Preferential orientation of pendent groups at polymer surfaces: Phenyl ring distribution on polystyrene film surfaces

• Published in: Applied surface science 1989-08, Vol.37 (4), p.406-418
• Main Authors: Akhter, S., Fahlquist, L., White, J.M., Hardegree, E.L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(89)90501-1

It is shown that preferential orientation of pendent groups at polymer surfaces can be modelled in terms of the patchy overlayer model. It then becomes possible to estimate the extent of preferentiai orientation from angular dependent XPS data. This method was applied to solvent-cast atactic and isotactic polystyrene film surfaces. The intensities of the π∗ ← π shake-up transition and the C(1s) peak were monitored for take-off angles between 90° and 15°. The C(1s)/shake-up intensity ratio was constant, as function of take-off angle, for both atactic and (amorphous and semi-crystalline) isotactic films. This suggests that the distribution of phenyl groups relative to the main chain is similar on surfaces of different tacticity and crystallinity Using the patchy overlayer model, it is estimated that a majority (> 75%) of the surface phenyl groups are located at or above the backbone plane; less than 25% are oriented towards the bulk.