Polymerization-induced self-assembly of block copolymer through dispersion RAFT polymerization has been demonstrated to be a valid method to prepare block copolymer nano-objects. However, volatile solvents are generally involved in this preparation. Herein, the in situ synthesis of block copolymer nano-objects of poly(ethylene glycol)-block-polystyrene (PEG-b-PS) in the ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIN][PF₆]) through the macro-RAFT agent mediated dispersion polymerization is investigated. It is found that the dispersion RAFT polymerization of styrene in the ionic liquid of [BMIN][PF₆] runs faster than that in the alcoholic solvent, and the dispersion RAFT polymerization in the ionic liquid affords good control over the molecular weight and the molecular weight distribution of the PEG-b-PS diblock copolymer. The morphology of the in situ synthesized PEG-b-PS diblock copolymer nano-objects, e.g., nanospheres and vesicles, in the ionic liquid is dependent on the polymerization degree of the solvophobic block and the concentration of the fed monomer, which is somewhat similar to those in alcoholic solvent. It is anticipated that the dispersion RAFT polymerization in ionic liquid broads a new way to prepare block copolymer nano-objects. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1517–1525

The in situ synthesis of the nano-assemblies of the high molecular weight ferrocene-containing block copolymer of poly(ethylene glycol)-block-poly(4-vinylbenzyl ferrocenecarboxylate) (PEG-b-PVFC) via dispersion reversible addition-fragmentation chain transfer (RAFT) polymerization was discussed. Taking the advantage of the accelerated polymerization rate of the dispersion RAFT polymerization, the nano-objects of the well-defined PEG-b-PVFC diblock copolymer with the polymerization degree (DP) of the ferrocene-containing PVFC block up to 300 were prepared. It was found that the morphology of the PEG-b-PVFC diblock copolymer nano-assemblies was dependent on the DP of the PEG and PVFC blocks, and nanospheres favorably formed in the case of the long PEG block and vesicles containing a thick and porous membrane were formed in the case of the short PEG block and long PVFC block, respectively. Our results demonstrate that the dispersion RAFT polymerization is an effective way to prepare the high molecular weight ferrocene-containing block copolymer with interesting morphologies. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 900–909

The thermoresponsive poly(ionic liquid) of poly[1-(4-vinylbenzyl)-3-methylimidozolium tetrafluoroborate] trithiocarbonate (P[VBMI][BF₄]-TTC) showing the soluble-to-insoluble phase transition in the methanol/water mixture at the upper critical solution temperature (UCST) was synthesized by solution RAFT polymerization and the synthesized P[VBMI][BF₄]-TTC was employed as macro-RAFT agent to mediate the RAFT polymerization under dispersion condition to afford the thermoresponsive diblock copolymer nanoparticles of poly[1-(4-vinylbenzyl)-3-methylimidozolium tetrafluoroborate]-b-polystyrene (P[VBMI][BF₄]-b-PS). The controllable solution RAFT polymerization was achieved as indicated by the linearly increasing polymer molecular weight with the monomer conversion and the narrow molecular weight distribution. The P[VBMI][BF₄]-TTC macro-RAFT agent mediated dispersion polymerization afforded the P[VBMI][BF₄]-b-PS nanoparticles, the size of which was uncorrelated with the polymerization degree of the P[VBMI][BF₄] block. Several parameters including the polymerization degree, the polymer concentration and the water content in the solvent of the methanol/water mixture were found to be correlated with the UCST of the poly(ionic liquid). The synthesized poly(ionic liquid) is believed to be a new thermos-responsive polymer and will be useful in material science. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 945–954

Synthesis of the ABA triblock copolymer nanoparticles of poly(N,N-dimethylacrylamide)-block-polystyrene-block-poly(N,N-dimethylacrylamide) (PDMA-b-PS-b-PDMA) by seeded RAFT polymerization is performed, and the effect of the introduced third poly(N,N-dimethylacrylamide) (PDMA) block on the size and morphology of the PDMA-b-PS-b-PDMA triblock copolymer nanoparticles is investigated. This seeded RAFT polymerization affords the in situ synthesis of the PDMA-b-PS-b-PDMA core-corona nanoparticles, in which the middle solvophobic PS block forms the compacted core, and the first solvophilic PDMA block and the introduced third PDMA block form the solvated complex corona. During the seeded RAFT polymerization, the introduced third PDMA block extends, and the molecular weight of the PDMA-b-PS-b-PDMA triblock copolymer linearly increases with the monomer conversion. It is found that, the size of the PS core in the PDMA-b-PS-b-PDMA triblock copolymer core-corona nanoparticles is almost equal to that in the precursor of the poly(N,N-dimethylacrylamide)-block-polystyrene diblock copolymer core-corona nanoparticles and it keeps constant during the seeded RAFT polymerization, and whereas the introduction of the third PDMA block leads to a crowded complex corona on the PS core. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1777–1784

Doubly thermoresponsive ABC brush-linear-linear triblock copolymer nanoparticles of poly[poly(ethylene glycol) methyl ether vinylphenyl]-block-poly(N-isopropylacrylamide)-block-polystyrene [P(mPEGV)-b-PNIPAM-b-PS] containing two thermoresponsive blocks of poly[poly(ethylene glycol) methyl ether vinylphenyl] [P(mPEGV)] and poly(N-isopropylacrylamide) (PNIPAM) are prepared by macro-RAFT agent mediated dispersion polymerization. The P(mPEGV)-b-PNIPAM-b-PS nanoparticles exhibit two separate lower critical solution temperatures or phase-transition temperatures (PTTs) corresponding to the linear PNIPAM block and the brush P(mPEGV) block in water. Upon temperature increasing above the first and then the second PTT, the hydrodynamic diameter (D_h) of the triblock copolymer nanoparticles undergoes an initial shrinkage at the first PTT and the subsequent shrinkage at the second PTT. The effect of the chain length of the PNIPAM block on the thermoresponsive behavior of the triblock copolymer nanoparticles is investigated. It is found that, the longer chains of the thermoresponsive PNIPAM block, the greater contribution on the transmittance change of the aqueous dispersion of the triblock copolymer nanoparticles. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2266–2278

The micellar macro-RAFT agent-mediated dispersion polymerization of styrene in the methanol/water mixture is performed and synthesis of temperature-sensitive ABC triblock copolymer nanoparticles is investigated. The thermoresponsive diblock copolymer of poly(N,N-dimethylacrylamide)-block-poly[N-(4-vinylbenzyl)-N,N-diethylamine] trithiocarbonate forms micelles in the polymerization solvent at the polymerization temperature and, therefore, the dispersion RAFT polymerization undergoes as similarly as seeded dispersion polymerization with accelerated polymerization rate. With the progress of the RAFT polymerization, the molecular weight of the synthesized triblock copolymer of poly(N,N-dimethylacrylamide)-block-poly[N-(4-vinylbenzyl)-N,N-diethylamine]-b-polystyrene linearly increases with the monomer conversion, and the PDI values of the triblock copolymers are below 1.2. The dispersion RAFT polymerization affords the in situ synthesis of the triblock copolymer nanoparticles, and the mean diameter of the triblock copolymer nanoparticles increases with the polymerization degree of the polystyrene block. The triblock copolymer nanoparticles contain a central thermoresponsive poly [N-(4-vinylbenzyl)-N,N-diethylamine] block, and the soluble-to-insoluble --transition temperature is dependent on the methanol content in the methanol/water mixture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2155–2165

The multi-thermo-responsive block copolymer of poly[2-(2-methoxyethoxy)ethyl methacrylate]-block-poly[N-(4-vinylbenzyl)-N,N-diethylamine] (PMEO₂MA-b-PVEA) displaying phase transition at both the lower critical solution temperature (LCST) and the upper critical solution temperature (UCST) in the alcohol/water mixture is synthesized by reversible addition-fragmentation chain transfer polymerization. The poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMEO₂MA) block exhibits the UCST phase transition in alcohol and the LCST phase transition in water, while the poly[N-(4-vinylbenzyl)-N,N-diethylamine] (PVEA) block shows the UCST phase transition in isopropanol and the LCST phase transition in the alcohol/water mixture. Both the polymer molecular weight and the co-solvent/nonsolvent exert great influence on the LCST or UCST of the block copolymer. By adjusting the solvent character including the water content and the temperature, the block copolymer undergoes multiphase transition at LCST or UCST, and various block copolymer morphologies including inverted micelles, core-corona micelles, and corona-collapsed micelles are prepared. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4399–4412

Dispersion RAFT polymerization of styrene in the alcohol/water mixture mediated with the brush macro-RAFT agent of poly[poly(ethylene oxide) methyl ether vinylphenyl-co-styrene] trithiocarbonate [P(mPEGV-co-St)-TTC] with similar molecular weight but different chemical composition is investigated. Well-controlled RAFT polymerization including an initial slow homogeneous polymerization and a subsequent fast heterogeneous polymerization at almost complete monomer conversion is achieved. The molecular weight of the synthesized block copolymer increases linearly with the monomer conversion, and the polydispersity is relatively narrow (PDI < 1.3). The RAFT polymerization kinetics is dependent on the chemical composition in the brush macro-RAFT agents, and those with high content of hydrophobic segment lead to fast RAFT polymerization. The growth of the block copolymer nano-objects during the RAFT polymerization is explored, and various block copolymer nano-objects such as nanospheres, worms, vesicles and large-compound-micelle-like particles are prepared. The parameters such as the chemical composition in the brush macro-RAFT agent, the chain length of the solvatophobic block, the concentration of the feeding monomer and the solvent character affecting the size and morphology of the block copolymer nano-objects are investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3177–3190

Aqueous RAFT polymerization of N-isopropylacrylamide (NIPAM) mediated with hydrophilic macro-RAFT agent is generally used to prepare poly(N-isopropylacrylamide) (PNIPAM)-based block copolymer. Because of the phase transition temperature of the block copolymer in water being dependent on the chain length of the PNIPAM block, the aqueous RAFT polymerization is much more complex than expected. Herein, the aqueous RAFT polymerization of NIPAM in the presence of the hydrophilic macro-RAFT agent of poly(dimethylacrylamide) trithiocarbonate is studied and compared with the homogeneous solution RAFT polymerization. This aqueous RAFT polymerization leads to the well-defined poly(dimethylacrylamide)-b-poly(N-isopropylacrylamide)-b-poly(dimethylacrylamide) (PDMA-b-PNIPAM-b-PDMA) triblock copolymer. It is found, when the triblock copolymer contains a short PNIPAM block, the aqueous RAFT polymerization undergoes just like the homogeneous one; whereas when the triblock copolymer contains a long PNIPAM block, both the initial homogeneous polymerization and the subsequent dispersion polymerization are involved and the two-stage ln([M]_o/[M])-time plots are indicated. The reason that the PNIPAM chain length greatly affects the aqueous RAFT polymerization is discussed. The present study is anticipated to be helpful to understand the chain extension of thermoresponsive block copolymer during aqueous RAFT polymerization. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The dispersion reversible addition-fragmentation chain transfer (RAFT) polymerization of 4-vinylpyridine in toluene in the presence of the polystyrene dithiobenzoate (PS-CTA) macro-RAFT agent with different chain length is discussed. The RAFT polymerization undergoes an initial slow homogeneous polymerization and a subsequent fast heterogeneous one. The RAFT polymerization rate is dependent on the PS-CTA chain length, and short PS-CTA generally leads to fast RAFT polymerization. The dispersion RAFT polymerization induces the self-assembly of the in situ synthesized polystyrene-b-poly(4-vinylpyridine) block copolymer into highly concentrated block copolymer nano-objects. The PS-CTA chain length exerts great influence on the particle nucleation and the size and morphology of the block copolymer nano-objects. It is found, short PS-CTA leads to fast particle nucleation and tends to produce large-sized vesicles or large-compound micelles, and long PS-CTA leads to formation of small-sized nanospheres. Comparison between the polymerization-induced self-assembly and self-assembly of block copolymer in the block-selective solvent is made, and the great difference between the two methods is demonstrated. The present study is anticipated to be useful to reveal the chain extension and the particle growth of block copolymer during the RAFT polymerization under dispersion condition. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The nonionic amphiphilic brush polymers such as poly[poly(ethylene oxide) methyl ether vinylphenyl-co-styrene] trithiocarbonate [P(mPEGV-co-St)-TTC] and poly[poly(ethylene oxide) methyl ether vinylphenyl-b-styrene-b-poly(ethylene oxide) methyl ether vinylphenyl] trithiocarbonate [P(mPEGV-b-St-b-mPEGV)-TTC] with different monomer sequence and chemical composition are synthesized and their application as macro-RAFT agent in the emulsion RAFT polymerization of styrene is explored. It is found that the monomer sequence in the brush polymers exerts great influence on the emulsion RAFT polymerization kinetics, and the fast polymerization with short induction period in the presence of P(mPEGV-co-St)-TTC is demonstrated. Besides, the chemical composition in the brush polymer macro-RAFT agent effect on the emulsion RAFT polymerization is investigated, and the macro-RAFT agent with high percent of the hydrophobic PS segment leads to fast and well controlled polymerization. The growth of triblock copolymer colloids in the emulsion polymerization is checked, and it reveals that the colloidal morphology is ascribed to the hydrophobic PS block extension, and the P(mPEGV-co-St) block almost have no influence just on the size of the colloids. This may be the first example to study the monomer sequence and the chemical composition in the macro-RAFT agent on emulsion RAFT polymerization, and will be useful to reveal the block copolymer particle growth. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

The reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in alcohol/water mixture mediated with the poly(N-isopropylacrylamide) trithiocarbonate macro-RAFT agent (PNIPAM-TTC) is studied and compared with the general RAFT dispersion polymerization in the presence of a small molecular RAFT agent. Both the homogeneous/quasi-homogeneous polymerization before particle nucleation and the heterogeneous polymerization after particle nucleation are involved in the PNIPAM-TTC-mediated RAFT polymerization, and the two-stage increase in the molecular weight (M_n) and nanoparticle size of the synthesized block copolymer is found. In the initial homogeneous/quasi-homogeneous polymerization, the M_n and nanoparticle size slowly increase with monomer conversion, whereas the M_n and particle size quickly increase in the subsequent heterogeneous RAFT polymerization, which is much different from those in the general RAFT dispersion polymerization. Besides, the PNIPAM-TTC-mediated RAFT polymerization runs much faster than the general RAFT dispersion polymerization. This study is anticipated to be helpful to understand the polymer chain extension through RAFT polymerization under dispersion conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Poly[N-(4-vinylbenzyl)-N,N-dibutylamine hydrochloride] trithiocarbonate, which contains the reactive trithiocarbonate group and the appending surface-active groups, is used as both surfactant and macromolecular reversible addition-fragmentation chain transfer (macro-RAFT) agent in batch emulsion polymerization of styrene. Under the conditions at high monomer content of ∼20 wt % and with the molecular weight of the macro-RAFT agent ranging from 4.0 to 15.0 kg/mol, well-controlled batch emulsion RAFT polymerization initiated by the hydrophilic 2-2′-azobis(2-methylpropionamidine) dihydrochloride is achieved. The polymerization leads to formation of nano-sized colloids of the poly[N-(4-vinylbenzyl)-N,N-dibutylamine hydrochloride]-b- polystyrene-b-poly[N-(4-vinylbenzyl)-N,N-dibutylamine hydrochloride] triblock copolymer. The colloids generally have core-shell structure, in which the hydrophilic block forms the shell and the hydrophobic block forms the core. The molecular weight of the triblock copolymer linearly increases with increase in the monomer conversion, and the values are well-consistent with the theoretical ones. The molecular weight polydispersity index of the triblock copolymer is below 1.2 at most cases of polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A coupling reaction is performed between polymeric nanoparticles and microparticles via the nucleophilic substitution of pendent β-diketone groups with benzyl chloride. The coupling reaction results in the formation of hierarchical particles, through the nanoparticles being covalently linked onto the microparticles. The coupling reaction is tracked by TEM and SEM, and the formation of covalent C–C bonds through the coupling reaction between the polymeric nanoparticles and microparticles is confirmed by solid-state ¹³C CP-MAS NMR spectroscopy and XPS. The proposed coupling reaction between the nanoparticles and the microparticles is believed to be a promising strategy in particle-surface modification.

Reversible addition-fragmentation chain transfer (RAFT) polymerization of a typical hydrophobic monomer of styrene within microreactor of shell-corona hollow microspheres of poly(styrene-co-methacrylic acid) suspending in water is studied. The shell-corona hollow microspheres contain a hydrophilic corona of poly(methacrylic acid) (PMAA) and a cross-linked polystyrene shell, which can suspend in water because of the hydrophilic corona of PMAA. The size of the shell-corona hollow microspheres is about 289 nm and the extent of the microcavity of the hollow microsphere is 154 nm. These shell-corona hollow microspheres can act as microreactor, within which the typical hydrophobic monomer of styrene, the RAFT agent of S-benzyl dithiobenzoate and the initiator of 2,2′-azobisisobutyronitrile can be encapsulated and RAFT polymerization of styrene takes place in well controlled manner in water. It is found that the resultant polymer of polystyrene has a competitively low polydispersity index and its number-average molecular weight linearly increases with monomer conversion. The method is believed to be a new strategy of RAFT polymerization of hydrophobic monomer in aqueous solution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

The pH-responsive core-shell microspheres of poly(styrene-co-methylacrylic acid) (PS-co-PMAA) containing a polystyrene (PS) core and a poly(methylacrylic acid) (PMAA) shell are synthesized by one-stage soap-free copolymerization and the catalyst system palladium-iminodiacetic acid (IDA-Pd) is immobilized on the outer shell-layer of the core-shell microspheres to form the quasi-homogeneous and easily accessible catalyst PS-co-PMAA-IDA-Pd. This quasi-homogeneous PS-co-PMAA-IDA-Pd catalyst is highly dispersed in the reaction medium just like a homogeneous one and can be separated like a heterogeneous catalyst by adjusting the pH of the reaction medium. Suzuki reactions employing the quasi-homogeneous PS-co-PMAA-IDA-Pd catalyst are efficiently performed in water as the sole solvent under mild conditions such as room temperature. The PS-co-PMAA-IDA-Pd catalyst is also used in Heck reactions of a wide range of aryl halides with styrene and proves to be efficient in aqueous solution. The PS-co-PMAA-IDA-Pd catalyst has a low leaching loss and can be reused at least 4 times without loss of activity.

A method of one-stage soap-free emulsion polymerization to synthesize narrowly dispersed core-shell microspheres is proposed. Following this method, core-shell microspheres of poly(styrene-co-4-vinylpyridine), poly(styrene-co-methyl acrylic acid), and poly[styrene-co-2-(acetoacetoxy)ethyl methacrylate-co-methyl acrylic acid] are synthesized by one-stage soap-free emulsion polymerization of a mixture of one or two hydrophobic monomers and a suitable hydrophilic monomer in water. The effect of the molar ratio of the hydrophobic monomer to the hydrophilic one on the size, the core thickness, and the shell thickness of the core-shell microspheres is discussed. The molar ratio of the hydrophobic and hydrophilic monomers and the hydrophilicity of the resultant oligomers of the hydrophilic monomer are optimized to synthesize narrowly dispersed core-shell microspheres. A possible mechanism of one-stage soap-free emulsion polymerization to synthesize core-shell microspheres is suggested and coagglutination of the oligomers of the hydrophilic monomers on the hydrophobic core is considered to be the key to form core-shell microspheres. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1192–1202, 2008