Molecular Forces And Chemical Bonding In Polymers Pdf
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When many molecules of a simple compound join together, the product is termed a polymer and the process polymerization. The simple compounds whose molecules join together to form the polymers are called monomers. The polymer is a chain of atoms, providing a backbone, to which atoms or groups of atoms are joined.
Teacher Notes: Chemical Bonds and Forces
Properties like melting and boiling points are a measure of how strong the attractive forces are between individual atoms or molecules. It all flows from this general principle: as bonds become more polarized, the charges on the atoms become greater, which leads to greater intermolecular attractions, which leads to higher boiling points. Now available — Download this awesome free 3-page handout on how to solve common boiling point problems. With 10 examples of solved problems! Hydrogen bonding occurs in molecules containing the highly electronegative elements F, O, or N directly bound to hydrogen. Since H has an electronegativity of 2. However, the bond to hydrogen will still be polarized and possess a dipole.
Intramolecular bonds are the bonds that hold atoms to atoms and make compounds. There are 3 types of intramolecular bonds: covalent, ionic, and metallic. Ionic Bond: a bond that holds atoms together in a compound; the electrostatic attraction between charged ions. Ionic compounds are formed between atoms that differ significantly in electronegativity. The electron s involved in bonding is are transferred from the less electronegative to the more electronegative atom s forming ions. Metallic Bond: a bond resulting from the attraction between positive ions and surrounding mobile electrons. Intermolecular forces are the forces that attract molecules or particles to like or unlike molecules or particles.
In molecular physics , the Van der Waals force , named after Dutch physicist Johannes Diderik van der Waals , is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds , these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The Van der Waals force quickly vanishes at longer distances between interacting molecules. Van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry , structural biology , polymer science , nanotechnology , surface science , and condensed matter physics. It also underlies many properties of organic compounds and molecular solids , including their solubility in polar and non-polar media. If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the Van der Waals contact distance ; this phenomenon results from the mutual repulsion between the atoms' electron clouds.
Physical Structure of Polymers
Figure 1. Addition reaction mechanism showing styrene monomer polymerizing into polystyrene. Figure 2. Condensation reaction mechanism showing the polymerization of a polyamide from a diacid and a diamine. Figure 3. Polymers contain a wide variety of functional groups, responsible for the diversity in physical properties. Figure 4.
Carbon forms a huge variety of both synthetic and natural molecules. A 'family' of organic compounds with the same functional group is called a homologous series. The properties of organic molecules depend on their structure being made of simple molecules. The atoms in an individual molecule are joined together by strong covalent bonds. The intermolecular forces between molecules are weaker. The intermolecular forces vary between molecules, so different organic compounds have different melting points and boiling points. Simple molecular substances have no overall charge, and their electrons are not free to move.
Table of Contents Structure Williams Home. Molecular interactions are attractive or repulsive forces between molecules and between non-bonded atoms. Molecular interactions are important in all aspects of chemistry, biochemistry and biophysics, including protein folding, drug design, pathogen detection, material science, sensors, gecko feet, nanotechnology, separations, and origins of life.
Molecules cohere even though their ability to form chemical bonds has been satisfied. The evidence for the existence of these weak intermolecular forces is the fact that gases can be liquefied, that ordinary liquids exist and need a considerable input of energy for vaporization to a gas of independent molecules, and that many molecular compounds occur as solids. The role of weak intermolecular forces in the properties of gases was first examined theoretically by the Dutch scientist Johannes van der Waals , and the term van der Waals forces is used synonymously with intermolecular forces. Under certain conditions, weakly bonded clusters of molecules such as an argon atom in association with a hydrogen chloride molecule can exist; such delicately bonded species are called van der Waals molecules.
Intramolecular forces are the forces that hold atoms together within a molecule. They were the first to provide As many as 10 8 kinds of small organic molecules are known to exist in the chemical space , while such a large space contains many target molecules. Covalent bonds are severed during fracture The common examples are nylon, dacron, and silk.
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