All About Polymer Adsorption

Polymers are organic chemical compounds where a single unit is joined through covalent or condensation bonds in a long chain. The number of units, also known as the monomers, can vary from one polymer to another. For example, low-density polyethylene and high-density polyethylene are only made from monomeric ethylene units. However, the number of monomer units is less than the HDPE in the LDPE. Polymers have replaced several materials in the construction and fabrication industry, so every compound is run through a series of steps. One crucial feature that is examined repeatedly is polymer adsorption.

Characteristics of a polymer

Polymers form one of the major groups of organic compounds that have found use in several industries. Even though many types of polymers like polyethylene, Teflon, rubber, nylon, styrene, and more exhibit some general physical and chemical properties. The study of these properties will help you understand the polymer adsorption process easily.

1. Polymers are made with repeated units of monomers that are nothing but different types of organic compounds.
2. Homogeneous polymers are made with similar monomers like polyvinyl chloride polymer, polyethylene, polypropylene, etc. ‘

iii. Heterogeneous polymers have two monomeric units: alkyl ground and an acid.

1. The surfaces of the polymers are almost stable because of the distribution of similar types of compounds throughout.
2. The monomeric units in the polymer chains are held together by weak covalent bonds.
3. When treated specially with other chemicals, polymers can exhibit outstanding chemical resistance, hardness, and durability.

Due to these features, one can easily draw the differences between polymer versus non-polymer adsorption.

What is polymer adsorption?

Adsorption is the process by which charged ions (both cations and anions) or molecules adhere to the surfaces of a substrate. The process can take place in two different ways:

1. Physical adsorption: The molecules or ions adhere to the substrate surface by physical bonds. There will be no chemical interactions between them.
2. Chemical adsorption: In this process, the molecules or ions chemically react with the substrate and form a strong layer that can’t be removed.

In polymer adsorption, different types of polymer solutions are prepared. It is then made to come in contact with a substrate surface. In most cases, a chemical reaction ensures that the bonds between the polymer molecules and the substrate are strong enough to create a permanent coating.

How does polymer adsorption take place?

The methods of polymeric adsorption might vary according to the type of polymer you are using and the substrate. All of them have three major steps, which have been listed below.

1. First, a polymeric solution is taken in bulk. It is then transferred onto the surface. This process is known as diffusion.
2. After this, the polymer molecules attach to the substrate surface in hydrophobic adsorption and electrostatic adsorption. This process is termed attachment.

iii. In the final stage, also known as the rearrangement, the polymer molecules rearrange themselves to form a strong bond with the substrate.

Factors affecting the polymer adsorption

The quality and speed of the polymeric adsorption process depend on many factors. These are:

1. Solvent quality: The solvent quality needs to be high so that the interaction of the polymer molecules and the substrate is weak. The weaker the interaction, the better will be the adsorption.
2. The molecular weight of the polymers: Since the high molecular weight of the polymers improves their longevity, it’s evident that these compounds can adhere easily, regardless of the methods of polymer adsorption.

iii. pH: If the substrate surface has higher pH and the polymer is also basic, it will cause repulsion, and because of that, adsorption can’t be carried out.

1. Polymeric density: Higher the polymeric density, the better will be the adsorption rate, as it helps in easier attachment with the substrate surface.
2. Surface to volume ratio: If the volume of the polymer is more while the substrate surface area is less, the adsorption rate will also be lower.
3. Temperature and pressure: Maximum adsorption rate can be achieved only when the temperature is low but the pressure is high.

Advantages of polymer adsorption

One of the major differences between polymer vs non-polymer adsorption is that polymeric adsorption has a lot of advantages in real-time. Some of the benefits have been listed in the below section:

1. When the implants are placed inside the body, protein adsorbs on their surfaces, leading to blood clots, corrosion, etc. As this can be detrimental to health, all the implants are coated with a polymer material whose adsorption property with the protein is low.
2. When the concrete surfaces are kept naked, they get damaged due to natural elements like sun and rain. This is why they are coated with polymers like epoxy or resins. Due to the adsorption property, ions and molecules adhere to the polymer surface rather than the concrete.

iii. Several polymer composites with low adsorption properties are used in the fabrication and construction industry due to their ability to resist corrosion from chemicals.

Conclusion

Polymers are organic compounds made from monomeric units. They are held together via a weak covalent bond, which is one of the prime reasons for the polymer adsorption phenomenon. It means that different types of ions and molecules can easily adhere to the concerned polymer’s surfaces. For example, when the epoxy resin, a type of polymer, is applied on a surface, dust, impurities, and other charged ions deposit themselves on the resin surface. Since it has low adsorption properties, you can clean them off easily, and no chemical reaction can take place.