13C and 15N solid state NMR of piezoelectric nylons

Solid state nuclear magnetic resonance (NMR) has been shown to be a unique spectroscopic tool for determining molecular composition, crystallinity, packing, orientation and motion in as-obtained and end-use materials. We have developed several methods for evaluating the molecular-level properties and behavior of polymeric materials, especially piezoelectric nylons. Analysis of nylon 7 homopolymer under various sample treatment histories related to poling and generation of piezoelectric properties allows qualitative evaluation of the two main types of crystal forms present, the (alpha) -form which appears to be the one responsible for piezoelectric behavior in this polymer, and the (gamma) -form which can co-exist with the (alpha) -form in some samples. Based on the possibility that molecular composition could be used to control crystallinity and microscopic packing, and thereby affect macroscopic properties such as piezoelectricity, we have synthesized and characterized two families of nylon co-polymers consisting of even-odd A-B monomer combinations. We have determined degrees and types of crystallinity for these materials using a combination of thermal, FTIR and NMR, measurements. The molecular-level behavior of these materials is related to observed properties. Evaluation of piezoelectric properties is underway, and initial results are summarized.