Engineering specific interactions in polymers, such as “face-to-face” or “head-to-tail” interactions, is central to advancing polymer-based optoelectronics. Barnes, Hayward and Emrick, working collaboratively in the Materials Research Science and Engineering Center on Polymers at UMass, showed that crystalline 2-D “nanowires” of conjugated polymers exhibit both types of interactions. Using single-molecule spectroscopy techniques, isolated nanowires were imaged and probed spectroscopically to reveal distinct spectral signatures of both J-type (head-to-tail), and H-type (face-to-face) electronic interactions.  Controlling the directionality of such interactions is important for directing charge- and energy flow in solar cells and related devices.