Jin-Shan Wang

Bio: Jin-Shan Wang is an academic researcher from Carnegie Mellon University. The author has contributed to research in topics: Radical polymerization & Living free-radical polymerization. The author has an hindex of 7, co-authored 12 publications receiving 7395 citations.

Controlled Living Radical Polymerization - Halogen Atom-Transfer Radical Polymerization Promoted by a Cu(I)Cu(II) Redox Process

Abstract: An extension of atom transfer radical addition, ATRA, to atom transfer radical polymerization, ATRP, provided a new and efficient way to conduct controlled/living radical polymerization. By using a simple alkyl halide, R-X (X = Cl and Br), as an initiator and a transition metal species complexed by suitable ligand(s), M t n /L x , e.g., CuX/2,2'-bipyridine, as a catalyst, ATRP of vinyl monomers such as styrenes and (meth)acrylates proceeded in a living fashion, yielding polymers with degrees of polymerization predetermined by Δ[M]/[I] 0 up to M n ≃ 10 5 and low polydispersities, 1.1 < M w /M n < 1.5. The participation of free radical intermediates was supported by analysis of the end groups and the stereochemistry of the polymerization. The general principle and the mechanism of ATRP are elucidated. Various factors affecting the ATRP process are discussed.

Novel (co)polymers and a novel polymerization process based on atom (or group) transfer radical polymerization

Abstract: A new polymerization process (atom transfer radical polymerization, or ATRP) based on a redox reaction between a transition metal (e.g., Cu(I)/Cu(II)), provides 'living' or controlled radical polymerization of styrene, (meth)acrylates, and other radically polymerizable monomers. Using various simple organic halides as model halogen atom transfer precursors (initiators) and transition metal complexes as a model halogen atom transfer promoters (catalysts), a 'living' radical polymerization affords (co)polymers having the predetermined number average molecular weight by Δ[M]/[I]o (up to Mn > 105) and a surprisingly narrow molecular weight distribution (Mw/Mn), as low as 1.15. The participation of free radical intermediates in ATRP is supported by end-group analysis and stereochemistry of the polymerization. In addition, polymers with various topologies (e.g., block, random, star, end-functional and in-chain functional copolymers [for example, of styrene and methyl (meth)acrylate]) have been synthesized using the present process. The polymeric products encompassed by the present invention can be widely used as plastics, elastomers, adhesives, emulsifiers, thermoplastic elastomers, etc.

Improved processes based on atom (or group) transfer radical polymerization and novel (co)polymers having useful structures and properties

Abstract: Improved processes for atom (or group) transfer radical polymerization (ATRP) and novel polymers have been developed and are described. In certain embodiments, novel copolymers comprising a least one polymeric branch or polymeric block with a predominantly alternating monomer sequence are described. Novel copolymers comprising a least one polymeric branch or polymeric block with a gradient monomer structure are described. Additionally, novel copolymers comprising a least one polymeric branch or polymeric block with a predominantly periodic monomer sequence are also described. Novel copolymers having a water soluble backbone and at least two hydrophobic polymeric branches grafted to the water soluble backbone are also described.

Living free-radical polymerization by reversible addition - Fragmentation chain transfer: The RAFT process

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