Investigation of Methacrylic Acid at High Pressure Using Neutron Diffraction

This
article shows that pressure can be a low-intensity route to
the synthesis of polymethacrylic acid. The exploration of perdeuterated
methacrylic acid at high pressure using neutron diffraction reveals
that methacrylic acid exhibits two polymorphic phase transformations
at relatively low pressures. The first is observed at 0.39 GPa, where
both phases were observed simultaneously and confirm our previous
observations. This transition is followed by a second transition at
1.2 GPa to a new polymorph that is characterized for the first time.
On increasing pressure, the diffraction pattern of phase III deteriorates
significantly. On decompression phase III persists to 0.54 GPa before
transformation to the ambient pressure phase. There is significant
loss of signal after decompression, signifying that there has been
a loss of material through polymerization. The orientation of the
molecules in phase III provides insight into the possible polymerization
reaction.