Abstract

A report is given of the surface forces measured as a function of distance between two molecularly smooth mica surfaces immersed in a 10 μg/ml poly(ethylene oxide) (PEO, MW = 39,000 or 596,000) solution in toluene at 22°C. Below the PEO chain melting temperature T m ⋍ 60°C , it is not possible to permanently disperse PEO in toluene. Adsorption on mica occurs mainly as aggregates which give rise to long-range hysteretic surface forces. On approaching the surfaces, the forces are always repulsive and are consistent with there being polymer extruded from between the surfaces. On withdrawing the surfaces, the force becomes adhesive, independent of the adsorbed amount, provided that the adsorbed layers are first compressed. Since toluene is a better than θ solvent for PEO, chain entanglements between inflexible PEO molecules below their melting temperature are most likely responsible for the observed adhesion and aggregation behaviour. It is concluded that below T m, the nonequilibrium nature of PEO solutions (following preheating) in toluene should be reflected in a coagulation of PEO homopolymer-covered colloidal dispersions in spite of apparent “good solvent” conditions. The results illustrate the importance of the T m of crystalline polymers with respect to their solution and surface behaviour. Similarities exist with the results reported by J. N. Israelachvili, R. K. Tandon, and L. R. White ( J. Colloid Interface Sci. 78, 430 (1980)) on PEO adsorption from aqueous solutions, but the results contrast with previous measurements by P. F. Luckham and J. Klein ( Macromolecules 18, 721 (1985)) on PEO adsorption from toluene.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.