Synthesis and characterization of water‐soluble gold nanoparticles stabilized by comb‐shaped copolymers

The water‐soluble gold nanoparticles stabilized by well‐defined comb‐shaped copolymers have been synthesized successfully. The hybrid nanoparticles consist of gold core and poly[poly(ethylene oxide) methyl ether acrylate]‐block‐poly(N‐isopropylacrylamide) [P(A‐MPEO)‐block‐PNIPAM] shell. The water‐soluble comb‐shaped copolymers, P(A‐MPEO)‐block‐PNIPAM with PNIPAM as a handle, were successfully synthesized via a macromonomer technique using reversible addition fragmentation chain transfer (RAFT) polymerization method. The terminal dithioester group of the comb‐shaped copolymer was reduced to a thiol end group forming SH‐terminated copolymers, P(A‐MPEO)‐block‐PNIPAM‐SH. Successively they were used to stabilize gold nanoparticles by the “grafting‐to” approach. The hybrid nanoparticles were characterized by TEM, UV–vis, and HRTEM. Because of the thermosensitive property of PNIPAM in aqueous solution, the comblike copolymer‐tethered gold nanoparticles show a sharp and reversible phase transition at 30 °C in aqueous solution, which was determined by microdifferential scanning calorimetry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 341–352, 2008     

Well‐defined polyisoprene‐grafted silica nanoparticles via the RAFT process

The preparation of well‐defined polyisoprene‐grafted silica nanoparticles (PIP‐g‐SiO₂ NPs) was investigated. Surface initiated reversible addition fragmentation chain transfer (SI‐RAFT) polymerization was used to polymerize isoprene from the surface of 15 nm silica NPs. A high temperature stable trithiocarbonate RAFT agent was anchored onto the surface of particles with controllable graft densities. The polymerization of isoprene mediated by silica anchored RAFT with different densities were investigated and compared to the polymerization mediated by free RAFT agents. The effects of different temperatures, initiators, and monomer feed ratios on the kinetics of the SI‐RAFT polymerization were also investigated. Using this technique, block copolymers of polyisoprene and polystyrene on the surface of silica particles were also prepared. The well‐defined synthesized PIP‐g‐SiO₂ NPs were then mixed with a polyisoprene matrix which showed a good level of dispersion throughout the matrix. These tunable grafted particles have potential applications in the field of rubber nanocomposites. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1493–1501     

The preparation and characterization of carboxylic acid‐coated silica nanoparticles

The preparation of carboxylic acid‐coated silica nanoparticles was investigated. A monolayer of carboxylic acid residues with controllable graft density was anchored to the nanoparticle by a ring‐opening reaction with succinic anhydride. Poly(methacrylic acid) [poly(MAA)] grafted nanoparticles were prepared via a polymerization–deprotection strategy. Tert‐butyl methacrylate was polymerized from the surface of silica nanoparticles in a predictable manner and with excellent control over the molecular weight distribution. Subsequent removal of the tert‐butyl group resulted in poly (MAA) grafted nanoparticles. The polymer nanoparticles were also functionalized with dyes, which may be useful in tracking the particles in biological systems. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Neoglycopolymers Based on 4‐Vinyl‐1,2,3‐Triazole Monomers Prepared by Click Chemistry

The synthesis of a new glycomonomer based on mannose, prepared via CuAAC, is reported. The resulting 1,2,3‐triazole linkage between mannose and the polymer backbone ensures the formation of highly stable glycopolymers, which will not undergo hydrolysis. The monomer 2′‐(4‐vinyl‐[1,2,3]‐triazol‐1‐yl)ethyl‐O‐α‐D ‐mannopyranoside was polymerized in the presence of a RAFT agent – 3‐benzylsulfanylthiocarbonylsulfanyl propionic acid – to yield well‐defined polymers with molecular weights up to 51 500 g mol^?1 and a PDI of 1.16. The resulting polymer was employed as a macroRAFT agent in the polymerization of NIPAAm in order to generate thermo‐responsive block copolymers, which undergo reversible micelle formation at elevated temperatures. The rapid interaction between the polymers prepared and ConA confirms the high affinity of these structures to proteins. While the linear glycopolymers already undergo a fast complexation with ConA, the reported rates have found to be exceeded by the micellar glycopolymer structure presented in the current contribution.

     

Synthesis of enantiopure homo and copolymers by raft polymerization and investigation of their enantioselective lipase‐catalyzed esterification

Homo and copolymers were synthesized from enantionpure (R)‐ and (S)‐1‐(4‐vinylphenyl)ethanol by reversible addition‐fragmentation chain transfer polymerization. The polymerization conditions were optimized resulting in dioxane as the preferred reaction solvent. First‐order polymerization kinetics and well‐defined enantiopure homopolymers with low dispersities were obtained. In agreement with their enantiomeric composition, the (R) and (S)‐polymers gave opposite optical rotation of light. Polymer analogous esterification of the chiral hydroxy groups catalyzed by enantioselective Candida antarctica Lipase B was strongly (R)‐selective. Esterification on the homopolymer and copolymers could be achieved to a maximum of around 50 %. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Single‐chain nanoparticles with well‐defined structure via intramolecular crosslinking of linear polymers with pendant benzoxazine groups

Controlled intramolecular collapse of linear polymer chains with crosslinkable groups is an efficient way to prepare single‐chain nanoparticles in the size range of 5–20 nm. However, the nature of the crosslinking group is critical. In present study, poly(styrene‐co‐chloromethyl styrene) [P(St‐co‐CMS)] was synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization and then was converted into polystyrene azide (PS? N₃). Polystyrene containing benzoxazine side groups [P(St‐co‐BS)], which can be used as the precusor for the later intramolecular collapse, was obtained from PS? N₃ and 3‐(4‐(prop‐2‐ynyloxy)phenyl)‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazine (P‐APPE) via the method of click chemistry. The sub‐20 nm polymeric nanoparticles with well‐defined structure via thermally intramolecular crosslinking of P(St‐co‐BS) were prepared. The structure change from the linear polymers to the single‐chain nanoparticles was confirmed by nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and gel permeation chromatography (GPC). The morphology and the dimension of the nanoparticles were characterized by using transmission electron microscope (TEM), atomic force microscopy (AFM), as well as dynamic light scattering (DLS). The results reveal that the size of the nanoparticles can be regulated by changing the molecular weight of the precursors and the amount of pendant benzoxazine groups by the use of controlled polymerization techniques. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

One‐pot synthesis of hyperbranched glycopolymers by RAFT polymerization

Soluble hyperbranched glycopolymers were prepared by copolymerization of glycan monomers with reversible addition‐fragmentation chain transfer polymerization (RAFT) inimers in a simple one‐pot reaction. Two novel RAFT inimers, 2‐(methacryloyloxy)ethyl 4‐cyano‐4‐(phenylcarbonothioylthio)pentanoate (MAE‐CPP) and 2‐(3‐(benzylthiocarbonothioylthio)propanoyloxy)ethyl acrylate (BCP‐EA) were synthesized and used to prepare hyperbranched glycopolymers. Two types of galactose‐based saccharide monomers, 6‐O‐methacryloyl‐1,2:3,4‐di‐O‐isopropylidene‐D ‐galactopyranose (proGal‐M) and 6‐O‐(2′‐acrylamido‐2′‐methylpropanoate)‐1,2:3,4‐di‐O‐isopropylidene‐D ‐galactopyranose (proGal‐A), containing a methacrylate and an acrylamide group, respectively, were also synthesized and polymerized under the mediation of the MAE‐CPP and BCP‐EA inimers, respectively. In addition, hyperbranched poly(proGal‐M), linear poly(proGal‐A), and hyperbranched poly(proGal‐A) were generated and their polymerization kinetics were studied and compared. An unexpected difference was observed in the kinetics between the two monomers during polymerization: the relationship between polymerization rate and concentration of inimer was totally opposite in the two monomer–inimer systems. Branching analysis was conducted by using degree of branching (DB) as the measurement parameter. As expected, a higher DB occurred with increased inimer content. Furthermore, these polymers were readily deprotected by hydrolysis in trifluoroacetic acid solution resulting in water‐soluble polymers. The resulting branched glycopolymers have potential as biomimetics of polysaccharides. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of chiral micelles and nanoparticles from amino acid based monomers using RAFT polymerization

Homopolymers of ^tbutyl acrylate (P^tBuA) and a monosubstituted acrylamide (PAM) having an amino acid moiety in the side chain, N‐acryloyl‐(L )‐phenylalanine methyl ester 1 , have been synthesized by Reversible Addition‐Fragmentation Chain Transfer (RAFT) polymerization. Diblock copolymers of these homopolymers were also synthesized by chain extending P^tBuA with monomer 1 and after modification, using simple acid deprotection chemistries of the acrylate block to afford a poly (acrylic acid) block, an optically active amphiphilic diblock copolymer was isolated. The optically active amphiphilic diblock copolymers, which contain chiral amino acid moieties within the hydrophobic segment, were then self‐assembled to afford spherical micelles which were subsequently crosslinked throughout the shell layer to afford robust chiral nanoparticles. The hydrodynamic diameters (D_h) of the block copolymer micelles and nanoparticles were measured by dynamic light scattering (DLS) and the dimensions of the nanoparticles were determined using tapping‐mode atomic force microscopy (AFM) and transmission electron microscopy (TEM). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3690–3702, 2008     

Polymer‐based fluoride‐selective chemosensor: Synthesis,sensing property,and its use for the design of molecular‐scale logic devices

A new styryl‐type monomer, 2‐(4‐vinylbenzyloxy)‐1 ‐naphthaldehyde thiosemicarbazone (VNT), was synthesized and then copolymerized with methyl methacrylate (MMA) by reversible addition fragmentation chain transfer polymerization affording a series of poly(MMA‐co‐VNT)s with different functional unit content, predetermined molecular weight, and narrow molecular‐weight distribution. The desired copolymers were structurally confirmed by various spectroscopic characterizations. Colorimetric and fluorescent titration spectra revealed that the copolymers are highly selective toward fluoride anions over other competitive species including Cl^?, Br^?, I^?, H₂PO₄^?, AcO^?, and HSO₄^?. On addition of F^?, a remarkable colorless‐to‐yellow color change is easily observed by naked eyes. The influence of the copolymer composition and molecular weight on its sensing capacity was then carefully investigated. The results showed that higher VNT‐incorporation amount within the copolymer chains leads to higher sensitivity toward F^? ions. Interestingly, the chromogenic process of the polymeric sensor can be switched back and forth by successively adding F^? and HSO₄^? anions into the dimethyl sulfoxide solution of the polymer, which may be represented by a complementary “IMPLICATION/INHIBIT” logic gate at molecular level using both the ions as the chemical inputs. Based on such a reversible and reproducible sensing system, we designed a molecular‐scale sequential information processing circuit displaying “writing–reading–erasing–reading” behavior and “multiwrite” function in the form of binary logic. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Facile synthesis of core‐surface crosslinked nanoparticles by interblock RAFT polymerization

A new, efficient method for synthesizing stable nanoparticles with poly(ethylene oxide) (PEO) functionalities on the core surface, in which the micellization and crosslinking reactions occur in one pot, has been developed. First, amphiphilic PEO‐b‐PS copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization of styrene using (PEO)‐based trithiocarbonate as a macro‐RAFT agent. The low molecular weight PEO‐b‐PS copolymer was dissolved in isopropyl alcohol where the block copolymer self‐assembled as core‐shell micelles, and then the core‐shell interface crosslink was performed using divinylbenzene as a crosslinking agent and 2,2′‐azobisisobutyronitrile as an initiator. The design of the amphiphilic RAFT agent is critical for the successful preparation of core‐shell interface crosslinked micellar nanoparticles, because of RAFT functional groups interconnect PEO and polystyrene blocks. The PEO functionality of the nanoparticles surface was confirmed by ¹H NMR and FTIR. The size and morphology of the nanoparticles was confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic laser light scattering analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Influence of small amounts of addition‐fragmentation capable monomers on polymerization‐induced shrinkage stress

The effects of the addition of small amounts of multifunctional monomers that contain functional groups capable of undergoing addition‐fragmentation during radical polymerizations are investigated. Specifically, up to 6 wt % of phenyl trithiocarbonate (TTC)‐containing diacrylate was added to conventional thiol‐multiacrylate photopolymerizations where its addition led to up to 60% reduction in polymerization‐induced shrinkage stress. The higher levels of TTC achieve the lowest stress though they also significantly depress the polymerization rate. Using up to 0.5 wt % phenyl TTC successfully reduces the stress by nearly 20%, demonstrating the effectiveness of the phenyl TTC, while minimizing the influence that the RAFT activity of the TTC unit has on the polymerization rate. When the polymerization rates of the TTC‐containing resins are increased by changing the incident light intensity, complete acrylate conversion is achieved and the stress remains up to 40% lower in the TTC‐containing resins. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1315–1321     

Synthesis of liquid‐filled nanocapsules via the miniemulsion technique

This study describes the synthesis of well‐defined nanocapsules via the miniemulsion technique. Pentaerythritol tetrakis(3‐mercaptopropionate) (TetraThiol) or 1,6‐hexanediol di(endo, exo‐norborn‐2‐ene‐5‐carboxylate) (DiNorbornene) is used as the oil phase. TetraThiol is encapsulated via the miniemulsion technique without polymerization, as this monomer would simultaneously act as a chain‐transfer agent, and DiNorbornene is encapsulated via miniemulsion polymerization of styrene. Various styrene‐maleic anhydride (PSMA) copolymers and poly(styrene‐maleic anhydride)‐block‐polystyrene (PSMA‐b‐PS) block copolymers were used as surfactant for the synthesis of well‐defined nanocapsules with TetraThiol as the core material. The nanocapsules had a diameter of 150–350 nm and the particle size distribution was narrow. The use of PSMA‐b‐PS block copolymers as surfactant in combination with post‐addition of formaldehyde provided improved stability to the nanocapsules. DiNorbornene was encapsulated via miniemulsion polymerization of styrene, and a stable latex with a bimodal particle size distribution was obtained. The distribution of small particles had a size of 60 nm and the distribution of large particles had a size of 150 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Facile fabrication of hybrid nanoparticles surface grafted with multi‐responsive polymer brushes via block copolymer micellization and self‐catalyzed core gelation

Poly(2‐(dimethylamino)ethyl methacrylate)‐b‐poly(γ‐methacryloxypropyl‐trimethoxysilane) (PDMA‐b‐PMPS) was synthesized via consecutive reversible addition‐fragmentation chain transfer (RAFT) polymerizations in 1,4‐dioxane. Subsequent micellization of the obtained amphiphilic diblock polymer in aqueous solution led to the formation of nanoparticles consisting of hydrophobic PMPS cores and well‐solvated PDMA shells. Containing tertiary amine residues, PDMA blocks in micelle coronas can spontaneously catalyze the sol–gel reactions of trimethoxysilyl groups within PMPS cores, leading to the formation of hybrid nanoparticles coated with PDMA brushes. Transmission electron microscopy (TEM) and laser light scattering (LLS) revealed the presence of monodisperse spherical hybrid nanoparticles, and the grafting density of PDMA chains at the surface of nanoparticle cores was estimated to be ～5.8 nm²/chain. PDMA brushes exhibit dual stimuli‐responsiveness, and the swelling/collapse of them can be finely tuned with solution pH and temperatures. The obtained multi‐responsive hybrid nanoparticles might find potential applications in fields such as smart devices, recyclable catalysts, and intelligent nanocarriers for drug delivery or gene transfection. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2379–2389, 2008     

Preparation,characterization, and chiral recognition of optically active polymers containing pendent chiral units via reversible addition‐fragmentation chain transfer polymerization

Optically active polymers bearing chiral units at the side chain were prepared via reversible addition‐fragmentation chain transfer (RAFT) polymerization in the presence of 2,2′‐azobisisobutyronitrile (AIBN)/benzyl dithiobenzoate (BDB), using a synthesized 6‐O‐p‐vinylbenzyl‐1,2:3,4‐Di‐O‐isopropylidene‐D ‐galactopyranose (VBPG) as the monomer. The experimental results suggested that the polymerization of the monomer proceeded in a living fashion, providing chiral group polymers with narrow molecular weight distributions. The optically active nature of the obtained poly (6‐O‐p‐vinylbenzyl‐1,2:3,4‐Di‐O‐isopropylidene‐D ‐galactopyranose) (PVBPG) was studied by investigating the dependence of specific rotation on the molecular weight of PVBPG and the concentration of PVBPG in tetrahydrofuran (THF). The results showed the specific rotation of PVBPG increased greatly with the decrease of the concentration of the PVBPG homopolymer. In addition, the effect of block copolymers of PVBPG on the optically active nature was also investigated by preparing a series of diblock copolymers of poly(methyl methacrylate) (PMMA)‐b‐PVBPG, polystyrene (PS)‐b‐PVBPG, and poly(methyl acrylate) (PMA)‐b‐PVBPG. It was found that both the homopolymer and the diblock copolymers possessed specific rotations. Finally, the ability of chiral recognition of the PVBPG homopolymer was investigated via an enantiomer‐selective adsorption experiment. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3788–3797, 2007     

Synthesis and characterization of fluorescence end‐labeled polystyrene via reversible addition‐fragmentation chain transfer (RAFT) polymerization

Fluorescence end‐labeled polystyrene (PS) with heteroaromatic carbazole or indole group were prepared conveniently via reversible addition‐fragmentation chain transfer (RAFT) polymerization using dithiocarbamates, ethyl 2‐(9H‐carbazole‐9‐carbonothioylthio)propanoate (ECCP) and benzyl 2‐phenyl‐1H‐indole‐1‐carbodithioate (BPIC) as RAFT agents. The end functionality of obtained PS with different molecular weights was high. The steady‐state and the time‐resolved fluorescence techniques had been used to study the fluorescence behaviors of obtained end‐labeled PS. The fluorescence of dithiocarbamates resulting PS in solid powder cannot be monitored; however, they exhibited structured absorptions and emissions in solvent DMF and the fluorescence lifetimes of PS had no obvious change with molecular weights increasing. These observations suggested that the polymer chains were possibly stretched adequately in DMF, that is, the fluorescence end group was exposed into solvent molecules and little quenching of excited state occurred upon incorporation into polymer chain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6198–6205, 2008     

Thermally amendable tailor‐made functional polymer by RAFT polymerization and “click reaction”

This investigation reports the preparation and characterization of thermally amendable functional polymer bearing furfuryl functionality via reversible‐addition fragmentation and chain transfer (RAFT) polymerization and Diels‐Alder (DA) reaction. In this case, furfuryl methacrylate (FMA) was polymerized using 4‐cyano‐4‐[(dodecylsulfanylthiocarbonyl)sulfanyl] pentanoic acid as RAFT reagent and 4,4′‐azobis(4‐cyanovaleric acid) as thermal initiator. ¹H NMR, ¹³C NMR, and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analysis showed that furfuryl group in poly(furfuryl methacrylate) (PFMA) was not affected during RAFT polymerization and the tailor‐made polymer had RAFT end group. The DA reaction was successfully carried out between the reactive furfuryl functionality of PFMA and different bismaleimides. The thermoreversible property of these DA polymers was characterized by FT‐IR and DSC analysis. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3365–3374     

Synthesis of poly(n‐butyl acrylate) containing multiblocks with a narrow molecular weight distribution using cyclic trithiocarbonates

The polymerization of n‐butyl acrylate in the presence of two cyclic trithiocarbonates (CTTCs) and the synthesis of multiblock poly(n‐butyl acrylate) have been investigated. The CTTCs not only can be stepwise incorporated into the polymer chain via reversible addition–fragmentation chain transfer (RAFT) but also can be polymerized into polytrithiocarbonate, which functions as a macro‐RAFT agent in turn. Through two kinds of mechanisms, multiblock poly(n‐butyl acrylate) containing narrow‐polydispersity blocks can be prepared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6600–6606, 2006     

Synthesis and swelling behavior of comb‐type grafted hydrogels by reversible addition–fragmentation chain transfer polymerization

The comb‐type grafted hydrogels poly(N‐isopropylacrylamide)‐g‐poly(N‐isopropylacrylamide) (PNIPAM‐g‐PNIPAM) and poly(acrylic acid)‐g‐poly(N‐isopropylacrylamide) (PAAc‐g‐PNIPAM) were prepared by reversible addition–fragmentation chain transfer polymerization. A macromolecular chain‐transfer agent was prepared first. Then, hydrogels were obtained by a reaction with a comonomer (N‐isopropylacrylamide or acrylic acid) in the presence of N,N‐methylenebisacrylamide as a crosslinker. The equilibrium swelling ratios and the swelling and deswelling kinetics of PNIPAM‐g‐PNIPAM were measured. The effects of the chain length and amount on the swelling behavior were investigated. The deswelling mechanism was illustrated. Meanwhile, the PAAc‐g‐PNIPAM hydrogel was used to confirm the versatility of this novel method. It was prepared in an alcoholic medium, whereas hydrogen‐bonding complexes formed in 1,4‐dioxane, which was chosen as the reaction medium for the PNIPAM‐g‐PNIPAM hydrogel. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2615–2624, 2005     

Temperature‐Responsive Glycopolymer Brushes Synthesized via RAFT Polymerization Using the Z‐group Approach

Summary: Stimuli‐responsive glycopolymer brushes composed of N‐acryloyl glucosamine (AGA) and N‐isopropylacrylamide (NIPAAm) were prepared using RAFT polymerization. The RAFT agent was immobilized on the surface of a treated silicon waver via covalent attachment using the Z‐group. PAGA and PNIPAAm brushes showed a linear increase in brush thickness with the consumption of monomer in solution. The polymers generated in solution confirm the living behavior with the molecular weight increasing linearly with monomer conversion while the molecular weight distribution remains narrow. Additionally, the ability of PAGA brushes to grow further in the presence of NIPAAm reveals the presence of an active RAFT end group indicative of a living system. PAGA and PNIPAAm homopolymer brushes up to 30 nm were grown using this technique. PAGA brushes were utilized for further chain extension to generate stimuli‐responsive brushes with block structures of PAGA and PNIPAAm. The PAGA‐block‐PNIPAAm brushes were found to grow in size with the consumption of NIPAAm. Contact angle measurements confirm the suggested mechanism showing that the second monomer is incorporated between the first layer and the silicon surface as expected using the Z‐group approach.

Structure of the stimuli‐responsive glycopolymer brushes.