Recently, paper-based materials have attracted increasing attention from industry as well as academic research due to the unique structure and properties of paper as a planar substrate. As a low-cost, lightweight and flexible substrate, functionalized paper can find applications ranging from simple sensors and actuators to “portable” diagnostic devices. Often, a response to an external stimulus is desirable to reversibly and dynamically switch surface properties of such materials and devices. To this end, modification of paper with functional modules becomes a key parameter to implement such “switchable” properties. An interesting method to prepare such paper is by immobilization of stimuli-responsive polymers on the paper fiber surface. Until now, paper with immobilized stimuli-responsive polymers is still in the infancy. Among various stimuli, light has many advantages due to its fast, straight-forward, non-invasive, non-diffusively restricted working mechanism.As a popular light-responsive molecule, spiropyran has gained great interest in the scientific world since the properties of its two isomers are vastly different, which results in interesting properties of spiropyran-modified materials. If spiropyran molecules are being attached onto paper substrates, novel paper properties can be obtained. Although there are two references based on the spiropyran-modified paper, the reversibility as well as surface morphology should be improved and new functions should be developed.
This thesis presents the preparation and characterization of spiropyran-functional paper. Such paper was prepared by dip-coating and benzophenone photocrosslinking strategies using spiropyran-functional polymer. The modified paper shows an obvious chromatic response to UV light, and its sensitivity can be dynamically controlled by a simple damping method. The modified paper can be applied as a colorimetric UV sensor. In order to understand the switching system in more detail, the switching kinetics of spiropyran molecules in the paper system was investigated. In addition, based on the research on the interaction between dissolved spiropyranfunctional
polymers and metal ions in solution, spiropyran-functional paper strips can be applied for the detection of Pb2+ ions in an aqueous solution. Finally, the first proof-of-concept application of modified paper for the control of capillary-driven transportation of water in paperbased microfluidic channel was studied.