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A direct method is described of measuring the mass of substances dissolved from muscovite mica in water. The mica sheets are weighed by the use of a Mettler ultramicrobalance both before and after the immersion in water. The decrease in weight is regarded as identical to the dissolved mass. An analysis by ICP-AES has confirmed that the dissolution is due to an ion exchange of metal ions, mainly potassium ions. As a result of the measurement of the change in weight of mica sheets with immersion time, it has been found that it takes about 30 min to finish the dissolution. The total mass dissolved from basal plane has been determined irrespective of the difference in fraction of metal ions shared with each of the two mica surfaces obtained by cleavage along the basal plane. The measured values of the total mass differ from specimen to specimen and fall in the range from 1 to 10 mg m−2. These values of the dissolved mass are comparable to the order of 10 monolayers of potassium ions included in basal plane. The present result suggests that internal metal ions as well as external ions contribute to the ion exchange occurring on the surface of muscovite mica.

This paper deals with a simple and direct method of determining absolute values of adsorbance, i.e., mass per unit area, of polymers adsorbed from solution onto mica surfaces. The method is based on direct weighing of mica sheets using a Mettler ultramicrobalance UMT2 or UM3 (readability 1 x 10(-4) mg), which is commercially available. A set of mica sheets is weighed twice: before and after the immersion of mica sheets in polymer solution for a given period of time. The difference in weight of the mica sheets gives the mass of adsorbed polymers, which is divided by the total area of mica surface to derive the adsorbance. Measurable change in adsorbance was 0.1 mg m-2 in consideration of the size of mica sheets (50 cm2 in total surface area) and the scatter of readings of the ultramicrobalance. A detailed description is given on the apparatus and procedures for weighing and adsorption experiments. The present method has been applied to the experiments on the adsorption kinetics of polystyrene from cyclohexane and of bovine serum albumin from aqueous solution onto mica surfaces. Some of the experimental results are presented to show the practical examples of the application of this method. Copyright 1999 Academic Press.

This paper describes an experimental study of ultrathin films of polystyrene adsorbed from cyclohexane at the θ-temperature (307.5 K) onto molecularly smooth surfaces of mica. The amount adsorbed is determined directly using a microbalance (sensitivity ∼-10 −6 g wt) so that adsorbances on the order of 0.2 mg m −2 can be detected on mica sheets of area 5 x 10 −3 m 2 . The films may then be floated offthe mica onto a water surface using a suitable markel (Chinese ink) to delineate the shape and area of the transferred film. These results are used to discuss the way in which film structure may vary with the adsorbance of polymer on mica.

A novel method has been developed for the study of the polymer adsorption at the mica-solution interface. The amount of polymer adsorbed on mica has been determined by the direct measurement of the weight change of mica sheets due to the polymer adsorption. For this purpose, a fused quartz torsion microbalance of sensitivity ⋍10−6 g wt has been constructed, which is capable of detecting the change in adsorbance by 0.2 mg m−2 on mica sheets 5 × 10−3 m2 (50 × 50 mm) in total area. This paper gives the detailed description of the experimental apparatus and procedure. An example is shown of the application of this method to the determination of the kinetics of adsorption and desorption of polystyrene at the mica-cyclohexane interface. The following points have been discussed on the basis of the results obtained: (i) adsorbance of polystyrene on mica at saturation, (ii) irreversibility of polymer adsorption, and (iii) occurrence of multilayer adsorption.