Relationships between Structure and Properties of Poly(aspartic acid)s

Various types of poly(aspartic acid)s, which were poly(α-<SCP>l</SCP>-aspartic acid), poly(α-<SCP>d</SCP>-aspartic acid), poly(β-<SCP>l</SCP>-aspartic acid), and poly(α,β-<SCP>d</SCP>,<SCP>l</SCP>-aspartic acid)s, were prepared, and their biodegradabilities using the OECD 301C method and calcium ion chelating abilities were measured to clarify the relationship between the structure of poly(aspartic acid)s and these properties. Distinct tendencies were found both between the number of amide protons and biodegradability and between the ratio of the dicarboxylic acid end groups to the dicarboxylic acid end group plus succinimide end group and biodegradability. The chirality of the aspartic acid unit and the type of amide linkage in poly(aspartic acid) had no apparent effect on the biodegradability of poly(aspartic acid). The result of repetitive biodegradability analyses for poly-aspartic acid suggested the complete biodegradation is possible. Regarding the calcium ion chelating ability, only the type of amide linkage affected the calcium ion chelating ability. Poly(α-aspartic acid) showed a higher calcium ion chelating ability than poly(β-aspartic acid) and poly(α,β-aspartic acid).