(193aq) Novel Chromogenic Sensors Enabled By Multi-Stimuli-Responsive Shape Memory Polymers Possessing Unconventional All-Room-Temperature Shape Memory Effects

Here we report novel chromogenic sensors based on a variety of smart shape memory polymers (SMPs) which exhibit nontraditional all-room-temperature shape memory (SM) effects. Macroporous SMP photonic crystals membranes with three-dimensional ordered macropores and microscopic thickness (~ 3 mm) are templated using self-assembled colloidal crystals as sacrificial templates. “Cold” programming of the permanent periodic structures into temporary disordered configurations can be achieved by slowly evaporating various swelling solvents (e.g., ethanol) imbibed in the interconnecting macropores. Stepwise recovery of the collapsed macropores leads to easily perceived color changes that can be correlated with the concentrations of the swelling analytes in complex, multicomponent non-swelling mixtures. High sensitivity (as low as 10 ppm) and unprecedented measurement range (from 10 ppm to 30 vol.%) for analyzing ethanol in octane and gasoline have been demonstrated by leveraging colorimetric sensing in both liquid and gas phases. Proof-of-concept tests for specifically detecting ethanol in consumer medical and healthcare products, as well as unreacted oligomers in solid polydimethylsiloxane (PDMS) matrix, have also been demonstrated. These sensors are inexpensive, reusable, durable, and readily deployable with mobile platforms for quantitative analysis. Additionally, theoretical modeling of solvent diffusion in macroporous SMPs provides fundamental insights into the mechanisms of nanoscopic SM recovery, which is a topic that has received little examination. These novel sensors are of great technological importance in a wide spectrum of applications ranging from environmental monitoring and workplace hazard identification to threat detection and process/product control in chemical, petroleum, and pharmaceutical industries.