Related Experiment Video
Updated: Jul 16, 2026
06:16
Monitoring the Effects of Illumination on the Structure of Conjugated Polymer Gels Using Neutron Scattering
Published on: December 21, 2017
Surface organization, light-driven surface changes, and stability of semifluorinated azobenzene polymers
Marvin Y Paik1, Sitaraman Krishnan, Fengxiang You
1Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|April 3, 2007
Summary
Polymers with light-sensitive azobenzene side groups show altered surface properties upon UV light exposure. Molecular order influences how these light-induced changes affect the polymer surface, with longer fluoroalkyl chains offering greater stability.
Area of Science:
- Polymer Science
- Materials Science
- Photochemistry
Background:
- Azobenzene-containing polymers exhibit photoresponsive behavior due to trans-cis isomerization.
- Surface properties of polymers can be tuned by modifying side groups and controlling molecular order.
- Understanding light-induced molecular reorganization is crucial for developing advanced functional materials.
Purpose of the Study:
- To investigate light-induced changes in surface properties of polymers with perfluoroalkyl-modified azobenzene side groups.
- To elucidate the influence of molecular order and orientation on photoisomerization-driven surface modifications.
- To correlate fluoroalkyl chain length with the stability of polymer surfaces under UV irradiation.
Main Methods:
- Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy for in situ UV irradiation studies.
- Water contact angle measurements to assess surface property changes.
- Differential scanning calorimetry and wide-angle X-ray scattering to analyze bulk and surface molecular order.
Main Results:
- UV light induced trans to cis isomerization of azobenzene groups, altering polymer surface properties.
- Well-ordered smectic mesophases formed in the bulk and on the surface with longer fluoroalkyl chains (perfluorohexyl, perfluorooctyl).
- Higher orientational order in perfluoroalkyl groups led to increased resistance to light-induced surface changes, with azobenzene rings reorienting while perfluoroalkyl segments remained ordered.
Conclusions:
- The length of the fluoroalkyl segment significantly influences the disruption of mesogen packing by photoisomerization.
- Surfaces with highly ordered perfluoroalkyl groups exhibit enhanced stability against light-induced molecular reorganization.
- Azobenzene phenyl rings are more susceptible to photoisomerization-induced disorder than the ordered terminal perfluoroalkyl segments.
