Other Condensation Polymers

An intensive investigation has been made of the thermal degradation of poly(dimethylsiloxane) and poly(methylphenylsiloxane). The main products are a mix of all the possible stereoisomeric cyclic trimers and tetramers together with small amounts of pentamer and cyclic oligomers. In the degradation of poly(dimethylsiloxane) fluids, however, significant amounts of linear products are 

A silicon-containing ester derivative of poly(methacrylic add) -l-CHjCCCH,)-(COOCH2Si(CH3)2R)l- where R is CH3 or CgH5, decomposes by rearrangement of the ester group leading to the formation of CH2=C(CH3)—COO—CHj—Si— (CH3)jR and CH2=C(CH3)-COO-Si-(CHjR)-(CH3)2 as degradation products.  

Polyl(trifluoroethoxy)(octafiuoro pentoxy)]phosphazene decomposes thermally by random chain scission. The decomposition process has been studied in detail for polyKbis trifluoroethoxy) phosphazene] using n.m.r., i.r. spectroscopy, gas chromotography, mass spectrometry, and electron spectroscopy for chemical analysis. Random chain scission is confirmed followed by depolymerization with an average zip length of 35 chain units. The thermo-oxidation of a hydroquinone-phosphorus oxychloride copolymer has also been investigated. Decomposition is a two-stage process, chain scission to form quinone followed by oxidation of the quinone to maleic anhydride.  

Nielsen, J. Appl. Polym. Set., Appl. Polym. Symp., 1979, 35, 223 

Terman, V. A. Chudakova, I. N. Kostrikov, and I. G. Kosolapova, Vysokomol. Soedin., iSer. 

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Comparable but equally specific considerations must be applied to other condensation polymer systems. The following example is an illustration of the application of these ideas to the molecular weight of polyamides. 

Heteroatom Chain Backbone Polymers. This class of polymers includes polyesters, which have been widely studied from the initial period of research on biodegradable polymers, polyamides, polyethers, polyacetals, and other condensation polymers. Their linkages are quite frequendy found in nature and these polymers are more likely to biodegrade than hydrocarbon-based polymers. 

Similar interchange processes may occur in other condensation polymers under suitable conditions. There is ample evidence in the literature on polyamides, and on monomeric amides as well, for the occurrence of the amine-amide interchange reaction (II)... 

A variety of methods are known for the synthesis of polyimides and other condensation polymers, however, the application of high pressure has seldom appeared in the literature to date. Early in 1969 Morgan and Scott reported on the high-pressure polycondensation and simultaneous hot-pressing of intractable polybenzimidazopyrrolone, that is infusible and insoluble, directly from the combination of 3,3f,4,4f-tetraaminobiphenyl and pyromellitic dianhydride (Eq.6) [29,30]. 

PPE is a key component of several blends. It is totally miscible with sPS and can interact with polar polymeric components, for instance polyamides (through hydrogen bonding interactions between PPE oxygens and amidic NH) and other condensation polymers moreover, other important properties are improved by PPE, such as mechanical properties (entry 1), and a better control of crystallinity is obtained (see Section 4.1.1 for discussion). PPE also acts as a processing aid, improving the melt flowability [15]. 

A condensation polymer is one in which the repeating unit lacks certain atoms which were present in the monomer(s) from which the polymer was formed or to which it can be degraded by chemical means. Condensation polymers are formed from bi- or polyfunctional monomers by reactions which involve elimination of some smaller molecule. Polyesters (e.g., 1-5) and polyamides like 1-6 are examples of such thermoplastic polymers. Phenol-formaldehyde resins (Fig. 5-1) are thermosetting condensation polymers. All these polymers are directly synthesized by condensation reactions. Other condensation polymers like cellulose (1-11) or starches can be hydrolyzed to glucose units. Their chemical structure indicates that their repealing units consist of linked glucose entities which lack the elements of water. They are also considered to be condensation polymers although they have not been synthesized yet in the laboratory. 

It has been established that random interchange reactions occur with polyesters and polyamides at the higli temperatures at which these thermoplastics are normally polymerized and subsequently extruded or molded. Other condensation polymers probably undergo similar shufflings of repeating units under the proper conditions. This implies that the equilibrium constant for condensation reactions like that in reaction (a) of Fig. 5-2 is independent of the sizes of the molecules which are reacting. 

Condensation reactions under acid catalysed conditions are much slower than hydrolysis reactions and generally start when the hydrolysis process is almost complete. The largest differences in reaction rate constants for hydrolysis and condensation are reported for pH = 0.9 and these differences decrease if the pH is increased [56]. As a consequence a large amount of hydrolysed species is present at the moment condensation becomes significant. Further condensation reactions then take place between individual hydrolysed species (clusters) and lead to aggregated clusters. This is schematically represented for a simple case in Fig. 8.22 where dimers react with each other leading to a linear molecule. Further condensation reactions with other condensed polymers will take place preferentially at the end groups [54]. 

Other condensation polymers of great significance in the textile industry... 

Other condensation polymers as polyamides should also be mentioned. For polyamides prepared by hydrolytic polymerization, the rate of thermooxidation is highly influenced by the content and ratio of carboxylic and amino end groups. In the case of polyamides with only carboxylic end groups, loss of molecular weight is... 

Hydrolysis has been the main method used for the chemical recycling of other condensation polymers, such as polyacetals and polycarbonates. Hydrolysis of polyacetals leads back to the starting monomers, formaldehyde or trioxane. Polycarbonates are polymers synthesized by the reaction of phosgene and a dihydric phenol, commonly bisphenol A. Chemical recycling of polycarbonate... 

The necessity for cooperative motion of an entire polymer chmn when a single segment makes a jump from one position to another is an indication that the bulk viscosity of poljmiers is dependent on their molecular weight. This dependence has been investigated by Flory, who found that the viscosity of linear polyesters and other condensation polymers fits the equation... 

The formation of low mass oligomers during polymerization has been ascertained in the synthesis of polyesters, polysulfides, polyureas, polyamides, polyethers, polysiloxanes, and in several other condensation polymers. ... 

Notice, in each case, that a small molecule, water, is eliminated as a product of the reaction. Several other condensation polymers are listed in Table 2. Linear (or branched) chain polymers, as well as cross-linked polymers, are produced in condensation reactions. 

When considering the use of MA in condensation polymers, it is automatic to think of unsaturated polyesters. In fact, the demand for MA is keyed primarily to the growth of these resins. In 1980, about 172 MM lb of MA were used to produce polyester resins in the United States.This represented approximately 52% of the 330 MM lb of MA demand in the United States in 1980 (see Sec. 1.4.1). MA is also very useful in other condensation polymers, including about 6 MM lb in alkyd resins. The value of using MA to prepare, crosslink, and/or modify condensation and addition polymers is discussed in this chapter. In recent times, the synthesis of maleinated vinyl esters and maleimide resins have had significant study. Because of this interest, we also give some attention to the use of MA in vinyl ester and maleimide technology. 

The product that forms between the reaction of two monomers is called a dimer. The polymer (nylon 6,6) forms as the dimer continues to add more monomers. Polymers that eliminate an atom or a small group of atoms during polymerization are called condensation polymers. Nylon 6,6 and other similar nylons can be drawn into fibers and used to make consumer products such as panty hose, carpet fibers, and fishing line. Table 20.11 shows other condensation polymers. 

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