Study On The Controllable Preparation And Properties Of The Poly(lactic Acid)/MOFs Composite Films With Multiple Forms

Polymer/nanoparticle composite films show great application potential in the fields of oil-water separation,gas adsorption,photocatalytic degradation as well as biomedical because of their combination of the advantages of polymers and nanoparticles.The metal-organic frameworks（MOFs）have the potential to regulate the morphology and structure of polymers due to its unique properties,such like the porous structure,the large specific surface area and the rich organic groups.In our study,nanoscale MOFs are introduced into the polylactic acid（PLA）matrix to fabricate PLA/MOFs films with unique structure and function.The structure and properties of the composite films are investigated.The main research contents and conclusions are as follows:MOFs with Zn-O-Zn dinuclear units and pyridine-2,5-dicarboxylate linkers（MPD）is synthesized by simple process.The PLA/MPD composite films are prepared by solution blending method.The crystallization behavior,mechanical properties and thermal properties of the composite film are investigated,respectively.The results show that MPD has good dispersibility in PLA matrix.The improvement of crystallization performance enhances the mechanical properties of PLA and increases the initial degradation temperature T_10%.Compared with the pure PLA,the tensile strength,storage modulus and T_g at 40°C of PM1 increase from 40 MPa,1507 MPa and 66.2°C to 56 MPa,3425 MPa and 77.9°C,respectively.The T_10%.of PLA/MPD composite films can be increased by 21°C.Zeolitic imidazolate-8（ZIF-8）is introduced into PLA to fabricate PLA/ZIF-8electrospinning films.It is shown that changing the ZIF-8 content can regulate fiber diameter and surface roughness.After adding a small amount of ZIF-8,the crystallinity of PLA/ZIF-8 is slightly increased,and the crystallization rate is accelerated.When the amount of ZIF-8 is larger than 0.5 wt%,the crystallinity of PLA/ZIF-8 is significantly decreased.Compared with the pure PLA fiber film,the tensile strength and elongation at break of PZD0.5 increase from 2.77 MPa and57.89%to 5.02 MPa and 88.81%,respectively.It takes 2 seconds for the paraffin droplets spread on the pure PLA fiber film.After adding 1.5 wt%ZIF-8,it takes no more than 0.3 seconds for the paraffin droplets spread on the film.Higher oil wettability improves the oil-water separation efficiency of the PLA/ZIF-8 films.The electrospinning parameters are further adjusted to fabricate the PLA/ZIF-8porous fiber film by phase separation.It is shown that changing the ZIF-8 content can successfully control the diameter and porous structure of the fiber when the preparation conditions are constant.The average pore size,pore area fraction and pores perimeter increase from 0.018μm²,20.7%and 0.53μm for pure PLA fiber to0.080μm²,35.7%and 1.09μm for PLA/ZIF-8 fiber with 2 wt%ZIF-8,respectively.Compared with the pure PLA,in presence of 2 wt%ZIF-8,the tensile strength and elongation at break of PLA/ZIF-8 film increase by 1.6 MPa and 43.9%,respectively.Furthermore,the PM2.5 removal efficiency and adsorption capacity increase from85.49%and 19.5%to 94.61%and 35.5%,respectively.The PLA/ZIF-8 porous films also show low pressure drops（<50 Pa）and regeneration ability.ZIF-8 nanoparticles are loaded on the surface of graphene oxide（GO）by in-situ growth method to form a ZIF-8@GO hybrid,which is then introduced into PLA electrospun films.The morphology and surface particle content of PLA/ZIF@GO fibre can be controlled by changing the content of ZIF@GO.Compared with the pure PLA fibre film,when the ZIF-8@GO addition amount is 1.0 wt%,the tensile strength and the elongation at break of the composite electrospun film increase from 2.77 MPa and 58%to 6.17 MPa and 87%,respectively.The addition of ZIF@GO significantly increases the hydrophilicity of the PLA/ZIF-8@GO electrospun films.Under the dual action of by adsorption and photocatalytic degradation,the final removal efficiency of methylene blue in water of the PLA/ZIF@GO electrospun film with 3 wt%ZIF-8@GO is 93.2%,which is 77.0%higher than that of pure PLA fibre film.ZIF-8 nanoparticles are utilized as a second component to fabricate the honeycomb-structured PLA film via water droplet templating method.Utilizing the unique structure and properties of ZIF-8,Pickering emulsification is formed during the condensation of water droplets to regulate water droplets and solvents.The regular honeycomb structured films are prepared successfully.The effects of temperature,humidity,PLA concentration and ZIF-8 content on the morphology of porous film are studied.The optimum preparation conditions are found to be 35°C,85%humidity,5mg/m L PLA concentration and 0.5 wt%ZIF-8 concentration.The axon length of the nerve on the PLA/ZIF-8 honeycomb porous film（198.4±11.5μm）is significantly higher than that on the PLA flat film（161.1±10.2μm）.DRG implants are also growth better on the PLA/ZIF-8 honeycomb porous film than on the PLA flat film.