Synthesis of aromatic benzoxazole polymers for high T, low dielectric properties/Title> - Polyimides and Other High Temperature Polymers - page 220

Scheme 7. Thermal and dielectric properties of O-allylated 6F/12F (50/50) benzoxazole copolymer
as a function of intramolecular rearrangement and crosslinking.
4. CONCLUSIONS
Aromatic benzoxazole polymers carrying perfluoroisopropyl groups in their
backbone and with hydroxyl pendants were found to exhibit high T g and low di-
electric characteristics. The dielectric constants were lowered as a function of the
fluorine content in these polymers and the high glass transition temperatures
could be attributed to the presence of fused rings due to intramolecular hydrogen
bonding. Their high thermo-oxidative stabilities and low moisture uptake ensured
that these materials were highly compatible with integrated circuit processing.
The coefficient of thermal expansion and dielectric anisotropy were also within
acceptable limits for such applications. A post-polymer reaction paradigm was
also examined in which Claisen rearrangement and polymer crosslinking were se-
quentially employed on O-allylated 6F-benzoxazole polymers, for T g enhance-
ment and for imparting solubility, respectively. The desired solvent-resistance of
the polymer films after the fabrication process along with overall retention of me-
chanical integrity and low dielectric properties render these materials eminently
suitable for future evaluation in microelectronic packaging technology.