Abstract

IF two bifunctional molecules such as ethylene glycol and adipic acid are esterified in equal proportions, linear super-ester molecules are produced. In a similar way polyamides and polyurethanes may be produced, the chemistry of the process being such that only linear polymers are, in fact, formed. On the other hand, if one of the reactants contain three or more functional groups, for example, glycerol, then instead of linear molecules, branched molecules are first formed ; but these branched products soon join up into three-dimensional networks which are insoluble and, therefore, not suitable for detailed investigation. Between these two extremes there must inevitably be produced molecules containing branched chains which, if the chains are not indefinitely long, should be soluble. Owing to the rapidity with which the network stage is reached, it has not hitherto been possible to isolate and characterize branched-chain molecules possessing long branches. Yet it is of great interest to know something of the thermo-dynamic and hydrodynamic behaviour of solutions of such molecules. The only branched molecule of which the structure has been determined is amylo-pectin. Here, however, it is not possible to vary the length of the branches while keeping the number fixed. It is, moreover, just the kind of variation that must be produced if the necessary information about branched-chain molecules is to be obtained. The present communication describes the attempts that have been made to synthesize, characterize and measure the properties of branched-chain super-ester molecules.