Measuring the spring constant of a single polymer chain

We present a measurement of the mechanical properties of single polystyrene molecules of size R approximate to 50 nm. Using a micromechanical technique, we show directly that the polymer chain behaves like a spring, and we measure the spring constant, We examine both cross-linked and non-cross-linked polystyrene. The former forms a stiffer spring, and the value of the spring constant is in agreement with theory, while in the latter case the measured value is larger than expected.