Copolycondensation

This dicarboxyhc ester is then copolycondensed with the other reactants in PET manufacture to produce a flame-retardant polyester [63745-01-7]. The advantage of this rather unusual phosphinate stmcture is its high thermal and hydrolytic stability. The fabric is probably used mainly for flirnishings in pubhc buildings in Japan. 

These poly(2-alkyl-2-oxazoline) silane coupling agents were copolycondensed with tetraethoxysilane by acid-catalyst to produce poly(2-alkyl-2-oxazoline)-modified silica gel. The composite gel from 2-ethyl-2-oxazoline was also homogeneous and transparent glass. Poly(2-alkyl-2-oxazoline)-modified silica gels, especially gels based on poly(2-ethyl-2-oxazoline) absorbed water and also organic solvents such as DMF or alcohols as shown in Table 7. This result means that the obtained composite gel shows the amphiphilic adsorption property. 

Alongside the radical distinction of the mechanism of this process from that of chain polymerization, linear polycondensation features a number of specific peculiarities. So, for instance, the theory of copolycondensation does not deal with the problem of the calculation of a copolymer composition which normally coincides with the initial monomer mixture composition. Conversely, unlike chain polymerization, of particular importance for the products of polycondensation processes with the participation of asymmetric monomers is structural isomerism, so that the fractions of the head-to-head and head-to-tail patterns of ar-... 

Such a consideration demonstrated [56] that the sequence distribution in products of arbitrary equilibrium copolycondensation can always be described by some Markov chain with the elements of the transition probability matrix ex-... 

The most interesting aminomethyl derivative of condensation polymers that we have prepared to date Is derived from direct reduction of poly(2-cyano-l,3-phenylene arylene ether), 20. Enchainment of benzonitrile repeat units Is accomplished by coupling 2,6-dichlorobenzonitrile with the potassium salt of bisphenol-A copolymers with lower nitrile contents can be produced by copolycondensation of bisphenol-A, 2,6-dichlorobenzonitrile and 4,4 -dichlorodiphenyl sulfone.21 The pendent nitrile function provides an active site for further elaboration. 

Adsorption is commonly used for catalyst removal/recovery. The process involves treating the polymer solution with suitable materials which adsorb the catalyst residue and are then removed by filtration. Panster et al. [105] proposed a method involving adsorbers made from organosiloxane copolycondensates to recover rhodium and ruthenium catalysts from solutions of HNBR. These authors claimed that the residual rhodium could be reduced to less than 5 ppm, based on the HNBR content which had a hydrogenation conversion of over... 

A polymer derived from the polycondensation of a single actual monomer, the molecules of which terminate in two different complementary functional groups (e.g. 6-aminohexanoic acid) is, by definition, a (regular) homopolymer. When two different monomers of this type react together, the product is a copolymer that can be named in appropriate fashion. For example, if 6-aminohexanoic acid is copolycondensed with 7-aminoheptanoic acid, leading to a statistical distribution of monomeric units, the product is named poly[(6-aminohexanoic acid)-stoi-(7-aminoheptanoic acid)]. 

Polycondensation of a diol with a dicarboxylic acid, either of which may contain a double bond, results in an unsaturated polyester. For this purpose suitable starting compounds are maleic anhydride and 2-butylene-1,4-diol.These can also be used mixed with saturated dicarboxylic acids or diols (copolycondensation) in order to vary the number of double bonds per macromolecule and thereby the properties of the polyester. Unsaturated polyesters are generally prepared by melt condensation.The resulting products are often viscous or waxy substances of relatively low molecular weight. 

Only a few publications have appeared in the literature on template copolycondensation, in spite of the fact, that the process is very important to understand the mechanisms of processes similar to natural synthesis of biopolymers. General mechanism of this reaction can be considered in terms of the examples of template step homopolymerization. A few published systems will be described in the Chapter 5. 

Copolymerization can be conducted stepwise (template copolycondensation), copolyaddition, radical or ionic copolymerization, ring-opening copolymerization, etc. 

A good example of template copolycondensation has been described by Ogata et al Copolycondensation of 2,6-dimethyl pyridine dicarboxylate and dimethyl adipate with hexamethylene diamine was carried out in the presence of polysaccharide - Pullulane (mol. weight 30,000) used as a template. The reaction was carried out in DMSO at 60 C. It was found that the content of 2,6-dimethyl pyridine dicarboxylate units in the copolyamide, determined by NMR analysis, increased in the presence of Pullulane in comparison with the amount obtained in the absence of the template. This effect can be explained by preferential adsorption by the template of monomer having pyridine groups in comparison with the adsorption of dimethyl adipate. A set of experiments was carried out under the same conditions, but in the presence of poly(acrylonitrile) instead of Pullulane. The composition of copolyamides was the same as in copolycondensation without the template. 

Polycondensates. Miscellaneous copolycondensates with ligands as comonomers bind metal ions to produce conducting materials. Table 3 collects a few available data on such systems. 

In copolycondensation for example, the more reactive monomer is expected to become exhausted more rapidly than the less reactive one. If the functionalities of the polyfunctional crosslinker are more reactive, short chains are formed in the beginning of the reaction and long chains in the end. If we assume equilibrium conditions throughout the reaction, the unreacted functionalities of the crosslinker on different growing trees, with short links in the beginning, are expected to react more likely with each other and as a result a part of the final network may be more crosslinked than the other part. This may eventually lead to phase separation. If the reaction is diffusion-controlled (177), cores with higher crosslinking density may be formed. 

The first success was achieved when optically active (chiral) monomeric units were combined with a nematic LC polymer 105,123,143,144). The approach was based on the idea that a cholesteric mesophase may actually be realized as a helical nematic structure. Then by chemical binding of chiral and mesogenic units into a chain, accomplished by copolymerization or copolycondensation (in case of linear polymers) of nematogenic and optically active compounds, it was found feasible to twist a nematic mesophase and obtain copolymers of cholesteric type (Table 13). 

Provided that a copolycondensation is continued to essentially 100% conversion, the polymer and the initial monomer mixture always have the same composition even if the different monomers have very different reactivities. However, since the molar masses of copolycondensation products axe generally much smaller than those from polymerizations a correspondingly higher concentration of the azo monomer is required to yield a similar number of azo functions per polymer molecule. 

The synthesis of block copolycondensates by condensation reactions has also been described very often indeed the ineluctable presence of reactive end groups makes these molecules especially suitable for reactions with dibasic acids, diisocyanates, diacid chlorides, diamines, diols, etc. Using this method it was for example possible to synthesize polycondensates in which crystalline blocks alternate with amorphous blocks similarly it makes possible the synthesis of high molecular weight polymers from polycondensates of relatively low degree of polymerization. 

Numerous authors took advantage of the reactivity of double bonds towards ozone to prepare a-(0 functional oligomers usable in the synthesis of multiblock copolymers by copolycondensation, or in the synthesis of precursors of surfactants or ionomer resins. Results in this field of investigation are numerous, mainly in terms of industrial applications. 

One embodiment of this general reaction led to a product which was commercially produced for several years by Stauffer as Fyrol 76 (9), a copolycondensation product of dimethyl methyl-phosphonate with bis(2-chloroethyl) vinylphosphonate. The features of Fyrol 76 were high phosphorus content (20%), water solubility, and ability to be polymerized by means of a radical initiator to a crosslinked polymer. A related polycondensation product was developed from tris(2-chloroethyl) phosphate and dimethyl methylphosphonate. By control of the reagents and procedure used for neutralization, these oligomeric products were produced with primary alcohol functional groups (7). 

Polymethylsiloxanes can also be obtained by the hydrolytic copolycondensation of methylchlorosilanes of various functionality. Thus, by the hydrolytic copolycondensation of methyltrichlorosilane and dimethyldichlo-rosilane one can obtain thermosetting polymethylsiloxane, which quickly solidifies at a relatively low temperature (approximately 150 °C) without any catalysts. It is used as a binding agent in pressure compositions, as well as as a 5% petrol solution to treat the surface of metal pressure molds to facilitate their splitting when molding polymer materials. 

The hydrolytic copolycondensation of trimethylchlorosilane and trimethylchlorosilane is used to obtain polymethylsiloxane, the xylene solution of which can be used as an additive to eliminate flotation (splitting) of pigments in enamel films. 

Recently [58], polyesters have been prepared from dimethylterephtalate, ethylene glycol and the diester CH302C—RF—O —RF—C02CH3. The copolycondensation by transesterification was studied and the authors investigated the morphology, the thermal and surface properties of these obtained polyesters. We can notice that the PET/copolymer (PET —PFPE) blend thus obtained contains up to 35% in weight of PFPE but 7% only are bond with the prepared PET. 

The sequence distribution of monomer residues in copolycondensation reactions of this type has been studied in detail by Peebles (18,39). If all monomers are assumed to have equal reactivity and if the reaction has gone to completion, the number-average sequence length of 3IG residues(g) is given by ... 

---