Polymer crystallinity refers to what kind of packing of chains?

• A. Disordered, amorphous arrangement
• B. Cross-link density variation with temperature
• C. Melt alignment of amorphous segments
• D. Packing of molecular chains to produce an ordered atomic array

Answer: (D)

Polymer crystallinity means the chains pack in a regular, repeating arrangement that forms a crystal-like lattice. In these crystalline regions, chain segments align and stack with consistent spacing, creating long-range order. Most polymers are semicrystalline, having both crystalline areas and amorphous, disordered regions; the crystalline portions lead to higher density, stiffness, and a defined melting temperature. The other ideas describe disordered amorphous packing, networks of cross-links, or alignment of random coils without true periodic order, which do not capture the ordered packing that crystallinity involves.