Intramolecular segregation in polymers and macromolecules studied by low-energy ion scattering

The intramolecular segregation in several generations of poly(propylene imi ne) dendrimers and oxygen plasma modified HDPE was studied with low-energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS). Although the different generations of poly(propylene imine) dendrimers contain almos t the same atomic carbon to nitrogen (C/N) ratio, it is shown that this rat io at the outermost surface depends strongly on the generation of the dendr imer. The conformation of a dendrimer is probably related to the flexibilit y of the bis(3-aminopropyl)amine endgroups, which becomes lower for higher generations. Furthermore, the formation of a metallodendrimer, by complexat ion of CuCl2 with the amine endgroups of a fourth generation dendrimer (D4) , was followed with LEIS. Compared to pure CuCl2, a relatively high copper concentration and a high atomic copper to chlorine ratio was found at the s urface of the metallodendrimer. The high copper concentration and the reduc ed sterical hindrance by chlorine demonstrate the high potential of the met allodendrimers as catalytic material. The hydrophobic surface of HDPE can be made hydrophilic by treating it in a n oxygen plasma. During such a treatment, oxygen containing functional grou ps are introduced at the surface, which improves wetting and thus adhesion. Unfortunately, the effect of an oxygen treatment is only temporary, an eff ect referred to as ageing or hydrophobic recovery. LEIS has been used to st udy this ageing process. We were able to follow the surface oxygen concentr ation as a function of the time between the plasma treatment and the LEIS a nalysis. Combined information obtained from LEIS and XPS measurements indic ates that the ageing is mainly confined to the outermost atomic layers. Mor eover, the ageing process depends strongly on the exact experimental condit ions. (C) 2001 Elsevier Science B.V. All rights reserved.