The State of Rubber in Solutions, Based on the Surface Properties of the Solutions
Abstract The problem of the constitution of rubber and especially of its state in solutions has recently again become the subject of active discussion. Based on a series of investigations, Staudinger reached the conclusion that dilute solutions contain free colloidal rubber molecules which are composed of closed chains of an unusually large number of isoprene residues. Pummerer considers the molecular weight of rubber to be much less than does Staudinger. (According to Staudinger the molecular weight of rubber is 50,000 to 170,000; according to Pummerer it is 1200 to 1600.) Meyer and Mark assume for the primary valence chain of rubber a molecular weight of about 5000. These latter investigators are of the opinion that there are secondary aggregates of rubber molecules in a rubber solution and that the high values which were found by a number of investigators (Caspari, Kroepelin, and others) do not represent the molecular weight but the average micellar weight of rubber. In deciding the question of the state of rubber in solution the majority of investigators make use of the classic cryoscopic and osmotic methods of investigation. Staudinger has used viscosimetric measurements in an original way in his experiments. In the present work we have turned to a study of the surface properties of rubber solutions, assuming that data along this line might explain some peculiarities in the structure of these solutions.