Direct Cationic Formaldehyde Condensation

The earliest polymeric cationic aftertreatments stemmed from the development of crease-resist finishes for cellulosic fibres. One such, promoted specifically for its colour fastness improvements when applied as an aftertreatment to direct dyeings, was a condensation product of formaldehyde with dicyandiamide (Scheme 10.82). Many similar compounds followed, such as condensation products of formaldehyde with melamine (10.212), polyethylene imine) with cyanuric chloride (10.213) and alkyl chlorides with polyethylene imine) (10.214 R = alkyl). 

Cyclotriveratrylene is formed in over 70 % yield by the condensation of the veratryl cation (7.42), whether it is produced from veratryl alcohol (7.41) or directly from veratrole (1,2-dimethoxybenzene) and formaldehyde in aqueous acid. In organic solvents such as acetic acid in the presence of a... 

Calixarenes are formed by condensation of a p-substituted phenol with formaldehyde [8]. These macrocycles are conformationally quite flexible but, by introducing suitable substituents in the aromatic subunits, the so-called cone conformation, in which all aromatic subunits point into the same direction, can be stabilized. This conformation is usually best suited to complex guest molecules because it has a well defined hydrophobic cavity. An inclusion of cations such as ammonium ions or quaternary ammonium ions into this cavity can be demonstrated, for example, by the characteristic upfield shifts of guest signals in the NMR, an effect that is a consequence of the close proximity of the corresponding protons to the surfaces of the aromatic receptor subunits in the complex. 

Formaldehyde polymerization has been studied in the liquid state, in solution of protic or aprotic solvents and in the gaseous state where gaseous formaldehyde forms directly crystalline polymer. It has been studied with anionic and cationic initiators and by high energy radiations. Although there are more than 100 MM lbs. of poly form aldehyde produced per year, very few papers have been published that are actually concerned with the kinetics of formaldehyde polymerizations. The reason for this lack of detail is understandable when one realizes how difficult it is to obtain pure formaldehyde (with impurities of less than 100 p.p.m). Even pure formaldehyde undergoes side reactions and self condensation which cause new introduction of impurities. 

Later resins of this type, i.e. strongly acidic cation exchangers, have been synthesized directly by condensation of compounds which already contain sulphonic acid groups and phenolic groups, to form polymers, e.g. a mixture of phenol, phenolsulphonic acid and formaldehyde, in the presence of sodium hydroxide as a catalyst. ... 

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