Urethane- and thioether (meth)acrylate alkoxysilanes have been used, as
sol-gel precursors, for the preparation of a special family of
inorganic/organic copolymers (ORMOCER®s). The basic silane type
offers the following structural and synthetic possibilities for modifying
the properties of the resulting copolymers: variation of the number of
alkoxy groups, combination with other, different, sol-gel precursors,
variation of the number of attached (meth)acrylate groups (1– 5), and
variation within the molecular segment (kind, structure and length)
connecting the inorganic with the organic polymer structure. To achieve the
additional organic polymer structure in the cured copolymer the use of
different radically induced polymerization approaches (UV-, visible light-,
thermal-and redox induced) is possible. Taking the incorporation of fillers
into account, the Young's modulus of these copolymers is adjustable in a
range of 1–17000 MPa, and the thermal expansion coefficient in a range of
17–250·10-6·K-1 (5 - 50 °C). Other advantages are
the low shrinkage (1 - 2,8 vol.-%), the high flexural strength (up to 160
MPa), and the high abrasion resistance. This new copolymer type seems to
have significant potential for medical applications, especially as dental
filling material to replace the currently used controversial amalgam
fillings.