H-bonding organocatalysis using (thio)urea/amine achieved massive success. H-bonding binding with Brønsted acid catalysis, especially in polymerizations, was scarcely explored. Here we disclosed 1,3-bis-(3,5-bis(trifluoromethyl)phenyl)thiourea (TU) as hydrogen bond donor (HBD), combined with trifluoroacetic acid (TFA) as a Brønsted acid (BA), promoted efficient controlled/living ring-opening polymerization (ROP) of δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL) at room temperature. The ROPs of δ-VL and ε-CL with benzyl alcohol (BnOH) as the initiator yielded poly(δ-valerolactone) (PVL, Mn, NMR = 1900–9900 g mol−1, Mw/Mn = 1.28–1.34) and poly(ε-caprolactone) (PCL, Mn, NMR = 2400–11,600 g mol−1, Mw/Mn = 1.19–1.35) with predicted molecular weights and narrow dispersities. A plausible mechanism of the ROP promoted by associations of TU with TFA through double hydrogen bonding was suggested, in which stabilizing of the carboxylate anion and enhancing of the Brønsted acidity made the catalytic ROPs by TU–TFA viable. The quantitative incorporation of the initiator into the polymer chains was demonstrated by 1H NMR and MALDI-ToF MS measurements. The controlled/living fashion of the polymerization was supported by the kinetics and chain extension experiments. Synthesis of well defined block copolymers of PVL-b-PCL and PCL-b-PVL verified again the ROPs were in controlled/living manner, and suggested the hydrogen bond donor binding with Brønsted acid catalysis to be a generally applicable method.
Polymer – Elsevier
Published: Feb 10, 2016
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera