Thin liquid films from aqueous solutions of polyoxyethylene-polyoxypropylene-block copolymer, cellulose acetate phthalate and pilocarpine hydrochloride

The liquid films formed from 1, 2 or 3% solutions of Lutrol F127 in 0.15 M aq. NaCl, and from dispersions containing cellulose acetophthalate, Lutrol F127 and pilocarpine hydrochloride, were studied in order to determine film stability and the size of dispersed particles, with a view to using cellul ose acetophthalate as a carrier of pilocarpine with sustained action. Thin liquid films were formed on glass or fused quartz plates (a model of the hy drophilic eye surface) by approaching an air bubble to the solid substrate immersed in the studied solution. It was found that films were stable. The thickness of the microscopic thin liquid films was measured using the micro interferometric method. The average film thickness was h = 100 +/- 10 nm. A n explanation of the results was sought in the existence of repulsion betwe en the macromolecules adsorbed at both film surfaces. The size of dispersed cellulose acetophthalate particles was determined using a method based on light interference. The average diameter of the particles was found to be 0 .32 mu m. It was concluded that the nonionic surfactant Lutrol F127 assiste d the formation of small dispersed particles and increased the stability of the dispersions.