Nylon 3 or polyamide 3 with a β-amino acid skeleton, which is different from other commercial nylons in the amide linkages, usually exhibits interesting properties such as high capacity of moisture up-take, high glass transition temperature and high crystallinity.1-5 Nylon 3 fibers are very close to silk in properties.We have synthesized nylon 3 via ring opening polymerization of 2-azetidinone (β-lactam) with (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-phosphoranylidenamino]-2A5,4A5-catenadi(phosphazene) (t-BuP4) as the catalyst in a mixture of dimethylacetamide (DMAc) and LiC1.The polymers have been characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), laser light scattering (LLS) and viscometry.