nancy189 said:Thanks Ryan. Could you further elaborate on that?
since the directions are opposite,how can i calculate the pl by '<u(0)·u（i）>=exp(-l/p)'.some values are negtive,so i can not fit the exponential line...what should i do?Ygggdrasil said:The persistence length of a long object (such as a polymer) is a measure of the flexibility of that object. Imagine a long cord that is slightly flexible. At short distance scales, the cord will basically be rigid. If you look at the direction the cord is pointing at two points that are very close together, the cord will likely be pointing in the same direction at those two points (i.e. the angles of the tangent vectors are highly correlated). If you choose two points on the this flexible cord (imagine a piece of cooked spaghetti that you've just tossed on your plate) that are very far apart, however, the tangent to the cords at those locations will likely be pointing in different directions (i.e. the angles will be uncorrelated). If you plot out how correlated the tangent angles at two different points are as a function of the distance between the the two points, you'll get a plot that starts out at 1 (perfect correlation) at a distance of zero and drops exponentially as distance increases. The persistence length is the characteristic length scale of that exponential decay.
Persistence length is a physical property that characterizes the stiffness or flexibility of a polymer chain. It is the average distance along the chain over which the chain maintains a relatively fixed direction.
Persistence length is typically measured using techniques such as light scattering, neutron scattering, or atomic force microscopy. These methods involve subjecting the polymer chain to an external force and measuring how far it bends before straightening back out.
The persistence length of a polymer chain is affected by factors such as the length and flexibility of the polymer segments, the temperature and solvent conditions, and the presence of any cross-linking or entanglements in the chain.
Persistence length is an important parameter in understanding the physical and mechanical properties of polymers. It can affect the behavior of polymers in various applications, such as in materials science, biophysics, and drug delivery.
Yes, persistence length can be controlled or modified through various methods such as changing the polymer structure, altering the solvent conditions, or introducing cross-linking or entanglements in the chain. Understanding and manipulating persistence length is important in designing polymers with desired properties for specific applications.