A cyclic ketene acetal of 2-methylene-1

3-dioxepane(MDO) was prepared and undergone free-radical ring-opening polymerization with acrylic acid (AA) to produce biodegradable copolymers P(AA-co-MDO) which had ester groups in the backbone and carboxyl as pendant functional groups.The structures and weight-average molecular weights(Mw) were characterized by Flourier transform infrared spectroscopy (FTIR)

nuclear magnetic resonance (1H-NMR) and multi-angle laser light scattering measurements (MALLS).Obvious changes of molecular weight could not be observed when the ratio of MDO to AA was varied.The thermal property of the copolymers was investigated by differential scanning calorimetry and termogravimetric analysis.It was found that the copolymers showed evident glass transition temperature.The thermostability of the copolymers declined as the MDO content increased

but still maintained at a high level to meet the requirement of production process of detergent builders.The X-ray diffraction results indicated that P(AA-co-MDO) copolymers were amorphous and these copolymers may have good biodegradable performance.The degradation experiments of copolymers in activated sludge revealed that the more MDO content was in copolymer

the faster degradation rate of the copolymer was.The performance of the copolymers and other detergent builders was studied and the results showed that the copolymers possessed high chelating capacity

good dispersancy and favorable pH buffer ability

and therefore were ideal detergent builders.