Shape Memory Composite Fabricating By In Situ Growth Of Hydroxyapatite In Poly (Vinyl Alcohol) Gels

Poly(vinyl alcohol) (PVA) hydrogel are important in a wide range of biomedical applications. For example, they were used as drug release system, wound dressing, articular cartilage and tissue engineering scaffolds. After some researchers discovered that PVA material had shape memory characteristic in the last 15 years, PVA was rapidly developed in many fields. However, a major bottleneck against more widespread use of these shape memory polymers is their lower mechanical function. For improving the mechanical properties of PVA shape memory materials to meet clinical needs, some researchers prepared PVA hydrogel using different crosslinking or modification methods. Others introduced the inorganic fillers into the PVA polymer matrix to fabricate inorganic/polymeric composites.Among them, HA/PVA composites have been used clinically in various forms. In hard tissue engineering, Hydroxyapatite(HA), an important biocompatible inorganic material with composition similar to bones and teeth, have been widely studied in inorganic/organic composite. However, the maintain of these high performances of composite materials mainly relies on the homogeneous dispersion of uniformly shaped and sized particles into the matrix. In the paper, an in situ method for the fabrication of hydroxyapatite particle-embedded Poly(vinyl alcohol) is detailed from the mechanistic aspect to the structural analysis and shape memory effect of the materials. At last, we get a useful and satisfying results, the main conclusions are drawn as follows:1. An in situ method for the fabrication of hydroxyapatite particle-embedded Poly (vinyl alcohol) (PVA) is detailed from the mechanistic aspect to the structural analysis. TEM and Particle Size analysis show that the in situ growth of HA crystallites in the PVA matrix are spherical particles with an average size of about 1μm. Tensile strength analysis show that the addition of HA significantly improved the mechanical properties of materials.2. X-ray diffraction (XRD) analysis, Moisture analysis and TG analysis all show that the HA crystallites grew homogeniously in PVA gels as the ammonia diffused into the gels. In this study, the calcium ions and phosphate groups from dissolved hydroxyapatite (HA) with the stoichiometric of 1.67 are embedded in the PVA gel when PVA chains was crosslinked in 3% countant of glutaraldehyde.3. Moreover, the effects of the composite ratios and recovery temperature on shape memory recovery ratio and shape memory recovery rate were investigated.In our experiment, the movement PVA chains in the composite material were selected as reversible phase and crosslinking points were selected as stationary phase. Shape memory recovery ratio of the composite is about 90% after 40 seconds and the material has shape memory property.4. The composites were found to have superior bioactivities, including a better osteoblasts adhesion, more active proliferation...