Ion‐exchanger synthesis using reversible addition‐fragmentation chain transfer polymerization

An ion‐exchanger with polyanionic molecular brushes was synthesized by a “grafting from” route based on “surface‐controlled reversible addition‐fragmentation chain transfer polymerization” (RAFT). The RAFT agent, PhC(S)SMgBr was covalently attached to monodisperse‐porous poly(dihydroxypropyl methacrylate‐co‐ethylene dimethacrylate), poly(DHPM‐co‐EDM) particles 5.8 μm in size. The monomer, 3‐sulfopropyl methacrylate (SPM), was grafted from the surface of poly(DHPM‐co‐EDM) particles with an immobilized chain transfer agent by the proposed RAFT protocol. The degree of polymerization of SPM (i. e. the molecular length of the polyanionic ligand) on the particles was controlled by varying the molar ratio of monomer/RAFT agent. The particles carrying polyanionic molecular brushes with different lengths were tested as packing material in the separation of proteins by ion exchange chromatography. The columns packed with the particles carrying relatively longer polyanionic ligands exhibited higher separation efficiency in the separation of four proteins. Plate heights between 130–200 μm were obtained. The ion‐exchanger having poly‐(SPM) ligand with lower degree of polymerization provided better peak‐resolutions on applying a salt gradient with higher slope. The molecular length and the ion‐exchanger group content of polyionic ligand were adjusted by controlling the degree of polymerization and the grafting density, respectively. This property allowed control of the separation performance of the ion‐exchanger packing.     

RAFT‐mediated synthesis and temperature‐induced responsive properties of poly(2‐(2‐methoxyethoxy)ethyl methacrylate) brushes

Well‐defined, high‐density poly(2‐(2‐methoxyethoxy)ethyl methacrylate) [poly(MEO₂MA)] brushes were fabricated through a reliable strategy by the combination of self‐assembly of a monolayer of 3‐aminopropyltrimethoxy silane on silicon surface to immobilize 4‐cyano‐4‐(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid chain transfer agent and reversible addition‐fragmentation chain transfer‐mediated polymerization of MEO₂MA. The whole fabrication process of the poly(MEO₂MA) brushes was followed by water contact angle, grazing angle‐Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and atomic force microscopy. Characterization of the poly(MEO₂MA) brushes, such as molecular weight and thickness determination, were measured by gel permeation chromatography and ellipsometry, and the grafting density was estimated. The temperature‐responsive property of the poly(MEO₂MA) brushes was further investigated and the result verified the brush‐to‐mushroom phase transition of the poly(MEO₂MA) chains from low to high temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Effects of Grafting Density and Film Thickness on the Adhesion of Staphylococcus epidermidis to Poly(2‐hydroxy ethyl methacrylate) and Poly(poly(ethylene glycol)methacrylate) Brushes

Thin polymer films that prevent the adhesion of bacteria are of interest as coatings for the development of infection‐resistant biomaterials. This study investigates the influence of grafting density and film thickness on the adhesion of Staphylococcus epidermidis to poly(poly(ethylene glycol)methacrylate) (PPEGMA) and poly(2‐hydroxyethyl methacrylate) (PHEMA) brushes prepared via surface‐initiated atom transfer radical polymerization (SI‐ATRP). These brushes are compared with poly(ethylene glycol) (PEG) brushes, which are obtained by grafting PEG onto an epoxide‐modified substrate. Except for very low grafting densities (ρ = 1%), crystal violet staining experiments show that the PHEMA and PPEGMA brushes are equally effective as the PEG‐modified surfaces in preventing S. epidermis adhesion and do not reveal any significant variations as a function of film thickness or grafting density. These results indicate that brushes generated by SI‐ATRP are an attractive alternative to grafted‐onto PEG films for the preparation of surface coatings that resist bacterial adhesion.

     

Preparation of poly(vinylphenylboronic acid) chain grafted poly(glycidylmethacrylate‐co‐ethylenedimethacrylate) beads for the selective enrichment of glycoprotein

Surface‐initiated atom transfer radical polymerization was successfully used to prepare 4‐vinylphenylboronic acid functionalized poly(glycidylmethacrylate‐co‐ethylenedimethacrylate) beads for the selective enrichment of glycoprotein from complex biological samples in this study. The modified bead surfaces were characterized using Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. The sorption behaviors, including adsorption isotherms, incubation time, and pH effect, were investigated. The results demonstrated that the boronated beads have a high affinity for glycoprotein, which is due to the well‐defined boronic acid brushes on the beads surfaces. Furthermore, the polyvinylphenylboronic acid grafted poly(glycidylmethacrylate‐co‐ethylenedimethacrylate) beads were used to efficiently enrich and purify glycoprotein from real egg white samples and α‐fetoprotein from human serum samples. The mass spectrometry results demonstrated that the polyvinylphenylboronic acid grafted poly(glycidylmethacrylate‐co‐ethylenedimethacrylate) beads are a suitable material for the enrichment of glycosylated protein from complex biological samples.     

Surface‐initiated single‐electron transfer reversible addition–fragmentation chain transfer polymerization of 2‐hydroxyethyl acrylamide on silicon substrate at ambient temperature

2‐Hydroxyethyl acrylamide was successfully polymerized via single‐electron transfer initiation on the silicon surface and propagation through the reversible addition–fragmentation chain transfer (SET‐RAFT) polymerization at ambient temperature for different polymerization times. This work is the first time application of the surface‐initiated SET‐RAFT mechanism to afford the preparation of well‐defined poly(2‐hydroxyethyl acrylamide) [poly(HEAAm)] brushes at ambient temperature. The polymerization was well controlled and produced poly(HEAAm) brushes on the silicon surface with a well‐defined target molecular weight. The controlled nature of the polymerization was further demonstrated in the presence of sulfur atoms at the chain ends in X‐ray photoelectron spectroscopy experiments. The grafting density (σ, chains nm^?2) and the average distance between grafting points (D, nm) were found to be 0.42 chains nm^?2 and 1.74 nm, respectively, indicating moderate grafting density. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1140–1146     

Synthesis of well‐defined polymer brushes on the surface of zinc antimonate nanoparticles through surface‐initiated atom transfer radical polymerization

Zinc antimonate nanoparticles consisting of antimony and zinc oxide were surface modified in a methanol solvent medium using triethoxysilane‐based atom transfer radical polymerization (ATRP) initiating group (i.e.,) 6‐(2‐bromo‐2‐methyl) propionyloxy hexyl triethoxysilane. Successful grafting of ATRP initiator on the surface of nanoparticles was confirmed by thermogravimetric analysis that shows a significant weight loss at around 250–410 °C. Grafting of ATRP initiator onto the surface was further corroborated using Fourier transform Infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS). The surface‐initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator‐fixed zinc antimonate nanoparticles in the presence of a sacrificial (free) initiator. The polymerization was preceded in a living manner in all examined cases; producing nanoparticles coated with well defined poly(methyl methacrylate) (PMMA) brushes with molecular weight in the range of 35–48K. Furthermore, PMMA‐grafted zinc antimonate nanoparticles were characterized using Thermogravimetric analysis (TGA) that exhibit significant weight loss in the temperature range of 300–410 °C confirming the formation of polymer brushes on the surface with the graft density as high as 0.26–0.27 chains/nm². The improvement in the dispersibility of PMMA‐grafted zinc antimonate nanoparticles was verified using ultraviolet‐visible spectroscopy and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and stability of BODIPY‐based fluorescent polymer brushes at different pHs

We report a simple strategy for the grafting of poly(methacrylic acid) [poly(MAA)] brushes from silicon substrate by surface‐initiated RAFT polymerization and the subsequent coupling of BODIPY to these brushes to render them fluorescent. The poly(MAA) brushes were first generated by functionalization of hydrogen‐terminated silicon substrate with methyl‐10‐undecenoate which both leads to the formation of an organic layer covalently linked to the surface via Si? C bonds without detectable reaction of the carboxylate groups and couples to the polymerization initiator, followed by surface‐initiated RAFT polymerization of tert‐butyl methacrylate from these substrate‐bound initiator centers, and finally conversion of tert‐butyl groups to carboxylic acid groups. The poly(MAA) brushes were then made fluorescent by grafting a BODIPY derivative via an ester linkage. The stability of the BODIPY‐based fluorescent polymer brushes in buffer solutions at pH 6.0 to 12.0 with added salt was investigated by ellipsometry, fluorescence microscopy, grazing angle‐Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy. The results of these measurements indicated that the organic molecule‐initiator bond (ester linkage) is unstable and can be hydrolyzed resulting in detaching of the immobilized polymer from the silicon substrate. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3586–3596     

Radio‐Analytical Determination of the Coating Efficiency of Cyclic RGD Peptides

Coating of artificial surfaces with RGD (= arginine‐glycine‐aspartate) peptides to enhance cell adhesion is an ongoing issue. Thereby, the physiological adhesion process to the extra‐cellular matrix (ECM) is mimicked by the peptide coating, leading to a strong cell‐surface contact, followed by spreading and proliferation of the cells. For comparable cell adhesion studies, it is important to know the density of the RGD peptides on the surface. Here, we present an approach to determine the amount of bound cyclic RGD peptide by radio labeling with ¹²⁵I of a tyrosine‐containing RGD peptide on different materials surfaces (poly(methyl methacrylate) (PMMA), titanium, and silicon). For all surfaces, the amount of bound peptides is in the range of pmol/cm¹.     

Solid‐supported amphiphilic triblock copolymer membranes grafted from gold surface

Gold‐supported amphiphilic triblock copolymer brushes composed of two hydrophilic poly(2‐hydroxyethyl methacrylate) (PHEMA) blocks and a hydrophobic poly(n‐butyl methacrylate) (PBMA) middle part were synthesized using a surface‐initiated ATRP. Attenuated total reflectance Fourier transform infrared spectroscopy, polarization modulation infrared reflection absorption spectroscopy (PM‐IRRAS), ellipsometry, contact angle measurements, and atomic force microscopy were used for the characterization of PHEMA‐co‐PBMA‐co‐PHEMA brushes. The PM‐IRRAS analysis revealed an increase of the chain tilt toward the gold surface during growth of the individual blocks. We suggest that the orientation of the amphiphilic polymer brushes is influenced by both the chain length and the interchain interactions. Additionally, a detachment of the polymer membranes from the solid support and subsequent gel permeation chromatography analyses allowed us to establish their compositions. We applied block‐selective solvents (water and hexane) as well as a good solvent for the whole polymer chain (ethanol) to study the morphology and solvent responsive behavior of the amphiphilic brushes. The presented results could serve as a good starting point for the fabrication of functional solid‐supported membranes for biosensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1–13, 2009     

Comparison of surface confined ATRP and SET‐LRP syntheses for a series of amino (meth)acrylate polymer brushes on silicon substrates

A series of poly(amino (meth)acrylate) brushes, poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA), poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA), poly(2‐(dimethylamino)ethyl acrylate) (PDMAEA), poly(2‐(tert‐butylamino)ethyl methacrylate) (PTBAEMA), has been synthesized via surface‐confined controlled/living radical polymerizations using surface‐confined initiator from silane self‐assembled monolayers (SAMs) on silicon (Si) wafer substrates. Chemical methods and efficacies for two types of living radical polymerization, atom transfer radical (ATRP) and single electron transfer (SET‐LRP), are described and contrasted for the surface confined polymerization of poly(amino (meth)acrylate)s. Effects of solvent, catalyst/ligand system, and temperature on polymerization success were examined. Chemical compositions after each reaction step were characterized with FTIR spectroscopy, contact angle goniometry, and X‐ray photoelectron spectroscopy while the SAM and polymer brush thicknesses were measured with spectroscopic ellipsometry. For the first time, this study demonstrates successful surface‐confined polymerization of a series of poly(amine (meth)acrylate) brushes from Si‐SAM substrates using a copper metal electron donor catalyst. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6552–6560, 2009     

Novel functionalized poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) microspheres for the solid‐phase extraction of glycopeptides/glycoproteins

Novel 3‐aminophenylboronic acid functionalized poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) microspheres were prepared for the solid‐phase extraction of glycopeptides/glycoproteins. The adsorption efficiency, maximum adsorption capacity, and specific recognition of the microspheres to glycoprotein were investigated. The results indicated excellent adsorption of glycoproteins by the microspheres, which are attributed to the well‐defined boronic acid brushes on the microsphere surfaces. Furthermore, a solid‐phase extraction microcolumn filled with the microspheres was used to efficiently enrich glycopeptides from enzymatic hydrolysates from human serum samples. The mass spectrometry results demonstrated that the method is suitable for the separation and enrichment of glycopeptides/glycoproteins from complex biological samples.     

表面引发的原子转移自由基聚合法在聚偏二氟乙烯表面制备可控的聚甲基丙烯酸甲酯刷

采用表面引发的原子转移自由基聚合法(ATRP)在聚偏二氟乙烯(PVDF)表面制备结构可控的聚甲基丙烯酸甲酯刷。通过碱处理和紫外光照溴代的方法,将ATRP引入到PVDF表面; 然后采用ATRP法将甲基丙烯酸甲酯接枝到溴代的PVDF表面。采用傅里叶变换红外光谱和X-射线光电子能谱对改性前后PVDF表面的结构进行了表征。结果表明甲基丙烯酸甲酯成功地接枝到了PVDF表面。     

Homopolymer and block copolymer brushes on gold by living anionic surface‐initiated polymerization in a polar solvent

Living anionic surface‐initiated polymerization on flat gold substrates has been conducted to create uniform homopolymer and diblock copolymer brushes. A 1,1‐diphenylethylene (DPE) self‐assembled monolayer was used as the immobilized precursor initiator. n‐BuLi was used to activate the DPE in tetrahydrofuran at –78 °C to initiate the polymerization of different monomers (styrene, isoprene, ethylene oxide, and methyl methacrylate). Poly(styrene) (PS) and poly(ethylene oxide) (PEO) in particular were first investigated as grafted homopolymers, followed by their copolymers, including poly(isoprene)‐b‐poly(methylmethacrylate) (PI‐b‐PMMA). A combined approach of spectroscopic (Fourier transform infrared spectroscopy, surface plasmon spectroscopy, ellipsometry, X‐ray photoelectron spectroscopy) and microscopic (atomic force microscopy) surface analysis was used to investigate the formation of the polymer brushes in polar solvent media. The chemical nature of the outermost layer of these brushes was studied by water contact angle measurements. The effect of the experimental conditions (solvent, temperature, initiator concentration) on the surface properties of the polymer brushes was also investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 769–782, 2006     

Peptide-mediated selective adhesion of smooth muscle and endothelial cells in microfluidic shear flow

Microfluidic devices have recently emerged as effective tools for cell separation compared to traditional techniques. These devices offer the advantages of small sample volumes, low cost, and high purity. Adhesion-based separation of cells from heterogeneous suspensions can be achieved by taking advantage of specific ligand-receptor interactions. The peptide sequences Arg-Glu-Asp-Val (REDV) and Val-Ala-Pro-Gly (VAPG) are known to bind preferentially to endothelial cells (ECs) and smooth muscle cells (SMCs), respectively. This article examines the roles of REDV and VAPG and fluid shear stress in achieving selective capture of ECs and SMCs in microfluidic devices. The adhesion of ECs in REDV-coated devices and SMCs in VAPG-coated devices increases significantly compared to that of the nontargeted cells with decreasing shear stress. Furthermore, the adhesion of these cells is shown to be independent of whether these cells flow through the devices as suspensions of only one cell type or as a heterogeneous suspension containing ECs, SMCs, and fibroblasts. Whereas the overall adhesion of cells in the devices is determined mainly by shear stress, the selectivity of adhesion depends on the type of peptide and on the device surface as well as on the shear stress.     

Synthesis of polymeric microspheres from a Merrifield resin by surface‐initiated nitroxide‐mediated radical polymerization

Polymeric microspheres were prepared from a Merrifield resin via nitroxide‐mediated radical polymerization. Polystyrene, poly(acetoxystyrene), and poly[styrene‐b‐(methyl methacrylate‐co‐styrene)], poly(acetoxystyrene‐b‐styrene), and poly(styrene‐co‐2‐hydroxyethyl methacrylate) copolymers were demonstrated to graft onto 2,2,6,6‐tetramethyl‐1‐piperidinyloxy nitroxide bound Merrifield resins. The polymerization control was enhanced both on the surface and in solution by the addition of sacrificial nitroxide. The significant increase in the particle diameter (more than a fivefold volume increase for polystyrene brushes) showed that polymer growth was not only on the surface but also within the particles, and this diameter increase could be adjusted through changes in the molecular weight of the polymers. The microspheres were characterized by elemental analysis, IR spectroscopy, particle size analysis, and optical microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2145–2154, 2005     

Semi‐micro reversed‐phase liquid chromatography for the separation of alkyl benzenes and proteins exploiting methacrylate‐ and polystyrene‐based monolithic columns

Monolithic columns were synthesized inside 1.02 mm internal diameter fused‐silica lined stainless‐steel tubing. Styrene and butyl, hexyl, lauryl, and glycidyl methacrylates were the functional monomers. Ethylene glycol dimethacrylate and divinylbenzene were the crosslinkers. The glycidyl methacrylate polymer was modified with gold nanoparticles and dodecanethiol (C₁₂). The separation of alkylbenzenes was investigated by isocratic elution in 60:40 v/v acetonitrile/water. The columns based on polystyrene‐co‐divinylbenzene and poly(glycidyl methacrylate)‐co‐ethylene glycol dimethacrylate modified with dodecanethiol did not provide any separation of alkyl benzenes. The poly(hexyl methacrylate)‐co‐ethylene glycol dimethacrylate and poly(lauryl methacrylate)‐co‐ethylene glycol dimethacrylate columns separated the alkyl benzenes with plate heights between 30 and 60 μm (50 μL min^?1 and 60°C). Similar efficiency was achieved in the poly(butyl methacrylate)‐co‐ethylene glycol dimethacrylate column, but only at 10 μL min^?1 (0.22 mm s^?1). Backpressures varied from 0.38 MPa in the hexyl methacrylate to 13.4 MPa in lauryl methacrylate columns (50 μL min^?1 and 60°C). Separation of proteins was achieved in all columns with different efficiencies. At 100 μL min^?1 and 60°C, the lauryl methacrylate columns provided the best separation, but their low permeability prevented high flow rates. Flow rates up to 500 μL min^?1 were possible in the styrene, butyl and hexyl methacrylate columns.     

Hydrophobic‐hydrophilic monolithic dual‐phase layer for two‐dimensional thin‐layer chromatography coupled with surface‐enhanced Raman spectroscopy detection

Hydrophobic‐hydrophilic monolithic dual‐phase plates have been prepared by a two‐step polymerization method for two‐dimensional thin‐layer chromatography of low‐molecular‐weight compounds, namely, several dyes. The thin 200 μm poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) layers attached to microscope glass plates were prepared using a UV‐initiated polymerization method within a simple glass mold. After cutting and cleaning the specific area of the layer, the reassembled mold was filled with a polymerization mixture of butyl methacrylate and ethylene dimethacrylate and subsequently irradiated with UV light. During the second polymerization process, the former layer was protected from the UV light with a UV mask. After extracting the porogens and hydrolyzing the poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) area, these two‐dimensional layers were used to separate a mixture of dyes with great difference in their polarity using reversed‐phase chromatography mode within the hydrophobic layer and then hydrophilic interaction chromatography mode along the hydrophilic area. In the latter dimension only the specific spot was developed further. Detection of the separated dyes could be achieved with surface‐enhanced Raman spectroscopy.     

Elucidation of the mechanism of surface‐initiated atom transfer radical polymerization from a diazonium‐based initiator layer

This study elucidates the influence of the atom transfer radical polymerization initiator structure, monolayer versus disordered multilayer, on the growth kinetics and the structural transition of poly(methyl methacrylate) (PMMA) brush layers. The multilayer initiator film, prepared by acylation of the electrografted 2‐phenylethanol layer using 2‐bromoisobutyryl bromide, consists of ～4.6 times more tert‐butyl bromide groups compared to monolayer initiator prepared by self assembly technique. The results demonstrate the formation of precursor complex between Cu^I catalyst and the bromine initiator as a prerequisite step before the onset of polymerization. Furthermore, the PMMA brushes formed by the polymerization from the multilayered initiator layer at 50 °C are 20‐fold thicker compared to the polymerization at 25 °C due to the swelling of the multilayered initiator film. In contrast, the thickness of the PMMA layer on the monolayer initiator is less affected by the polymerization temperature. By varying the initiator density on the surface, the solvent content in the PMMA layer is shown to vary from 15% to 94%, resulting in the transition from concentrated over semidiluted to diluted brushes. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of dual‐functional poly(6‐azidohexylmethacrylate) brushes by a RAFT agent carrying carboxylic acid end groups

Novel types of dual‐functional surface‐attached polymer brushes were developed by interface‐mediated reversible addition‐fragmentation chain transfer (RAFT) polymerization of 6‐azidohexylmethacrylate using the surface‐immobilized RAFT agent and the free initiator. The interface‐mediated RAFT polymerization produced silicon substrate coated with dual‐functional (azido groups from monomer and carboxylic acid groups from RAFT agent) poly(6‐azidohexylmethacrylate) [poly (AHMA)] with a grafting density as high as 0.59 chains/nm². Dual‐functional polymer brushes can represent an attractive chemical platform to deliberately introduce other molecular units at specific sites. The azido groups of the poly(AHMA) brushes can be modified with alkyl groups via click reaction, known for their DNA hybridization, while the carboxylic acid end groups can be reacted with amine groups via amide reaction, known for their antifouling properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1696–1706     

Hairy polymeric nanocapsules with ph‐responsive shell and thermoresponsive brushes: Tunable permeability for controlled release of water‐soluble drugs

The hairy poly(methacrylic acid‐co‐divinylbenzene)‐g‐poly(N‐isopropylacrylamide) (P(MAA‐co‐DVB)‐g‐PNIPAm) nanocapsules with pH‐responsive P(MAA‐co‐DVB) inner shell and temperature‐responsive PNIPAm brushes were prepared by combined distillation–precipitation copolymerization and surface thiol‐ene click grafting reaction using 3‐(trimethoxysilyl)propyl methacrylate‐modified silica (SiO₂‐MPS) nanospheres as a sacrificial core material. The well‐defined PNIPAm was synthesized by a reversible addition fragmentation chain transfer (RAFT) polymerization. The chain end was converted to a thiol by chemical reduction. The PNIPAm was integrated into the nanocapsules via thiol‐ene click reaction. The surface thiol‐ene click reaction conduced to tunable grafting density of PNIPAm brushes. The grafting densities decreased from 0.70 chains nm^?2 to 0.15 chains nm^?2 with increasing the molecular weight of grafted PNIPAm chains. Using water soluble doxorubicin hydrochloride (DOX·HCl) as a model molecular, the tunable shell permeability of the nanocapsule was investigated in detail. The permeability constant can be tuned by controlling the thickness of the P(MAA‐co‐DVB) inner shell, the grafting density of PNIPAm brushes, and the environmental pH and temperature. The tunable shell permeability of these nanocapsules results in the release of the loaded guest molecules with manipulable releasing kinetics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2202–2216