The bulk ring-opening polymerization(ROP) of ε-caprolactone(ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted.1,1’-bi-2-Naphthol(BINOL)-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃.The overall conversion to poly(ε-caprolactone) was more than 96% and poly(ε-caprolactone) with M w of 8400 and polydispersity index of 1.13 was obtained.1 H NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent.The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio.In addition,the present protocol provided an easy-to-handle,inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications. The bulk ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted.1,1’-bi-2-Naphthol (BINOL) -based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90 ° C. The overall conversion to poly (ε-caprolactone) was more than 96% and poly (ε-caprolactone) with M w of 8400 and polydispersity index of 1.13 was obtained.1 H NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent. The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer -to-initiator ratio. In addition, the present protocol provides an easy-to-handle, inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications.