The Chicago researchers revealed the microstructure evolution of a common block copolymer of relevance to protective coatings and other responsive materials, when confined within nanoscale linear channels on semiconductor substrates. This resulted in direct observation of the mechanism for cylinder alignment within the nanochannels using time-resolved Atomic Force Microscope (AFM) imaging and computerised image analysis. This work has potential implications in improved processing of coatings for sensing and protection of chemical and biological threats. Such coatings could be exploited, for example, in future treatments for protective garments or tactical vehicles, enabling them to sense and respond to threat environments.

 

Other recent work at Penn State is also relevant to future polymer treatments able to sense and respond to chemical and biological threats. Polymers that are capable of depolymerising completely from head-to-tail upon cleavage of an end-cap from the terminus of the polymer, have emerged recently as a new strategy for creating stimuli-responsive solid-state materials with amplified responses to chemical or biological threats. In theory, solid-state materials made from these polymers will respond most efficiently to a stimulus in solution when the polymer end-caps are displayed into solution at the solid−liquid interface, rather than being buried in the solid state material. 

 

The researchers have defined two strategies for increasing the likelihood that end-caps are displayed at this interface. A microscale-pump made from films of a model depolymerisable polymer serves as a test system for evaluating the location of end-caps in the films. By measuring the flow rate initiated by depolymerisation of the polymers within the films, the researchers determined that both the polymer length and hydrophilicity of the end-caps affected the density of end-caps at the solid−liquid interface. The resulting ability to construct responsive coatings with a greater fraction of exposed, instead of “buried,” functionality, will enable sensing and response that is sensitive, selective, and rapid, allowing warfighters to respond quickly and appropriately to rapidly evolving threat environments.