Condensation polymer, definition

The difficulties of devising a basis for conveniently classifying various polymerizations in an appropriate manner have been discussed earlier in this chapter and several borderline examples which offer particular difficulty have been mentioned. One of these, the polymerization of the N-carboxyanhydrides, falls within the definition of a condensation polymerization, proceeds by a mechanism resembling a vinyl addition polymerization, and yields a product which possesses the structure of a typical condensation polymer. Definitions have been... 

Representative condensation polymers are listed in Table I. The list is by no means exhaustive, but it serves to indicate the variety of condensation reactions which may be employed in the synthesis of polymers. Cellulose and proteins, although their syntheses have not been accomplished by condensation polymerization in the laboratory, nevertheless are included within the definition of condensation polymers on the ground that they can be degraded, hydrolytically, to monomers differing from the structural units by the addition of the elements of a molecule of water. This is denoted by the direction of the arrows in the table, indicating depolymerization. 

The chemical and physical properties of the polymers obtained by these alternate methods are identical, except insofar as they are affected by differences in molecular weight. In order to avoid the confusion which would result if classification of the products were to be based on the method of synthesis actually employed in each case, it has been proposed that the substance be referred to as a condensation polymer in such instances, irrespective of whether a condensation or an addition polymerization process was used in its preparation. The cyclic compound is after all a condensation product of one or more bifunctional compounds, and in this sense the linear polymer obtained from the cyclic intermediate can be regarded as the polymeric derivative of the bifunctional monomer(s). Furthermore, each of the polymers listed in Table III may be degraded to bifunctional monomers differing in composition from the structural unit, although such degradation of polyethylene oxide and the polythioether may be difficult. Apart from the demands of any particular definition, it is clearly desirable to include all of these substances among the condensation... 

The polyamide made from caprolactam is technically an addition polymer by the above definition, while the product made from the amino acid would be a condensation polymer. Actually, only the caprolactam synthesis is used commercially, and the product (polycaprolaclam = nyIon-6) is called a condensation polymer because all polyamides are so classified. 

With the development of polymer science and the synthesis of new polymers, the previous definition of condensation polymer is inadequate. For... 

The term "condensation polymers" was introduced by W. H. Carothers in his early work on the preparation of polyesters and polyamides to distinguish this class of polymers from vinyl polymers made by addition reactions. Condensation polymers were defined as polymeric molecules that may be converted by hydrolysis, or its equivalent, into monomers that differ from the structural units by one molecule of H2O, HCl, NHj, etc. This broad definition includes many polymers made by ring-opening or addition reactions, for example, lactone and lactam polymers, polyurethanes, polyureas, polyimides, and polyhydrazides, as well as polymers made by true condensation reactions. 

With the development of polymer science and the synthesis of new polymers, the previous definition of condensation polymer is inadequate. For example, in polyurethanes (Table 1.2), which are classified as condensation polymers, the repeating unit has the same net composition as the two monomers (i.e., a diol and a diisocyanate), which react without eliminating any small molecule. To overcome such problems, chemists have introduced a definition which describes condensation polymers as consisting of structural units joined by internal functional groups... 

A polymer satisfying either or both of the above definitions is classified as a condensation polymer. Phenol-formaldehyde, for example, satisfies the first definition but not the second. Some condensation polymers along with their repeating units and condensation reactions by which they can be synthesized are shown in Table 1.2. Some high-performance polymers prepared by polycondensation are listed in Table 1.3. 

According to the original classification of Carothers, condensation polymers are formed from hi- or polyfunctional monomers by reactions which involve elimination of some smaller molecule. A condensation polymer, according to t his definition, is one in which the repeating unit lacks certain atoms which were present in the monomers(s) from which the polymer was formed. 

To overcome such problems, an alternative definition has been introduced. According to this definition, polymers whose main chains consist entirely of C-C bonds are classified as addition polymers, whereas those in which heteratoms (O, N, S, Si) are present in the polymer backbone are considered to be condensation polymers. A polymer which satisfies both the original definition (of Carothers) and the alternative definition or either of them, is classified as a condensation polymer. Phenol-formaldehyde condensation polymers, for example, satisfy the first definition but not the second. 

In 1929 Carothers suggested a separation of all polymers into two classes, condensation and addition polymers. By condensation polymers he defined those polymers that lack certain atoms from the monomer units from which they were formed or to which they may be degraded by chemical means. He also defined addition polymers as polymers with identical structures of the repeat units to the monomers from which they are derived. Thus, according to the above definition, an example of a condensation polymer can be a polyamide formed by condensing a diacid chloride with a diamine and splitting off hydrochloric acid ... 

Note The definition ignores loss of double bonds. The Carothers definition fails to describe all the polymers that can fit into the category of condensation polymers, yet form without an evolution of a byproduct. An example is a polyurethane that can form from a reaction of a glycol with a diisocyanate ... 

Synonyms Condensation prods., epoxy Epoxides, polymers, epoxy resins Epoxy compds. Ethers, cyclic, epoxides, polymers Plastics, epoxy Polyethers, epoxy resins Classification Polymer Definition A thermosetting resin based on the reactivity of the epoxide group Toxicology LD50 (oral, rat) 2200 mg/kg strong skin irritant in uncured state poison by inhalation moderately toxic by ingestion little or no toxicity in cured state Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of Cr... 

Definition Condensation polymer of sucrose benzoate, sucrose acetate isobutyrate, and butyl benzyl phthalate monomers... 

There is also uncertainty in the regulatory status of tertiary recycling when it does not result in the direct production of monomers suitable for polymerization into new plastic. The European Commission has at times supported the chemical recycling (depolymerization) of condensation polymers such as polyethylene terephthalate back to monomer (e.g., dimethyl terephthalate) as recycling for the purpose of government-mandated plastics recycling rate calculations, but not the liquefaction of polyolefin plastics back to petrochemical feedstocks for reprocessing in a refinery. Discussions around these types of definitional issues, and their environmental and economic implications, are likely to continue for many years to come. 

Poly(butylene terephthalate) is usually called PBT by analogy with PET, the well known fiber forming thermoplastic polyester. Like PET, PBT Is a linear condensation polymer based on tere-phthallc acid,, but Instead pf the ethylene glycol used in PET, PBT employs 1,4-butanedlol. ] The more definitive name, poly (tetramethylene terephthalate) or PTMT, never did catch on, perhaps an Indication of the power of three letter strings In the English alphabet. 

The thermal depolymerisation of condensation polymers through thermofracto-graphy is excellently suited to group analysis of this polymer class but definitive identification of the particular type is guaranteed in only few cases. This is due to the lack of uniformity of the thermolysis reaction and the resulting variety of thermolysis products. Further, there is no thin-layer chromatographic system which... 

---