Jump to main content
Jump to site search
Access to RSC content Close the message box

Continue to access RSC content when you are not at your institution. Follow our step-by-step guide.


Issue 18, 2018
Previous Article Next Article

Normal, ICAR and photomediated butadiene-ATRP with iron complexes

Author affiliations

Abstract

The ligand (L) and halide effects of a series of iron complexes (FeX2 or FeX3, X = Cl, Br)/L supported by carbon (Cp2Fe2(I)(CO)4 > Cp2Fe > Fe(CO)5 > (Ph2PCp)2Fe), nitrogen (phthalocyanine ≫ bpy ≥ MeO-bpy ≫ PMDETA > phen), halide (FeXmY4−m/Bu4N, X, Y = Cl ≫ Br > I), oxygen (12-crown-4 ≫ 15-crown-5 ≥ dibenzo-18-crown-6) and phosphorous (P[Ph(2,4,6-OMe)3]3 > P(t-Bu)3 ≫ P(n-Bu)3, PPh3, P[Ph(4-CF3)]3, P(C6F5)3) ligands, as well as ligand-free FeX3, were evaluated in the normal, ICAR, and photo-ATRP of butadiene (BD) initiated from bromoesters, α,α-dichloro-p-xylene, or FeX3 in toluene at 110 °C. Good polymerization control was observed in many cases, and two clear trends i.e. P[Ph(OMe)3]3 ≫ Bu4NX > crown ethers > amines > C-ligands and FeCl2, FeCl3 ≫ FeBr2, FeBr3 occur consistently across all polymerizations. These effects correlate with the higher stability of the allyl PBD-Cl vs. PBD-Br chain ends and with FeCl3 likely being a better deactivator than FeBr3. Conversely, while basic enough to reduce FeX3, P[Ph(2,4,6-OMe)3]3 is not nucleophilic enough to quaternize PBD-X in the apolar toluene and successfully enables a faster activation/deactivation equilibrium than all other ligands. As such, e.g. N-ATRP with [BD]/[R–Br]/[FeCl3]/P[Ph(2,4,6-OMe)3]3 = 100/1/2/3 affords a linear Mnvs. conversion profile with PDI as low as 1.15–1.2 and a halide chain end functionality (CEF) = 0.65 at up to 50% conversion. While controlled polymerizations occur in photo-ATRP even without ligand and initiator, photoirradiation of catalytic N-ATRP with BD/R–Br/FeCl3/P[Ph(2,4,6-OMe)3]3 = 100/1/0.05/0.15 significantly improves the rate (×10 vs. dark), conversion (up to 70%) and X-CEF (0.9) via the additional initiation afforded by FeX3 photolysis, albeit with a slight PDI increase to ∼1.4. Thus, Fe-mediated BD-ATRP is achievable, and the rational selection of the polymerization variables enables minimization of side reactions and the successful synthesis of well-defined PBD with a wide range of molecular weights, narrow PDI and reasonably high X-CEF, suitable for the preparation of e.g. block copolymers.

Graphical abstract: Normal, ICAR and photomediated butadiene-ATRP with iron complexes

Back to tab navigation

Article information


Submitted
23 Mar 2018
Accepted
19 Apr 2018
First published
20 Apr 2018

Polym. Chem., 2018,9, 2389-2406
Article type
Paper
Author version available

Normal, ICAR and photomediated butadiene-ATRP with iron complexes

V. Vasu, J. Kim, H. Yu, W. I. Bannerman, M. E. Johnson and A. D. Asandei, Polym. Chem., 2018, 9, 2389
DOI: 10.1039/C8PY00463C

Social activity

Search articles by author

Spotlight

Advertisements