Question

How does a condensation polymer differ from an addition polymer? Give an example of each.

Short answer

Condensation polymers are formed from monomers reacting together with the elimination of a small molecule, usually water, and involve reactions between functional groups like alcohols, carboxylic acids, or amines. An example is polyester formed from the reaction between a dicarboxylic acid and a diol. Addition polymers are formed by the addition reaction of unsaturated monomers containing carbon-carbon double bonds, with no elimination of small molecules. An example of an addition polymer is polyethylene, formed by the polymerization of ethylene.

Step-by-step solution

Define condensation polymers and addition polymers

Condensation polymers are formed from monomers reacting together with the elimination of a small molecule, usually water. Addition polymers are formed by the addition reaction of unsaturated monomers without the elimination of any molecule.

Explain the formation mechanism of condensation polymers

The formation of condensation polymers involves reactions between functional groups present on the monomers, such as alcohol, carboxylic acid, or amine groups. During the polymerization process, a covalent bond is formed between the two monomers, and a small molecule, such as water or methanol, is eliminated. This process continues, linking the monomers together into a polymer chain. Example: Polyester is a type of condensation polymer formed by the reaction between a dicarboxylic acid (e.g., terephthalic acid) and a diol (e.g., ethylene glycol). The carboxylic acid and alcohol groups on the monomers react to form ester linkages, eliminating water molecules in the process. \[ HOOC-R_1-COOH + HO-R_2-OH \rightarrow [-OC-R_1-COO-R_2-O-]_n + (n-1)H_2O \]

Explain the formation mechanism of addition polymers

Addition polymers are formed by the polymerization of unsaturated monomers containing carbon-carbon double bonds. During the polymerization process, the double bond of the monomer is broken, and new carbon-carbon single bonds are formed with other monomers. In contrast to condensation polymerization, there is no elimination of any small molecules during the formation of addition polymers. Example: Polyethylene is an example of an addition polymer formed by the polymerization of ethylene (ethene), which is an unsaturated hydrocarbon with a carbon-carbon double bond. \[ nCH_2=CH_2 \rightarrow [-CH_2-CH_2-]_n \]

Summary

In summary, condensation polymers are formed by reactions between monomers with the elimination of a small molecule, usually water, while addition polymers are formed by the addition reaction of unsaturated monomers with no elimination of small molecules. Examples of a condensation polymer and an addition polymer are polyester and polyethylene, respectively.

Key concepts

Polymerization Process

Polymerization is a chemical process that connects small molecules known as monomers into long, repeating chains to form polymers. There are several methods by which polymers can be synthesized, but the two primary types are condensation polymerization and addition polymerization.

In condensation polymerization, monomers react and join together with the simultaneous loss of small molecules like water or methanol. This is well represented in the production of polyester, where the elimination of water is part of forming the ester linkage that gives the polyester its structure. A simple representation of this reaction is as such: \[ HOOC-R_1-COOH + HO-R_2-OH \rightarrow [-OC-R_1-COO-R_2-O-]_n + (n-1)H_2O \].

On the other hand, in addition polymerization, unsaturated monomers (typically containing double bonds) link up without the loss of any other atoms or molecules. The monomers simply add to one another in a chain-growth fashion, as seen in the polymerization of ethylene to form polyethylene, showcased by the equation: \[ nCH_2=CH_2 \rightarrow [-CH_2-CH_2-]_n \].

Both types of polymerization are crucial in the production of various synthetic materials that we use in everyday life.

Monomers and Polymers

Understanding the relationship between monomers and polymers is central to grasping the basics of polymer science. Monomers are small, simple molecules that serve as the building blocks of polymers. They can join with other monomers, often in repeated sequences, to form complex and larger molecules known as polymers.

Take for instance, the monomers of ethylene glycol and terephthalic acid in the production of polyester. These monomers react through their functional groups – an alcohol and a carboxylic acid respectively – to form polyester chains while releasing water.

Similarly, the monomer ethylene undergoes addition polymerization to become polyethylene. The carbon-carbon double bond in ethylene is key as it opens up to link with other ethylene molecules, forming the long chains characteristic of polymers.

Essentially, monomers are the alphabets that make up the words (polymers), and the polymerization process is like forming sentences from these words to create a meaningful narrative – in this case, materials with diverse properties and applications.

Chemical Structure of Polymers

The chemical structure of polymers determines their properties and functions. Polymers consist of long chains of atoms, primarily carbon, hydrogen, and sometimes other elements like oxygen, nitrogen, and sulfur. The arrangement of these atoms in the chain, the type of monomers involved, and the nature of the bonds connecting these monomers define the polymer’s characteristics.

Condensation polymers such as polyesters have a characteristic structure with ester linkages. The repeated unit in the chain often contains a part from both reacting monomers interlinked by an ester bond, as shown in the reaction for polyester synthesis. This arrangement imparts properties like strength and flexibility to the material.

For addition polymers like polyethylene, the chains consist of carbon atoms linked by single bonds, and the simplicity of the repeating -CH2- units imparts properties like toughness and plasticity. These polymers often exhibit high resistance to chemicals and electrical insulation properties due to their saturation and the absence of reactive double bonds.

A polymer's molecular weight, degree of branching, and cross-linking also play crucial roles in determining its mechanical strength, elasticity, and other physical properties.