Herein, we report a method to synthesize a series of alternating copolymers that consist exclusively of acrylamide units. Crucial to realizing this polymer synthesis is the design of a divinyl monomer that contains acrylate and acrylamide moieties connected by two activated ester bonds. This design, which is based on the reactivity ratio of the embedded vinyl groups, allows a “selective” cyclopolymerization, wherein the intramolecular and intermolecular propagation are repeated alternately under dilute conditions. The addition of an amine to the resulting cyclopolymers afforded two different acryl amide units, i.e., an amine‐substituted acryl amide and a 2‐hydroxy‐ethyl‐substituted acryl amide in alternating sequence. Using this method, we could furnish ten types of alternating copolymers; some of these exhibit unique properties in solution and in the bulk, which are different from those of the corresponding random copolymers, and we attributed the differences to the alternating sequence.
An alternating copolymer of methacrylic acid and N-isopropyl acrylamide (NIPAM) was synthesized by selective cyclopolymerization of a special divinyl monomer and transformation of repeating cyclo-units in the resultant cyclopolymer. Crucial to the breakthrough is the monomer design in view of two types of cleavable bonds (3° ester and activated ester) in the pendant group of the monomer and the lower reactivity ratio of the two double bonds (methacrylate and electron-poor acrylate) for the polymerizable groups. The thus-obtained cyclopolymer was transformed into the alternating copolymer by transformation of the activated ester into amide by isopropyl amine and cleavage of the 3° ester by trifluoroacetic acid. The resultant copolymer showed thermal and pH response in aqueous solution that was different from the 1:1 random copolymer as well as the homopolymers.
In this article, we report an unusual reactivity of saccharin-pendant methacrylamide (1) in radical copolymerization. The bulky vinylidene molecule showed no homopolymerization ability under general radical polymerization condition likely due...
In this work, we synthesized an acrylamide-based
terpolymer that
is a block copolymer composed of an AB alternating copolymer and a
C homopolymer. The key to the unprecedented achievement is rational
design of an acrylate–acrylamide divinyl monomer carrying CF3-substituted salicylic acid ester bonds (AAm-CF
3
) to realize the efficient and selective
cyclopolymerization as well as the quantitative transformation of
the resultant cyclorepeating units. The selectivity in the cyclopolymerization
and the pendant transformation ability were evaluated through reactivity
ratios of the corresponding model monomers and quantitative aminolysis
reactions of the model compound. The cyclopolymerization via the photoinduced
electron transfer-reversible addition–fragmentation chain transfer
(PET-RAFT) process with a macrochain-transfer agent and subsequent
aminolysis reaction afforded the homopolymer-block-alternating copolymer. The sequence-controlled terpolymer exhibited
a very unique thermal response behavior in water that was strikingly
different from the corresponding sequence-uncontrolled terpolymers,
such as homopolymer-block-statistical copolymers
and all statistical terpolymers, despite the fact that the structure
cannot be distinguished by 1H NMR.
A series of methacrylate/styrene
alternating copolymers were efficiently
and systematically synthesized via alternating copolymerization of
saccharin methacrylamide (1) with styrene and subsequent
one-pot alcoholysis transformation with alcohols. The saccharin amide
bond in 1 was stable enough that 1 was used
as a bench-stable monomer, but the bond became reactive toward alcohols
after the copolymerization. Thanks to the specific feature, the postpolymerization
modification could be performed under mild conditions despite easy
handling of the monomer. The quantitative transformation as well as
the alternating sequence were certainly supported by 1H
NMR and MALDI-TOF-MS analyses. The alternating copolymers carrying
relatively short alkyl pendants expressed lower glass transition temperatures
than those of the statistical counterparts. Moreover, the alternating
copolymerization was controlled via a RAFT polymerization system,
affording a unique block copolymer composed of alternating copolymer
segments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.