Polymer adsorption

Adsorption is the adhesion of ions or molecules onto the surface of another phase.Adsorption may occur via physisorption and chemisorption. Ions and molecules can adsorb to many types of surfaces including polymer surfaces. A polymer is a large molecule composed of repeating subunits bound together by covalent bonds. The adsorption of ions and molecules to polymer surfaces plays a role in many applications including: biomedical, structural, and coatings.

Polymer surfaces differ from non-polymer surfaces in that the subunits that make up the surface are covalently bonded to one another. Non-polymer surfaces can be bound by ionic bonds, metallic bonds or intermolecular forces (IMFs). In a two component system, non-polymer surfaces form when a positive net amount of energy is required to break self-interactions and form non-self-interactions. Therefore, the energy of mixing is positive. This amount of energy, as described by interfacial tension, varies for different combinations of materials. However, with polymer surfaces, the subunits are covalently bonded together and the bulk phase of the solid surface does not allow for surface tension to be measured directly. The intermolecular forces between the large polymer molecules are difficult to calculate and cannot be determined as easily as non-polymer surface molecular interactions.[2] The covalently bonded subunits form a surface with differing properties as compared to non-polymer surfaces. Some examples of polymer surfaces include: polyvinyl chloride (PVC), nylon, polyethylene (PE), and polypropylene (PP). Polymer surfaces have been analyzed using a variety of techniques, including: scanning electron microscopy, scanning tunneling microscopy, and infrared spectroscopy.

Different polymer surfaces have different side chains on their monomers that can become charged due to the adsorption or dissociation of adsorbates. For example, polystyrene sulfonate has monomers containing negatively charged side chains which can adsorb positively charged adsorbates. Polystyrene sulfonate will adsorb more positively charged adsorbate than negatively charged. Conversely, for a polymer that contains positively charged side chains, such as poly(diallyldimethylammonium chloride), negatively charged adsorbates will be strongly attracted.

Structural

Advanced polymer composites:Advanced polymer composites are used in the strengthening and rehabilitation of old structures. These advanced composites can be made using many different methods including prepreg, resin, infusion, filament winding and pultrusion. Advanced polymer composites are used in many airplane structures and their largest market is in aerospace and defense.

Fiber reinforced polymers:Fiber-reinforced polymers (FRP) are commonly used by civil engineers in their structures. FRPs respond linear-elastically to axial stress, making them a great material to hold a load. FRPs are usually in a laminate formation with each lamina having unidirectional fibers, typically carbon or glass, embedded within a layer of light polymer matrix material. FRPs have great resistance against environmental exposure and great durability.

Polytetrafluoroethylene:Polytetrafluoroethylene (PTFE) is a polymer used in many applications including non-stick coatings, beauty products, and lubricants. PTFE is a hydrophobic molecule composed of carbon and fluorine. Carbon-fluorine bonds cause PTFE to be a low-friction material, conducive in high temperature environments and resistant to stress cracking. These properties cause PTFE to be non-reactive and used in a wide array of applications.

Polymer adsorption in porous media:Physical adsorption and mechanical entrapment are two major causes of polymer retention in porous media. Low polymer retention in the reservoir is essential to the success of a polymer EOR operation.