Difference Between Monomeric and Polymeric Vinyl

Main Difference – Monomeric vs Polymeric Vinyl

The term vinyl refers to a functional group composed of two carbon atoms bonded with a double bond. It is similar to the ethylene structure which lacks one hydrogen atom. The chemical formula of vinyl group is given as –CH=CH₂. Monomers containing vinyl groups can be linked to form vinyl polymers. The main difference between monomeric and polymeric vinyl is that monomeric vinyl has a double bond between two carbon atoms whereas polymeric vinyl has no double bonds in their carbon backbone.

Key Areas Covered

1. What is Monomeric Vinyl
     – Definition, Properties, Examples
2. What is Polymeric Vinyl
     – Definition, Properties, Examples
3. What is the difference between Monomeric and Polymeric Vinyl
     – Comparison of Key Differences

Key Terms: Chain Growth Polymerization, Ethylene, Monomeric Vinyl, Polymeric Vinyl, Vinyl 

What is Monomeric Vinyl

Monomeric vinyl is composed of two carbon atoms bonded with each other through a double bond and three hydrogen atoms attached to those carbon atoms. Two hydrogen atoms are attached to the same carbon atom and the other hydrogen atom is attached to the other carbon atom along with a different atom or a group such as chlorine (then it is called vinyl chloride), benzene (then it is styrene), hydrogen (ethylene), etc.  A vinyl polymer is built from a monomeric vinyl.

Figure 1: Vinyl Group (blue color)

Monomeric vinyl is able to undergo chain growth polymerization due to its unsaturation. In the presence of an initiator, the double bond can be broken and the monomer can be made active to attach with another monomer. This leads to the formation of a polymer chain.

What is Polymeric Vinyl

Polymeric vinyl is the repeating unit of a vinyl polymer. It is located in the carbon backbone of the polymer. The carbon backbone is made out of carbon atoms bonded covalently with each other. There are no double bonds found in the carbon backbone since the double bond is broken in order to make the monomer reactive in the polymerization process. If not, the monomer cannot attach with other monomers.

Every vinyl polymer has a repeating unit. This repeating unit is repeated all over the polymer chain. Vinyl polymer of vinyl chloride is called polyvinyl chloride.

Figure 2: Polystyrene

When representing the polymeric vinyl symbolically, the symbol is included inside the brackets and outside the brackets; letter “n” is used to show that the repeating unit is repeated “n” times throughout the polymer. This is to show that the repeating unit is repeated in the polymer for n times. This n is a very large number because polymers are composed of a large number of repeating units. The side bonds of the polymeric vinyl should be shown in such a manner that they cross the brackets. That is to show that it is continuous.

Figure: Polymeric Vinyl of Styrene

Although there are no double bonds in between the carbon atoms which make the carbon backbone, double bonds may be present in the side groups. For example, polyvinyl sulfate has double bonds between S and O atoms in the side group.

Difference Between Monomeric and Polymeric Vinyl

Definition

Monomeric Vinyl: Monomeric vinyl is the monomer from which a particular vinyl polymer is built.

Polymeric Vinyl: Polymeric vinyl is the repeating unit of a vinyl polymer.

Presence of Double Bonds in Carbon Backbone

Monomeric Vinyl: Monomeric vinyl has a double bond between two carbon atoms.

Polymeric Vinyl: Polymeric vinyl has no double bond between two carbon atoms.

Hybridization

Monomeric Vinyl: Monomeric vinyl has a sp² hybridized carbon.

Polymeric Vinyl: Polymeric carbon has a sp³ hybridized carbon.

Chain Length

Monomeric Vinyl: Monomeric vinyls are single molecules and do not give any details about the polymer chains it can form.

Polymeric Vinyl: Polymeric vinyl gives details on the chain length.

Repeating Units

Monomeric Vinyl: Monomeric vinyl is not a repeating unit.

Polymeric Vinyl: Polymeric vinyl represents a repeating unit.

Unsaturation

Monomeric Vinyl: Unsaturation is present in monomeric vinyl.

Polymeric Vinyl: Unsaturation is absent between two carbon atoms but can be present in side groups.

Conclusion

The main difference between monomeric vinyl and polymeric vinyl is that monomeric vinyl has a double bond between two carbon atoms whereas polymeric vinyl has no double bonds in their carbon backbone.

References:

1. “Vinyl Polymers.” The Polymer Science Learning Center. N.p., n.d. Web. Available here. 23 June 2017. 
2. “Polyvinyl chloride (PVC).” Encyclopædia Britannica. Encyclopædia Britannica, inc., 22 Apr. 2016. Web. Available here. 23 June 2017. 

Image Courtesy:

1. “Vinyl Group General Structure” By Jü – Own work (Public Domain) via Commons Wikimedia 
2. “Polystyrene” (CC BY-SA 3.0) via Commons Wikimedia
3. “Polystyrene linear” By Leyo – Own work (Public Domain) via Commons Wikimedia