Polymer intermolecular forces from repeat unit polarity

Steps:

• Analyze the repeat unit structure for functional groups that create permanent dipoles, such as C-Cl bonds.
• Confirm absence of groups enabling hydrogen bonding, like O-H or N-H.
• Identify polar regions inducing temporary dipoles in neighboring chains.
• Rule out solely temporary interactions due to inherent molecular polarity.

Why B is correct:

• Permanent dipole-induced dipole interactions occur when polar groups (e.g., electronegative Cl) create fixed dipoles that polarize adjacent nonpolar or less polar segments, per dipole induction principles.

Why the others are wrong:

• A: Temporary dipole interactions dominate nonpolar molecules; here, permanent dipoles from polar bonds prevail.
• C: No N, O, or F atoms bonded to H, preventing hydrogen bond formation.
• D: Not enough information on option D, but it lacks relevance to the observed polarity.

Final answer: B