Synthesis of refractive star‐shaped polysulfide by anionic polymerization of phenoxy propylene sulfide using an initiating system consisting of trifunctional thiol derived from five‐membered cyclic dithiocarbonate and amine

Star‐shaped poly(phenoxy propylene sulfide) [poly (PPS)] were synthesized by anionic polymerization using a trifunctional initiator ( I ₁) derived from a trifunctional five‐membered cyclic dithiocarbonate and benzyl amine. Conditions for the anionic polymerization of PPS were optimized to obtain polymers with desired M_ns and narrow M_w/M_ns. The best catalyst and solvent were DBU and DMF, respectively. The star‐shaped structure of the resulting star poly(PPS) was supported by SEC analysis. The refractive indexes (n_D) of the star poly (PPS) were relatively high (>1.64). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 525–531, 2010     

Star‐like PAA‐g‐PPO well‐defined amphiphilic graft copolymer synthesized by ATNRC and SET‐NRC reaction

A series of well‐defined amphiphilic star graft copolymers consisting of hydrophilic poly(acrylic acid) backbone and hydrophobic poly(propylene oxide) side chains were synthesized by the sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization and atom transfer nitroxide radical coupling (ATNRC) or single electron transfer‐nitroxide radical coupling (SET‐NRC) reaction followed by the selective hydrolysis of poly(tert‐butyl acrylate) backbone. A Br‐containing acrylate monomer, tert‐butyl 2‐((2‐bromopropanoyloxy)methyl)acrylate, was first homopolymerized via RAFT polymerization using a new star‐like chain‐transfer agent with four arms in a controlled way to give a well‐defined star‐like backbone with a narrow molecular weight distribution (M_w/M_n = 1.23). The grafting‐onto strategy was used to synthesize the well‐defined PtBA‐g‐PPO star graft copolymers with narrow molecular weight distributions (M_w/M_n = 1.14–1.25) via ATNRC or SET‐NRC reaction between the Br‐containing PtBA‐based star‐like backbone and poly(propylene oxide) with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl end group using CuBr/PMDETA or Cu/PMDETA as catalytic system. PAA‐g‐PPO amphiphilic star graft copolymers were obtained by the selective acidic hydrolysis of star‐like PtBA‐based backbone in acidic environment without affecting the side chains. The critical micelle concentrations in aqueous media and brine were determined by the fluorescence probe technique. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2084–2097, 2010     

Synthesis of star‐shaped polystyrenes via nitroxide‐mediated stable free‐radical polymerization

High molecular weight star‐shaped polystyrenes were prepared via the coupling of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) terminated polystyrene oligomers with divinylbenzene (DVB) in m‐xylene at 138 °C. The optimum ratio of the coupling solvent (m‐xylene) to divinylbenzene was determined to be 9 to 1 based on volume. Linear polystyrene oligomers (M_n = 19,300 g/mol, M_w/M_n = 1.10) were prepared in bulk styrene using benzoyl peroxide in the presence of TEMPO at approximately 130 °C under an inert atmosphere. Coupling of the TEMPO‐terminated oligomers under optimum conditions resulted in a product with a number average molecular weight exceeding 300,000 g/mol (M_w/M_n = 3.03) after 24 h, suggesting the formation of relatively well‐defined star‐shaped polymers. Additionally, the intrinsic viscosities of the star‐shaped products were lower than calculated values for linear analogs of equivalent molecular weight, which further supported the formation of a star‐shaped architecture. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 216–223, 2001     

Star‐shaped cyclopolymers: A new category of star polymer with rigid cyclized arms prepared by controlled cationic cyclopolymerization and subsequent microgel formation of divinyl ethers

The combination of living/controlled cationic cyclopolymerization and crosslinking polymerization of bifunctional vinyl ethers (divinyl ethers) was applied to the synthesis of core‐crosslinked star‐shaped polymers with rigid cyclized arms. Cyclopolymerization of 4,4‐bis(vinyloxymethyl)cyclohexene ( 1 ), a divinyl ether with a cyclohexene group, was investigated with the hydrogen chloride/zinc chloride (HCl/ZnCl₂) initiating system in toluene at 0 °C. The reaction proceeded quantitatively to give soluble poly( 1 )s in organic solvents. The content of the unreacted vinyl groups in the produced polymers was less than ～3 mol%, and therefore, the degree of cyclization of the polymers was determined to be ～97%. The number‐average molecular weight (M_n) of the polymers increased in direct proportion to monomer conversion and further increased on addition of a fresh monomer feed to the almost completely polymerized reaction mixture, indicating that living cyclopolymerization of 1 occurred. The chain linking reactions among the formed living cyclopolymers with 1,4‐bis(vinyloxy)cyclohexane ( 3 ) as a crosslinker in toluene at 0 °C produced core‐crosslinked star‐shaped cyclopoly( 1 )s [star‐poly( 1 )s] in high yield (100%). Dihydroxylation of the cyclohexene double bonds of star‐poly( 1 ) gave hydrophilic water‐soluble star‐shaped polymers with rigid arm structure [star‐poly( 1 )‐OH] with thermo‐responsive function in water. T_gs of star‐poly( 1 ) and star‐poly( 1 )‐OH were 135 °C and 216 °C, respectively; these values are very high as vinyl ether‐based star‐shaped polymers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1094–1102     

H‐shaped (ABCDE type) quintopolymer via click reaction [3 + 2] strategy

H‐shaped quintopolymer containing different five blocks: poly(ε‐caprolactone) (PCL), polystyrene (PS), poly(ethylene glycol) (PEG), and poly(methyl methacrylate) (PMMA) as side chains and poly(tert‐butyl acrylate) (PtBA) as a main chain was simply prepared from a click reaction between azide end‐functionalized PCL‐PS‐PtBA 3‐miktoarm star terpolymer and PEG–PMMA‐block copolymer with alkyne at the junction point, using Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as a catalyst in DMF at room temperature for 20 h. The H‐shaped quintopolymer was obtained with a number–average molecular weight (M_n) around 32,000 and low polydispersity index (M_w/M_n) 1.20 as determined by GPC analysis in THF using PS standards. The click reaction efficiency was calculated to have 60% from ¹H NMR spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4459–4468, 2008     

Combination of nitroxide‐mediated polymerization and SET‐LRP for the synthesis of high molar mass branched and star‐branched poly(n‐butyl acrylate) characterized by size exclusion chromatography and rheology

Branched and star‐branched polymers were successfully synthesized by the combination of two successive controlled radical polymerization methods. A series of linear and star poly(n‐butyl acrylate)‐co‐poly(2‐(2‐bromoisobutyryloxy) ethyl acrylate) statistical copolymers, P(nBA‐co‐BIEA)_x, were first synthesized by nitroxide‐mediated polymerization (NMP at T > 100 °C). The subsequent polymerization of n‐butyl acrylate by single electron transfer‐living radical polymerization (SET‐LRP at T = 25 °C), initiated from the brominated sites of the P(nBA‐co‐BIEA)_x copolymer, produced branched or star‐branched poly(n‐butyl acrylate) (PnBA). Both types of polymerizations (NMP and SET‐LRP) exhibited features of a controlled polymerization with linear evolutions of logarithmic conversion versus time and number‐average molar masses versus conversion for final M_n superior to 80,000 g mol^?1. The branched and star‐branched architectures with high molar mass and low number of branches were fully characterized by size exclusion chromatography. The Mark–Houwink Sakurada relationship and the analysis of the contraction factor (g′ = ([η]_branched/[η]_linear)_M) confirmed the elaboration of complex PnBA. The zero‐shear viscosities of the linear, star‐shaped, branched, and star‐branched polymers were compared. The modeling of the rheological properties confirmed the synthesis of the branched architectures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of well‐defined cyclodextrin‐core star polymers

The synthesis of 21‐arm methyl methacrylate (MMA) and styrene star polymers is reported. The copper (I)‐mediated living radical polymerization of MMA was carried out with a cyclodextrin‐core‐based initiator with 21 independent discrete initiation sites: heptakis[2,3,6‐tri‐O‐(2‐bromo‐2‐methylpropionyl]‐β‐cyclodextrin. Living polymerization occurred, providing well‐defined 21‐arm star polymers with predicted molecular weights calculated from the initiator concentration and the consumed monomer as well as low polydispersities [e.g., poly(methyl methacrylate) (PMMA), number‐average molecular weight (M_n) = 55,700, polydispersity index (PDI) = 1.07; M_n = 118,000, PDI = 1.06; polystyrene, M_n = 37,100, PDI = 1.15]. Functional methacrylate monomers containing poly(ethylene glycol), a glucose residue, and a tert‐amine group in the side chain were also polymerized in a similar fashion, leading to hydrophilic star polymers, again with good control over the molecular weight and polydispersity (M_n = 15,000, PDI = 1.03; M_n = 36,500, PDI = 1.14; and M_n = 139,000, PDI = 1.09, respectively). When styrene was used as the monomer, it was difficult to obtain well‐defined polystyrene stars at high molecular weights. This was due to the increased occurrence of side reactions such as star–star coupling and thermal (spontaneous) polymerization; however, low‐polydispersity polymers were achieved at relatively low conversions. Furthermore, a star block copolymer consisting of PMMA and poly(butyl methacrylate) was successfully synthesized with a star PMMA as a macroinitiator (M_n = 104,000, PDI = 1.05). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2206–2214, 2001     

Star‐shaped and photocrosslinked poly(1,5‐dioxepan‐2‐one): Synthesis and characterization

New star‐shaped and photocrosslinked poly(1,5‐dioxepan‐2‐one) (PDXO) has been synthesized through ring‐opening polymerization initiated by SnOct₂/pentaerythritol. The star‐shaped PDXO was end‐functionalized by acrolyol chloride to form acrylate end groups. The end‐functionalized PDXO was photocrosslinked initiated by 2,2‐dimethoxy‐2‐phenylacetophenone. The gel content ranged from 80 to 99%, indicating a high degree of crosslinking. The thermal properties of the star‐shaped PDXO and the photocrosslinked PDXO were analyzed by differential scanning calorimetry. The glass‐transition temperature was determined to approximately ?32 °C for the crosslinked PDXO. The viscosity numbers were determined for star‐shaped PDXO, with reference to linear homologues. The star‐shaped PDXO had lower viscosity numbers than the linear counterparts. The crosslinked PDXO showed a rather hydrophilic surface as compared with other resorbable polyesters. The advancing contact angle was 64 ± 2, and the receding angle was 57 ± 4. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2049–2054, 2002     

Multiarm star block and multiarm star mixed‐block copolymers via azide‐alkyne click reaction

The synthesis of multiarm star block (and mixed‐block) copolymers are efficiently prepared by using Cu(I) catalyzed azide‐alkyne click reaction and the arm‐first approach. α‐Silyl protected alkyne polystyrene (α‐silyl‐alkyne‐PS) was prepared by ATRP of styrene (St) and used as macroinitiator in a crosslinking reaction with divinyl benzene to successfully give multiarm star homopolymer with alkyne periphery. Linear azide end‐functionalized poly(ethylene glycol) (PEG‐N₃) and poly (tert‐butyl acrylate) (PtBA‐N₃) were simply clicked with the multiarm star polymer described earlier to form star block or mixed‐block copolymers in N,N‐dimethyl formamide at room temperature for 24 h. Obtained multiarm star block and mixed‐block copolymers were identified by using ¹H NMR, GPC, triple detection‐GPC, atomic force microscopy, and dynamic light scattering measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 99–108, 2010     

Synthesis of starlike PtBA‐g‐PEO amphiphilic graft copolymer via highly efficient Cu‐catalyzed SET‐NRC reaction at ambient temperature

Two new amphiphilic star graft copolymers bearing hydrophobic poly(tert‐butyl acrylate) backbone and hydrophilic poly(ethylene oxide) (PEO) side chains with different molecular weights were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization and single electron transfer‐nitroxide radical coupling (SET‐NRC) reaction under mild conditions. RAFT homopolymerization of tert‐butyl 2‐((2‐bromopropanoyloxy)methyl)acrylate was mediated by a four‐armed chain transfer agent in a controlled way to afford a well‐defined starlike backbone with a narrow molecular weight distribution (M_w/M_n = 1.26). The target poly(tert‐butyl acrylate)‐g‐PEO (PtBA‐g‐PEO) star graft copolymers were synthesized by SET‐NRC reaction between Br‐containing PtBA‐based starlike backbone and PEO end functionalized with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) group using copper/N,N,N′,N′,N″‐pentamethyldiethylenetriamine as catalytic system at ambient temperature via grafting‐onto strategy. The critical micelle concentration values of the obtained amphiphilic star graft copolymers in aqueous media and brine were determined by fluorescence probe technique using pyrene as probe. Diverse micellar morphologies were formed by varying the content of hydrophilic PEO segment as well as the initial concentration of stock solution. In addition, poly(acrylic acid)‐g‐PEO double hydrophilic star graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA starlike backbone without affecting PEO side chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Star polymers by cross‐linking of linear poly(benzyl‐L‐glutamate) macromonomers via free‐radical and RAFT polymerization. A simple route toward peptide‐stabilized nanoparticles

Poly(benzyl‐L ‐glutamate) (PBLG) macromonomers were synthesized by N‐carboxyanhydride (NCA) polymerization initiated with 4‐vinyl benzylamine. MALDI‐ToF analysis confirmed the presence of styrenic end‐groups in the PBLG. Free‐radical and RAFT polymerization of the macromonomer in the presence of divinyl benzene produced star polymers of various molecular weights, polydispersity, and yield depending on the reaction conditions applied. The highest molecular weight (M_w) of 10,170,000 g/mol was obtained in a free‐radical multibatch approach. It was shown that the PBLG star polymers can be deprotected to obtain poly(glutamic acid) star polymers, which form water soluble pH responsive nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of 4μ‐PS2PEO2, 4μ‐PS2PCL2, 4μ‐PI2PEO2, and 4μ‐PI2PCL2 star‐shaped copolymers by the combination of glaser coupling with living anionic polymerization and ring‐opening polymerization

4μ‐A₂B₂ star‐shaped copolymers contained polystyrene (PS), poly(isoprene) (PI), poly(ethylene oxide) (PEO) or poly(ε‐caprolactone) (PCL) arms were synthesized by a combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). Firstly, the functionalized PS or PI with an alkyne group and a protected hydroxyl group at the same end were synthesized by LAP and then modified by propargyl bromide. Subsequently, the macro‐initiator PS or PI with two active hydroxyl groups at the junction point were synthesized by Glaser coupling in the presence of pyridine/CuBr/N,N,N ′,N ″,N ″‐penta‐methyl diethylenetri‐amine (PMDETA) system and followed by hydrolysis of protected hydroxyl groups. Finally, the ROP of EO and ε‐CL monomers was carried out using diphenylmethyl potassium (DPMK) and tin(II)‐bis(2‐ethylhexanoate) (Sn(Oct)₂) as catalyst for target star‐shaped copolymers, respectively. These copolymers and their intermediates were well characterized by SEC, ¹H NMR, MALDI‐TOF mass spectra and FT‐IR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of multiarmed poly(3‐hexyl thiophene) star polymer with microgel core by GRIM and ATRP methods

Regioregular poly(3‐hexyl thiophene) (rr‐P3HT)‐based star polymers were synthesized by a crosslinking reaction of the linear rr‐P3HT macroinitiator and ethylene glycol dimethacrylate (EGDMA) crosslinker through Ru‐based atom transfer radical polymerization (ATRP), where the rr‐P3HT macroinitiator was prepared by Grignard metathesis method (GRIM) followed by end functionalization of the ATRP initiator with chlorophenylacetate (CPA) to the rr‐P3HT. Relatively high molecular weight of the star polymers were obtained (M_p = 8,988,000 g/mol), which consisted of large numbers of the rr‐P3HT arm chains radiating from the EGDMA‐based microgel core. The yield of the star polymers were strongly affected by the added amount of the EGDMA crosslinker. The crystalline structure of the rr‐P3HT by intermolecular π‐π stacking interaction gradually decreased as the star polymer formed, which was confirmed by differential scanning calorimeter (DSC), atomic force microscopy (AFM), and electro‐optical analyses. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of cyclic polysulfides: Controlled ring‐expansion polymerization of cyclic tetrathioester with thiirane

We synthesized cyclic tetrathioesters containing thioester moieties at the o‐position (o‐CTE) and m‐position (m‐CTE) of an aromatic skeleton. The reaction of phenoxy propylenesulfide (PPS) with o‐CTE and m‐CTE was examined using tetrabutylammonium chloride as a catalyst in 1‐methyl‐2‐pyrrolidinone, yielding the corresponding cyclic polysulfides poly[o‐CTE(PPS)_n] with M_n's = 37,000–54,000 at 34–61% yields and poly[m‐CTE(PPS)_n] with M_n's = 46,600–107,200 at 63–>99% yields. Although the molecular weights of poly[o‐CTE(PPS)_n] could not be controlled, those of poly[m‐CTE(PPS)_n] could be controlled by the feed ratios of PPS and reaction temperature. Furthermore, the glass transition temperature (T_g) and thermal decomposition temperature (T_dⁱ) of poly[m‐CTE(PPS)_n] increased with decreasing molecular weights. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 857–866     

Syntheses of 12‐arm star polymers and star diblock copolymers by nitroxide‐mediated radical polymerization using dendritic dodecafunctional macroinitiators

Dendritic multifunctional macroinitiators having 12 TEMPO‐based alkoxyamines were prepared by the reaction of a benzyl alcohol having 4 TEMPO‐based alkoxyamines with 1,3,5‐tris[(4‐chlorocarbonyl)phenyl]benzene and 1,3,5‐tris(4‐isocyanatophenyl)benzene. Using the dodecafunctional macroinitiators, TEMPO‐mediated radical polymerizations of styrene (St) were carried out at 120 °C, and 12‐arm star polymers ( star‐12 ) with narrow polydispersities of M_w/M_n = 1.06–1.26 were obtained. To evaluate the livingness for the TEMPO‐mediated radical polymerizations of St, hydrolysis of the ester bonds of the 12‐arm star polymers and subsequent SEC measurements were carried out. Furthermore, using star‐12 as the macroinitiator, TEMPO‐mediated radical polymerization of 4‐vinylpyridine (4‐VP) was carried out, and well‐defined poly(St)‐b‐poly(4‐VP) 12‐arm star diblock copolymers with M_w/M_n = 1.18–1.19 were obtained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3689–3700, 2005     

Three‐arm star block copolymers of ε‐caprolactone and acrylic acid: Synthesis and micellization behavior

A series of well‐defined three‐arm star poly(ε‐caprolactone)‐b‐poly(acrylic acid) copolymers having different block lengths were synthesized via the combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). First, three‐arm star poly(ε‐caprolactone) (PCL) (M_n = 2490–7830 g mol^?1; M_w/M_n = 1.19–1.24) were synthesized via ROP of ε‐caprolactone (ε‐CL) using tris(2‐hydroxyethyl)cynuric acid as three‐arm initiator and stannous octoate (Sn(Oct)₂) as a catalyst. Subsequently, the three‐arm macroinitiator transformed from such PCL in high conversion initiated ATRPs of tert‐butyl acrylate (^tBuA) to construct three‐arm star PCL‐b‐P^tBuA copolymers (M_n = 10,900–19,570 g mol^?1; M_w/M_n = 1.14–1.23). Finally, the three‐arm star PCL‐b‐PAA copolymer was obtained via the hydrolysis of the PtBuA segment in three‐arm star PCL‐b‐P^tBuA copolymers. The chain structures of all the polymers were characterized by gel permeation chromatography, proton nuclear magnetic resonance (¹H NMR), and Fourier transform infrared spectroscopy. The aggregates of three‐arm star PCL‐b‐PAA copolymer were studied by the determination of critical micelles concentration and transmission electron microscope. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

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     

Synthesis of well‐defined AB20‐type star polymers with cyclodextrin‐core by combination of NMP and ATRP

The synthesis of an AB₂₀‐type heteroarm star polymer consisting of a polystyrene arm and 20‐arms of poly(methyl methacrylate) or poly(tert‐butyl acrylate) was carried out using the combination of nitroxide‐mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono‐6‐[4‐(1′‐(2″,2″,6″,6″‐tetramethyl‐1″‐piperidinyloxy)‐ethyl)benzamido]‐β‐cyclodextrin peracetate ( 1 ) to afford end‐functionalized polystyrene with an acetylated β‐cyclodextrin (β‐CyD) unit (prepolymer 2 ) with a number‐average molecular weight (M_n) of 11700 and a polydispersity (M_w/M_n) of 1.17. After deacetylation of prepolymer 2 , the resulting polymer was reacted with 2‐bromoisobutyric anhydride to give end‐functionalized polystyrene with 20(2‐bromoisobutyrol)s β‐CyD, macroinitiator 4 . The copper (I)‐mediated ATRP of methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) was carried out using macroinitiator 4 . The resulting polymers were isolated by SEC fractionation to produce AB₂₀‐type star polymers with a β‐CyD‐core, 5 . The well‐defined structure of 5 with weight‐average molecular weight (M_w)s of 13,500–65,300 and M_w/M_n's of 1.26–1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4271–4279, 2005     

Synthesis of perfectly bifunctional polyacrylates by single‐electron‐transfer living radical polymerization

Poly(methyl acrylate)s, poly(ethyl acrylate)s, and poly(butyl acrylate)s with α,ω‐di(bromo) chain ends and M_n from 8500 to 35,000 were synthesized by single‐electron‐transfer living radical polymerization (SET‐LRP). The analysis of their chain ends by a combination of ¹H and 2D‐NMR, GPC, MALDI‐TOF MS, chain end functionalization, chain extension, and halogen exchange experiments demonstrated the synthesis of perfectly bifunctional polyacrylates by SET‐LRP. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4684–4695, 2007     

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