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ABSTRACT Four families of hyperbranched amphiphilic block copolymers of styrene (Sty, less polar monomer) and 2-vinylpyridine (2VPy, one of the two more polar monomers) or 4-vinylpyridine (4VPy, the other polar monomer) were prepared via self-condensing vinyl reversible addition-fragmentation chain transfer polymerization (SCVP-RAFT). Two families contained 4VPy as the more polar monomer, one of which possessing a Sty -b-4VPy architecture, and the other possessing the reverse block architecture. The other two families bore 2VPy as the more polar monomer and had either a 2VPy -b-Sty or a Sty -b-2VPy architecture. Characterization of the hyperbranched block copolymers in terms of their molecular weights and compositions indicated better control when the VPy monomers were polymerized first. Control over the molecular weights of the hyperbranched copolymers was also confirmed with the aminolysis of the dithioester moiety at the branching points to produce linear polymers with number-average molecular weights slightly greater than the theoretically expected ones, due to recombination of the resulting thiol-terminated linear polymers. The amphiphilicity of the hyperbranched copolymers led to their self-assembly in selective solvents, which was probed using atomic force microscopy and dynamic light scattering, which indicated the formation of large spherical micelles of uniform diameter. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1310-1319 [ABSTRACT FROM AUTHOR]

ABSTRACT Amphiphilic hyperbranched copolymer chains made of large hyperbranched poly(acrylic acid) cores grafted with short polystyrene stickers (HB-PAA n- g-PS n + 1) with different n values ( n = 1, 10, 47) were well prepared and confirmed by size exclusion chromatography, Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance. The study on the interchain association behavior of these amphiphilic chains indicates that larger HB-(PAA) n- g-(PS) n + 1 copolymer chains have a less tendency to undergo interchain association. Moreover, the simple vial-inversion and rheological experiments show that the apparent critical gel concentration ( Cg) decreases with n, but no sol-gel transition was observed for triblock PS-PAA-PS even when the concentration is up to 200 g L−1. Further transmission electron microscopy study of the latex particles prepared with HB-(PAA) n- g-(PS) n + 1 as surfactant reveals that the latex particles are spherical and narrowly dispersed; while the measured latex particle number ( Np) indicates the surfactant efficiency of HB-(PAA)47- g-(PS)48 is poorer than that of triblock PS-PAA-PS ( n = 1). Finally, pyrene solubilization measurement shows the solubilization efficiency of HB-(PAA) n- g-(PS) n + 1 copolymers decreases with n, consistent with the previous observed interchain association result. The present study demonstrates that both the chain topology and the styrene weight fraction dominates the final solution properties of amphiphilic HB-(PAA) n- g-(PS) n + 1 chains in aqueous solution. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 128-138 [ABSTRACT FROM AUTHOR]

ABSTRACT Copper-catalyzed azide-alkyne cycloaddition (CuAAC) was used to prepare glycosylated polyethylene (PE)-poly(ethylene glycol) (PEG) amphiphilic block copolymers. The synthetic approach involves preparation of alkyne-terminated PE- b-PEG followed by CuAAC reaction with different azide functionalized sugars. The alkyne-terminated PE- b-PEG was prepared by etherification reaction between hydroxyl-terminated PE- b-PEG ( Mn ∼ 875 g mol−1) and propargyl bromide and azidoethyl glycosides were prepared by glycosylation of 2-azidoethanol. Atmospheric pressure solids analysis probe-mass spectrometry was used as a novel solid state characterization tool to determine the outcome of the CuAAC click reaction and end-capping of PE- b-PEG by the azidoethyl glycoside group. The aqueous solution self-assembly behavior of these amphiphilic glycosylated polymers was explored by TEM and dye solubilization studies. Carbohydrate-bearing spherical aggregates with the ability to solubilize a hydrophobic dye were observed. The potential of these amphiphilic glycosylated polymers to self-assemble via electro-formation into giant carbohydrate-bearing polymersomes was also investigated using confocal fluorescence microscopy. An initial bioactivity study of the carbohydrate-bearing aggregates is furthermore presented. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 5184-5193 [ABSTRACT FROM AUTHOR]

ABSTRACT An approach to the synthesis of new regular graft-copolymers polyimide (PI)- graft-polymethacrylic acid is elaborated, including (1) synthesis of multicenter PI macroinitiators, (2) controlled ATRP of tert-butylmethacrylate on the prepared macroinitiators, and (3) protonolysis of tert-butyl ester groups of side chains of the resulting PI- graft-poly( tert-butylmethacrylate). Experimental conditions for attaining complete conversions of the first and the third stages of the process are determined by means of 1H NMR and FTIR-spectroscopy. Polymer products of the first and the second stages of the process, as well as poly( tert-butylmethacrylate) side chains cleaved from the PI- graft-poly( tert-butylmethacrylate) copolymers by complete decomposition of the PI backbone under alkaline hydrolysis conditions, are characterized by GPC. The kinetics of poly( tert-butylmethacrylate) chain growth on a PI macroinitiator under ATRP conditions are studied. The results obtained provide evidence for the controlled character of the ATRP process and the regular structure of the synthesized graft-copolymers. It is shown that PI- g-PMAA PI brushes are significantly more efficient intracellular delivery agents for the potential photosensitizer [tetra(4-fluorophenyl)tetracyanoporhyrazine free base] than are the commonly used PEG-micelles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4267-4281 [ABSTRACT FROM AUTHOR]

Long-subchain hyperbranched polystyrene (lsc-hp PSt) with uniform subchain length was obtained through copper-catalyzed azide-alkyne cycloaddition click chemistry from seesaw macromonomer of PSt having one alkynyl group anchored at the chain centre and two azido group attached to both chain ends [alkynyl-(PSt-N3)2]. After precipitation fraction, different portions of lsc-hp PSt having narrow overall molecular weight distribution were obtained for further grafting with alkynyl-capped poly( N-isopropylacrylamide) (alkynyl-PNIPAM), which was obtained via single-electron transfer living radical polymerization of NIPAM with propargyl 2-bromoisobutyrate as the initiator and grafted onto the peripheral azido groups of lsc-hp PSt via click chemistry. Thus, amphiphilic lsc-hp PSt grafted with PNIPAM chains (lsc-hp PSt- g-PNIPAM) was obtained and would have star-like conformation in tetrahydrofuran (THF). By replacing THF with water, lsc-hp PSt- g-PNIPAM was dissolved at molecular level in aqueous solution due to the hydrophilicity of PNIPAM and exhibited thermal induced shrinkage of PNIPAM arms. The water-insoluble lsc-hp PSt would collapse densely and could be served as a reservoir to absorb hydrophobic chemicals in aqueous solution. The influence of overall molecular weight of lsc-hp PSt on the absorption of pyrene was studied. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

Two chiral amphiphilic diblock copolymers with different relative lengths of the hydrophobic and hydrophilic blocks, poly(6‐O‐p‐vinylbenzyl‐1,2:3,4‐Di‐O‐isopropylidene‐D‐galactopyranose)‐b‐poly(N‐isopropylacrylamide) or poly(VBCPG)‐b‐poly(NIPAAM) and poly(20‐(hydroxymethyl)‐pregna‐1,4‐dien‐3‐one methacrylate)‐b‐poly(N‐isopropylacrylamide) or poly(MAC‐HPD)‐b‐poly(NIPAAM) were synthesized via consecutive reversible addition‐fragmentation chain‐transfer polymerizations of VBCPG or MAC‐HPD and NIPAAM. The chemical structures of these diblock copolymers were characterized by 1H nuclear magnetic resonance spectroscopy. These amphiphilic diblock copolymers could self‐assemble into micelles in aqueous solution, and the morphologies of micelles were investigated by transmission electron microscopy. By comparison with the lower critical solution temperatures (LCST) of poly(NIPAAM) homopolymer in deionized water (32 °C), a higher LCST of the chiral amphiphilic diblock copolymer (poly(VBCPG)‐b‐poly(NIPAAM)) was observed and the LCST increased with the relative length of the poly(VBCPG) block in the copolymer from 35 to 47 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7690–7701, 2008 [ABSTRACT FROM AUTHOR]