The key difference between linear and branched polymers is that linear polymers have a linear structure without any branches whereas branched polymers have a branched structure.
Polymers are giant molecules having a very large number of repeating units attached to each other via covalent chemical bonds. Moreover, the process of formation of a polymer is “polymerization”. Thus, the repeating unit gives the structure of monomers that involved in the polymerization process. Accordingly, we can categorize polymers into three sub-categories according to the structure of the polymer; linear, branched and network polymers.
CONTENTS
1. Overview and Key Difference
2. What are Linear Polymers
3. What are Branched Polymers
4. Side by Side Comparison – Linear vs Branched Polymers in Tabular Form
5. Summary
What are Linear Polymers?
Linear polymers are macromolecules containing a large number of repeating units or monomers that attach to each other forming a straight linear structure. Hence, these polymers contain a single continuous chain. The backbone of this polymer chain consists of the atoms that bind with each other covalently to form the chain structure. Therefore, if these atoms are of the same type, then they are linear homopolymers whereas if the atoms are different from each other, then the polymer is a linear heteropolymer.
Figure 01: Tacticity in Polymers (top to bottom; atactic, syndiotactic and isotactic forms)
Furthermore, there can be side groups or pendant groups in these polymer structures but no branches (side chains). According to the arrangement of the pendant groups, there are three forms of linear polymers as isotactic, atactic and syndiotactic. Together, we call it the tacticity of the polymer. Isotactic polymers have pendant groups on the same side of the polymer chain; syndiotactic forms have the pendant groups in an alternating pattern whereas atactic polymers have pendant groups in a random manner.
What are Branched Polymers?
Branched polymers are macromolecules containing a large number of repeating units arranged in a branched structure. The properties of these polymers mainly depend on the degree of branching. The side chains can be either short chains or long chains. There are different types of branched polymers as graft polymers, comb polymers, brush polymers, etc. depending on the structure.
Figure 02: A Polymer Branch
Some examples of natural branched polymers include starch and glycogen while synthetic branched polymers include low density polyethene. These are often amorphous since they cannot pack tightly in a regular pattern.
What is the Difference Between Linear and Branched Polymers?
Linear polymers are macromolecules containing a large number of repeating units or monomers that attach to each other forming a straight linear structure while branched polymers are macromolecules containing a large number of repeating units arranged in a branched structure. Hence the key difference between linear and branched polymers is that linear polymers have a linear structure without any branches whereas branched polymers have a branched structure.
Also, as linear polymers have simple structures, they pack tightly but, since branched polymers have complex structures, they pack loosely. Therefore, based on this, we can identify a difference between linear and branched polymers. That is; the density of linear polymers is high in comparison to that of branched polymers. As another important difference between linear and branched polymers, we can denote that the melting and boiling points of linear polymers are higher to that of branched polymers.
The below infographic on difference between linear and branched polymers tabulates more differences between both.
Summary – Linear vs Branched Polymers
Polymers are macromolecules. There are three types as linear, branched and network polymers. The key difference between linear and branched polymers is that linear polymers have a linear structure without any branches whereas branched polymers have a branched structure.
Reference:
1. “Branching (Polymer Chemistry).” Wikipedia, Wikimedia Foundation, 2 Nov. 2018. Available here
2. Carr, Kevin. “Difference Between Linear & Branched Polymers.” Sciencing, 25 May 2018. Available here
Image Courtesy:
1.”Tacticidad de polimeros” (Public Domain) via Commons Wikimedia
2.”Polymer Branch”By Ilmari Karonen – Own work (Public Domain) via Commons Wikimedia