Polyisobutylene-b-poly(N,N-diethylacrylamide) (PIB-b-PDEAAm) well-defined amphiphilic diblock copolymers were synthesized by sequential living carbocationic polymerization and reversible addition-fragmentation chain transfer (RAFT) polymerization. The hydrophobic polyisobutylene segment was first built by living carbocationic polymerization of isobutylene at −70 °C followed by multistep transformations to give a well-defined (M_w/M_n = 1.22) macromolecular chain transfer agent, PIB-CTA. The hydrophilic poly(N,N-diethylacrylamide) block was constructed by PIB-CTA mediated RAFT polymerization of N,N-diethylacrylamide at 60 °C to afford the desired well-defined PIB-b-PDEAAm diblock copolymers with narrow molecular weight distributions (M_w/M_n ≤1.26). Fluorescence spectroscopy, transmission electron microscope, and dynamic light scattering (DLS) were employed to investigate the self-assembly behavior of PIB-b-PDEAAm amphiphilic diblock copolymers in aqueous media. These diblock copolymers also exhibited thermo-responsive phase behavior, which was confirmed by UV-Vis and DLS measurements. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1143–1150

A novel oridonin derivative substituted with 3-((2,3-dihydroxypropyl)dithio)-propionyl group at 14-O position was synthesized through a two-step procedure: Esterification of oridonin with 3-(2-pyridyldithio)propanoic acid and the subsequent thiol-disul?de exchange reaction with 3-mercapto-1,2-propanediol. The bioreduction-responsive disulfide bond in the compound leads to high leaving ability of the 14-O acyl moiety when treated with glutathione as monitored by reverse phase high-performance liquid chromatography.

A well-defined amphiphilic graft copolymer, consisting of hydrophobic poly(tert-butyl acrylate) (PtBA) backbone and hydrophilic poly(N-vinylcaprolactam) (PNVCL) side chains, was synthesized by successive reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP). A new acrylate monomer bearing a chlorine-based initiating group, tert-butyl 2-((2-chloropropanoyloxy)methyl)acrylate, was first RAFT homopolymerized in a controlled way to give a well-defined homopolymer with a narrow molecular weight distribution (M_w/M_n=1.15). This homopolymer directly initiated ATRP of N-vinylcaprolactam (NVCL) to afford a well-defined PtBA-g-PNVCL graft copolymer (M_w/M_n=1.22) via the grafting-from strategy without polymeric functionality transformation. PAA-g-PNVCL graft copolymer was prepared by selectively hydrolyzing PtBA-g-PNVCL. Ornidazole (ONZ)-loaded polymeric micelles using PAA-g-PNVCL copolymer as carrier were prepared by physical entrapping. Drug release experiment of the nano-carrier indicated the pH-dependent drug release characteristics.

A series of well-defined amphiphilic diblock copolymers consisting of hydrophobic polyisobutylene (PIB) and hydrophilic poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) segments was synthesized via the combination of living carbocationic polymerization and reversible addition fragmentation chain transfer (RAFT) polymerization. Living carbocationic polymerization of isobutylene followed by end-capping with 1,3-butadiene was first performed at −70 °C to give a well-defined allyl-Cl-terminated PIB with a low polydispersity (M_w/M_n =1.29). This end-functionalized PIB was further converted to a macromolecular chain transfer agent for mediating RAFT block copolymerization of 2-(diethylamino)ethyl methacrylate at 60 °C in tetrahydrofuran to afford the target well-defined PIB-b-PDEAEMA diblock copolymers with narrow molecular weight distributions (M_w/M_n ≤1.22). The self-assembly behavior of these amphiphilic diblock copolymers in aqueous media was investigated by fluorescence spectroscopy and transmission electron microscope, and furthermore, their pH-responsive behavior was studied by UV-vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1478–1486

A well-defined amphiphilic graft copolymer, consisting of hydrophobic polyallene-based backbone and hydrophilic poly(N-isopropylacrylamide) (PNIPAM) side chains, was prepared by the combination of living coordination polymerization, single electron transfer-living radical polymerization (SET-LRP), and the grafting-from strategy. First, the double-bond-containing backbone was prepared by [(η³-allyl)NiOCOCF₃]₂-initiated living coordination polymerization of 6-methyl-1,2-heptadiene-4-ol (MHDO). Next, the pendant hydroxyls in every repeating unit of poly(6-methyl-1,2-heptadiene-4-ol) (PMHDO) homopolymer were treated with 2-chloropropionyl chloride to give PMHDO-Cl macroinitiator. Finally, PNIPAM side chains were grown from PMHDO backbone via SET-LRP of N-isopropylacrylamide initiated by PMHDO-Cl macroinitiator in N,N-dimethylformamide/2-propanol using copper(I) chloride/tris(2-(dimethylamino)ethyl)amine as catalytic system to afford PMHDO-g-PNIPAM graft copolymers with a narrow molecular weight distribution (M_w/M_n = 1.19). The critical micelle concentration (cmc) in water was determined by fluorescence probe technique and the effects of pH and salinity on the cmc of PMHDO-g-PNIPAM were also investigated. The micellar morphology was found to be spheres using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

A series of well-defined amphiphilic graft copolymer containing hydrophobic polyallene-based backbone and hydrophilic poly(2-(diethylamino)ethyl acrylate) (PDEAEA) side chains was synthesized by sequential living coordination polymerization of 6-methyl-1,2-heptadiene-4-ol (MHDO) and single electron transfer-living radical polymerization (SET-LRP) of 2-(diethylamino)ethyl acrylate (DEAEA). Ni-catalyzed living coordination polymerization of MHDO was first performed in toluene to give a well-defined double-bond-containing poly(6-methyl-1,2-heptadiene-4-ol) (PMHDO) homopolymer with a low polydispersity (M_w/M_n = 1.10). Next, 2-chloropropionyl chloride was used for the esterification of pendant hydroxyls in every repeating unit of the homopolymer so that the homopolymer was converted to PMHDO-Cl macroinitiator. Finally, SET-LRP of DEAEA was initiated by the macroinitiator in tetrahydrofuran/H₂O using CuCl/tris(2-(dimethylamino)ethyl)amine as catalytic system to afford well-defined PMHDO-g-PDEAEA graft copolymers (M_w/M_n ≤ 1.22) through the grafting-from strategy. The critical micelle concentration (cmc) was determined by fluorescence spectroscopy with N-phenyl-1-naphthylamine as probe and the micellar morphology was visualized by transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Two polyisobutylene-grafted graphene nanocomposites were prepared by CuBr-catalyzed atom transfer nitroxide radical coupling (ATNRC) and Cu-catalyzed single electron transfer-nitroxide radical coupling (SET-NRC) chemistry under mild conditions, respectively, through the grafting-onto strategy. Graphene oxide was first reduced to graphene by diazonium addition reaction followed by treating graphene with ethyl 2-bromoisobutyrate for introducing Br-containing groups onto the surface to give G-Br. The presynthesized well-defined functional polyisobutylene (PIB) possessing 2,2,6,6-tetramethylpiperidine-1-oxyl terminal group obtained via cationic polymerization of isobutylene was then coupled with G-Br through ATNRC or SET-NRC at room temperature to afford polymer-modified graphene, G-PIB. SET-NRC method has a faster coupling rate using cheaper reagent (Cu wire instead of CuBr) in comparison with ATNRC approach. Detailed characterizations including FT-IR, Raman, ¹H NMR, TGA, AFM, and TEM assured us of successful anchoring of PIB chains onto the surface of graphene sheets. The resulting G-PIB nanocomposites still maintain the separated single layers in dispersion and the dispersibilities in organic solvents are significantly improved. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4505–4514

A series of new well-defined amphiphilic graft copolymers containing hydrophobic poly(tert-butyl acrylate) backbone and hydrophilic poly(ethylene oxide) side chains were reported. Reversible addition-fragmentation chain transfer homopolymerization of tert-butyl 2-((2-bromopropanoyloxy)methyl)acrylate was first performed to afford a well-defined backbone with a narrow molecular weight distribution (M_w/M_n = 1.07). The target poly(tert-butyl acrylate)-g-poly(ethylene oxide) (PtBA-g-PEO) graft copolymers with low polydispersities (M_w/M_n = 1.18–1.26) were then synthesized by atom transfer nitroxide radical coupling or single electron transfer-nitroxide radical coupling reaction using CuBr(Cu)/PMDETA as catalytic system. Fluorescence probe technique was employed to determine the critical micelle concentrations (cmc) of the obtained amphiphilic graft copolymers in aqueous media. Furthermore, PAA-g-PEO graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA backbone while PEO side chains kept inert. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this study, we report a mild and efficient strategy for growing thermosensitive polymers directly from the surface of exfoliated graphene oxide (GO). Exfoliated GO sheets were sequentially subject to the epoxide ring-opening reaction with tris(hydroxymethyl) aminomethane (TRIS) to increase the amount of reactive sites, the esterification with 2-bromo-2-methylpropionyl bromide to introduce the Br-containing initiating groups, and the surface-initiated single electron transfer–living radical polymerization of N-isopropylacrylamide (NIPAM) to tune the molecular weights of grafted polymers. All these reactions were performed at ambient temperature without losing any other oxygen-containing functionality on GO. The resulting TRIS-GO-PNIPAM nanocomposites still maintain the separated single layers in dispersion, and the dispersibilities in organic solvents are significantly improved. Meanwhile, the aqueous dispersion of TRIS-GO-PNIPAM shows reversible temperature switching self-assembly and disassembly behavior at about 40°C. Such smart graphene-based hybrid materials are promising for applications in nanoelectronics, sensors, and microfluidic switches. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A series of well-defined amphiphilic graft copolymers bearing hydrophilic poly(ethylene oxide) (PEO) side chains with tunable grafting densities were synthesized by atom transfer nitroxide radical coupling (ATNRC) reaction using CuBr/PMDETA as catalytic system via the grafting-onto strategy. PEO side chains were linked to α-C of carbonyl of polyacrylate-based backbone, not to the ester side groups as usual, so that every repeating unit of the backbone possessed a pendant steric bulky tert-butyl group. The critical micelle concentrations of the obtained amphiphilic graft copolymers in aqueous media determined by fluorescence probe technique using pyrene as probe increased with the raising of molecular weights. These amphiphilic graft copolymers with novel chemical structure showed unprecedented diverse nanostructures visualized by transmission electron microscopy in aqueous media and micellar morphologies varied with the changing of experiment parameters. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

A mild and efficient strategy is presented for growing thermo-sensitive polymers directly from the surface of exfoliated graphene oxide (GO). This method involves the covalent attachment of Br-containing initiating groups onto the surface of GO sheets followed by in situ growing poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) via single-electron-transfer living radical polymerization (SET-LRP). Considering the lack of reactive functional groups on the surface of GO, exfoliated GO sheets were subjected to an epoxide ring opening reaction with tris(hydroxymethyl) aminomethane (TRIS) at room temperature. The initiating groups were grafted onto TRIS-GO sheets by treating hydroxyls with 2-bromo-2-methylpropionyl bromide at room temperature. PPEGEEMA chains were synthesized by in situ SET-LRP using CuBr/Me₆TREN as catalytic system at 40 °C in H₂O/THF. The resulting materials were characterized using a range of testing techniques and it was proved that polymer chains were successfully introduced to the surface of GO sheets. After grafting with PPEGEEMA, the modified GO sheets still maintained the separated single layers and the dispersibility was significantly improved. This TRIS-GO-PPEGEEMA hybrid material shows reversible self-assembly and deassembly in water by switching temperature at about 34 °C. Such smart graphene-based materials promise important potential applications in thermally responsive nanodevices and microfluidic switches. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A series of well-defined amphiphilic graft copolymers bearing hydrophobic poly(tert-butyl acrylate) backbone and hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate)] (PPEGMEMA) side chains were synthesized by sequential reversible addition fragmentation chain transfer (RAFT) polymerization and single-electron-transfer living radical polymerization (SET-LRP) without any polymeric functional group transformation. A new Br-containing acrylate monomer, tert-butyl 2-((2-bromoisobutanoyloxy)methyl)acrylate (tBBIBMA), was first prepared, which can be homopolymerized by RAFT to give a well-defined PtBBIBMA homopolymer with a narrow molecular weight distribution (M_w/M_n = 1.15). This homopolymer with pendant Br initiation group in every repeating unit initiated SET-LRP of PEGMEMA at 45 °C using CuBr/dHbpy as catalytic system to afford well-defined PtBBIBMA-g-PPEGMEMA graft copolymers via the grafting-from strategy. The self-assembly behavior of the obtained graft copolymers in aqueous media was investigated by fluorescence spectroscopy and TEM. These copolymers were found to be stimuli-responsive to both temperature and ions. Finally, poly(acrylic acid)-g-PPEGMEMA double hydrophilic graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA backbone while PPEGMEMA side chains kept inert. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A series of well-defined double hydrophilic graft copolymers, consisting of poly(N-isopropylacrylamide)-b-poly(ethyl acrylate) backbone and poly(2-vinylpyridine) side chains, were synthesized by successive single-electron-transfer living radical polymerization (SET-LRP) and atom transfer radical polymerization (ATRP). The backbone was prepared by sequential SET-LRP of N-isopropylacrylamide and 2-hydroxyethyl acrylate at 25 °C using CuCl/tris(2-(dimethylamino)ethyl)amine as the catalytic system. The obtained diblock copolymer was transformed into the macroinitiator by reacting with 2-chloropropionyl chloride. Next, grafting-from strategy was used for the synthesis of poly(N-isopropylacrylamide)-b-[poly(ethyl acrylate)-g-poly(2-vinylpyridine)] double hydrophilic graft copolymer. ATRP of 2-vinylpyridine was initiated by the macroinitiator at 25 °C using CuCl/hexamethyldiethylenetriamine as the catalytic system. The synthesis of both the backbone and the side chains are controllable. Thermo- and pH-responsive schizophrenic micellization behaviors were investigated by ¹H NMR, fluorescence spectroscopy, dynamic light scattering, and transmission electron microscopy. Unimolecular micelles with PNIPAM-core formed in acidic environment (pH = 2) with elevated temperature (T ≥ 32 °C), whereas the aggregates turned into spheres with PEA-g-P2VP-core accompanied with the lifting of pH values (pH ≥ 5.3) at room temperature. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 15–23, 2010

A series of well-defined double hydrophilic graft copolymers containing poly[poly(ethylene glycol) methyl ether acrylate] (PPEGMEA) backbone and poly[poly(ethylene glycol) ethyl ether methacrylate] (PPEGEEMA) side chains were synthesized by the combination of single electron transfer-living radical polymerization (SET-LRP) and atom transfer radical polymerization (ATRP). The backbone was first prepared by SET-LRP of poly(ethylene glycol) methyl ether acrylate macromonomer using CuBr/tris(2-(dimethylamino)ethyl)amine as catalytic system. The obtained comb copolymer was treated with lithium diisopropylamide and 2-bromoisobutyryl bromide to give PPEGMEA-Br macroinitiator. Finally, PPEGMEA-g-PPEGEEMA graft copolymers were synthesized by ATRP of poly(ethylene glycol) ethyl ether methacrylate macromonomer using PPEGMEA-Br macroinitiator via the grafting-from route. The molecular weights of both the backbone and the side chains were controllable and the molecular weight distributions kept narrow (M_w/M_n ≤ 1.20). This kind of double hydrophilic copolymer was found to be stimuli-responsive to both temperature and ion (0.3 M Cl⁻ and SO). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 647–655, 2010

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

A series of well-defined double-hydrophilic graft copolymers, consisting of poly(N-isopropylacrylamide)-b-poly(ethyl acrylate) (PNIPAM-b-PEA) backbone and poly(2-(dimethylamino)ethyl acrylate) (PDMAEA) side chains, were synthesized by the combination of single-electron-transfer living radical polymerization (SET-LRP) and atom-transfer radical polymerization (ATRP). PNIPAM-b-PEA backbone was first prepared by sequential SET-LRP of N-isopropylacrylamide and 2-hydroxyethyl acrylate at 25 °C using CuCl/tris(2-(dimethylamino)ethyl)amine as catalytic system followed by the transformation into the macroinitiator by treating the pendant hydroxyls with 2-chloropropionyl chloride. The final graft copolymers with narrow molecular weight distributions were synthesized by ATRP of 2-(dimethylamino)ethyl acrylate initiated by the macroinitiator at 40 °C using CuCl/tris(2-(dimethylamino)ethyl)amine as catalytic system via the grafting-from strategy. These copolymers were employed to prepare stable colloidal gold nanoparticles with controlled size in aqueous solution without any external reducing agent. The morphology and size of the nanoparticles were affected by the length of PDMAEA side chains, pH value, and the feed ratio of the graft copolymer to HAuCl₄. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1811–1824, 2009

A well-defined double hydrophilic graft copolymer, with polyacrylate as backbone, hydrophilic poly(ethylene glycol) and poly(methacrylic acid) as side chains, was synthesized via successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl methacrylate) side chains. The grafting-through strategy was first used to prepare poly[poly(ethylene glycol) methyl ether acrylate] comb copolymer. The obtained comb copolymer was transformed into macroinitiator by reacting with lithium diisopropylamine and 2-bromopropionyl chloride. Afterwards, grafting-from route was employed for the synthesis of poly[poly(ethylene glycol) methyl ether acrylate]-g-poly(methoxymethyl methacrylate) amphiphilic graft copolymer. The molecular weight distribution of this amphiphilic graft copolymer was narrow. Poly(methoxymethyl methacrylate) side chains were connected to polyacrylate backbone through stable CC bonds instead of ester connections. The final product, poly[poly(ethylene glycol) methyl ether acrylate]-g-poly(methacrylate acid), was obtained by selective hydrolysis of poly(methoxymethyl methacrylate) side chains under mild conditions without affecting the polyacrylate backbone. This double hydrophilic graft copolymer was found be stimuli-responsive to pH and ionic strength. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4056–4069, 2008

A series of well-defined double hydrophilic graft copolymers, consisting of poly(N-isopropylacrylamide)-b-poly(ethyl acrylate) (PNIPAM-b-PEA) backbone and poly(2-(diethylamino)ethyl methacrylate) (PDEA) side chains, were synthesized by successive atom transfer radical polymerization (ATRP). The backbone was firstly prepared by sequential ATRP of N-isopropylacrylamide and 2-hydroxyethyl acrylate at 25 °C using CuCl/tris(2-(dimethylamino)ethyl)amine as catalytic system. The obtained diblock copolymer was transformed into macroinitiator by reacting with 2-chloropropionyl chloride. Next, grafting-from strategy was employed for the synthesis of poly(N-isopropylacrylamide)-b-[poly(ethyl acrylate)-g-poly(2-(diethylamino)ethyl methacrylate)] (PNIPAM-b-(PEA-g-PDEA)) double hydrophilic graft copolymer. ATRP of 2-(diethylamino)ethyl methacrylate was initiated by the macroinitiator at 40 °C using CuCl/hexamethyldiethylenetriamine as catalytic system. The molecular weight distributions of double hydrophilic graft copolymers kept narrow. Thermo- and pH-responsive micellization behaviors were investigated by fluorescence spectroscopy, ¹H NMR, dynamic light scattering, and transmission electron microscopy. Unimolecular micelles with PNIPAM-core formed in acidic environment (pH = 2) with elevated temperature (≥32 °C); whereas, the aggregates turned into vesicles in basic surroundings (pH ≥ 7.2) at room temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5638–5651, 2008