scispace - formally typeset
Search or ask a question
Author

Julia Krstina

Bio: Julia Krstina is an academic researcher from Commonwealth Scientific and Industrial Research Organisation. The author has contributed to research in topics: Chain transfer & Radical polymerization. The author has an hindex of 14, co-authored 20 publications receiving 6849 citations.

Papers
More filters
Journal ArticleDOI
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

4,561 citations

Journal ArticleDOI
TL;DR: In this article, free radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization) is discussed with a view to answering the following questions: (a) How living is RAFT polymerization? (b) What controls the activity of thiocarbonylthio compounds in RAFT polymers, and (c) How do rates of polymerization differ from those of conventional radical polymerisation? (d) Can RAFT agents be used in emulsion polymerization; and (e) Retardation, observed when high concentra-
Abstract: Free radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization) is discussed with a view to answering the following questions: (a) How living is RAFT polymerization? (b) What controls the activity of thiocarbonylthio compounds in RAFT polymeriza- tion? (c) How do rates of polymerization differ from those of conventional radical polymerization? (d) Can RAFT agents be used in emulsion polymerization? Retardation, observed when high concentra- tions of certain RAFT agents are used and in the early stages of emulsion polymerization, and how to overcome it by appropriate choice of reaction conditions, are considered in detail. Examples of the use of thiocarbonylthio RAFT agents in emulsion and miniemulsion polymerization are provided. # 2000 Society of Chemical Industry

803 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of substituents R of dithiobenzoate RAFT agents [SC(Ph)S−R] on the outcome of polymerizations of styrene, methyl methacrylate (MMA), and butyl (BA) or methyl acrylate(MA).
Abstract: Radical polymerization with reversible addition−fragmentation chain transfer (RAFT polymerization) can be used to synthesize a wide range of polymers of controlled architecture and narrow molecular weight distribution. The polymerizations use addition−fragmentation chain transfer agents (RAFT agents) that possess high transfer coefficients in free radical polymerization and confer living character on the polymerization. This paper explores the effect of the substituents R of dithiobenzoate RAFT agents [SC(Ph)S−R] on the outcome of polymerizations of styrene, methyl methacrylate (MMA) and butyl (BA) or methyl acrylate (MA). In MMA polymerization at 60 °C, effectiveness depends strongly on R decreasing in the order where R is: −C(Alkyl)2CN ∼ −C(Me)2Ar > −C(Me)2C(O)O(alkyl) > −C(Me)2C(O)NH(alkyl) > −C(Me)2CH2C(Me)3 ≥ −C(Me)HPh > −C(Me)3 ∼ −CH2Ph. Of these, only the compounds with R = −C(Me)2Ph and −C(Me)2CN provided polymers with substantially narrowed polydispersities in batch polymerization and gave molec...

721 citations

Journal ArticleDOI
TL;DR: In this paper, it is shown that a small number of dead chains are produced by radical-radicaltermination of a trithio-carbonate moiety, and that the active functionality should be located in the center of the chain.
Abstract: (calcd) is basedon the assumption that all chains contain one trithio-carbonate moiety, it is important to realize that a smallnumber of dead chains are produced by radical-radicaltermination.Polymers prepared with symmetrical trithiocarbon-ates should have the active functionality located in thecenter, e.g.,

402 citations


Cited by
More filters
Journal ArticleDOI
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

4,561 citations

Journal ArticleDOI
TL;DR: In this article, a review of recent mechanistic developments in the field of controlled/living radical polymerization (CRP) is presented, with particular emphasis on structure-reactivity correlations and "rules" for catalyst selection in ATRP, for chain transfer agent selection in reversible addition-fragmentation chain transfer (RAFT) polymerization, and for the selection of an appropriate mediating agent in stable free radical polymerisation (SFRP), including organic and transition metal persistent radicals.

2,869 citations

Journal ArticleDOI
TL;DR: A review of living radical polymerization achieved with thiocarbonylthio compounds by a mechanism of reversible addition-fragmentation chain transfer (RAFT) is presented in this article.
Abstract: This paper presents a review of living radical polymerization achieved with thiocarbonylthio compounds [ZC(=S)SR] by a mechanism of reversible addition–fragmentation chain transfer (RAFT). Since we first introduced the technique in 1998, the number of papers and patents on the RAFT process has increased exponentially as the technique has proved to be one of the most versatile for the provision of polymers of well defined architecture. The factors influencing the effectiveness of RAFT agents and outcome of RAFT polymerization are detailed. With this insight, guidelines are presented on how to conduct RAFT and choose RAFT agents to achieve particular structures. A survey is provided of the current scope and applications of the RAFT process in the synthesis of well defined homo-, gradient, diblock, triblock, and star polymers, as well as more complex architectures including microgels and polymer brushes.

2,127 citations