Solid-state n.m.r. investigation of crosslinkable blends of novolac and poly(∈-caprolactone)

The miscibility, phase behavior, and intermolecular interaction of novolac/poly(∈-caprolactone) (PCL) blends, before and after curing, were investigated by the high resolution solid-state nuclear magnetic resonance (n.m.r.) technique. It was found that there exists hydrogen-bonding interaction between the carbonyl groups of PCL and the hydroxyl groups of novolac, which results in the downfield shift of carbonyl carbon resonance of PCL and the upfield shift of hydroxyl-substituted carbon resonance of novolac. The interaction also broadens the line width of carbonyl carbon resonance. After curing with 15 wt% hexamine (relative to novolac content), hydrogen-bonding interaction still exists between the components in the crosslinked blends. However, the relative amount of hydrogen bonds decreases significantly. Both the uncured and the cured novolac/PCL blends exhibit composition-dependent miscibility. The curing causes an increase of the domain size in the amorphous phase and a reaction of miscibility between the two components.