Living free‐radical polymerization of sterically hindered monomers: Improving the understanding of 1,1‐disubstituted monomer systems

The sterically hindered, 1,1‐disubstituted monomers di‐n‐butyl itaconate (DBI), dicyclohexyl itaconate (DCHI), and dimethyl itaconate (DMI) were polymerized with reversible addition–fragmentation chain transfer (RAFT) free‐radical polymerization and atom transfer radical polymerization (ATRP). Cumyl dithiobenzoate, cumyl phenyl dithioacetate, 2‐cyanoprop‐2‐yl dithiobenzoate, 4‐cyanopentanoic acid dithiobenzoate, and S‐methoxycarbonylphenylmethyl dithiobenzoate were employed as RAFT agents to mediate a series of polymerizations at 60 °C yielding polymers ranging in their number‐average molecular weight from 4500 to 60,000 g mol^?1. The RAFT polymerizations of these hindered monomers displayed hybrid living behavior (between conventional and living free‐radical polymerization) of various degrees depending on the molecular structure of the initial RAFT agent. In addition, DCHI was polymerized via ATRP with a CuCl/methyl benzoate/N,N,N′,N″,N″‐pentamethyldiethylenetriamine/cyclohexanone system at 60 °C. Both the ATRP and RAFT polymerization of the hindered monomers displayed living characteristics; however, broader than expected molecular weight distributions were observed for the RAFT systems (polydispersity index = 1.15–3.35). To assess the cause of this broadness, chain‐transfer‐to‐monomer constants for DMI, DBI, and DCHI were determined (1.4 × 10^?3, 1.3 × 10^?3, and 1.0 × 10^?3, respectively) at 60 °C. Simulations carried out with the PREDICI program package suggested that chain transfer to monomer contributed to the broadening process. In addition, the experimental results indicated that viscosity had a pronounced effect on the broadness of the molecular weight distributions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3692–3710, 2006     

Narrow disperse polymers using amine functionalized dithiobenzoate RAFT agent and easy removal of thiocarbonyl end group from the resultant polymers

A novel amine functionalized RAFT agent, 2‐cyanoprop‐2‐yl(4‐N,N‐dimethylaminophenyl) dithiobenzoate has been synthesized and used to control the polymerization of vinyl monomers. This dithiobenzoate RAFT agent, although air sensitive, controlled the polymerization of MMA and St very well in an inert atmosphere and the polymerization results obtained were marginally better than using the most popular 2‐cyanoprop‐2‐yl dithiobenzoate RAFT agent. The living nature of these polymerizations was confirmed by kinetics study and chain extension reactions to yield narrow disperse di‐block copolymers. Most importantly, use of this novel RAFT agent simplified the removal procedure of the color causing end thiocarbonyl group from the RAFT derived polymers and thereby leading to polymers with improved appearance. The removal of end group from the polymer was confirmed by ¹H NMR and UV‐vis spectroscopic techniques. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Reversible addition–fragmentation chain‐transfer polymerization: Unambiguous end‐group assignment via electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry was performed to identify the structure of polymeric methyl acrylates generated via the cumyl dithiobenzoate (CDB), cumyl p‐fluorodithiobenzoate (CPFDB), and 1‐phenylethyl dithiobenzoate (PEDB) mediated reversible addition–fragmentation chain‐transfer (RAFT) polymerizations. The relatively simple spectra clearly demonstrate the end groups of this living free‐radical polymerization technique. Only polymeric chains carrying one leaving group of the RAFT agent and the dithiobenzoate end group as the active RAFT center were discovered. Multiple‐stage mass spectrometric experiments and oxidation of the dithioester end group confirmed the structure of the generated polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4032–4037, 2002     

Precision synthesis of acrylate multiblock copolymers from consecutive microreactor RAFT polymerizations

Well‐defined acrylate RAFT polymers and multiblock‐copolymers have been synthesized via the use of a continuous‐flow microreactor, in which polymerizations could be executed in 5?20 min reaction time. First, Poly(n‐butyl acrylate) (PnBuA) was synthesized in the micro‐flowreactor by using two different trithiocarbonate RAFT agents. Reaction time and reaction temperature were optimized and collected samples were directly studied with NMR, SEC and ESI‐MS to determine conversion, molar mass and end group fidelity. Using the continuous flow technique, highly reproducible and fast polymerizations yielded quantitatively functionalized PnBuA in a very facile and efficient manner. One batch of RAFT acrylate polymer with a molar mass of 1100 g mol^?1 and excellent end group fidelity was employed as a macro‐RAFT agent for the subsequent copolymerization with different acrylate monomers (2‐ethylhexyl acrylate, t‐butyl acrylate, n‐butyl acrylate). Using this procedure, a sequential multiblock‐copolymer (M_n = 31,200 g mol^?1, PDI = 1.46) consisting of five consecutive acrylate blocks was synthesized. This study clearly demonstrates the potential of using a continuous‐flow microreactor for subsequent RAFT polymerizations towards well‐defined multiblock‐copolymers. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013, 51, 2366–2374     

Synthesis of comb polymers via grafting‐onto macromolecules bearing pendant diene groups via the hetero‐Diels‐Alder‐RAFT click concept

Comb polymers were synthesized by the “grafting‐onto” method via a combination of Reversible Addition‐Fragmentation Chain Transfer (RAFT) polymerization and the hetero‐Diels‐Alder (HDA) cycloaddition. The HDA reactive monomer trans, trans‐hexa‐2,4‐dienylacrylate (ttHA) was copolymerized with styrene via the RAFT process. Crosslinking was minimized by decreasing the monomer concentration—whilst keeping monomer to polymer conversions low—resulting in reactive backbones with on average one reactive pendant diene groups for 10 styrene units. The HDA cycloaddition was performed between the diene functions of the copolymer and a poly(n‐butyl acrylate) (PnBA) prepared via RAFT polymerization with pyridin‐2‐yldithioformate, which can act as a dienophile. The coupling reactions were performed within 24 h at 50 °C and the grafting yield varies from 75% to 100%, depending on the number average molecular weight of the PnBA (3500 g mol^?1 < M_n < 13,000 g mol^?1) grafted chain and the reaction stoichiometry. The molecular weights of the grafted block copolymers range from 19,000 g mol^?1 to 58,000 g mol^?1 with polydispersities close to 1.25. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1773–1781, 2010     

Novel perfluorocyclobutyl aryl ether‐based well‐defined amphiphilic block copolymer

A series of fluorine‐containing amphiphilic diblock copolymers comprising hydrophobic poly(p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate) (PTPFCBPMA) and hydrophilic poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) segments were synthesized via successive reversible addition fragmentation chain transfer (RAFT) polymerizations. RAFT homopolymerization of p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate was first initiated by 2,2′‐azobisisobutyronitrile using cumyl dithiobenzoate as chain transfer agent, and the results show that the procedure was conducted in a controlled way as confirmed by the fact that the number‐average molecular weights increased linearly with the conversions of the monomer while the polydispersity indices kept below 1.30. Dithiobenzoate‐capped PTPFCHPMA homopolymer was then used as macro‐RAFT agent to mediate RAFT polymerization of 2‐(diethylamino)ethyl methacrylate, which afforded PTPFCBPMA‐b‐PDEAEMA amphiphilic diblock copolymers with different block lengths and narrow molecular weight distributions (M_w/M_n ≤ 1.28). The critical micelle concentrations of the obtained amphiphilic diblock copolymers were determined by fluorescence spectroscopy technique using N‐phenyl‐1‐naphthylamine as probe. The morphology and size of the formed micelles were investigated by transmission electron microscopy and dynamic light scattering, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of degradable poly(methyl methacrylate) star polymers via RAFT copolymerization with cyclic ketene acetals

Copolymerization of the cyclic ketene acetal 5,6‐benzo‐2‐methylene‐1,3‐dioxepane (BMDO) with methyl methacrylate (MMA) is studied with respect to its copolymerization parameters and the suitability to control BMDO/MMA copolymerizations via the reversible addition‐fragmentation chain transfer (RAFT) technique to obtain linear and 4‐arm star polymers. BMDO shows disparate copolymerization behavior with MMA and r₁ = 0.33 ± 0.06 and r₂ = 6.0 ± 0.8 have been determined for polymerization at 110 °C in anisole from fitting copolymer composition vs. comonomer feed data to the Lewis–Mayo equation. Copolymerization of the two monomers is successful in RAFT polymerization employing a trithiocarbonate control agent. As desired, polymers contain only little amount of polyester units stemming from BMDO units and preliminary degradation experiment show that the polymer degrades slowly, but steadily in aqueous 1 M NaOH dispersion. Within ten days, the polymers are broken down to low molecular weight segments from an initial molecular weight of M_n = 6000 g mol^?1. Star (co)polymerization with an erythritol‐based tetra‐functional RAFT agent following the Z‐group approach proceeds efficiently and polymers with a number‐average molecular weight of 10,000 g mol^?1 are readily obtained that degrade in similar manner as the linear copolymer counterparts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1633–1641     

Synthesis of statistical and block copolymers containing adamantyl and norbornyl moieties by reversible addition‐fragmentation chain transfer polymerization

The synthesis of statistical and block copolymers, consisting of monomers often used as resist materials in photolithography, using reversible addition‐fragmentation chain transfer (RAFT) polymerization is reported. Methacrylate and acrylate monomers with norbornyl and adamantyl moieties were polymerized using both dithioester and trithiocarbonate RAFT agents. Block copolymers containing such monomers were made with poly(methyl acrylate) and polystyrene macro‐RAFT agents. In addition to have the ability to control molecular weight, polydispersity, and allow block copolymer formation, the polymers made via RAFT polymerization required end‐group removal to avoid complications during the photolithography. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 943–951, 2010     

Unexpected reactivity for the RAFT copolymerization of oligo(ethylene glycol) methacrylates

Homo‐ and copolymers of di(ethylene glycol) methyl ether methacrylate (DEGMA) and oligo(ethyleneglycol) methyl ether methacrylate (OEGMA₁₁₀₀) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization in ethanol using [M]/[RAFT] ratios of 100 and 200. Kinetic investigations on the homo‐ and copolymerization of these monomers were performed using a parallel synthesizer resulting in well‐defined polymers with polydispersity indices mostly below 1.3. The polymerization kinetics are presented and discussed in detail surprisingly revealing that the DEGMA homopolymerization is slower than the OEGMA₁₁₀₀ homopolymerization. Transfer coefficients c were estimated to be ～0.5 for the RAFT polymerization of both DEGMA and OEGMA₁₁₀₀ resulting in hybrid behavior at the beginning of the polymerizations. Subsequent copolymerization also revealed fast incorporation of the OEGMA₁₁₀₀ and relatively slow incorporation of DEGMA resulting in well‐defined copolymers with a molecular weight up to 100 kDa and polydispersities around 1.20. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2811–2820, 2009     

Synthesis of comb‐like polystyrene with poly(N‐phenyl maleimide‐alt‐p‐chloromethyl styrene) as macroinitiator

The copolymerization of N‐phenyl maleimide and p‐chloromethyl styrene via reversible addition–fragmentation chain transfer (RAFT) process with AIBN as initiator and 2‐(ethoxycarbonyl)prop‐2‐yl dithiobenzoate as RAFT agent produced copolymers with alternating structure, controlled molecular weights, and narrow molecular weight distributions. Using poly(N‐phenyl maleimide‐alt‐p‐chloromethyl styrene) as the macroinitiator for atom transfer radical polymerization of styrene in the presence of CuCl/2,2′‐bipyridine, well‐defined comb‐like polymers with one graft chain for every two monomer units of backbone polymer were obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2069–2075, 2006     

Well‐defined phosphonate‐functional copolymers through RAFT copolymerization of dimethyl‐p‐vinylbenzylphosphonate

Dibenzyltrithiocarbonate‐mediated RAFT polymerization of dimethyl‐p‐vinylbenzylphosphonate and its copolymerization with styrene are studied in order to access well‐defined statistical and block copolymers containing controlled amounts of dimethylphosphonate groups. NMR and SEC analysis of the (co)polymers confirm the controlled character of the polymerizations. ABA triblock copolymers are treated with TMSiBr/MeOH in order to transform the dimethylphosphonate groups into phosphonic acids while keeping the midchain trithiocarbonate group and triblock nature unaffected. Alternatively, the combination of trithiocarbonate aminolysis with TMSiBr/MeOH treatment of the same triblock copolymers leads to phosphonic acid‐functional diblock copolymer counterparts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2616‐2624     

Dendrimers as scaffolds for multifunctional reversible addition–fragmentation chain transfer agents: Syntheses and polymerization

The synthesis and characterization of novel first‐ and second‐generation true dendritic reversible addition–fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3‐benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z‐group architecture based on 1,1,1‐hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free‐radical polymerization at 60 °C. The novel dendrimer‐based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number‐average molecular weight (M_n) with the monomer–polymer conversion, yielding star polymers with molecular weights of up to M_n = 160,000 g mol^?1 for PBA (based on a linear PBA calibration) and up to M_n = 70,000 g mol^?1 for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1‐hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star‐shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star‐shaped polymeric materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5877–5890, 2004     

Synthesis of SAN‐containing block copolymers using RAFT polymerization

Copolymerization of styrene and acrylonitrile was carried out via reversible addition‐fragmentation chain transfer process (RAFT) in the presence of cumyl dithiobenzoate with AIBN as initiator. Copolymerization proceeded in a controlled/“living” fashion, and the copolymer composition depended on the feed ratio of monomer pairs. Block copolymers comprising styrene and acrylonitrile (SAN) segments and various functional blocks were synthesized through chain extension using the first blocks as macromolecular chain transfer agents (macroCTAs). Since the polymerization of both blocks proceeded through the RAFT process, the resulting block copolymers exhibited relatively narrow molecular weight distribution, with polydispersity indices in the range of 1.29–1.46. Gel permeation chromatography (GPC), and ¹H NMR and FTIR measurements confirmed the successful synthesis of the functionalized block copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2260–2269, 2006     

Synthesis of ultra‐high molecular weight polymers by controlled production of initiating radicals

This study demonstrates that the gradual and slow production of initiating radicals (i.e., hydroxyl radicals here) is the key point for the synthesis of ultra‐high molecular weight (UHMW) polymers via controlled radical polymerization. Hydrogen peroxide (H₂O₂) and ferrous iron (Fe²⁺) react via Fenton redox chemistry to initiate RAFT polymerization. This work presents two enzymatic‐mediated (i.e., Bio‐Fenton‐RAFT and Semi Bio‐Fenton‐RAFT) and one syringe pump‐driven Fenton‐RAFT polymerization processes in which the initiating radicals are carefully and gradually dosed into the reaction solution. The “livingness” of the synthesized UHMW polymers is demonstrated by chain extension and aminolysis experiments. Zimm plots obtained from static light scattering (SLS) technique are used to characterize the UHMW polymers. This Fenton‐RAFT polymerization provides access to polymers of unprecedented UHMW (M_w ~ 20 × 10⁶ g mol^?1) with potential in diverse applications. The UHMW polymers made via the controlled Fenton‐RAFT polymerization by using a syringe pump shows that it is possible to produce such materials through an easy‐to‐set up and scalable process. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1922–1930     

Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT Polymerization

Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl‐based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The PFCB‐containing acrylate monomer, p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)‐phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2′‐azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number‐average molecular weights (M_n) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (M_w/M_n≦1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4‐cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG‐CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB‐based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique.     

Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n‐butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free‐radical process. Although the polyester‐core‐based RAFT agent mediated polymerization of n‐butyl acrylate displayed a linear evolution of the number‐average molecular weight (M_n) up to high monomer conversions (>70%) and molecular weights [M_n > 140,000 g mol^?1, linear poly(methyl methacrylate) equivalents)], the corresponding styrene‐based system reached a maximum molecular weight at low conversions (≈30%, M_n = 45,500 g mol^?1, linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n‐butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene‐based star polymers were successfully cast into highly regular honeycomb‐structured microarrays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3847–3861, 2003     

Visible light‐induced RAFT polymerization of methacrylates with benzaldehyde derivatives as organophotoredox catalysts

The benzaldehyde derivatives, such as 2,4‐dimethoxy benzaldehyde (PC1) and p‐anisaldehyde (PC2), were successfully used as photoredox catalysts (PCs) in combination with typical RAFT agent 4‐cyano‐4‐(phenylcarbonothioylthio)pentanoic acid (CTP) for the controlled photoinduced electron transfer RAFT polymerization (PET‐RAFT) of methyl methacrylate (MMA) and benzyl methacrylate (BnMA) at room temperature. The kinetics of the polymerizations showed first order with respect to monomer conversions. Besides, the average number molecular weights (M_n) of the produced polymers increased linearly with the monomer conversions and kept relatively narrow polydispersity (PDI = M_w/M_n). For example, the M_n of PMMA increased from about 3400 to 17,300 g mol⁻¹ with the increasing in monomer conversion from 11% to 85%, and the PDI maintained around 1.36. The living features of polymerizations with the PC1 and PC2 as catalysts have also been further supported by chain extension and synthesis of PMMA‐b‐PBnMA diblock copolymer. As a result, the simplicity and efficiency of benzaldehyde derivatives catalyzed PET‐RAFT polymerization have been demonstrated under mild conditions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 229–236     

R‐RAFT approach for the polymerization of N‐isopropylacrylamide with a star poly(ε‐caprolactone) core

Reversible addition‐fragmentation chain transfer (RAFT) polymerization is a more robust and versatile approach than other living free radical polymerization methods, providing a reactive thiocarbonylthio end group. A series of well‐defined star diblock [poly(ε‐caprolactone)‐b‐poly(N‐isopropylacrylamide)]₄ (SPCLNIP) copolymers were synthesized by R‐RAFT polymerization of N‐isopropylacrylamide (NIPAAm) using [PCL‐DDAT]₄ (SPCL‐DDAT) as a star macro‐RAFT agent (DDAT: S‐1‐dodecyl‐S′‐(α, α′‐dimethyl‐α″‐acetic acid) trithiocarbonate). The R‐RAFT polymerization showed a controlled/“living” character, proceeding with pseudo‐first‐order kinetics. All these star polymers with different molecular weights exhibited narrow molecular weight distributions of less than 1.2. The effect of polymerization temperature and molecular weight of the star macro‐RAFT agent on the polymerization kinetics of NIPAAm monomers was also addressed. Hardly any radical–radical coupling by‐products were detected, while linear side products were kept to a minimum by careful control over polymerization conditions. The trithiocarbonate groups were transferred to polymer chain ends by R‐RAFT polymerization, providing potential possibility of further modification by thiocarbonylthio chemistry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Facile synthesis of controlled‐structure primary amine‐based methacrylamide polymers via the reversible addition‐fragmentation chain transfer process

We report here a novel direct method for the syntheses of primary aminoalkyl methacrylamides that requires mild reagents and no protecting group chemistry. The reversible addition‐fragmentation chain transfer polymerization (RAFT) of the aminoalkyl methacrylamide revealed to be highly efficient with 4‐cyanopentanoic acid dithiobenzoate (CTP) as chain transfer agent and 4,4′‐azobis(4‐cyanovaleric acid) (ACVA) as initiator. Cationic amino‐based homopolymers of reasonably narrow polydispersities (M_w/M_n < 1.30) and predetermined molecular weights were obtained without recourse to any protecting group chemistry. A range of block and random copolymers were also synthesized via the RAFT process. The homopolymers and copolymers were characterized by aqueous conventional and triple detection gel permeation chromatography systems. Furthermore, the primary amine‐based methacrylamide monomers and polymers revealed to be highly stable both with the primary amino group in the protonated and deprotonated form. We have also demonstrated that stabilized gold nanoparticles can be generated with the RAFT‐synthesized amine‐based polymers via a photochemical process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4984–4996, 2008     

A facile route to ureidopyrimidinone‐functionalized polymers via RAFT

Three new ureidopyrimidinone(UPy)‐functionalized chain‐transfer agents (CTAs) have been synthesized for use in reversible addition‐fragmentation chain transfer (RAFT) polymerization. These UPy‐CTAs are able to polymerize a wide variety of vinyl monomers to yield UPy‐functionalized polymers, including homopolymers, block copolymers, and amphiphilic block copolymers. These polymers have been characterized via ¹H and ¹³C NMR spectroscopy, gel permeation chromatography (GPC), UV/visible spectroscopy and differential scanning calorimetry (DSC) to demonstrate end‐group fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010