INVESTIGATIONS ON SURFACE-MODIFIED BULK POLYMERS .1. COPOLYMERS OF STYRENE WITH A STYRENE MOIETY CONTAINING A SUGAR MONOMER

Copolymers containing vinyl sugar units were synthesized by copolymeri zing ylidene-1-(4-vinylphenyl)-D-gluco(D-manno)pentitol (1) with styre ne. Films and plates of the copolymers and blends were prepared by cas ting solutions on glass plates or by hot-pressing. Isopropylidene grou ps, the hydrophobic protecting groups of the sugars (1), were hydrolyz ed only in the sample surface layers by treating the films and plates with aqueous acid. The surfaces showed hydrophilic properties afterwar d and were studied by water contact angle measurement. The accumulatio n and reorientation of the hydrophilic sugar segments at the surface w as demonstrated by a decrease of the receding contact angle and found to depend on the copolymer composition and on sample preparation. The surface compositions of the solution-cast copolymer films were investi gated by means of X-ray photoelectron spectroscopy (XPS). The results clearly showed that the isopropylidene groups at the surfaces were rem oved and the percentage of the sugar carbon at the surfaces accordingl y increased. Angle-dependent XPS measurements indicated that the hydro lysis took place evenly to a depth of 10 nm. The surface conductivity of the copolymer plates increased by several orders of magnitude owing to adsorption of water on the hydrolyzed, hydrophilic surfaces under defined air humidities.