Substitution Polycondensations

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accompHshed almost exclusively via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in the early 1960s (3,4), involves reaction of the bisphenol of choice with 4,4 -dichlorodiphenylsulfone in a dipolar aprotic solvent in the presence of an alkaUbase. Examples of dipolar aprotic solvents include A/-methyl-2-pyrrohdinone (NMP), dimethyl acetamide (DMAc), sulfolane, and dimethyl sulfoxide (DMSO). Examples of suitable bases are sodium hydroxide, potassium hydroxide, and potassium carbonate. In the case of polysulfone (PSE) synthesis, the reaction is a two-step process in which the dialkah metal salt of bisphenol A (1) is first formed in situ from bisphenol A [80-05-7] by reaction with the base (eg, two molar equivalents of NaOH),... 

In spite of the large number of grafted and side functionalized polysilox-anes commercially available and the variety of modification techniques available [25,50] (hydrosilylation, thiol-ene chemistry, halogen substitution, polycondensation), only a few of them have been used as in situ-formed graft copolymer compatibilizers. 

Catalytic Cracker Bottoms (CCB) which is the heavy residue from the catalytic cracking of petroleum distillate is a common aromatic feedstock used for synthetic carbons and pitch production. CCB, like other heavy aromatic feedstock, is composed of alkyl-substituted polycondensed aromatics with a very wide molecular weight distribution. 

Sulfonated PAES random copolymers can be prepared by the by potassium carbonate mediated direct aromatic nucleophilic substitution polycondensation of disodium 3,3 -disulfonate-4,4 -dichlorodiphenyl sulfone, 4,4 -dichlorodiphenyl sulfone and BP. The condensation reaction proceeds quantitatively to high molecular weight in A-methyl-2-pyrroUdone (NMP) at 190°C. In addition, a monofunctional monomer, 4-tert-butyl-phenol, can be used as an end capping reagent. The phenol functional group has a similar reactivity as biphenol. In this way, the molecular weight can be controlled. 

From these monomers, poly(phenylene ether)s can be formed by the aromatic nucleophilic substitution polycondensation with dihydroxy-monomers in the presence of potassium carbonate. 

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. 

PAES with pendant sulfonated aliphatic side chains have been prepared by a nucleophilic substitution polycondensation and sulfoakylation reaction [94]. 3, 3-Bis(4-hydroxyphenyl)-l-isobenzopyrrolidone and 4,4 -difluorodiphenyl sulfone or 3,3, 4,4 -tefrafluoro-diphenylsulfone were used as monomers. Membranes formed from these polymers displayed a low water uptake and swelling ratio both at ambient temperature... 

Since such a polyaddition proceeds mechanistically like a condensation polymerization, many authors refer to it as an addition polycondensation, in contrast to the substitution polycondensation of Equation (lS-2). 

Polyamide and polyester bonds are especially important m substitution polycondensations. Polyesters are formed by AA/BB polycondensations according to the general equation ... 

Rare kinds of substitution polycondensations also include reaction of dihalides with dimetallic compounds ... 

Two other substitution polycondensations are also used with aromatic compounds, and these are... 

Nucleophilic Substitution Route. Commercial synthesis of poly(arylethersulfone)s is accomplished via the nucleophilic substitution polycondensation route. This synthesis route, discovered at Union Carbide in... 

New heat-resistant polymers containing -iiitrophenyl-substituted quinoxaline units and imide rings as well as flexible amide groups have been synthesi2ed by polycondensation reaction of a dianainoquinoxaline derivative with diacid dichlorides (80). These polymers are easily soluble in polar aprotic solvents with inherent viscosities in the range of 0.3—0.9 dL/g in NMP at 20°C. AH polymers begin to decompose above 370°C. 

The bulk polycondensation of (10) is normally carried out in evacuated, sealed vessels such as glass ampules or stainless steel Parr reactors, at temperatures between 160 and 220°C for 2—12 d (67). Two monomers with different substituents on each can be cocondensed to yield random copolymers. The by-product sdyl ether is readily removed under reduced pressure, and the polymer purified by precipitation from appropriate solvents. Catalysis of the polycondensation of (10) by phenoxide ion in particular, as well as by other species, has been reported to bring about complete polymerisation in 24—48 h at 150°C (68). Catalysis of the polycondensation of phosphoranimines that are similar to (10), but which yield P—O-substituted polymers (1), has also been described and appears promising for the synthesis of (1) with controlled stmctures (69,70). 

The first mechanistic studies of silanol polycondensation on the monomer level were performed in the 1950s (73—75). The condensation of dimethyl sil oxanediol in dioxane exhibits second-order kinetics with respect to diol and first-order kinetics with respect to acid. The proposed mechanism involves the protonation of the silanol group and subsequent nucleophilic substitution at the siHcone (eqs. 10 and 11). 

At the same time, ring-opening-polymerization (ROP) processes, which dominated the phosphazene field for decades [38], tend now to be substituted by polycondensation reactions. These seem to be more feasible and reproducible, easier to carry out, and able to guarantee predictable MWs and MW distributions for these materials [10]. 

Use of polycondensation processes of substituted phosphoranimines to obtain already substituted poly(organophosphazenes)... 

A variety of synthetic procedures have been described based on the ringopening polymerization processes of (NPCl2)3 to (NPCl2)n followed by the nucleophilic replacement of the reactive chlorines with carefully selected nucleophiles, and on polycondensation reaction processes of new monomers and of substituted phosphoranimines. 

Poly(para-phenylenevinylene)s (PPVs) represent one of the most intensively investigated classes of rr-conjugated materials. Many synthetic procedures to generate unsubstituted and substituted PPVs have been developed. They include 1,6-polymerizations of 1,4-xylylene intermediates as well as several polycondensation methods. Parallel to the polymer syntheses, several series of PPV oligomers (OPVs) have been synthesized and characterized. Such model oligomers of different molecular size allow for a study of the dependence of electronic and optical properties on the length of the conjugated Ti-system. 

Horhold et al. and Lenz et al. [94,95]. The polycondensation provides the cyano-PPVs as insoluble, intractable powders. Holmes et al. [96], and later on Rikken et al. [97], described a new family of soluble, well-characterized 2,5-dialkyl- and 2,5-dialkoxy-substituted poly(pflrfl-phenylene-cyanovinylene)s (74b) synthesized by Knoevenagel condensation-polymerization of the corresponding alkyl-or alkoxy-substituted aromatic monomers. Careful control of the reaction conditions (tetra-n-butyl ammonium hydroxide as base) is required to avoid Michael-type addition. 

Furfuryl alcohol in an acid medium gives rise to reactions of polycondensation reactions of successive electrophilic substitutions involving furan molecules. This reaction is identical to the reaction described for benzyl alcohol on p.256 and represents the same dangers. It is carried out under the same conditions, ie in a sulphuric medium. The electrophilic species that comes into play is very similar to the benzyl cation. 

Monomers employed in a polycondensation process in respect to its kinetics can be subdivided into two types. To the first of them belong monomers in which the reactivity of any functional group does not depend on whether or not the remaining groups of the monomer have reacted. Most aliphatic monomers meet this condition with the accuracy needed for practical purposes. On the other hand, aromatic monomers more often have dependent functional groups and, thus, pertain to the second type. Obviously, when selecting a kinetic model for the description of polycondensation of such monomers, the necessity arises to take account of the substitution effects whereas the polycondensation of the majority of monomers of the first type can be fairly described by the ideal kinetic model. The latter, due to its simplicity and experimental verification for many systems, is currently the most commonly accepted in macromolecular chemistry of polycondensation processes. 

For preparation of dipolar polymers with dielectric properties and nonlinear optical applications, a piperidino-substituted a-cyanocinnamic acid was polycondensed with CDI.[551,tl54]... 

Mamyama et al.25 have obtained high-molecular-weight poly(benzoxazole)s by the low-temperature solution polycondensation of A,A 0,0 -tetrais(trimethyl-silyl)-substituted 2,2-bis(3-amino-4-hydroxyphenyl)-l,l,l,3,3,3-hexafluoro-propane (25) with aromatic diacids and subsequent thermal cyclodehydration of the resulting poly(o-hydroxy amide)s in vacuo. In this method, aromatic diamines with low nucleophilicity are activated more positively through the conversion to the /V-silylated diamines, and the nucleophilicity of the fluorine-containing bis(o-aminophenol) can be improved by silylation. 

Traditional polymerizations usually involve AB-type monomers based on substituted ethylenes, strained small ring compounds using chain reactions that may be initiated by free radical, anionic or cationic initiators [20]. Alternatively, AB-type monomers may be used in polycondensation reactions. 

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