Organically modified montmorillonite improves interfacial compatibility between PLLA and PGA in bone scaffold

Abstract

Slowly degradable poly(l-lactide) (PLLA) and fast degradable polyglycolic acid (PGA) are expected to bring an intermediate degradation rate through their blending towards bone regeneration. However, PLLA is thermodynamically immiscible with PGA, resulting in poor interfacial bonding and phase separation. In this study, montmorillonite (MMT) was modified by octedacy trimethyl ammonium chloride (denoted as OMMT) and then introduced into PLLA/PGA scaffold to improve the compatibility between PLLA and PGA. On one hand, MMT possesses layered spacing structure, thus accommodating the intercalated polymer chains. On the other hand, the modification can enlarge the interlayer spacing of MMT, which is beneficial for the intercalation of PLLA and PGA molecules chains. Noticeably, the intercalated PLLA and PGA molecules chains move restrictedly in MMT interlayer, which is attributed to that the NH2 group in OMMT not only formed hydrogen bonding with OH group of PLLA but also formed hydrogen bonding with OH group of PGA. Consequently, PLLA and PGA are forced to be compatible through the action of OMMT. The results demonstrated that the scaffold had two distinct melting peaks corresponding to PLLA and PGA, respectively. Meanwhile, there was no obvious sheet-like inclusion structure in the fractured surface of the scaffold, indicating that the interfacial compatibility between PLLA and PGA was significantly improved. Correspondingly, the tensile strength and tensile modulus of the scaffold were increased by 110% and 70%, respectively. In addition, the scaffold exhibited good cytocompatibility for human osteoblast-like MG-63 cells adhesion and proliferation.