Thermal characterization of self-assembled monolayers of dialkyl disulfides containing the urea moiety.
Thermal behaviors of urea-containing dialkyl disulfides 4-(3-octadecylureido)phenyl disulfide (ODPD) and 3-(octadecylureido)ethane disulfide (ODED) and octadecyl disulfide (ODDS) self-assembled monolayers (SAMs) were investigated by infrared reflection-absorption spectroscopy (IRRAS). Among the SAMs, the alkyl chain of ODPD is thermally reversible in the temperature region between 30 and 138 degrees C, whereas alkyl chains of ODED and ODDS are irreversible. With regard to the thermal stability of alkyl chains, ODED is superior to ODPD and ODDS. It is considered that the good thermal reversibility of the ODPD SAM is due to the rigid phenyl ring and the good thermal stability of the ODED SAM is due to the flexible ethylene linker. Moreover, 2D correlation analysis provides an enhancement of spectral resolution in amide II and CH2 antisymmetric stretching bands and suggests from the comparison of sequences of spectral events of ODPD and ODED SAMs that the last reorientation of the phenyl ring in the ODPD SAM is responsible for the good thermal reversibility.
Shin
Hyeon Suk
HS
Department of Chemistry, Pohang University of Science & Technology, Pohang 790-784, Republic of Korea. shs0902@postech.ac.kr
Kim
Jang Hoon
JH
Kim
Seung Bin
SB
Jung
Young Mee
YM
D004220:Disulfides / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D014508:Urea / Q000737:chemistry*