Cross-linked poly(dimethylsiloxane) (PDMS) was irradiated with a Xe2*-excimer lamp (172
nm) under ambient conditions. The irradiation in combination with the formed ozone results in an
oxidation of PDMS to SiO2 at the polymer−air interface. The surface properties of the irradiated surfaces
were studied by means of contact angle measurements, infrared spectroscopy, and X-ray photoelectron
spectroscopy. The photochemical conversion of surface methylsilane groups to silanol groups is responsible
for the large increase in surface free energy. Subsequent degradation of the polymer and formation of
SiO
x
was monitored by infrared spectroscopy. As determined by X-ray photoelectron spectroscopy, the
binding energy shifts reach values corresponding to SiO2. The atomic ratio concentration O:Si changes
from about 1:1 (PDMS) to about 2:1 (SiO2). On the basis of the XPS and IR results, the photochemical
reaction pathway from PDMS to silicon oxide via surface silanol groups is discussed. The strict linearity
of the contact angle versus irradiation time and the clear dependence from irradiation intensity allows
the tuning of the chemical surface functionalities.
In this article common synthetic routes toward telechelics, which are polymers with well‐defined functional end groups, are described. Telechelic polymers are available via radical, cationic, and anionic polymerization including reversible addition–fragmentation chain transfer polymerization, atom transfer radical polymerization, and nitroxide mediated polymerization. Furthermore, metathesis has become a valuable tool for the preparation of telechelics. Last but not least selected examples are presented in which step‐growth polymerization has been successfully applied for the synthesis of such well‐defined macromolecules. In specific cases chain scission can also be a useful route.
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