Topic
Gradient copolymers
About: Gradient copolymers is a research topic. Over the lifetime, 307 publications have been published within this topic receiving 19715 citations.
Papers published on a yearly basis
Papers
TL;DR: The authors proposed a reversible additive-fragmentation chain transfer (RAFT) method for living free-radical polymerization, which can be used with a wide range of monomers and reaction conditions and in each case it provides controlled molecular weight polymers with very narrow polydispersities.
Abstract: mechanism involves Reversible Addition-Fragmentation chain Transfer, and we have designated the process the RAFT polymerization. What distinguishes RAFT polymerization from all other methods of controlled/living free-radical polymerization is that it can be used with a wide range of monomers and reaction conditions and in each case it provides controlled molecular weight polymers with very narrow polydispersities (usually <1.2; sometimes <1.1). Living polymerization processes offer many benefits. These include the ability to control molecular weight and polydispersity and to prepare block copolymers and other polymers of complex architecturesmaterials which are not readily synthesized using other methodologies. Therefore, one can understand the current drive to develop a truly effective process which would combine the virtues of living polymerization with versatility and convenience of free-radical polymerization.2-4 However, existing processes described under the banner “living free-radical polymerization” suffer from a number of disadvantages. In particular, they may be applicable to only a limited range of monomers, require reagents that are expensive or difficult to remove, require special polymerization conditions (e.g. high reaction temperatures), and/or show sensitivity to acid or protic monomers. These factors have provided the impetus to search for new and better methods. There are three principal mechanisms that have been put forward to achieve living free-radical polymerization.2,5 The first is polymerization with reversible termination by coupling. Currently, the best example in this class is alkoxyamine-initiated or nitroxidemediated polymerization as first described by Rizzardo et al.6,7 and recently exploited by a number of groups in syntheses of narrow polydispersity polystyrene and related materials.4,8 The second mechanism is radical polymerization with reversible termination by ligand transfer to a metal complex (usually abbreviated as ATRP).9,10 This method has been successfully applied to the polymerization of various acrylic and styrenic monomers. The third mechanism for achieving living character is free-radical polymerization with reversible chain transfer (also termed degenerative chain transfer2). A simplified mechanism for this process is shown in
4,955 citations
IBM1
3,827 citations
TL;DR: In this paper, a review of the development of addition-fragmentation chain transfer agents and related ring-opening monomers highlighting recent innovation in these areas is presented, including dithioesters, trithiocarbonates, dithioco-baramates and xanthates.
1,416 citations
Journal Article•
TL;DR: A review of surface-initiated living radical polymerization (LRP) can be found in this article, where a high-density polymer brush has characteristics, in both swollen and dry states, quite different and unpredictable from those of the semi-dilute or moderately dense polymer brushes previously studied.
Abstract: Surface modifications by polymers are becoming increasingly important for various applications ranging from biotechnology to advanced microelectronics. Recent successful applications of living radical polymerization (LRP) made it possible to graft various low-polydispersity polymers including simple homopolymers, end-functionalized polymers, block/random/gradient copolymers, and functional polymers. At the same time, this technique has brought about a striking increase of graft density. Graft chains in such a high-density polymer brush were found to be highly extended in good solvent, even to the order of their full lengths. It was also found that a high-density polymer brush has characteristic properties, in both swollen and dry states, quite different and unpredictable from those of the semi-dilute or moderately dense polymer brushes previously studied. This review highlights the recent development of surface-initiated LRP and the structures, properties, and potential applications of thereby obtainable high-density polymer brushes. It is believed that surface-initiated LRP is opening up a new route to "precision" surface modification.
605 citations
TL;DR: In this article, the lower critical solution temperature (LCST) of poly(2-alkyl-2-oxazoline)s (POx) was precisely tuned over a broad range of temperatures via the well-defined gradient or random copolymerization between 2-n-propyl-1-ox-azoline (nPrOx) and either 2-isopropyl- 2-oxoxylate (iPr Oxazoline), or 2-ethyl-2oxoxoline (EtOx), resulting in an extremely narrow molecular weight
Abstract: The lower critical solution temperature (LCST) of the poly(2-alkyl-2-oxazoline)s (POx) was precisely tuned over a broad range of temperatures via the well-defined gradient or random copolymerization between 2-n-propyl-2-oxazoline (nPrOx) and either 2-isopropyl-2-oxazoline (iPrOx) or 2-ethyl-2-oxazoline (EtOx). All the copolymerizations were cationically initiated by methyl p-tosylate at the optimum condition (42 °C in acetonitrile) for the living polymerization, resulting in an extremely narrow molecular weight distribution (Mw/Mn ≤ 1.05). It was determined from the composition analysis by 1H NMR and MALDI−TOF mass spectrometry that the respective monomer reactivity ratios were found to be 3.15 and 0.57 for nPrOx and iPrOx, respectively, sufficiently different to form the gradient copolymers P(nPrOx-grad-iPrOx), and 1.28 and 1.04 for nPrOx and EtOx, respectively, indicating the favorable formation of the random copolymers P(nPrOx-ran-EtOx). Both gradient and random copolymers followed a simple and practic...
200 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 15 |
| 2020 | 16 |
| 2019 | 10 |
| 2018 | 14 |
| 2017 | 16 |
| 2016 | 17 |