Ailin Gao

Facile preparation of patterned petal-like PLA surfaces with tunable water micro-droplet adhesion properties based on stereo-complex co-crystallization from non-solvent induced phase separation processes

A facile method to prepare rose petal-like quasi-superhydrophobic poly(lactide) (PLA) membrane surfaces with tunable water droplet adhesion properties based on the stereo-complex co-crystallization of PLAs via non-solvent induced phase separation processes is reported. The co-crystallization of the D- and L-enantiomer of PLA on the bottom surfaces contacting the base glass has led to the formation of hierarchical microstructures containing half-developed to well-developed micrometer-scale papilla or spheres and nanometer-scale folds depending on the thickness of the primary membranes. The bottom surfaces of thinner PLA membranes with primary thicknesses of 100–200 micrometers containing half-developed smaller microspheres and a wider gap space could firmly pin water droplets even upside down with an extremely high adhesion force of about 118–132 μN with water drop breakup, while the bottom surfaces of thicker PLA membranes with a primary thickness of 300–500 micrometers containing larger well developed microspheres with narrower gap space could allow the rolling of water droplets with lower adhesion forces of 74–99 μN. Strategies were developed to create patterned PLA quasi-superhydrophobic membrane surfaces with zoned water droplet adhesion properties for controllable micro-droplet transportation and potentially image encrypting applications.

Investigation of the heat resistance, wettability and hemocompatibility of a polylactide membrane via surface crosslinking induced crystallization

Polylactide (PLA) has attracted much attention as a sustainable and environmentally friendly material. However, the poor heat resistance restricts its potential application as a porous membrane. Herein, a PLA membrane with excellent heat resistance, hydrophilicity and hemocompatibility was developed via a surface crosslinking induced crystallization strategy, which involved two key reactions, namely, copolymerization of N-vinyl-2-pyrrolidone (NVP) and triethoxyvinylsilane (VTES) and the subsequent hydrolysis condensation on the surface of the PLA membrane. Attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were applied to analyse the surface chemistry and crystallization evolution, which confirmed that the P(VP-VTES) copolymer was hydrothermally crosslinked and induced the crystallization of the PLA membrane. The surface crystallization significantly improved the heat resistance and preserved membrane morphology, which was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and the dimension shrinkage. The modified PLA membrane with χc ∼ 37% remained almost unchanged dimensions and morphology even after annealing at 100 °C for 5 min. The improved hemocompatibility was verified by the prolonged clotting time and recalcification time, which was consistent with the enhanced hydrophilicity. All results showed that surface crosslinking induced crystallization strategy simultaneously improved the heat resistance and hemocompatibility, indicating a promising method for preparing robust and compatible PLA membranes.

Tunable adhesion of superoleophilic/superhydrophobic poly (lactic acid) membrane for controlled-release of oil soluble drugs

Superhydrophobic membranes with tunable adhesion have attracted intense interests for various engineering applications. In this work, superhydrophobic sustainable poly (lactic acid) (PLA) porous membrane with tunable adhesive force from 101μN to 29μN was successfully fabricated via one-step phase separation method. The incorporation of Perfluoro-1-decene (PFD) into the PLLA/PDLA membrane via the in situ polymerization can facilely tune the PLLA/PDLA stereocomplex crystallization during phase inversion, which consequently caused the unique morphology blooming evolution from bud to full-blown state. The resulted membrane showed tunable pore size, porosity, surface area, surface roughness and superhydrophobicity, which enabled the membrane with controlled-release of oil soluble drugs.

Dual layer hollow fiber PVDF ultra-filtration membranes containing Ag nano-particle loaded zeolite with longer term anti-bacterial capacity in salt water

Dual layer polyvinylidene fluoride (PVDF), antibacterial, hollow fiber, ultra-filtration composite membranes with antibacterial particles (silver (Ag) nano-particles loaded zeolite (Z-Ag)) in the outer layer were prepared with high water flux and desired pore sizes. The amounts of Ag(+) released from the composite membranes, freshly made and stored in water and salt solution, were measured. The result indicated that dual layer PVDF antibacterial hollow fiber containing Z-Ag (M-1-Ag) still possessed the ability of continuous release of Ag(+) even after exposure to water with high ionic content, showing a longer term resistance to bacterial adhesion and antibacterial activity than membrane doped with Z-Ag(+) (M-1). Results from an anti-adhesion and bacteria killing test with Escherichia coli supported that the antibacterial efficiency of dual hollow fiber PVDF membranes with Z-Ag was much higher than those with Z-Ag(+) after long time storage in water or exposure to phosphate buffered saline (PBS) solution. This novel hollow fiber membrane may find applications in constructing sea water pretreatment devices with long term antifouling capability for the desalination processes.