-CONHCONHCONHCONH- is a theoretically possible polymer, as shown below... =D

BrCO2H + NH3 -heat in sealed tube-> NH2CO2H

NH2CO2H + NH2CO2H -> NH2CONHCO2H

                                                 +
                                                      
                                          NH2CO2H 

                                                  |
                                                  \/
                                           
                                  NH2CONHCONHCO2H

                                                  +

                                              ......... chem is great for taking your mind off things and relaxing... really love the creativity and room for flexibility it allows... =)
To get:

          O         O        O                       
          ||       ||       ||                     
H - O - C - N - C - N - C - N - H       
                |         |         |                 
                H         H        H                 
   
And so on... >)