Liquid–liquid interfacial slip induced layer instability in a thin polymer bilayer

From spherical compartments to polymer films: exploiting vesicle fusion to generate solid supported thin polymer membranes

Solid supported polymer membranes as scaffold for the insertion of functional biomolecules provide the basis for mimicking natural membranes. They also provide the means for unraveling biomolecule-membrane interactions and engineering platforms for biosensing. Vesicle fusion is an established procedure to obtain solid supported lipid bilayers but the more robust polymer vesicles tend to resist fusion and planar membranes rarely form. Here, we build on vesicle fusion to develop a refined and efficient way to produce solid supported membranes based on poly(dimethylsiloxane)-poly(2-methyl-2-oxazoline) (PMOXA-b-PDMS-b-PMOXA) amphiphilic triblock copolymers. We first create thiol-bearing polymer vesicles (polymersomes) and anchor them on a gold substrate. An osmotic shock then provokes polymersome rupture and drives planar film formation. Prerequisite for a uniform amphiphilic planar membrane is the proper combination of immobilized polymersomes and osmotic shock conditions. Thus, we explored the impact of the hydrophobic PDMS block length of the polymersome on the formation and the characteristics of the resulting solid supported polymer assemblies by quarz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM) and spectroscopic ellipsometry (SE). When the PDMS block is short enough, attached polymersomes restructure in response to osmotic shock, resulting in a uniform planar membrane. Our approach to rapidly form planar polymer membranes by vesicle fusion brings many advantages to the development of synthetic planar membranes for bio-sensing and biotechnological applications.

Three-dimensional viscoelastic numerical analysis of the effects of gas flow on L-profiled polymers in gas-assisted coextrusion

In this study, polymer gas-assisted coextrusion experiments were performed. The influence of a traditional coextrusion flow zone on the gas groove and the relationship between the gas pressure and the melt flow rate were studied. To determine the effects of the gas flow on gas-assisted coextrusion, a three-dimensional simulation was developed in which the gas layer was considered as an independent flow zone. The influence of the gas pressure, gas layer thickness and melt flow rate on the melts’ profile and the deflection deformation degree (DDD) was studied, and the relationship between the gas pressure, gas layer thickness and melt flow rate was obtained. The numerical results indicated that a traditional coextrusion flow zone in front of a gas-assisted coextrusion flow zone could allow products to avoid a gas groove. The quality of the products could be improved by decreasing the gas pressure and gas layer thickness or increasing the melt flow rate. Additionally, the minimum gas pressure decreased as the gas layer thickness increased and increased as the melt flow rate increased. The numerical results were in good agreement with the experimental results, despite a slight quantitative error. Therefore, reasonably controlling the gas flow condition is key in practical applications of gas-assisted coextrusion, and the effects of the gas layer should be considered in gas-assisted coextrusion simulations.

Dewetting of a pre-patterned thin polymer bilayer: influence of the instability mode

Different surface structures are fabricated via adjusting the instability mode from a thermodynamically controlled one to a kinetically controlled one.

Enhanced Self-Organized Dewetting of Ultrathin Polymer Blend Film for Large-Area Fabrication of SERS Substrate

We study the enhanced dewetting of ultrathin Polystyrene (PS)/Poly (methyl methacrylate) (PMMA) blend films in a mixed solution, and reveal the dewetting can act as a simple and effective method to fabricate large-area surface-enhanced Raman scattering (SERS) substrate. A bilayer structure consisting of under PMMA layer and upper PS layer forms due to vertical phase separation of immiscible PS/PMMA during the spin-coating process. The thicker layer of the bilayer structure dominates the dewetting structures of PS/PMMA blend films. The diameter and diameter distribution of droplets, and the average separation spacing between the droplets can be precisely controlled via the change of blend ratio and film thickness. The dewetting structure of 8 nm PS/PMMA (1:1 wt%) blend film is proved to successfully fabricate large-area (3.5 cm × 3.5 cm) universal SERS substrate via deposited a silver layer on the dewetting structure. The SERS substrate shows good SERS-signal reproducibility (RSD < 7.2%) and high enhancement factor (2.5 × 10⁷). The enhanced dewetting of polymer blend films broadens the application of dewetting of polymer films, especially in the nanotechnology, and may open a new approach for the fabrication of large-area SERS substrate to promote the application of SERS substrate in the rapid sensitive detection of trace molecules.