Show a mechanism for the first two propagation steps of polymerization (just use X• to denote the radical initiator), and show a structure for the plexiglass polymer. To make a real gel, with pores fo...Show a mechanism for the first two propagation steps of polymerization (just use X• to denote the radical initiator), and show a structure for the plexiglass polymer. To make a real gel, with pores for the proteins to slip through, we need a crosslinker - something to tie the chains together, forming a three-dimensional 'web'. Usually, a small amount of bis-acrylamide is added to the acrylamide solution for this purpose.