In situ measurement of humidity induced changes in the refractive index and thickness of polyethylene glycol thin films

Bukem Bilen; Yani Skarlatos; Gulen Aktas; M. Naci Inci; Tugba Dispinar; M. Merve Kose; Amitav Sanyal

doi:10.1117/12.818038

18 November 2008 In situ measurement of humidity induced changes in the refractive index and thickness of polyethylene glycol thin films

Bukem Bilen, Yani Skarlatos, Gulen Aktas, M. Naci Inci, Tugba Dispinar, M. Merve Kose, Amitav Sanyal

Author Affiliations +

Proceedings Volume 7138, Photonics, Devices, and Systems IV; 71381G (2008) https://doi.org/10.1117/12.818038
Event: Photonics, Devices, and Systems IV, 2008, Prague, Czech Republic

Abstract

Humidity induced changes in the refractive index and thickness of polyethylene glycol (PEG) thin films are in situ determined by optical waveguide spectroscopy. PEG brushes are covalently attached to the surface of a thin gold film on a borosilicate crown glass (BK7) using a grafting-from chemical synthesis technique. The measurements are carried out in an attenuated total internal reflection setup. At low humidity levels, both the refractive index and the thickness change gradually due to swelling of the PEG thin films upon water intake. At around 80% relative humidity, a steep decrease in the refractive index and a steep increase in the thickness are observed as a result of a phase change from a semicrystalline state to a physical gel state. The hydrogenation of PEG films causes a less pronounced phase change from a semicrystalline state to a gel state. Due to fewer ether oxygen atoms available for the water molecules to make hydrogen bonding, the polymer has a more stable structure than before and the phase change is observed to shift to higher humidity levels. It is discussed that such a humidity induced change in the index of refraction can be utilized in constructing of a PEG based humidity sensor.

Citation Download Citation

Bukem Bilen, Yani Skarlatos, Gulen Aktas, M. Naci Inci, Tugba Dispinar, M. Merve Kose, and Amitav Sanyal "In situ measurement of humidity induced changes in the refractive index and thickness of polyethylene glycol thin films", Proc. SPIE 7138, Photonics, Devices, and Systems IV, 71381G (18 November 2008); https://doi.org/10.1117/12.818038

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available