In this work, high molecular weight polyvinyl acetate (PVAc) (M_n,GPC = 123,000 g/mol, M_w/M_n = 1.28) was synthesized by reversible addition-fragmentation chain transfer polymerization (RAFT) under high pressure (5 kbar), using benzoyl peroxide and N,N-dimethylaniline as initiator mediated by (S)-2-(ethyl propionate)-(O-ethyl xanthate) (X1) at 35 °C. Polymerization kinetic study with RAFT agent showed pseudo-first order kinetics. Additionally, the polymerization rate of VAc under high pressure increased greatly than that under atmospheric pressure. The “living” feature of the resultant PVAc was confirmed by ¹H NMR spectroscopy and chain extension experiments. Well-defined PVAc with high molecular weight and narrow molecular weight distribution can be obtained relatively fast by using RAFT polymerization at 5 kbar. © 2015 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem. 2015, 53, 1430–1436

Photothermal therapy (PTT), as a minimally invasive and highly effective cancer treatment approach, has received widespread attention in recent years. Tremendous effort has been devoted to explore various types of photothermal agents with high near-infrared (NIR) absorbance for PTT cancer treatment. Despite many exciting progresses in the area, effective yet safe photothermal agents with good biocompatibility and biodegradability are still highly desired. In this work, a new organic PTT agent based on polyethylene glycol (PEG) coated micelle nanoparticles encapsulating a heptamethine indocyanine dye IR825 is developed, showing a strong NIR absorption band and a rather low quantum yield, for in vivo photothermal treatment of cancer. It is found that the IR825–PEG nanoparticles show ultra-high in vivo tumor uptake after intravenous injection, and appear to be an excellent PTT agent for tumor ablation under a low-power laser irradiation, without rendering any appreciable toxicity to the treated animals. Compared with inorganic nanomaterials and conjugated polymers being explored in PTT, the NIR-absorbing micelle nanoparticles presented here may have the least safety concern while showing excellent treatment efficacy, and thus may be a new photothermal agent potentially useful in clinical applications.

Poly(glycidyl methacrylate)-block-poly(4-vinylbenzyl chloride), or P(GMA)-b-P(VBC), is synthesized via consecutive reversible addition-fragmentation chain transfer (RAFT) polymerizations. Subsequent functionalization via atom-transfer radical polymerization (ATRP) of methyl methacrylate (MMA) and styrene (St) gives rise to two functional brush-type diblock graft copolymers, P(GMA)-b-(P(VBC)-g-P(MMA)) and P(GMA)-b-(P(VBC)-g-PS). These graft copolymers are further functionalized by a ring-opening reaction of the P(GMA) block with diethylamine (DEA) to produce two diblock copolymer brushes, P(DEAHPMA)-b-(P(VBC)-g-P(MMA) and P(DEAHPMA)-b-(P(VBC)-g-PS (Brush-2A). Single molecules of the copolymers are imaged by atomic force microscopy (AFM). Brush-2A can be cast into porous membranes with well-defined micropores from tetrahydrofuran (THF) solutions by phase inversion in an aqueous medium.

Well-defined copolymer of acrylonitrile (AN) and maleic anhydride (MAn) has been successfully synthesized via reversible addition-fragmentation chain transfer polymerization. The polymerization kinetics and “living”/controlled features were thoroughly studied and confirmed. The thermal properties and spinnability of the prepared copolymers were investigated via differential scanning calorimetry, thermogravimetric analyzer, and electrospinning subsequently. When PAN-co-PMAn was used as precursors, nonwoven with “crosslinked” structures was obtained during electrospinning. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5263–5269

A facile soap-free miniemulsion polymerization of methyl methacrylate (MMA) was successfully carried out via a reverse ATRP technique, using a water-soluble potassium persulfate (KPS) or 2,2′-azobis(2-methylpropionamidine) dihydrochloride (V-50) both as the initiator and the stabilizer, and using an oil-soluble N,N-n-butyldithiocarbamate copper (Cu(S₂CN(C₄H₉)₂)₂) as the catalyst without adding any additional ligand. Polymerization results demonstrated the “living”/controlled characteristics of ATRP and the resultant latexes showed good colloidal stability with average particle size around 300–700 nm in diameter. The monomer droplet nucleation mechanism was proposed. NMR spectroscopy and chain-extension experiments under UV light irradiation confirmed the attachment and livingness of UV light sensitive SC(S)N(C₄H₉)₂ group in the chain end.

An environmentally friendly iron catalyst system was successfully developed in water for the AGET ATRP (activator generated by electron transfer for atom transfer radical polymerization) of water-soluble monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) for the first time. A kinetic study indicated that the polymerization was a living/controlled process in which molecular weight increased linearly with monomer conversion. A lower molecular weight distribution (/ < 1.5) was maintained. The nontoxic and biocompatible characteristics of the iron catalyst facilitate its mediated polymerization to be used in the preparation of functional polymer materials for biomedical use.

In this work, copolymerization of two functional monomers, glycidyl methacrylate (GMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA), was firstly carried out via reversible addition-fragmentation chain transfer (RAFT) polymerization successfully. The copolymerization kinetics was investigated under the molar ratio of n[GMA+DMAEMA]₀/n[AIBN]₀/n[CPDN]₀=300/1/3 at 60°C. The copolymerization showed typical "living" features such as first-order polymerization kinetics, linear increase of molecular weight with monomer conversion and narrow molecular weight distribution. The reactivity ratios of GMA and DMAEMA were calculated by the extended Kelen-Tüdös linearization methods. The epoxy group of the copolymer PGMA-co-PDMAEMA remained intact under the conditions of RAFT copolymerization and could easily be post-modified by ethylenediamine. Moreover, the modified copolymer could be used as a gene carrier.

The RAFT agents RAFT-1 and RAFT-2 were used for RAFT polymerization to synthesize well-defined bimodal molecular-weight-distribution (MWD) polymers. The system showed excellent controllability and “living” characteristics toward both the higher- and lower-molecular-weight fractions. It is important that bimodal higher-molecular-weight (HMW) polymers and block copolymers with both well-controlled molecular weight (MW) and MWD could be prepared easily due to the “living” features of RAFT polymerization. The strategy realized a mixture of higher/lower-molecular-weight polymers at the molecular level but also preserved the features of living radical polymerization (LRP) of the RAFT polymerization.

Well-defined bimodal molecular weight distribution (MWD) polystyrene and polystyrene-b-poly(acrylonitrile) were successfully synthesized using a pair of mono/difunctional trithiocarbonate RAFT agents 1 and 2 via one-pot RAFT polymerization. The kinetics of RAFT polymerization for styrene in bulk with a molar ratio of [St]₀:[AIBN]₀:[1]₀:[2]₀ = 1200:1:2.5:2.5 was studied at 75°C. The results indicated that the system showed excellent controllability and “living” characteristics to both higher and lower molecular weight fractions, providing an efficient and facile way to producing bimodal MWD (co)polymers with both controlled molecular weight (MW) and MWD in molecular level, and the plausible mechanism was discussed in this work. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Methyl methacrylate (MMA) were successfully polymerized by atom transfer radical polymerization with activator generated by electron transfer (AGET ATRP) using copper or iron wire as the reducing agent at 90°C. Well-controlled polymerizations were demonstrated using an oxidatively stable iron(III) chloride hexahydrate (FeCl₃·6H₂O) as the catalyst, ethyl 2-bromoisobutyrate (EBiB) as the initiator, and tetrabutylammonium bromide (TBABr) or triphenylphosphine as the ligand. The polymerization rate was fast and affected by the amount of catalyst and type of reducing agents. For example, the polymerization rate of bulk AGET ATRP with a molar ratio of [MMA]₀/[EBiB]₀/[FeCl₃·6H₂O]₀/[TBABr]₀ = 500/1/0.5/1 using iron wire (the conversion reaches up to 82.2% after 80 min) as the reducing agent was faster than that using copper wire (the conversion reaches up to 86.1% after 3 h). At the same time, the experimental M_n values of the obtained poly(methyl methacrylate) were consistent with the corresponding theoretical ones, and the M_w/M_n values were narrow (∼1.3), showing the typical features of “living”/controlled radical polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this work, living radical polymerizations of a water-soluble monomer poly(ethylene glycol) monomethyl ether methacylate (PEGMA) in bulk with low-toxic iron catalyst system, including iron chloride hexahydrate and triphenylphosphine, were carried out successfully. Effect of reaction temperature and catalyst concentration on the polymerization of PEGMA was investigated. The polymerization kinetics showed the features of “living”/controlled radical polymerization. For example, M_n,GPC values of the resultant polymers increased linearly with monomer conversion. A faster polymerization of PEGMA could be obtained in the presence of a reducing agent Fe(0) wire or ascorbic acid. In the case of Fe(0) wire as the reducing agent, a monomer conversion of 80% was obtained in 80 min of reaction time at 90 °C, yielding a water-soluble poly(PEGMA) with M_n = 65,500 g mol⁻¹ and M_w/M_n = 1.39. The features of “living”/controlled radical polymerization of PEGMA were verified by analysis of chain-end and chain-extension experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Iron-mediated atom transfer radical polymerization using activators generated by electron transfer directly from the secondary fluorine atoms on the poly(vinylidene fluoride) (PVDF) backbone, using methyl methacrylate (MMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA) as the monomers, FeCl₃·6H₂O as the catalyst, PPh₃ as the ligand, and vitamin C as the reducing agent, was demonstrated in the presence of limited amounts of air. The successful syntheses of the corresponding graft copolymers PVDF-g-PMMA and PVDF-g-PPEGMA were characterized by nuclear magnetic resonance, Fourier transform infrared and X-ray photoelectron spectroscopy, respectively. The graft copolymers PVDF-g-PPEGMA can be readily cast into porous hydrophilic microfiltration membranes by phase inversion in an aqueous medium. The morphologies were characterized by scanning electron microscopy. The surface and bulk hydrophilicity were evaluated on the basis of static water contact angle and the steady adsorption of bovine serum albumin. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

The catalytic amount of inorganic bases (i.e., NaOH, Na₃PO₄, NaHCO₃, and Na₂CO₃) and organic bases such as pyridine and triethylamine was used as the additives in an iron-mediated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of a polar monomer methyl methacrylate (MMA) using FeCl₃·6H₂O as the catalyst, ethyl 2-bromoisobutyrate (EBiB) as the initiator, ascorbic acid (AsAc) as the reducing agent, and tetrabutylammonium bromide (TBABr) as the ligand. All these bases can result in dual enhancement of polymerization rate and controllability over molecular weight while keeping low M_w/M_n values (<1.3) for the resultant polymers. For example, the polymerization rate of AGET ATRP with a molar ratio of [MMA]₀/[EBiB]₀/[FeCl₃·6H₂O]₀/[TBABr]₀/[AsAc]₀/[NaOH]₀ = 500/1/1/2/2/1.5 using NaOH as the additives was more than two times of that without NaOH. The nature of “living”/controlled free radical polymerization in the presence of base was confirmed by chain-extension experiments. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Three kinds of alumina (acidic, neutral, and basic Al₂O₃) were effective as additives for the control and rate enhancement of iron-mediated AGET (activators generated by electron transfer) ATRP (atom transfer radical polymerization) of methyl methacrylate (MMA) in the presence of limited amount of air, using FeCl₃·6H₂O as the catalyst, tetrabutylammonium bromide or tetra-n-butylphosphonium bromide as the ligand, ethyl 2-bromoisobutyrate as the initiator, and ascorbic acid as the reducing agent. The conversion could be up to 83.9% in the case of basic Al₂O₃ and 75.3% with neutral Al₂O₃ only in 13 h, respectively, whereas no polymer could be obtained even in 50 h without additives. The polymers obtained with neutral and basic Al₂O₃ had controlled molecular weights and low M_w/M_n values (∼1.2). Tacticities of the as-prepared PMMA in the presence of these three kinds of Al₂O₃ were consistent with that obtained from conventional free-radical polymerization of MMA. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Well-defined polymer-nanoparticle hybrids were prepared by a newly reported method: atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) mediated by iron catalyst. The kinetics of the surface-initiated AGET ATRP of methyl methacrylate from the silica nanoparticles, which was mediated by FeCl₃/triphenylphosphine as a catalyst complex, ascorbic acid as a reducing agent, N,N-dimethylformamide as the solvent in the presence of a “sacrificial” (free) initiator, was studied. Both the free and grafted polymers were grown in a control manner. The chemical composition of the nanocomposites was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and ¹H nuclear magnetic resonance spectroscopy. Thermogravimetric analysis was used to estimate the content of the grafted organic compound, and transmission electron micrographs was used to observe the core-shell structure of the hybrid nanoparticles. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2006–2015, 2010

A commercially available tris(3,6-dioxaheptyl)amine (TDA-1) was used as a novel ligand for activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) of styrene in bulk or solution mediated by iron(III) catalyst in the presence of a limited amount of air. FeCl₃·6H₂O and (1-bromoethyl)benzene (PEBr) were used as the catalyst and initiator, respectively; and environmentally benign ascorbic acid (VC) was used as the reducing agent. The polymerizations show the features of “living”/controlled free-radical polymerizations and well-defined polystyrenes with molecular weight M_n = 2400–36,500 g/mol and narrow polydispersity (M_w/M_n = 1.11–1.29) were obtained. The “living” feature of the obtained polymer was further confirmed by a chain-extension experiment. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2002–2008, 2009