Nanomechanical measurements on glutamine molecularly imprinted nylon films

Thin, selectively imprinted films of nylon-6 are produced by spin casting with glutamine used as a template molecule. The template molecules can be extracted from the films by a formic acid wash and later reloaded with a similar solution. Infra-red spectroscopy gives a clear characterization of the chemical components of the films. sensing nanoindentation is applied to determine the mechanical properties of the molecularly imprinted polymer films. An optimized multi-cycling test function with a sequence of several loading and unloading procedures was developed. Typical hysteresis loops are visible in the load-displacement charts, which allow the quantitative measurement of the visco-elasticity of the material and a comparison relative to the total elastic contribution during deformation. The characteristic depth dependent hardness and the elastic indentation modulus are also obtained from the nanomechanical tests. s in the polymer network caused by the inclusion of the template molecules are clearly related to the nanomechanical properties and are systematically studied in this work. The relative energy loss for pure nylon films lies between 35 and 50% depending on the crystallinity of the films. The glutamine template molecule makes the polymer matrix stiffer due to strong hydrogen bonds between the amino acid and the nylon chains. Removal of the glutamine molecules results in a considerable increase of the visco-elastic energy loss of approximately 16%, whereas reloading again results in an increase of the indentation modulus and the hardness.