Match List-I with List-II.

	List-I		List-II
A	Weak intermolecular forces of attraction	I	Hexamethylenediamine + adipic acid
B	Hydrogen bonding	II	AlEt$$_3$$ + TiCl$$_4$$
C	Heavily branched polymer	III	2-chloro-1, 3-butadiene
D	High density polymer	IV	Phenol + formaldehyde

Choose the correct answer from the options given below

We need to match the polymer properties in List-I with the monomers/catalysts in List-II.

A. Weak intermolecular forces of attraction

Polymers with weak intermolecular forces are elastomers (rubbers). These polymers have weak van der Waals forces between chains, allowing them to be stretched and then return to their original shape.

From List-II, 2-chloro-1,3-butadiene (III) is chloroprene, which polymerizes to form neoprene -- a synthetic rubber/elastomer with weak intermolecular forces.

Therefore: A matches III.

B. Hydrogen bonding

Polymers with significant hydrogen bonding are typically polyamides or polyesters, which have N-H and C=O groups capable of forming hydrogen bonds between chains.

From List-II, hexamethylenediamine + adipic acid (I) undergoes condensation polymerization to form Nylon 6,6. Nylon has amide linkages (-CO-NH-) that form strong intermolecular hydrogen bonds between adjacent polymer chains. This hydrogen bonding gives nylon its high strength and crystallinity.

Therefore: B matches I.

C. Heavily branched polymer

Heavily branched (cross-linked) polymers are thermosetting plastics that form 3D network structures.

From List-II, phenol + formaldehyde (IV) produces Bakelite (when excess formaldehyde is used). Bakelite is a heavily cross-linked, branched polymer with a rigid 3D network structure. The phenol molecules can react at multiple positions (ortho and para), creating extensive branching and cross-linking.

Therefore: C matches IV.

D. High density polymer

High density polyethylene (HDPE) is produced using specific catalysts that promote linear chain growth with minimal branching.

From List-II, AlEt$$_3$$ + TiCl$$_4$$ (II) is the Ziegler-Natta catalyst. This catalyst system is specifically used to produce HDPE -- a high-density, linear polymer with very little chain branching, resulting in close packing of chains and high density (0.94-0.97 g/cm$$^3$$).

Therefore: D matches II.

The correct matching is: A-III, B-I, C-IV, D-II.

The correct answer is Option 4.