Polymer networks possessing reversible covalent crosslinks constitute a class of materials with unique capabilities including the capacity for adapting to an externally applied stimulus. These covalent adaptable networks (CANs) represent a paradigm in polymer network fabrication aimed at the rational design of structural materials possessing dynamic characteristics for specialty applications and functions. Here, we explore two distinct classes of CANs with either photochemically or thermally triggered responses. First, those in which the reversible bond formation is controlled by exposure to light will be discussed along with the subsequent initiation of the addition-fragmentation process that facilitates polymer network relaxation, photo induced actuation and shape memory effects, and stress relaxation. These results will be discussed in the context of thiol-ene-based photopolymerization reactions as well as their potential for implementation in thiol-yne photopolymerizations. Secondly, consideration of thermally inducible CANs will be presented; focusing on polymer networks formed from thermoreversible Diels-Alder adduct structures. In particular, the unique temperature dependent rheological behavior will be discussed as well as the potential for these materials to be healed through remotely controlled triggers that induce localized temperature changes. Ultimately, the potential for CANs-based materials to impact numerous materials applications will be presented in light of their distinctive array of material properties.

Developing economic and green methods to supply our future energy needs is perhaps the grand challenge of our time. Due to its abundant and distributed supply, solar energy may play a key role in this revolution. However, limitations in cost and efficiency have hindered solar photovoltaic energy conversion from supplying a large fraction of our energy. The seminar will focus on our progress towards solving the key challenges to decrease the cost and increase the efficiency of photovoltaic energy conversion by developing new nanomaterials and devices. In particular, I will discuss recent developments on a new low-cost route to solar cells based on colloidal semiconductor nanocrystal inks and on a new nanofabrication method for forming solar cells based on semiconductor quantum wire arrays. The materials for the latter are made using self-assembly and have the potential to take advantage of photophysics that can exceed the Shockley-Queisser limit (33%, the upper limit of energy conversion for a conventional single junction solar cell).