Surface-tension experiments

Typical Simple laboratory demonstrations and surface tension experiments involving thin films... 

Chemicals. Sulfur. For viscosity and surface tension experiments, laboratory-grade sublimed powdered flowers of sulfur from Fisher Scientific Co. are used without further purification. For synthetic and characterization purposes, 99.9995% sulfur from PCR Inc. is used. 

Dicyclopentadiene. For visocity and surface tension experiments DCP from Exxon Chemical Co. is used without further purification. This is around 98% pure, with the remainder primarily acyclic dienes. The isomer composition is 98.5% endo and 1.5% exo. 

The surface-active properties of the ii.onomers were also confirmed by surface-tension experiments. Figure 3 shows the variation of the surface tension 7 with the concentration of a cationic monomer (MADQUAT) (29) and a neutral one (AM) (Graillat, C.. Pichot, C. unpublished results). The surface-tension drops for example from 70 dyn./cm to 40 dyn/cm when the MADQUAT concentration varies from 10 to eibout 3M (a 3M is the monomer concentration based on the aqueous phase used in most polymerization reactions). However, the amphiphilic character of monomers is not sufficiently pronounced to give rise to micellization since no sharp transition corresponding to the C.M.C. is detectable. 

In order to assess the viability of the membrane-casting system, surface tension experiments were carried out in the second study by Tan et al. The data was obtained from solvent (chloroform)-nonsolvent additive solutions. It is illustrated how surface tension data can be used to elucidate the role of nodules on the surface of the asymmetric membranes. While different types of nonsolvent additive were used, the solvent was fixed to chloroform. 

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