Microstructure And Shape Memory Effect Of Biodegradable Pgs And Pggs

Poly (glycerol-sebacate) (PGS) copolymers and poly (glycol-glycerol- sebacate) (PGGS) terpolymers with different compositions and gel content were polymerized by melting copolycondensation, respectively. The microstructure, mechanical properties, degradable properties, cytocompatibilities and one-way and two way shape memory effect of PGS and PGGS were investigated by FTIR, XPS, DSC, XRD, POM, tensile test, degradation test in vitro and cell culture test in vitro. The relationship between the microstructure and the properties were revealed. The mechanism of shape memory effect was illuminated.The results of structure analysis show that molar ratio of monomers and crosslink times obviously effect on structure of PGS and PGGS. The crosslink degree of PGS increases with increasing sebacic acid (SA) content. When the crosslink time is 134h, the gel degree of PGS with SA contents of 45 mol% is only 35.2%. PGS crystal is spherulite, and the crystallinity degree decrease with increasing SA contents. Crystalline phase of PGGS crosslinked for 36h with glycol contents of 30.8mol% is spherulite. When the crosslink time is 48h, crystalline phase of PGGS is spherulite and a small amount of lamellar crystal. As the crosslinking time continued to increase, lamellar crystal content increased, and interlamellar spacing of lamellar crystal decrease.Based on tensile test, it is found that stress and strain at break of PGS with SA contents of 50mol% and 55mol% decreases with increase of crosslink time. The stress at break of PGGS is higher than that of PGS. When crosskink time is 60h and 72h,the stress and strain at break of PGGS increase after a modest decline with the glycol content growing. When the glycol content is 30.8mol%, stresses of PGGS crosslinked for 60h and 72h are 9.4MPa and 11.3MPa, strains of that are 482% and 417%, respectively. At that time, the stress-strain curve has the hard-elastic characteristic.The results of degradation test and cell culture test indicate that degradation of PGS with SA content of below 50 mol% is surface degradation, and that of PGGS and PGS with SA content of above 50 mol% is bulk degradation. The degradation rate of PGGS is slower than that of PGS. PGS with SA contents of 55mol% is beneficial to MSCs adhesion and growth, because its water contact angle is 55°and its hydrophilicity is good. Cell compatibility of PGS is better than that of PGGS.The experimental results indicate that PGS copolymers with SA contents of 50-55mol% show one-way shape memory effect. The three-dimension chemical crosslink network serves as fixed phase, the PGS crystal serves as reversible phase. With the SA contents increasing, the shape recovery rate of PGS increases, the shape retention rate of PGS decreases, and the shape recovery temperature of PGS increase initially and then decrease. PGS with SA contents of 50mol% in the specimen deformed to 100% exhibits shape recovery rate of 100% and shape retention rate of 96.5%. When the deformation is 300%, the shape recovery rate and shape retention rate of that are more than 90%. PGGS terpolymers show good one-way shape memory effect. Shape retention rate and shape recovery temperature of PGGS are higher than those of PGS. With crosslink time increasing, the shape recovery rate of PGGS increases, and the shape recovery temperature decreases. PGGS crosslinked for 72h with glycol content of 30.8mol% in the specimen deformed to 100% exhibits shape recovery rate and shape retention rate of above 90% and shape recovery temperature of 40℃. When the deformation is 300%, the shape recovery rate and shape retention rate are more than 95%.The research show that PGGS crosslinked for 60h and 72h with glycol content of 30.8mol% show two-way shape memory effect after thermomechanical training,. When the training deformation is 100%, two-way shape recovery rate of PGGS cosslinked for 72h is 20.9%. It is a necessary condition for two-way shape memory effect of PGGS that lamellae content should be enough. The physical crosslinked network with lamellar crystal as the cross-linking serves as fixed phase, the PGGS spherulite serves as reversible phase. The bend of lamellae resulting from the shrinkage of molecular chains stretched in thermomechanical training provide the driving force of molecular chain elongation during the cooling process.