Interfacial Molecular Design, Fabrication Of HA/PLA Composite Biomaterials And Their Related Properties

Hydroxyapatite /poly-lactic acid (HA/ PLA) composites as Advanced bone-subsituted materials represent the development trend of internal fixation materials since they may combine bone binding property of HA filler with the resorbability and the easy processing property of polymer matrix. However, their ultimate mechanical properties still need to be improved. In addition, the interface failures of the materials are emerged. Therefore, the title subject, interfacial molecular design, faricatlon of HA/ PLA composite biomaterials and their related properties, is important for us to solve the above practical problems, and to develop new interfacial design methods and theory. Through the above research, the following resuts are obtained:Based on the review of domestic and abroad references, two types of interfacial models for HA/ PLA composite internal fixation materials, interfacial model of homogenious dispersing rigid HA particles toughening HA/ PLA and matrix self-modified interfacial model are suggested. Their toughened mechanism, fibrication and possible reactions are also discussed.6 modified HA particles are prepared using silane derivatives WD-50, WD-60, and WD-70, respectively in non-proton medium (toluent) and proton medium (HiO-EtOH). Again, another 2 modified HA products synthesized via PDLLA (Mv^T.OxlO4) matrix self-modified method. The suspended stability of the above 6 modified HA products and un-modified HA particle in dispersing media EtOH, Me2CO and HaO is investigated. Stability orders of the 7 samples are obtained, their stability mechanism is also discussed. By comparing the stability orders, we can obtain the following conclusion: silane modified HA products have good dispering property in EtOH. Meanwhile, PLA-modified HA products is easy to disperse in MeaCO. This conclusion provide a basis for us to select the dispersing media in preparation of HA/ PLA composite via absorption process in liquid phase.Silane-modified HA particles are characterized by XPS method. The results indicate that P2P electron binding energy (EBE) of the HA productsmodified in non-proton medium decrease about 0.3eV~0.4eV compared to that in non-modified HA, which suggesting electron environment changes surrounding the atom P and formation of new chemical bond; that the EBE values of PIP in HA modified in proton medium (H2O-EtOH) remain same, showing no formation of chemical bond; that Ca2p EBE values of the HA products both in the above two media unchanged, indicating that Ca2+ in HA could not participate in the interfacial reaction during the modification. The differences of Pap EBE values are clarified. In H2O-EtOH system, group -OR, one of active groups in silane derivatives, is out of work and can not be coupled with group -OH in HA, because it is hydrolyzed to Si OH group by H2O in the system. But in non-proton system (toluent), the-OR group remain active, it can be coupled chmically with surface-OH group in HA, yielding a new chemical structure "P-O-Si". It is the formation of the struclune above lead P2p EBE values to decrease 0.3~0.4eV. According to the XPS results, a formula for thickness calculation of silane-modified layer is also given. Based on the formula, the silane-modified layer thickness are calculated. The results show that they are about l~2nm, which are equivalent to 1~2 monomolecular layers. This thickness is enough to make a strong interfacial adhesion between HA toughened phase and polymer matrix. Furthermore, the new structure P-O-Si is identified by IR spectra. Taking AMMO- and COPP-modified HA as examples, their IR differential spectra before andl after modification contain the characteristics absorption of AMMO or COPP molecules. By the presence of new adsorption peaks, 997.96cm"1 and 1011cm"1, it is concluded that AMMO or COPP molecules and HA are connected via the P--O - Si structure.calcium release and calcium precipitation in physiological environment is an important experiment for testing bioactivity and bone binding ability of biomaterials. In this paper, the calcium release...