Photochemical control of polymers

Materials that change properties upon exposure to applied stimuli have received tremendous interest. Among various stimuli, light has unique advantages because it allows precise control over the location and timing. Moreover, irradn. parameters, such as light intensity and wavelength, can easily be modulated to comply with the system. Mol. design of polymers incorporating photocleavable groups enables photochem. control of covalent bonds or non-covalent intermol. interactions in polymer materials. We have developed three classes of new light-responsive polymer systems: 1) layer-by-layer polyelectrolyte films that switch interlayer charge-charge interactions from attractive to repulsive, 2) photopatternable conjugated polymers with photocleavable solubilizing sidechains that switches soly. in orthogonal solvents, and 3) polymer gels with phototunable viscoelastic properties and solubilities. Such novel photochem. approaches to control polymers have potential applications in three-dimensional photolithog. and photolabile drug delivery systems