Synthesis and characterization of well‐defined poly(2‐hydroxyethyl methacrylate‐co‐styrene)‐graft‐poly(ε‐caprolactone) by sequential controlled polymerization

A new graft copolymer, poly(2‐hydroxyethyl methacrylate‐co‐styrene) ‐graft‐poly(?‐caprolactone), was prepared by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with coordination‐insertion ring‐opening polymerization (ROP). The copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) was carried out at 60 °C in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDTB) using AIBN as initiator. The molecular weight of poly (2‐hydroxyethyl methacrylate‐co‐styrene) [poly(HEMA‐co‐St)] increased with the monomer conversion, and the molecular weight distribution was in the range of 1.09 ～ 1.39. The ring‐opening polymerization (ROP) of ?‐caprolactone was then initiated by the hydroxyl groups of the poly(HEMA‐co‐St) precursors in the presence of stannous octoate (Sn(Oct)₂). GPC and ¹H‐NMR data demonstrated the polymerization courses are under control, and nearly all hydroxyl groups took part in the initiation. The efficiency of grafting was very high. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5523–5529, 2004     

Preparation of nanoparticles of double‐hydrophilic PEO‐PHEMA block copolymers by AGET ATRP in inverse miniemulsion

Atom transfer radical polymerization with activators generated by electron transfer initiating/catalytic system (AGET ATRP) of 2‐hydroxyethyl methacrylate (HEMA) was carried out in inverse miniemulsion. Water‐soluble ascorbic acid as a reducing agent and mono‐ and difunctional poly(ethylene oxide)‐based bromoisobutyrate (PEO‐Br) as a macroinitiator were used in the presence of CuBr₂/tris[(2‐pyridyl)methyl]amine (TPMA) and CuCl₂/TPMA complexes. The use of poly(ethylene‐co‐butylene)‐block‐poly(ethylene oxide) as a polymer surfactant resulted in the formation of stable HEMA cyclohexane inverse dispersion and PHEMA colloidal particles. All polymerizations were well‐controlled, allowing for the preparation of well‐defined PEO‐PHEMA and PHEMA‐PEO‐PHEMA block copolymers with relatively high molecular weight (DP > 200) and narrow molecular weight distribution (M_w/M_n < 1.3). These block copolymers self‐assembled to form micellar nanoparticles being 10–20 nm in diameter with uniform size distribution, and aggregation number of ～10 confirmed by atomic force microscopy and transmission electron microscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4764–4772, 2007     

Simultaneous control of the stereospecificity and molecular weight in the ruthenium‐catalyzed living radical polymerization of methyl and 2‐hydroxyethyl methacrylates and sequential synthesis of stereoblock polymers

The stereospecific living radical polymerizations of methyl methacrylate (MMA) and 2‐hydroxyethyl methacrylate (HEMA) were achieved with a combination of ruthenium‐catalyzed living radical and solvent‐mediated stereospecific radical polymerizations. Among a series of ruthenium complexes [RuCl₂(PPh₃)₃, Ru(Ind)Cl(PPh₃)₂, and RuCp*Cl(PPh₃)₂], Cp*–ruthenium afforded poly(methyl methacrylate) with highly controlled molecular weights [weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 1.08] and high syndiotacticity (r = 88%) in a fluoroalcohol such as (CF₃)₂C(Ph)OH at 0 °C. On the other hand, a hydroxy‐functionalized monomer, HEMA, was polymerized with RuCp*Cl(PPh₃)₂ in N,N‐dimethylformamide and N,N‐dimethylacetamide (DMA) to give syndiotactic polymers (r = 87–88%) with controlled molecular weights (M_w/M_n = 1.12–1.16). This was the first example of the syndiospecific living radical polymerization of HEMA. A fluoroalcohol [(CF₃)₂C(Ph)OH], which induced the syndiospecific radical polymerization of MMA, reduced the syndiospecificity in the HEMA polymerization to result in more or less atactic polymers (mm/mr/rr = 7.2/40.9/51.9%) with controlled molecular weights in the presence of RuCp*Cl(PPh₃)₂ at 80 °C. A successive living radical polymerization of HEMA in two solvents, first DMA followed by (CF₃)₂C(Ph)OH, resulted in stereoblock poly(2‐hydroxyethyl methacrylate) with syndiotactic–atactic segments. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3609–3615, 2006     

Ruthenium‐catalyzed fast living radical polymerization of methyl methacrylate: The R?Cl/Ru(Ind)Cl(PPh3)2/n‐Bu2NH initiating system

A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)₂? Cl/Ru(Ind)Cl(PPh₃)₂ initiating system in the presence of n‐Bu₂NH as an additive [where (MMA)₂? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (M_n's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (M_w/M_n) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (M_n ～ 10⁵) and narrow MWD (M_w/M_n ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu₃N, whereas n‐BuNH₂ resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148     

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     

Facile one‐pot/one‐step technique for preparation of side‐chain functionalized polymers: Combination of SET‐RAFT polymerization of azide vinyl monomer and click chemistry

An azido‐containing functional monomer, 11‐azido‐undecanoyl methacrylate, was successfully polymerized via ambient temperature single electron transfer initiation and propagation through the reversible addition–fragmentation chain transfer (SET‐RAFT) method. The polymerization behavior possessed the characteristics of “living”/controlled radical polymerization. The kinetic plot was first order, and the molecular weight of the polymer increased linearly with the monomer conversion while keeping the relatively narrow molecular weight distribution (M_w/M_n ≤ 1.22). The complete retention of azido group of the resulting polymer was confirmed by ¹H NMR and FTIR analysis. Retention of chain functionality was confirmed by chain extension with methyl methacrylate to yield a diblock copolymer. Furthermore, the side‐chain functionalized polymer could be prepared by one‐pot/one‐step technique, which is combination of SET‐RAFT and “click chemistry” methods. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone: Selective formation of polythioester

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone was examined. The corresponding polythioester with the number‐average molecular weight (M_n ) of 57,000 was obtained in the polymerization with 1 mol % of BF₃ · OEt₂ as an initiator in CH₂Cl₂ at 28 °C for 5 h with quantitative monomer conversion. The M_n of the polymer increased with the solvent polarity and monomer‐to‐initiator ratio. No polymerization took place below −30 °C, and the monomer conversion and M_n of the polymer increased with the temperature in the range of −15 to 28 °C. The increase of initial monomer concentration was effective to improve the monomer conversion and the M_n of the obtained polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4057–4061, 2000     

Controlled polymerization of carbazole‐based vinyl and methacrylate monomers at ambient temperature: A comparative study through ATRP,SET, and SET‐RAFT polymerizations

The polymerization of N‐vinylcarbazole (NVK) and carbazole methacrylate (CMA) was carried out using controlled radical polymerization methods such as atom transfer radical polymerization (ATRP), single electron transfer (SET)‐LRP, and single electron transfer initiation followed by reversible addition fragmentation chain transfer (SET‐RAFT). Well‐controlled polymerization with narrow molecular weight distribution (M_w/M_n) < 1.25 was achieved in the case of NVK by high‐temperature ATRP while ambient temperature SET‐RAFT polymerization was relatively slow and controlled. In the case of CMA, SET‐RAFT is found to be more suitable for the ambient temperature polymerization. The polymerization rate followed first order kinetics with respect to monomer conversion and the molecular weight of the polymer increased linearly with conversion. The controlled nature of the polymerization is further demonstrated by the synthesis of diblock copolymers from PNVK and PCMA macroinitiators using a new flavanone‐based methacrylate (FMA) as the second monomer. All the polymers exhibited fluorescence. The excimer bands in the homopolymers of PNVK and PCMA were very broad, which may be attributed to the carbazole–carbazole overlap interaction. The scanning electron microscopy analysis of the block copolymer reveals interesting morphological features. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Formation of CdS nanoclusters in phase‐separated poly(2‐hydroxyethyl methacrylate)‐l‐polyisobutylene amphiphilic conetworks

Nanophase‐separated poly(2‐hydroxyethyl methacrylate)‐l‐polyisobutylene (PHEMA‐l‐PIB) amphiphilic conetworks were obtained by crosslinking α,ω‐bismethacrylate‐terminated polyisobutylene (PIB) via copolymerization with silylated 2‐hydroxyethyl methacylate, followed by the hydrolysis of the silylether groups. Morphology development of a sample containing 64% PIB was monitored by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), and small‐angle X‐ray scattering. For comparison, the morphology of a sample containing 53% PIB was investigated by AFM. The dry conetworks exhibited hydrophilic and hydrophobic phases with average 8–10‐nm domain sizes and were swellable in water as well as in heptane. Swelling amphiphilic conetworks with aqueous cadmium–chloride solution followed by exposure to H₂S resulted in nanosized CdS clusters located in the amphiphilic conetworks, that is, for the first time, new inorganic–organic hybrid materials composed of CdS semiconducting nanocrystals and PHEMA‐l‐PIB amphiphilic conetworks were prepared. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1429–1436, 2001     

Controlled radical polymerization of 2‐hydroxyethyl methacrylate with a hydrophilic ruthenium complex and the synthesis of amphiphilic random and block copolymers with methyl methacrylate

A hydrophilic ruthenium complex with ionic phosphine ligands { 1 : RuCl₂[P(3‐C₆H₄SO₃Na)(C₆H₅)₂]₂} induced controlled radical polymerization of 2‐hydroxyethyl methacrylate (HEMA) in methanol under homogeneous conditions; the initiator was a chloride (R‐Cl) such as CHCl₂COPh. The number‐average molecular weights of poly(HEMA) increased in direct proportion to monomer conversion, and the molecular weight distributions were relatively narrow (M_w/M_n = 1.4–1.7). A similar living radical polymerization was possible with (MMA)₂‐Cl [(CH₃)₂C(CO₂CH₃)CH₂C(CH₃)(CO₂CH₃)Cl] as an initiator coupled with amine additives such as n‐Bu₃N. In a similar homogeneous system in methanol, methyl methacrylate (MMA) could also be polymerized in living fashion with the R‐Cl/ 1 initiating system. Especially for such hydrophobic polymers, the water‐soluble ruthenium catalyst was readily removed from the polymers by simple washing with an aqueous dilute acid. This system can be applied to the direct synthesis of amphiphilic random and block copolymers of HEMA and MMA. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2055–2065, 2002     

Amphiphilic star‐block copolymers based on a hyperbranched core: Synthesis and supramolecular self‐assembly

Novel amphiphilic star‐block copolymers, star poly(caprolactone)‐block‐poly[(2‐dimethylamino)ethyl methacrylate] and poly(caprolactone)‐block‐poly(methacrylic acid), with hyperbranched poly(2‐hydroxyethyl methacrylate) (PHEMA–OH) as a core moiety were synthesized and characterized. The star‐block copolymers were prepared by a combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA–OH with 18 hydroxyl end groups on average was used as an initiator for the ring‐opening polymerization of ε‐caprolactone to produce PHEMA–PCL star homopolymers [PHEMA = poly(2‐hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA–PCL were converted to 2‐bromoesters, and this gave rise to macroinitiator PHEMA–PCL–Br for ATRP. Then, 2‐dimethylaminoethyl methacrylate or tert‐butyl methacrylate was polymerized from the macroinitiators, and this afforded the star‐block copolymers PHEMA–PCL–PDMA [PDMA = poly(2‐dimethylaminoethyl methacrylate)] and PHEMA–PCL–PtBMA [PtBMA = poly(tert‐butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl methacrylate) blocks gave the star‐block copolymer PHEMA–PCL–PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star‐block copolymers could self‐assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534–6544, 2005     

Synthesis and characterization of amphiphilic copolymer of linear poly(ethylene oxide) linked with [poly(styrene‐co‐2‐hydroxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] using sequential controlled polymerization

A well‐defined amphiphilic copolymer of ‐poly(ethylene oxide) (PEO) linked with comb‐shaped [poly(styrene‐co‐2‐hydeoxyethyl methacrylate)‐graft‐poly(ε‐caprolactone)] (PEO‐b‐P(St‐co‐HEMA)‐g‐PCL) was successfully synthesized by combination of reversible addition‐fragmentation chain transfer polymerization (RAFT) with ring‐opening anionic polymerization and coordination–insertion ring‐opening polymerization (ROP). The α‐methoxy poly(ethylene oxide) (mPEO) with ω,3‐benzylsulfanylthiocarbonylsufanylpropionic acid (BSPA) end group (mPEO‐BSPA) was prepared by the reaction of mPEO with 3‐benzylsulfanylthiocarbonylsufanyl propionic acid chloride (BSPAC), and the reaction efficiency was close to 100%; then the mPEO‐BSPA was used as a macro‐RAFT agent for the copolymerization of styrene (St) and 2‐hydroxyethyl methacrylate (HEMA) using 2,2‐azobisisobutyronitrile as initiator. The molecular weight of copolymer PEO‐b‐P(St‐co‐HEMA) increased with the monomer conversion, but the molecular weight distribution was a little wide. The influence of molecular weight of macro‐RAFT agent on the polymerization procedure was discussed. The ROP of ε‐caprolactone was then completed by initiation of hydroxyl groups of the PEO‐b‐P(St‐co‐HEMA) precursors in the presence of stannous octoate (Sn(Oct)₂). Thus, the amphiphilic copolymer of linear PEO linked with comb‐like P(St‐co‐HEMA)‐g‐PCL was obtained. The final and intermediate products were characterized in detail by NMR, GPC, and UV. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 467–476, 2006     

Synthesis of block and end‐functionalized polyesters by triflimide‐catalyzed ring‐opening polymerization of ε‐caprolactone, 1,5‐dioxepan‐2‐one,and rac‐lactide

The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf₂) as the catalyst at room temperature with the [monomer]₀/[initiator]₀ ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an ¹H NMR analysis (PCL, M_n,NMR = 5380; PDXO, M_n,NMR = 5820; PLA, M_n,NMR = 6490) showed good agreement with the calculated values. The ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf₂‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf₂‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463     

Macromolecular brushes synthesized by “grafting from” approach based on “click chemistry” and RAFT polymerization

Well‐defined macromolecular brushes with poly(N‐isopropyl acrylamide) (PNIPAM) side chains on random copolymer backbones were synthesized by “grafting from” approach based on click chemistry and reversible addition‐fragmentation chain transfer (RAFT) polymerization. To prepare macromolecular brushes, two linear random copolymers of 2‐(trimethylsilyloxy)ethyl methacrylate (HEMA‐TMS) and methyl methacrylate (MMA) (poly(MMA‐co‐HEMA‐TMS)) were synthesized by atom transfer radical polymerization and were subsequently derivated to azide‐containing polymers. Novel alkyne‐terminated RAFT chain transfer agent (CTA) was grafted to polymer backbones by copper‐catalyzed 1,3‐dipolar cycloaddition (azide‐alkyne click chemistry), and macro‐RAFT CTAs were obtained. PNIPAM side chains were prepared by RAFT polymerization. The macromolecular brushes have well‐defined structures, controlled molecular weights, and molecular weight distributions (M_w/M_n ≦ 1.23). The RAFT polymerization of NIPAM exhibited pseudo‐first‐order kinetics and a linear molecular weight dependence on monomer conversion, and no detectable termination was observed in the polymerization. The macromolecular brushes can self‐assemble into micelles in aqueous solution. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 443–453, 2010     

Reversible addition–fragmentation chain transfer/miniemulsion polymerization of butyl methacrylate in the presence of β‐cyclodextrin

In the presence of β‐cyclodextrin (β‐CD), reversible addition–fragmentation chain transfer (RAFT) polymerization has been successfully applied to control the molecular weight and polydispersity [weight‐average molecular weight/number‐average molecular weight (M_w/M_n)] in the miniemulsion polymerization of butyl methacrylate, with 2‐cyanoprop‐2‐yl dithiobenzoate as a chain‐transfer agent (or RAFT agent) and 2,2′‐azoisobutyronitrile (AIBN) as an initiator. β‐CD acted as both a stabilizer and a solubilizer, assisting the transportation of the water‐insoluble, low‐molecular‐weight RAFT agent into the polymerization loca (i.e., droplets or latex particles) and thereby ensuring that the RAFT agent was homogeneous in the polymerization loca. The polymers produced in the system of β‐CD exhibited narrower polydispersity (1.2 < M_w/M_n < 1.3) than those without β‐CD. Moreover, the number‐average molecular weight in the former case could be controlled by a definite amount of the RAFT agent. Significantly, β‐CD was proved to have a favorable effect on the stability of polymer latex, and no coagulum was observed. The effects of the concentrations of the RAFT agent and AIBN on the conversion, the molecular weight and its distribution, and the particle size of latices were investigated in detail. Furthermore, the influences of the variations of the surfactant (sodium dodecyl sulfate) and costabilizer (hexadecane) on the RAFT/miniemulsion polymerization were also studied. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2931–2940, 2005     

Synthesis of poly(2‐hydroxyethyl methacrylate) in protic media through atom transfer radical polymerization using activators generated by electron transfer

Atom transfer radical polymerization (ATRP) using activators generated by electron transfer (AGET) was investigated for the controlled polymerization of 2‐hydroxyethyl methacrylate (HEMA) in a protic solvent, a 3/2 (v/v) mixture of methyl ethyl ketone and methanol. The AGET process enabled ATRP to be started with an air‐stable Cu(II) complex that was reduced in situ by tin(II) 2‐ethylhexanoate. The reaction temperature, Cu catalysts with different ligands, and variation of the initial concentration ratio of HEMA to the initiator were examined for the synthesis of well‐controlled poly(2‐hydroxyethyl methacrylate) and a poly(methyl methacrylate)‐b‐poly(2‐hydroxyethyl methacrylate) block copolymer. The level of control in AGET ATRP was similar to that in normal ATRP in protic solvents, and this resulted in a linear increase in the molecular weight with the conversion and a narrow molecular weight distribution (weight‐average molecular weight/number‐average molecular weight < 1.3). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3787–3796, 2006     

Reversible addition–fragmentation chain transfer polymerization of 2‐naphthyl acrylate with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate as a chain‐transfer agent

The reversible addition–fragmentation chain transfer (RAFT) polymerizations of 2‐naphthyl acrylate (2NA) initiated by 2,2′‐azobisisobutyronitrile were investigated with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as a RAFT agent at various temperatures in a benzene solution. The results of the polymerizations showed that 2NA could be polymerized in a controlled way by RAFT polymerization with CPDN as a RAFT agent; the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with the monomer conversion. The polydispersities of the polymer were relatively low up to high conversions in all cases. The chain‐extension reactions of poly(2‐naphthyl acrylate) (P2NA) with methyl methacrylate and styrene successfully yielded poly(2‐naphthyl acrylate)‐b‐poly(methyl methacrylate) and poly(2‐naphthyl acrylate)‐b‐polystyrene block polymers, respectively, with narrow polydispersities. The P2NA obtained by RAFT polymerization had a strong ultraviolet absorption at 270 nm, and the molecular weights had no apparent effect on the ultraviolet absorption intensities; however, the fluorescence intensity of P2NA increased as the molecular weight increased and was higher than that of 2NA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2632–2642, 2005     

“Living”/controlled free radical polymerization of MMA in the presence of cobalt(II) 2‐ethylhexanoate: A switch from RAFT to ATRP mechanism

A metal complex, cobalt(II) 2‐ethylhexanoate (CEH), was added to the system of thermal‐initiated reversible addition‐fragmentation chain transfer (RAFT) polymerization of methyl methacrylate (MMA) with 2‐cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN) as the RAFT agent at 115 °C. The polymerization rate was remarkably enhanced in the presence of CEH in comparison with that in the absence of CEH, and the increase of the CPDN concentration also accelerated the rate of polymerization. The polymerization in the concurrence of CPDN and CEH demonstrated the characters of “living”/controlled free radical polymerization: the number‐average molecular weights (M_n) increasing linearly with monomer conversion, narrow molecular weight distributions (M_w/M_n) and obtained PMMA end‐capped with the CPDN moieties. Meanwhile, CEH can also accelerate the rate of RAFT polymerization of MMA using the PMMA as macro‐RAFT agent instead of CPDN. Similar polymerization profiles were obtained when copper (I) bromide (CuBr)/N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine was used instead of CEH. Extensive experiments in the presence of butyl methacrylate, bis(cyclopentadienyl) cobalt(II) and cumyl dithionaphthalenoate were also conducted; similar results as those of MMA/CPDN/CEH system were obtained. A transition of the polymerization mechanism, from RAFT process without CEH addition to atom transfer radical polymerization in the presence of CEH, was possibly responsible for polymerization profiles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5722–5730, 2007     

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

The titanium complexes with one ( 1a , 1b , 1c ) and two ( 2a , 2b ) dialkanolamine ligands were used as initiators in the ring‐opening polymerization (ROP) of ε‐caprolactone. Titanocanes 1a and 1b initiated living ROP of ε‐caprolactone affording polymers whose number‐average molecular weights (M_n) increased in direct proportion to monomer conversion (M_n ≤ 30,000 g mol^?1) in agreement with calculated values, and were inversely proportional to initiator concentration, while the molecular weight distribution stayed narrow throughout the polymerization (M_w/M_n ≤ 1.2 up to 80% monomer conversion). ¹H‐NMR and MALDI‐TOF‐MS studies of the obtained poly(ε‐caprolactone)s revealed the presence of an isopropoxy group originated from the initiator at the polymer termini, indicating that the polymerization takes place exclusively at the Ti–OⁱPr bond of the catalyst. The higher molecular weight polymers (M_n ≤ 70,000 g mol^?1) with reasonable MWD (M_w/M_n ≤ 1.6) were synthesized by living ROP of ε‐caprolactone using spirobititanocanes ( 2a , 2b ) and titanocane 1c as initiators. The latter catalysts, according MALDI‐TOF‐MS data, afford poly(ε‐caprolactone)s with almost equal content of α,ω‐dihydroxyl‐ and α‐hydroxyl‐ω(carboxylic acid)‐terminated chains arising due to monomer insertion into “Ti–O” bond of dialkanolamine ligand and from initiation via traces of water, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1230–1240, 2010     

Synthesis and characterization of fluorine‐containing PAA‐b‐PTPFCBPMA amphiphilic block copolymer

A series of perfluorocyclobutyl (PFCB) aryl ether‐based amphiphilic diblock copolymers containing hydrophilic poly(acrylic acid) (PAA) and fluorophilic poly(p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate) segments were synthesized via successive atom transfer radical polymerization (ATRP). 2‐MBP‐initiated and CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine‐catalyzed ATRP homopolymerization of the PFCB‐containing methacrylate monomer, p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate, can be performed in a controlled mode as confirmed by the fact that the number‐average molecular weights (M_n) increased linearly with the conversions of the monomer while the polydispersity indices kept below 1.38. The block copolymers with narrow molecular weight distributions (M_w/M_n ≤ 1.36) were synthesized by ATRP using Br‐end‐functionalized poly(tert‐butyl acrylate) (PtBA) as macroinitiator followed by the acidolysis of hydrophobic PtBA block into hydrophilic PAA segment. The critical micelle concentrations of the amphiphilic diblock copolymers in different surroundings were determined by fluorescence spectroscopy using N‐phenyl‐1‐naphthylamine as probe. The morphology and size of the micelles were investigated by transmission electron microscopy and dynamic laser light scattering, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010