Final answer:
Kevlar and Kodel fibers owe their stiffness to strong hydrogen bonds and aromatic stacking in their molecular structures, unlike nylon fibers which lack this level of structural order and rigidity.
Step-by-step explanation:
Kevlar and Kodel fibers are stiff and resistant to forming creases compared to nylon fibers because they have a more linear molecular structure, which allows for stronger intermolecular interactions.
The structural reason for the stiffness of Kevlar and Kodel fibers, as compared to nylon fibers, is that Kevlar and Kodel have a more linear molecular structure (option c). This means that the polymer chains in Kevlar and Kodel are aligned in a straighter, more organized manner. This arrangement allows for stronger intermolecular interactions, such as hydrogen bonding and aromatic stacking, resulting in increased stiffness and resistance to forming creases.
The stiffness of Kevlar and Kodel fibers compared to nylon fibers can be attributed to the strong hydrogen bonding between polymer chains. In the Kevlar structure, this occurs between the carbonyl group oxygen atom and the partially positively charged hydrogen atom of an adjacent monomer. This is further enhanced by aromatic stacking, which involves the interaction between the unhybridized p orbitals in the six-membered benzene rings integral to the polymer's structure. These intermolecular interactions lead to a highly ordered and rigid molecular architecture, providing the fibers with their incredible tensile strength and resistance to deformation. Unlike Kevlar, typical nylon lacks this level of ordered hydrogen bonding and aromatic stacking, resulting in less rigid and more pliable fibers.