Rigidity of the backbone for poly(bis(4-butoxycarbonylphenyl))carbodiimide and poly(bis(4-butylphenyl))carbodiimide studied by solid state 13C T1p measurements Original Research Article

The structure and rigidity of the backbone of two polycarbodiimides as a function of the side chains were studied by 13C CP/MAS NMR. From these results, the structures of the polycarbodiimides were determined, and the 13C spin–lattice relaxation times in the rotating frame were measured. Based on our findings, we discuss the mobility for the backbone of the two polycarbodiimides with and without ester linkage between the aromatic and aliphatic side chains. The backbone carbon of polycarbodiimide I with ester linkage has a lower activation energy, 18.63 kJ/mol, than the polycarbodiimide II without ester linkage, 23.20 kJ/mol. Also, the activation energies of the aliphatic side chains show gradually increasing values. We think that this increase results from the greater mobility of the alkyl chain toward its free end.