Aliphatic poly(H-phosphonate)s were obtained by polyesterification of dimethyl H-phosphonate with bio-based long-chain diols. Nonadecane-1,19-diol), tricosane-1,23-diol, and octatetracontane-1,48-diol with dimethyl H-phosphonate yield the corresponding polyphosphoesters (PPE19H, PPE23H, and PPE48H) with molecular weights (M-n) up to 4.3 X 10(4) g mol(-1). Postfunctionalization of these polymers via Hirao cross-coupling yields the selectively functionalized poly(H-phosphonate)s PPE19Ph, PPE23Ph, and PPE48Ph. DSC analysis revealed significantly enhanced crystallinities and melting points (up to T-m = 110 degrees C) with increasing methylene sequence lengths. Hydrolytic degradation of polymer powder of poly-(H-phosphonate) occurred up to 95% in 2 days. The degradation rates decreased with increasing methylene sequence length,After post-functionalization, degradation occurred only to a minimal extent over 3 months in basic and in acidic media.