Synthesis and photoisomerization characteristics of a 2,4,4′- substituted azobenzene tethered to the side chains of polymethacrylamide

Surjith K. Kumar, Jong Dal Hong, Chang Keun Lim, Soo Young Park

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

A side-chain methacrylamide copolymer, poly{(N-[3-(4-(4′- methoxyphenylazo)-2-nitrophenoxy)-propyl]-N-[3-(dimethylamino)propyl] methacrylamide)-co-(N-[3-(dimethylamino)propyl]methacrylamide)} (PNA) functionalized with a 2,4,4′-substituted chromophore, 2-nitro-4′- methoxyazobenzene was prepared and characterized. The branched structure of the azo chromophore was specifically designed to prevent the aggregate formation by minimizing the ground-state aromatic stacking interactions between the azo molecules. This cationic polyelectrolyte, together with the oppositely charged τ-carrageenan (CAG) polysaccharide, was alternately dip-coated onto a fused silica substrate to produce a multilayered film by layer-by-layer electrostatic self-assembly. A UV/vis spectroscopic study of PNA, performed during both a heating-cooling (25-85°C) and an E-Z-E photoisomerization cycle, revealed that the maximum absorbance wavelength of the chromophore did not shift in either DMSO/H2O (1:20) solution or the multilayer assembly comprising 10 PNA/CAG bilayers. This result indicates that the PNA chromophores do not undergo aggregation. Monitoring of the E/Z photoisomerization of the solution- and film-based PNA chromophores revealed that the intensity of the π-π* transition band of its E-isomer decreased during irradiation with UV light. Also, the Z/E reverse isomerization induced by visible light (λ > 460 nm) was observed with almost full recovery of the E isomer. The kinetics of the photoisomerization step was determined to be monoexponential, indicating that photoisomerization proceeds via a single pathway. Unlike in general cases, one distinguishable property of the film-based PNA chromophore is the E/Z switching speed under experimental conditions (360 nm, P = 2 mW/cm2), which is remarkably similar to that observed in solution.

Original languageEnglish
Pages (from-to)3217-3223
Number of pages7
JournalMacromolecules
Volume39
Issue number9
DOIs
Publication statusPublished - May 2 2006
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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