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).

Absolute and per-capita energy consumption is bound to increase globally, leading to a projected increase in energy requirements of 50% by 2020. The primary source for providing a majority of the energy will continue to be fossil fuels. However, an array of enabling technologies needs to be proven for the realization of a zero emission power, fuel or chemical plants in the near future. Opportunities to develop new processes, driven by the regulatory requirements for the reduction or elimination of gaseous and particulate pollutant abound. This presentation will describe the chemistry, reaction mechanisms, particle technology, system engineering, process economics, and regulations that surround the modern utilization of fossil energy. The presentation will illustrate the salient features pertaining to the fundamental and applied characteristics of the state-of-the-art technologies in practice as well as emerging technologies in development. Emerging technologies evolve largely from the urge for CO2 emission control in fossil energy conversion systems. Further, novel gasification systems based on the chemical looping concepts as well as the calcium looping process for CO2 separation from the combustion flue gas stream will be elucidated in the context of the looping particle design, process heat integration, energy conversion efficiency and economics.

Electrostatic and secondary interactions of polyelectrolytes and amphiphilic block copolymers can be used to generate new drug and gene delivery systems capable of controlled release triggered by pH or temperature. The 2D and 3D assembly of drug delivery systems will be addressed, including the generation of responsive, multi-agent thin films for localized targeting and controlled delivery from implant surfaces, and the generation of amphiphilic systems that enable highly controlled presentation of ligand for molecularly targeted chemotherapy agents. The manipulation of the solution assembly behavior of new amphiphilic and charged linear dendritic block copolymers, and their use as gene and drug carriers and in novel biomaterials systems will be described. We explore the role of cluster presentation of ligand on patchy micelles generated by the self-assembly of linear dendritic block copolymers. Key to this approach is the synthesis of new amphiphilic linear peptide-dendritic block copolymers that self-assemble in the solution state to generate stable micelles with highly branched, dense dendritic groups in the exterior shell. Due to the unique nature of the dendritic outer block, these micelles act as vessels with a highly tunable 3D presentation of ligand, enabling the creation of delivery nanoparticles with homo- or heterogeneous surfaces that enable cluster presentation of ligand. On the other hand, the alternating adsorption of oppositely charged molecular species, known as the electrostatic layer-by-layer (LBL) process, is a simple and elegant method of constructing highly tailored ultrathin polymer and organic-inorganic composite thin films. We have utilized this method to develop thin films that can deliver proteins and biologic drugs with highly preserved activity from surfaces with sustained release periods of several days; manipulation of the 2D composition of the thin films can lead to simultaneous or sequential release of different components, resulting in highly tunable multi-agent delivery (MAD) nanolayered release systems.

GSO Symposium

GSO Symposium