Pressure Induced Topochemical Polymerizationof Solid Acryalmide Facilitated by Anisotropic Response of Hydrogen Bond Network
The pressure induced polymerization of molecular
solids is an appealing route to obtain pure,
crystalline polymers without the need for radical
initiators. Here, we report a detailed density
functional theory (DFT) based study of the
structural and chemical changes that occur in
defect free solid acrylamide, a hydrogen bonded
crystal, when it is subjected to hydrostatic pressures.
Our calculations predict a polymerization
pressure of 94 GPa, in contrast to experimental
estimates of 17 GPa, while being able
to reproduce the experimentally measured pressure
dependent spectroscopic features. Interestingly,
we find that the two-dimensional hydrogen
bond network templates a topochemical
polymerization by aligning the atoms through
an anisotropic response at low pressures. This
results not only in conventional C-C, but also
unusual C-O polymeric linkages, as well as a
new hydrogen bonded framework, with both NH...
O and C-H...O bonds.