Persistence length: What are the beginning and end points in an polymer? Hello, can you tell me where the starting point and the ending point of the (parts of the) persistence length in a polymer are? I thought the persistence length was the greatest length that only just is not bent. This, however, cannot be as every part of the molecule down to the beginning is bent at least a little (maybe invisible). You would have to say, e.g.: "Every part of the molecule that is bent less than 3% belongs to the persistence length."