cationic polymerization of lactams [Bertalan et al., 1988a,b Kubisa, 1996 Kubisa and Penczek, 1999 Puffr and Sebenda, 1986 Sebenda, 1988]. The reaction follows the mechanism of acid-catalyzed nucleophilic substitution reactions of amides. More specibcally, polymerization follows an activated monomer mechanism. Initiation occurs by nucleophilic attack of monomer on protonated (activated) monomer (XXIV) to form an ammonium salt (XXV) that subsequently undergoes proton exchange with monomer to yield XXVI and protonated monomer. The conversion of XXIV to XXV involves several steps—attachment of nitrogen to C+, proton transfer from... 

Nucleophilic substitution of the chlorine atom present in 2-chlorothiepane (132) using Grignard reagents has provided a synthetic route to 2-methyl- (133) or 2-phenyl- (134) thiepanes (equation 27) (69JHC115). An a-sulfinyl carbanion (114), generated by alkyllithium attack on thiepane 1-oxide (115), was found to act as nucleophile in the synthesis of cis and trans sulfoxides of thiepane (133 equation 28) (78TL5239). Polymerization of 2-thiepanone (135) has been initiated by attack of the f-butoxide anion and concomitant liberation of a thiolate anion (Scheme 26) (64MI51700). 

Poly(arylene ether triazole)s have also been prepared by heterocyclic-activated displacement polymerization [36], The 1,2,4-triazole unit sufficiently activated, albeit weakly, aryl fluorides for nucleophilic displacement. Several 3,5-bis(4-fluorophenyl)-4-aryl-l,2,4-triazoles were polymerized with various bis-phenols to yield polymers with Tgs from 185 to 230 °C [36]. The 1,2,4-triazole unit appears to be one of the more weakly activating heterocycles towards nucleophilic substitution polymerization. 

The most straightforward way to obtain polymeric phosphonium salts involves introducing the phosphonio groups on to a suitable polymeric structure, for example by reacting tertiary phosphines with a poly(chloromethylstyrene) (reaction 99). The polymeric phosphonium salts obtained in this way are mostly used as polymer-supported phase-transfer catalysts for nucleophilic substitutions reactions under triphase conditions. 

Polymeric phosphonium salt-bound carboxylate, benzenesulphinate and phenoxide anions have been used in nucleophilic substitution reactions for the synthesis of carboxylic acid esters, sulphones and C/O alkylation of phenols from alkyl halides. The polymeric reagent seems to increase the nucleophilicity of the anions376 and the yields are higher than those for corresponding polymer phase-transfer catalysis (reaction 273). 

The addition of these reagents at the end of the polymerization reaction resulted in the consumption of the catalyst and the formation of tert-alkyl chloride chain ends on the PIB rather than the desired nucleophilic substitution (5). 

In the presence of 4-amino-2,2,6,6-tetramethyl-piperidine, a partial nucleophilic substitution of the bromine atom occured it resulted in the formation of a new polymeric stabilizer which has been treated by peracetic acid vapor. 

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