Jump to main content
Jump to site search

Issue 7, 2012
Previous Article Next Article

Ambient temperature polymer modification by in situ phototriggered deprotection and thiol–ene chemistry

Author affiliations

Abstract

A novel and efficient methodology for the light-triggered release of thiols at ambient temperature is presented, which can be utilized for the in situ modification of polymeric backbones prepared via radical polymerization. Initially, a model reaction on poly(ethylene glycol) methyl ether was examined via size-exclusion chromatography coupled with electrospray ionization-mass spectrometry (SEC/ESI-MS) to establish the photodeprotection feasibility of 2-nitrobenzyl thioether moieties in the presence of variable activators or catalysts employed are Michael-type or radical thiol–ene chemistries, respectively. When 0.01 eq. of dimethylphenylphosphine is employed, disulfide coupling is reduced to its minimum and quantitative phototriggered formation of thiol-capped poly(ethylene glycol) methyl ether species is observed after a 16 hour irradiation period at 320 nm by a low-cost light source. The concept is extended to polymer backbone modification by atom transfer radical polymerization of the novel photosensitive monomer: 2-((3-((2-nitrobenzyl)thio)propanoyl)oxy)ethyl methacrylate containing the 2-nitrobenzyl thioether moiety. Well-defined homopolymers (4700 g·mol−1Mn ≤ 20 000 g·mol−1, 1.29 ≤ PDI ≤ 1.40) containing one protected thiol per repeating unit were obtained and, upon a light stimulus (λmax = 320 nm), thiol entities are released along the lateral polymer chain. The photodeprotection process is mapped by exploiting the increased absorbance of photocleaved o-nitrosobenzaldehyde molecules at 345 nm and UV-Vis data suggests a quantitative backbone deprotection after a 16 hour irradiation time period. Further in situ functionalization of polymeric backbone is achieved via base-catalyzed maleimidethiol addition at ambient temperature and its outcome is evidenced by a re-increased molecular weight in SEC, by virtue of decreased signal intensity of the 2-nitrobenzyl thioether moiety and the appearance of characteristic product protons in NMR spectroscopy (the polymer backbone functionalization is estimated as >90% by NMR analysis).

Graphical abstract: Ambient temperature polymer modification by in situ phototriggered deprotection and thiol–ene chemistry

Back to tab navigation

Supplementary files

Publication details

The article was received on 22 Aug 2011, accepted on 17 Sep 2011 and first published on 20 Oct 2011


Article type: Paper
DOI: 10.1039/C1PY00372K
Citation: Polym. Chem., 2012,3, 1740-1749
  •   Request permissions

    Ambient temperature polymer modification by in situ phototriggered deprotection and thiol–ene chemistry

    T. Pauloehrl, G. Delaittre, M. Bastmeyer and C. Barner-Kowollik, Polym. Chem., 2012, 3, 1740
    DOI: 10.1039/C1PY00372K

Search articles by author

Spotlight

Advertisements