The modified MgO nanoparticles (m-MgO-NPs) by a copolymer containing the malic acid and low molecular weight poly(L-lactide) (poly(L-lactide-co-malic acid), PLMA) have been successfully prepared. MgO nanoparticles (MgO-NPs) were coated by the PLMA and m-MgO-NPs were uniformly dispersed in the PLLA matrix to a novel biocomposite material (PLLA/m-MgO-NPs) with more excellent interface bonding and uniformer dispersion, compared to the PLLA/MgO-NPs. Compared to neat PLLA and PLLA/MgO-NPs film, the m-MgO-NPs not only shown the obvious neutralization effect on the acidic solution in the degradation of the PLLA and better hydrophilicity, but also exhibited the higher cell viability and decrease the toxicity to the cell in the degradation process of PLLA in vitro. In addition, m-MgO-NPs also reduced the degradation rate of the PLLA. The mechanisms for the excellent dispersion of nanoparticles, enhanced pH stability, reduced degradation rate of the PLLA and the cell viability in vitro in the case of PLLA/m-MgO-NPs have also been proposed and discussed in detail.

To improve the mechanical properties and shelf‐life of barium sulfate nanoparticles (BaSO4‐NPs)/polyethylene (PE) composites, which are used as the scaffold of T‐shaped copper intrauterine devices (Cu‐IUDs) in the clinic, an Al coupling agent was used to modify BaSO4‐NPs. The influence of the Al coupling agent on the microstructures, properties, and shelf‐life of the nanocomposites were investigated. The results showed that: (1) a chemical reaction occurred between the Al coupling agent and the hydroxyl groups adsorbed by BaSO4‐NPs. (2) BaSO4‐NPs modified by the Al coupling agent dispersed in the PE matrix were much better than unmodified NPs. The interface bonding between modified NPs and the PE matrix was better than unmodified NPs. (3) the maximum tensile strength of nanocomposites containing modified NPs was 11.87 MPa, flexural strength was 6.61 MPa, and the elongation rate was 66.78%. (4) After an accelerated aging experiment, the tensile strength of the nanocomposites only decreased 5–15%. All of these results indicate that m‐BaSO4‐NPs/PE nanocomposites are more clinically useful than unmodified nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40393.