Polylactic acid CAS 26100-51-6 PLA

Experiments have found that poly-L-lactic acid can be deformed below 100 °C, and the deformation recovery temperature is also lower than 100 °C. Therefore, poly-L-lactic acid has shape memory properties below 100 °C, that is, it has shape memory properties and biodegradability. As a medical material, poly-L-lactic acid has advantages unmatched by other materials: because poly-L-lactic acid has shape memory properties, it can be implanted into the body in a compressed form, and heated in the human body to make it self-recovery. The required shape can reduce the wound and relieve the pain of the patient; poly-L-lactic acid is a biodegradable material, which can be degraded into non-toxic products in the human body, so as to avoid the long-term existence of non-degradable implant materials in the body. It also avoids the pain caused by the non-degradable materials that need to be removed by a second operation in some cases. At the same time, poly-L-lactic acid has good biocompatibility: poly-L-lactic acid can be passed through conventional Copolymerization and blending methods can adjust its properties in a wide range to meet different medical needs, which is unmatched by traditional medical shape memory alloys; It has good mechanical properties and slow degradation rate, and is more suitable as a fracture fixation material. Compared with the existing degradable shape memory polymers, poly-L-lactic acid has extremely superior mechanical properties, which is very important for fracture internal fixation and stent applications. The deformation process of poly-L-lactic acid in use is as follows: when the shaped poly-L-lactic acid is heated to the deformation temperature Tf (Tf is higher than the glass transition temperature and lower than 100 ° C), the reversible phase softens, and under the action of external force Deformation into the second shape; under the action of maintaining stress, the poly-L-lactic acid is cooled below the glass transition temperature, the reversible phase enters the glass state, the molecular chain is frozen, and the poly-L-lactic acid is hardened into a deformed shape. Stable solid; when the poly-L-lactic acid with the second shape is heated to the shape recovery temperature (above the Tf temperature and below 100 °C), the reversible phase softens again, and the poly-L-lactic acid returns to the original shape memorized by the stationary phase . The deformation modes mentioned therein can be any one or a mixture of expansion, stretching, compression, bending and torsion.

Poly-L-lactic acid can also be copolymerized with other degradable monomers to form copolymers through ring-opening polymerization. The copolymers of poly-L-lactic acid are mainly copolymers of L-lactide and other lactides, L-lactide and Copolymers of lactones and copolymers of L-lactide and ether segments. The degradation rate of poly-DL-lactic acid is faster than that of poly-L-lactic acid, and the copolymer of the two can adjust its degradation performance; the glass transition temperature of poly-glycolide is lower than that of poly-L-lactic acid, about 45 °C, The glass transition temperature of polyε-caprolactone is very low, about -60 °C, and the copolymerization of poly-L-lactic acid with any monomer or the copolymerization of the three can adjust its shape recovery temperature in a wide range, and at the same time Its mechanical properties and degradation properties can be adjusted to a large extent. At the same time, poly-L-lactic acid can also be blended with other biodegradable polymers to form a blend to adjust its shape recovery temperature, mechanical properties and degradation properties, so as to be more suitable for biomedical applications. Poly-L-lactic acid composite material made by adding biologically active hydroxyapatite particles, dicalcium phosphate, tricalcium phosphate and bioglass to poly-L-lactic acid, wherein hydroxyapatite is the main component of natural bone, It has excellent biological activity and osteoconductivity, and can form a direct osseointegration with bone tissue. Therefore, the poly-L-lactic acid shape memory polymer containing HA particles has great application potential in bone fixation.