Thicker is Better? Synthesis and Evaluation of Well-Defined Polymer Brushes with Controllable Catalytic Loadings

Polymer brushes (PBs) have been used as supports for the immobilization of palladium complexes on silicon surfaces. The polymers were grown by surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) and postdecorated with dipyridylamine (dpa) ligands. The pendant dpa units were in turn comp...

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Vydáno v:Chemistry : a European journal Ročník 18; číslo 50; s. 16226 - 16233
Hlavní autoři: Fernandes, Antony E., Dirani, Ali, d'Haese, Cécile, Deumer, Gladys, Guo, Weiming, Hensenne, Peter, Nahra, Fady, Laloyaux, Xavier, Haufroid, Vincent, Nysten, Bernard, Riant, Olivier, Jonas, Alain M.
Médium: Journal Article
Jazyk:angličtina
Vydáno: Weinheim WILEY-VCH Verlag 07.12.2012
WILEY‐VCH Verlag
Wiley Subscription Services, Inc
Témata:
Chemistry
Leaching
Mass spectrometry
Palladium
Polymers
silicon
supported catalysts
surface chemistry
X-rays
ISSN:0947-6539, 1521-3765, 1521-3765
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Shrnutí:Polymer brushes (PBs) have been used as supports for the immobilization of palladium complexes on silicon surfaces. The polymers were grown by surface‐initiated atom‐transfer radical polymerization (SI‐ATRP) and postdecorated with dipyridylamine (dpa) ligands. The pendant dpa units were in turn complexed with [Pd(OAc)2] to afford hybrid catalytic surfaces. A series of catalytic samples of various thicknesses (ca. 20–160 nm) and associated palladium loadings (ca. 10–45 nmol cm−2) were obtained by adjusting the SI‐ATRP reaction time and characterized by ellipsometry, X‐ray reflectivity, X‐ray photoelectron spectroscopy, and inductively coupled plasma mass spectrometry (ICP‐MS). ICP‐MS revealed a near‐linear relationship between thickness of the polymer brush and palladium content, which confirmed the robustness of the preparation and postmodification sequence presented herein, rendering possible the creation of functional architectures with predefined catalytic potential. The activities of the catalytic PBs were determined by systematically exploring a full range of substrate‐to‐catalyst ratios in a model palladium(0)‐catalyzed reaction. Quantitative transformations were observed for loadings down to 0.03 mol % and a maximum turnover number (TON) of around 3500 was established for the system. Comparison of the catalytic performances evidenced a singular influence of the thickness on conversions and TONs. The limited recyclability of the hairy catalysts has been attributed to palladium leaching. Hairy catalysts! Polymer brushes (PBs) have been used as platforms for the construction of well‐defined catalytic surfaces (see scheme; PHEMA=poly(2‐hydroxyethyl methacrylate), dpa=dipyridylamine) by using a simple, robust, post‐modification sequence. Varying the PB thickness allows accurate control over catalyst loadings. The effect of PB thickness on activity (conversions, turnovers) has carefully been examined.
Bibliografie:FRS-FNRS
Communauté Française de Belgique - No. ARC 06-11/339
ark:/67375/WNG-6R16S744-K
istex:44B2E59DF5AE2D51AD35E1417ABF379B688C39AA
Belgian Federal Science Policy - No. IAP-PAI P6/27
ArticleID:CHEM201202531
ObjectType-Article-1
SourceType-Scholarly Journals-1
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ISSN:0947-6539
1521-3765
1521-3765
DOI:10.1002/chem.201202531