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.