Electrospining: Optimization of parameters for preparing PDMS/PMMA nanofibers by emulsion electrospinning

Background

With the ever-expanding demand for new materials that must be able to tap into currently untapped potential energy sources and additional functionalities, polymer nanocomposites have recently attracted considerable attention. The electronegativity of most polymers and the impressive flexibility, durability, and multifunctionality of many make them ideal candidates for applications in nanoelectronics and wearable electronics. Nanomaterials are materials with at least one dimension below 100 nanometers, which have a higher effective surface area compared to smooth surfaces. However, the low activity and chemical inertness of polymers have limited the high demand for nanostructured polymer materials. Bulk modification of polymers has attracted much attention in manufacturing, while surface tuning at the micro/nanoscale remains largely unexplored. To obtain nanostructured polymer surfaces, the surface morphology must be modified during the polymer curing process to facilitate fabrication. In the case of casting smooth films on substrates, the subsequent nanostructuring steps can be challenging and are widely limited to physical etching of the surface material using methods such as plasma nanotexturing or lasers.

The main point of this paper

Introduction to electrospinning technology:

Electrospinning is a simple, fast and large-scale method for preparing uniform and continuous one-dimensional nanostructured materials. By using electrostatic forces to transform polymer materials from liquid to fiber state, it has high fiber diameter adjustability and good fiber organization structure control ability

Nanofiber characteristics:

Nanofibers (NFs) have an impressive surface area to volume ratio, allowing more surface charge to be transferred between each contact point while minimizing charge loss due to saturation effects, thereby improving electrical output

Classification of electrospinning methods:

When producing polymer nanofibers, two main electrospinning methods are usually considered: emulsion electrospinning and coaxial electrospinning. Emulsion electrospinning is to emulsify two or more liquids in a solution and then spin them through a spinneret nozzle to obtain a single mixed NF. Coaxial electrospinning layers different materials through a spinneret to produce core-sheath NFs

Application of polydimethylsiloxane (PDMS):

PDMS is one of the most tribo-negative materials in the triboelectric material series, with a charge density of 1.42 W/m^2. Once cured, PDMS is non-toxic, flexible, hydrophobic, chemically and thermally inert, and has good transparency, making it an ideal candidate for wearable electronics applications

Challenges of PDMS:

PDMS is insoluble in many different solvents and once cast, requires curing. Its use is mostly limited to material coatings and polymer films, which reduces the overall gas permeability of the material and is detrimental when the material is used in wearable electronics

Advantages of Electrospinning Polymers:

By electrospinning polymers, nanofiber mats can be created and applied directly to fabric substrates while retaining the breathability of the fabric and all the beneficial properties of PDMS NFs. This also improves the overall electrical properties of the material due to the large increase in surface area to volume ratio.

Optimization of emulsion electrospinning method for preparing PDMS/PMMA superhydrophobic nanofibers: process parameters, performance characterization and application potential

Importance of electrospinning technology:

Electrospinning technology has attracted much attention due to its ability to produce nanostructured polymer films in a scalable one-step process, especially for textile triboelectric nanogenerators (T-TENGs). Nanofibers have a high surface area to volume ratio, allowing more surface charge to be transferred between each contact point, thereby improving the electrical output

Preparation of PDMS/PMMA nanofibers:

Due to chemical or instrumental limitations, some polymer nanofibers can only be synthesized using coaxial or emulsion electrospinning methods. To date, the preparation of PDMS/PMMA nanofibers by electrospinning has been limited to the coaxial method. These nanofibers have been used in the medical field as well as in environmental remediation efforts, such as membranes and filters, and in new-age wearable electronics

Studies on parameter optimization:

There has been no systematic study on the optimization of electrospinning parameters for PDMS/PMMA nanofibers, especially regarding applied voltage, flow rate, and collector distance. In this paper, a PDMS/PMMA copolymer nanofiber was synthesized and characterized by an optimized emulsion electrospinning method

Optimization of preparation conditions:

Through a systematic study of the electrospinning process parameters, superhydrophobic nanofibers with an average diameter of ~199 nm and a contact angle of ~162° were prepared at a supply voltage of 18.5 kV, a tip-collector distance of 10 cm, and a flow rate of 0.2 mL/h

Characteristics of PDMS:

Polydimethylsiloxane (PDMS) is one of the most tribo-negative materials in the triboelectric material family with a charge density of 1.42 W/m^2. After curing, PDMS is non-toxic, flexible, hydrophobic, chemically and thermally inert, and has good transparency, making it an ideal candidate for wearable electronics applications.

Summarize

The synthesis of PDMS/PMMA nanofibers by emulsion electrospinning was explored. The optimized supply voltage was 18.5 kV, the tip-collector distance was 10 cm, and the flow rate was 0.2 mL/h to ensure the lowest possible cross-talk effects. The NFs possessed desirable physical and chemical properties with an average diameter of approximately 199 nm, high surface area, relative uniformity, and superhydrophobicity of approximately 160°, showing inherited properties from both parent polymers, making them ideal candidates for further investigation of their applications in wearable electronics. Preliminary studies on the deposition of NFs onto commercial fabrics were performed using polyethylene. The results showed that while deposition onto this material is a feasible synthetic approach, the adhesion between the two materials requires further investigation.