Final answer:
Crystalline polymers are stronger and more resistant to heat due to their ordered structures that provide a specific melting temperature and uniform strength in their intermolecular attractions.
Step-by-step explanation:
Crystalline polymers are usually stronger and more resistant to heat. These materials exhibit higher melting points due to the ordered structure of their crystalline regions, ensuring that energy is uniformly needed to disrupt the attractive forces between the polymer chains. In contrast to amorphous polymers, which soften over a range of temperatures because of the structural nonequivalence of molecules, crystalline polymers have a specific melting temperature due to uniform intermolecular attractions.The strength and flexibility of a polymer can also depend on other factors, such as chain length, the presence of polar side groups, the degree of branching, and cross-linking. Polymers with longer chains, polar side groups, and extensive cross-linking might be stronger, but it's the crystalline regions that specifically contribute to the polymer's resistance to heat. In the context of crystalline structures, side groups, branching, and cross-linking can play a role in how closely the chains can pack, affecting crystallinity and therefore, the thermal properties.