(a) What molecular features make a polymer flexible? (b) If you cross-link a polymer, is it more flexible or less flexible than it was before?

Verified step by step guidance

1. Step 1: Understand that polymer flexibility is influenced by the structure of the polymer chains. Flexible polymers typically have long, linear chains with few or no branches, allowing them to move and rotate freely.
2. Step 2: Recognize that the presence of side groups or bulky substituents on the polymer chain can hinder flexibility by restricting the movement of the chains.
3. Step 3: Consider the role of intermolecular forces. Polymers with weaker intermolecular forces, such as van der Waals forces, tend to be more flexible because the chains can slide past each other more easily.
4. Step 4: Analyze the effect of cross-linking on polymer flexibility. Cross-linking involves forming covalent bonds between polymer chains, which restricts their movement and typically makes the polymer less flexible.
5. Step 5: Conclude that cross-linking generally decreases the flexibility of a polymer by creating a more rigid, three-dimensional network that limits the ability of the chains to move freely.