IR study on hydrogen bonding in epoxy resin–silica nanocomposites

The chemical and physical interactions between ingredients in composites play an important role in the improvement of service properties. The nucleophilic addition between polymer and isophoron diisocyanate molecules was monitored by FT-IR technique. The intensity loss of isocyanate absorption band in conjunction with the intensity growth of carboxyl absorption band indicates the progress of reaction. FT-IR spectroscopy was also adopted to examine the intermolecular hydrogen bonding of epoxy resin with silica as well as intramolecular one within polymer matrix. The vibration frequency of carboxyl group (CO) and hydroxyl group (OH) shifts from 1736 to 1728 cm−1and 3420 to 3414 cm−1, respectively, indicating the occurrence of hydrogen bonding between CO and OH. The vibration frequency of SiOH moves from 3435 to 3414 cm−1, suggesting the involvement of silica. Whereas the vibration frequency of pending OH in polymer chain moves from 3435 to 3420 cm−1 or 3414 cm−1, proposing that this kind of interaction can also happen within polymer matrix.