Answer: Functional groups can lead to intra molecular condensation.
Explanation: 6 -aminohexanoic acid is a molecule which have 2 functional groups - one is amine group (-NH2) and the other one is carboxylic group (-COOH).
The non bonding electrons or lone pairs present on the amine group being nucleophillic in nature will attack on the electrophillic carbon of carboxylic group to form the amide bond, the structure of which is hereby attached.
Thus due to the presence of 2 active functional groups, polymerization with itself can take place easily.