Study On The Preparation And Compatibilization Of Polycaprolactone/Polylactic Acid Porous Materials

With the rapid development of society and economy,the demand for plastic products has increased dramatically.However,plastic waste has brought serious environmental pollution.Meanwhile,the development of petroleum-based polymers is limited because of the low content of global petroleum reserves and the imminent energy shortage.Polymers will inevitably follow the path of recycling,regeneration,and degradation in order to achieve the goal of reducing environmental pollution and sustainable green development.Polylactic acid(PLA)stands out because of its good mechanical properties,processing properties,biodegradability,and recycling capabilities.However,PLA is brittle,weak in impact resistance,and low elongation at break,which limits its wide application.Polycaprolactone(PCL)is a biodegradable aliphatic polyester with a flexible molecular chain and has excellent toughness and good ductility,but its mechanical strength is low.The preparation of PCL/PLA materials by blending method can achieve toughening of PLA and strengthening of PCL to obtain materials with good performance.However,how to improve the compatibility of PCL/PLA blends is a problem that researchers have been paying attention to.Poly(lactic acid-co-caprolactone)(PLCL),a random copolymer of caprolactone and lactic acid,has many merits,such as biodegradability and biocompatibility.However,the effect of PLCL as a compatibilizer on the interface compatibilization of the PCL/PLA blend system is not yet known.In this paper,the PCL/PLA porous materials were prepared by the solution blending phase separation method with simple equipment and convenient operation.Firstly,the influence of different weight ratios of PCL/PLA on the micromorphology,compressive mechanical properties and crystallization behavior of porous materials was discussed.Then,PLCL was used as the compatibilizer of the PCL/PLA blend system,and the influence of the compatibilizer PLCL on the structure and properties of the PCL/PLA porous material was discussed.The main work and results are as follows:(1)The PCL/PLA porous materials were prepared by the solution blending and phase separation method,and the influence of the different weight ratio of PCL/PLA on the morphology and performance of the porous material was discussed.First,the PCL and PLA pellets were dissolved by heating in a mixed solvent composed of a good solvent dioxane and non-solvent water,and the PCL/PLA porous materials were obtained after phase separation by lowering the temperature and drying.The solubility space parameters were calculated and used to theoretically predict the morphology,mechanical properties and crystallization behavior of PCL/PLA porous materials.In the scanning electron microscope(SEM)results,the PCL/PLA porous materials in different proportions showed a phase-separated "sea-island" structure.The compressibility of PCL/PLA blends was affected by the type,content and microstructure of the matrix phase and dispersed phase of the material.The compressive modulus and yield stress decreased first and then slightly increased with the increase of PCL content in the blend.Differential scanning calorimeter(DSC)results showed that as the proportion of PCL increased from 0% to 30%,the crystallinity of PLA increased from 46.10% to 51.24%,and after the PCL content exceeded 30%,the crystallinity of PLA began to decrease.The crystallinity of PCL increased with the addition of PLA,and finally maintained a stable value of 78.04%.(2)The PCL/PLA/PLCL porous material was prepared,and the influence of PLCL as a compatibilizer on the compatibilization of PCL/PLA was studied.The influence of PLCL content on the morphology,compressive mechanical properties and crystallization behavior of PCL/PLA porous materials was discussed.The interfacial tension and wetting coefficient were used to theoretically predict the compatibilization effect of PLCL,and then the good compatibilization effect of PLCL was further verified by the results of microscopic morphology and mechanical properties.The SEM results showed that with the addition of PLCL,the PCL/PLA microscopic morphology changed from a "sea-island" structure to a homogeneous porous morphology.Through polarized light microscope(POM),it was found that the dispersed phase of PCL has better dispersibility in the PLA matrix.Both the compressive modulus and the yield stress have increased,with the highest increase of 101% and 97%,respectively.The crystallinity of both PCL phase and PLA phase decreased with the addition of the compatibilizer PLCL.(3)Dopamine(DA)was deposited on the surface of PCL/PLA/PLCL porous material by oxidative polymerization of dopamine(DA)to obtain polydopamine(PDA)modified PDA@PCL/PLA/PLCL porous material.The loading effect of PDA@PCL/PLA/PLCL as a carrier with doxorubicin hydrochloride(DOX)as the target drug was explored.Infrared spectroscopy(FTIR),SEM,X-ray photoelectron spectroscopy(XPS)and X-ray energy spectroscopy(EDS)can all prove that PDA was successfully modified on the surface of PCL/PLA/PLCL porous materials.The surface water contact angle of the modified material was reduced from 120° to 0°,and the hydrophilicity was greatly improved.The drug adsorption capacity of PDA@PCL/PLA/PLCL porous material is 7.17 mg/g,and the encapsulation efficiency is 90.32%.