Polymeric surface
Polymeric materials have widespread application due to their versatile characteristics, cost-effectiveness, and highly tailored production.
However, surface interactions of polymer substrates are an essential area of study in biotechnology, nanotechnology, and in all forms of coating applications.
[1] A polymeric material can be functionalized by the addition of small moieties, oligomers, and even other polymers (grafting copolymers) onto the surface or interface.
Because pre-polymerized chains used in the 'grafting onto' method have a thermodynamically favored conformation in solution (an equilibrium hydrodynamic volume), their adsorption density is self-limiting.
Grafting onto allows a preformed polymer, generally in a "mushroom regime", to adhere to the surface of either a droplet or bead in solution.
Due to the larger volume of the coiled polymer and the steric hindrance this causes, the grafting density is lower for 'onto' in comparison to 'grafting from'.
This grafting technique allows for excellent control over the peptide composition as the bonded chain can be washed without desorption from the polymer.
Most commonly, a thin polymer sheet is rolled through an array of high-voltage electrodes, using the plasma created to functionalize the surface.
The limited penetration depth of such treatment provides vastly improved adhesion while preserving bulk mechanical properties.
Commercially, corona treatment has been used widely for improved dye adhesion before printing text and images on plastic packaging materials.
The hazardous nature of remnant ozone after corona treatment stipulates careful filtration and ventilation during processing, restricting its implementation to applications with strict catalytic filtered systems.
This limitation prevents widespread use within open-line manufacturing processes Several factors influence the efficiency of the flame treatment such as air-to-gas ratio, thermal output, surface distance, and oxidation zone dwell time.
The process begins with production of plasma via ionization either by deposition on monomer mixtures or gaseous carrier ions.
is the ion loss by diffusion, convection, attachment, and recombination Dissipation is generally initiated via direct current (DC), radio frequency (RF), or microwave power.
Flame treatment is a controlled, rapid, cost-effective method of increasing surface energy and wettability of polyolefins and metallic components.
Thermoplastic polyethylene and polypropylene treated with brief oxygen plasma exposure have seen contact angles as low as 22°, and the resulting surface modification can last years with proper packaging.
Flame plasma treatment has become increasingly popular with intravascular devices such as balloon catheters due to the precision and cost-effectiveness demanded in the medical industry.
The modification of inert surfaces of polyolefins, polyesters, and polyamides by grafting functional vinyl monomers has been used to increase hydrophobicity, dye absorption, and polymer adhesion.
The low adhesion and absorption of polyolefins, polyesters, and polyamides is improved by UV-irradiation of an initiator and monomer transferred through the vapor phase to the substrate.
[6] The adverse turbulent flow in microfluidic applications can compound component failure modes due to the increased level of channel interdependency and network complexity.
[7] In industrial corona and plasma processes, cost-efficient and rapid analytical methods are required for confirming adequate surface functionality on a given substrate.
In the case of oxidizing treatments, spectra taken from treated surfaces will indicate the presence of functionalities in carbonyl and hydroxyl regions according to the Infrared spectroscopy correlation table.
These techniques provide characterization at surface depths of 1–10 nanometers, approximately the range of oxidation in plasma and corona treatments.
AFM was developed to overcome the material conduction limitations of electron transmission and scanning microscopy methods (SEM & STM).
The modification of surfaces to keep polymers biologically inert has found wide uses in biomedical applications such as cardiovascular stents and in many skeletal prostheses.
Functionalizing polymer surfaces can inhibit protein adsorption, which may otherwise initiate cellular interrogation upon the implant, a predominant failure mode of medical prostheses.
Narrow biocompatibility requirements within the medical industry have over the past ten years driven surface modification techniques to reach an unprecedented level of accuracy.
The association of other additives, such as thickeners shown in the schematic to the right, with adsorbed polymer material give rise to complex rheological behavior and excellent control over a coating's flow properties.
