Co-reporter:Elisabeth Gau, Diana M. Mate, Zhi Zou, Alex Oppermann, Alexander Töpel, Felix Jakob, Dominik Wöll, Ulrich Schwaneberg, and Andrij Pich
Biomacromolecules September 11, 2017 Volume 18(Issue 9) pp:2789-2789
Publication Date(Web):July 26, 2017
DOI:10.1021/acs.biomac.7b00720
In this work we explored an enzyme-mediated method for selective and efficient decoration of aqueous microgels with biomolecules. Poly(N-vinylcaprolactam) (VCL) microgels with varied amounts of glycidyl methacrylate (GMA) as comonomer incorporated in the microgel shell were synthesized and characterized in regard to their size, swelling degree, and temperature-responsiveness in aqueous solutions. The surface of the PVCL/GMA microgel containing 5 mol % glycidyl methyacrylate was modified by grafting of a specific recognition peptide sequence (LPETG) for Sortase A from Staphylococcus aureus (Sa-SrtAΔ59). Sortase-mediated conjugation of the enhanced Green Fluorescent Protein (eGFP) carrying a N-terminal triglycine tag to LPETG-modified microgels was successfully performed. Conjugation of eGFP to the microgel surface was qualitatively proven by confocal microscopy and by fluorescence intensity measurements. The developed protocol enables a precise control of the amount of eGFP grafted to the microgel surface as evidenced by the linear increase of fluorescence intensity of modified microgel samples. The kinetic of the sortase-mediated coupling reaction was determined by time-dependent fluorescence intensity measurements. In summary, sortase-mediated coupling reactions are a simple and powerful technique for targeted surface functionalization of stimuli-responsive microgels with biomolecules.
Co-reporter:Wenjie Sun, Sabrina Thies, Jiulong Zhang, Chen Peng, Guangyu Tang, Mingwu Shen, Andrij Pich, and Xiangyang Shi
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 4) pp:
Publication Date(Web):January 9, 2017
DOI:10.1021/acsami.6b14219
We report the synthesis of poly(N-vinylcaprolactam) nanogels (PVCL NGs) loaded with gadolinium (Gd) for tumor MR imaging applications. The PVCL NGs were synthesized via precipitation polymerization using the monomer N-vinylcaprolactam (VCL), the comonomer acrylic acid (AAc), and the degradable cross-linker 3,9-divinyl-2,4,8,10-tetraoxaspiro-[5,5]-undecane (VOU) in aqueous solution, followed by covalently binding with 2,2′,2″-(10-(4-((2-aminoethyl)amino)-1-carboxy-4-oxobutyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (NH2-DOTA-GA)/Gd complexes. We show that the formed Gd-loaded PVCL NGs (PVCL-Gd NGs) having a size of 180.67 ± 11.04 nm are water dispersible, colloidally stable, uniform in size distribution, and noncytotoxic in a range of the studied concentrations. The PVCL-Gd NGs also display a r1 relaxivity (6.38–7.10 mM–1 s–1), which is much higher than the clinically used Gd chelates. These properties afforded the use of the PVCL-Gd NGs as an effective positive contrast agent for enhanced MR imaging of cancer cells in vitro as well as a subcutaneous tumor model in vivo. Our study suggests that the developed PVCL-Gd NGs could be applied as a promising contrast agent for T1-weighted MR imaging of diverse biosystems.Keywords: Gd-DOTA; MR imaging; nanogels; poly(N-vinylcaprolactam); tumors;
Co-reporter:Nicolas A. Riensch;Ayse Deniz;Sebastian Kühl;Lars Müller;Alina Adams;Holger Helten
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 35) pp:5264-5268
Publication Date(Web):2017/09/12
DOI:10.1039/C7PY01006K
The synthesis of borazine-based hybrid cyclomatrix polymers has been studied under various conditions. Crosslinked polymers obtained via a novel silicon/boron exchange precipitation polycondensation approach form hybrid cyclomatrix microspheres with a mean diameter of about 900 nm.
Co-reporter:Richard A. Meurer;Steffen Kemper;Sra Knopp;Dr. Thomas Eichert;Dr. Felix Jakob; Dr. Heiner E. Goldbach; Dr. Ulrich Schwaneberg; Dr. Andrij Pich
Angewandte Chemie International Edition 2017 Volume 56(Issue 26) pp:
Publication Date(Web):2017/06/19
DOI:10.1002/anie.201782661
Plant Fertilizer A foliar fertilizer delivery system based on biohybrid microgels is presented in the Communication by U. Schwaneberg, A. Pich et al. on page 7380 ff. The system requires no auxiliaries and is loadable, storable, and applicable from aqueous dispersion.
Co-reporter:Richard A. Meurer;Steffen Kemper;Sra Knopp;Dr. Thomas Eichert;Dr. Felix Jakob; Dr. Heiner E. Goldbach; Dr. Ulrich Schwaneberg; Dr. Andrij Pich
Angewandte Chemie International Edition 2017 Volume 56(Issue 26) pp:7380-7386
Publication Date(Web):2017/06/19
DOI:10.1002/anie.201701620
AbstractFoliar application of micronutrients (e.g. Fe3+) onto plants over an extended time is challenging and often not possible due to insufficient rainfastness. Smart delivery systems which enable micronutrient release over several weeks would offer innovative and sustainable options to improve plant health and food production. Herein, we report a novel foliar fertilizer delivery system based on functional pH-responsive biohybrid microgels that have orthogonal functionality as carriers of micronutrients and employ peptides (termed anchor peptides) as foliar adhesion promoters. The anchor peptides bind to hydrophobic surfaces and the waxy “islands” of plant leaves. Our system requires no auxiliaries and is loadable, storable, and applicable from aqueous dispersion. We report the synthesis and functionalization of microgels, their loading with Fe3+ ions, and a proof of concept for the biofunctional microgel-based fertilizer system is demonstrated for iron-deficient cucumber plants.
Co-reporter:Christian Bergs;Lisa Brück;Ruben R. Rosencrantz;Georg Conrads;Lothar Elling
RSC Advances (2011-Present) 2017 vol. 7(Issue 62) pp:38998-39010
Publication Date(Web):2017/08/08
DOI:10.1039/C7RA06332F
Oxygen is one of the most important substances for physiological reactions and metabolisms in biological systems. Through the tailored design of oxygen-releasing materials it might be possible to control different biological processes. In this work we synthesized for the first time zinc peroxide nanoparticles with controlled sizes and biofunctionalized surfaces using a one-step reaction procedure. The zinc peroxide nanoparticles were obtained with tunable sizes (between 4.0 ± 1.2 nm and 9.4 ± 5.2 nm) and were decorated with glucose 1-phosphate (Glc-1P). The specific interaction of the phosphate function of Glc-1P with the nanoparticle surface was monitored by solid state 31P-NMR and zeta-potential measurements. Furthermore, using fluorescence measurements we demonstrated that anchored glucose molecules on the nanoparticle surface are accessible for specific interactions with lectins. It could be shown that these interactions strongly depend on the amount of Glc-1P attached to the nanoparticle surface. Additionally it was demonstrated that the oxygen release from biofunctionalized zinc peroxide nanoparticles could be tuned according to the chemical composition of the nanoparticles and the pH of the aqueous solution. The antibacterial efficiency of the synthesized nanoparticles against Enterococcus faecalis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia was evaluated by determination of minimal bactericidal concentration (MIC).
Co-reporter:K. Wiemer;K. Dörmbach;I. Slabu;G. Agrawal;F. Schrader;T. Caumanns;S. D. M. Bourone;J. Mayer;J. Steitz;U. Simon;A. Pich
Journal of Materials Chemistry B 2017 vol. 5(Issue 6) pp:1284-1292
Publication Date(Web):2017/02/08
DOI:10.1039/C6TB02342H
We report the synthesis of a new multifunctional colloidal hybrid system consisting of thermoresponsive amphiphilic biocompatible poly(N-vinylcaprolactam) microgels loaded with hydrophobic superparamagnetic FePt nanoparticles (NPs). In the first step, water swellable poly(N-vinylcaprolactam) microgels were mixed with hydrophobically coated sub-10 nm superparamagnetic FePt NPs in a tetrahydrofuran (THF) solution. In the second step, changing the surrounding solvent from THF to water forces the FePt NPs to migrate into the amphiphilic microgels. These new hybrid microgels (i) are colloidally stable in water and their thermo-responsive properties in terms of volume phase transition are retained, (ii) exhibit superparamagnetic characteristics introduced by FePt NPs, (iii) show a drastically reduced cytotoxicity compared to water-soluble FePt NPs of similar size, as known from the literature. This makes the new hybrid microgels suitable e.g. as biocompatible containers for drug delivery or for imaging.
Co-reporter:Andrea Melle, Andreea Balaceanu, Michael Kather, Yaodong Wu, Elisabeth Gau, Wenjie Sun, Xiaobin Huang, Xiangyang Shi, Marcel Karperien and Andrij Pich
Journal of Materials Chemistry A 2016 vol. 4(Issue 30) pp:5127-5137
Publication Date(Web):05 Jul 2016
DOI:10.1039/C6TB01196A
Herein we report the synthesis of biocompatible stimuli-responsive core–shell microgels consisting of a poly(N-vinylcaprolactam) (PVCL) core and a poly(2-methoxyethyl acrylate) (PMEA) corona via one-step surfactant-free precipitation copolymerization. The copolymerization process was investigated by reaction calorimetry, microgel growth was monitored by in situ dynamic light scattering and the chemical structure of core–shell microgels was characterized by Raman spectroscopy. It was possible to incorporate up to 32 mol% MEA into the PVCL/MEA microgels without loss of colloidal stability and broadening of the size distribution. The core–shell morphology of microgels was confirmed by transverse magnetization relaxation 1H-NMR, dynamic light scattering (DLS), atomic force microscopy (AFM) and viscosimetry. By means of the NMR data, calorimetry and viscosity measurements it could be shown that MEA is mainly located in the microgel shell. This leads to hindered temperature-induced swelling and collapsing of the PVCL-core, as demonstrated by DLS measurements, due to the fact that the PMEA-shell exhibits a very low LCST around 5 °C. These results could also be confirmed by AFM: an increasing MEA-content leads to the formation of dense and compact core–shell microgels and results in a loss of their softness and deformability. Due to the presence of the PMEA-shell these microgels can be endocytosed much faster by HeLa cells maintaining their viability and can be suitable candidates for the design of drug carriers or imaging/diagnostic systems.
Co-reporter:Huan Peng, Wenjing Xu and Andrij Pich
Polymer Chemistry 2016 vol. 7(Issue 31) pp:5011-5022
Publication Date(Web):13 Jul 2016
DOI:10.1039/C6PY00885B
A series of well-defined statistical copolymers based on cyclic N-vinyl lactams (N-vinylcaprolactam, N-vinylpiperidine and N-vinylpyrrolidone) and N-vinylformamide (VFA) were successfully synthesized via RAFT polymerization. The less-polar solvents (anisole and 1,4-dioxane) were more favorable over the highly-polar solvents (DMSO and DMF) while 2-(ethoxycarbonothioylthio)propanoate was more suitable than dithiobenzoate derivatives as the chain transfer agent (CTA) for copolymerization. The optimal polymerization conditions were explored with methyl 2-(ethoxycarbonothioylthio)propanoate as the CTA and anisole as the solvent. The narrow dispersity (Đ) of the copolymers, linear relationship between conversion and molecular weight, and symmetrical unimodal GPC traces confirmed the controlled character of the polymerization process. The polymerization process was progressively disfavored by the enhanced steric hindrance from the enlarged lactam ring while the VFA composition could be well controlled up to as high as 50% by continuously feeding VFA with a syringe pump. The lower critical solution temperatures (LCSTs) of the thermo-responsive copolymers poly(N-vinylcaprolactam-co-N-vinylformamide) and poly(N-vinylpiperidine-co-N-vinylformamide) in aqueous solutions reflected by the appearance of the cloud points can be tunable by the molecular weights and compositions of the copolymers. Primary amine functionalized temperature/pH dual responsive reactive copolymers were obtained by the controlled hydrolysis of the VFA components under alkaline conditions. The influence of the lactam ring on the hydrolysis rates was investigated. The LCSTs of the hydrolyzed copolymers can be elegantly adjusted by the hydrolysis degree. Amine-enriched nanogels were prepared in W/O emulsions utilizing the coupling between the reactive amine side-groups of polymer chains and diacrylate functionalities of a poly(ethylene glycol) cross-linker via Michael addition reaction, which displayed temperature and pH double responsiveness. The nanogels were labelled with fluorescein isothiocyanate (FITC) through conjugation with the residual primary amine groups on the surface. This facile chemistry has opened up routes to synthesize water-soluble reactive stimuli-responsive copolymers with well-defined architectures for design of functional macromolecular materials.
Co-reporter:Huan Peng, Kristin Rübsam, Xiaobin Huang, Felix Jakob, Marcel Karperien, Ulrich Schwaneberg, and Andrij Pich
Macromolecules 2016 Volume 49(Issue 19) pp:7141-7154
Publication Date(Web):September 22, 2016
DOI:10.1021/acs.macromol.6b01210
Herein, we report the synthesis of a series of novel pyridyl disulfide (PDS)-functionalized statistical reactive copolymers that enable facile access to complex polymeric architectures through highly selective thiol–disulfide exchange reaction with thiol-containing ligands or proteins. Functional reactive poly(N-vinyl lactam)-based copolymers including poly(N-vinylpyrrolidone-co-pyridyl disulfide ethyl methacrylate) (PVPD), poly(N-vinylpiperidone-co-pyridyl disulfide ethyl methacrylate) (PVPID), and poly(N-vinylcaprolactam-co-pyridyl disulfide ethyl methacrylate) (PVD) with PDS side groups were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization at 60 °C in anisole with methyl 2-(ethoxycarbonothioylthio)propanoate as chain transfer agent. The PDS contents in the synthesized copolymers were varied from 2 to 10 mol % (as confirmed by systematical characterization with FTIR/Raman and 1H NMR spectroscopy) using well-controlled continuous feeding method. The kinetics study suggested that copolymerizations were less favored with the enlargement of the lactam rings, indicated by lower conversions and larger dispersity indexes (Đ). The PDS-functionalized reactive polymers were amenable to functionalization with a variety of thiol-containing molecules, including 3-mercaptopropionic acid (3M), 2-phenylethanethiol (2P), methyl 3-mercaptopropionate (M3), 2-mercaptoethanol (2M), 2-aminoethanethiol (2A), poly(ethylene glycol) methyl ether thiol (PEG-SH), and enhanced green fluorescent protein (EGFP) via thiol–disulfide exchange reaction under mild conditions, confirmed by 1H NMR and SDS-PAGE. The conversions in all cases were higher than 95%, displaying that the thiol–disulfide exchange reaction to PDS groups with thiol-containing molecules is highly selective and tolerant to different ligands including amine, carboxyl, hydroxyl, phenyl, PEG and even polypeptides, providing a versatile scaffold for facile conjugation of various biological components. The contact angle measurement results and fluorescence microscopy study indicated that the reactive films based on the PDS-functionalized copolymers allowed facile, direct, and environmental-friendly surface engineering of surfaces from aqueous solution suggesting potential application in surface decoration of tissue-engineering scaffolds and medical implants. The initial cell culture experiments with HeLa cells displayed that the unmodified PVPD film was nontoxic and biocompatible while the film modified with PEG (a type of antifouling polymer) showed diminished cell attachment and growth, indicating that elegant engineering of the film surface can meet demands of particular applications.
Co-reporter:Huan Peng, Kristin Rübsam, Felix Jakob, Ulrich Schwaneberg, and Andrij Pich
Biomacromolecules 2016 Volume 17(Issue 11) pp:3619
Publication Date(Web):September 19, 2016
DOI:10.1021/acs.biomac.6b01119
This paper reports a facile approach for encapsulation of enzymes in nanogels. Our approach is based on the use of reactive copolymers able to get conjugated with enzyme and build 3D colloidal networks or biohybrid nanogels. In a systematic study, we address the following question: how the chemical structure of nanogel network influences the biocatalytic activity of entrapped enzyme? The developed method allows precise control of the enzyme activity and improvement of enzyme resistance against harsh store conditions, chaotropic agents, and organic solvents. The nanogels were constructed via direct chemical cross-linking of water-soluble reactive copolymers poly(N-vinylpyrrolidone-co-N-methacryloxysuccinimide) with proteins such as enhanced green fluorescent protein (EGFP) and cellulase in water-in-oil emulsion. The water-soluble reactive copolymers with controlled amount of reactive succinimide groups and narrow dispersity were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. Poly(ethylene glycol) bis(3-aminopropyl) and branched polyethylenimine were utilized as model cross-linkers to optimize synthesis of nanogels with different architectures in the preliminary experiments. Biofluorescent nanogels with different loading amount of EGFP and varying cross-linking densities were obtained. We demonstrate that the biocatalytic activity of cellulase-conjugated nanogels (CNG) can be elegantly tuned by control of their cross-linking degrees. Circular dichroism (CD) spectra demonstrated that the secondary structures of the immobilized cellulase were changed in the aspect of α-helix contents. The secondary structures of cellulase in highly cross-linked nanogels were strongly altered compared with loosely cross-linked nanogels. The fluorescence resonance energy transfer (FRET) based study further revealed that nanogels with lower cross-linking degree enable higher substrate transport rate, providing easier access to the active site of the enzyme. The biohybrid nanogels demonstrated significantly improved stability in preserving enzymatic activity compared with free cellulase. The functional biohybrid nanogels with tunable enzymatic activity and improved stability are promising candidates for applications in biocatalysis, biomass conversion, or energy utilization fields.
Co-reporter:Dazril I. Phua, Krisztian Herman, Andreea Balaceanu, Juri Zakrevski, and Andrij Pich
Langmuir 2016 Volume 32(Issue 16) pp:3867-3879
Publication Date(Web):March 14, 2016
DOI:10.1021/acs.langmuir.6b00241
Aqueous microgels that respond orthogonally to external temperature and light stimuli and to a combination of both stimuli were developed. N-Vinylcaprolactam (VCL) was copolymerized with small feed amounts (<5 mol %) of 4-[(4-methacryloyloxy)phenylazo] benzenesulfonic acid (ABSA) and cross-linked with N,N′-methylenebis(acrylamide) (BIS) to synthesize monodisperse and colloidally stable P(VCL-BIS-ABSA) microgels. The volume phase transition information on the microgels under both orthogonal and combined application of temperature and light stimuli was investigated in situ by dynamic light scattering (DLS) instrument. Modeling of this information by the Flory–Rehner theory describes and aids the preliminary understanding of the main features in the volume phase transition of these photoresponsive microgels. Interestingly, the microgels rapidly deswell upon UV irradiation (λ = 365 nm), even as the trans-ABSA pendant groups are converted to the more polar cis state. The variation in the content of the pendant azobenzene groups in the microgels allows for reversible modulation of the phototriggered volume change. We propose that the approach of the sulfonic acid groups of cis-ABSA toward the polymer backbone causes the disruption of hydrogen bonding interactions between water molecules and the carbonyl groups of VCL.
Co-reporter:He Jia, Dominik Schmitz, Andreas Ott, Andrij Pich and Yan Lu
Journal of Materials Chemistry A 2015 vol. 3(Issue 11) pp:6187-6195
Publication Date(Web):13 Feb 2015
DOI:10.1039/C5TA00197H
We report a facile and green method for the fabrication of hybrid microgels by the immobilization of catalytically active Au nanoparticles in α-cyclodextrin (α-CD) modified poly(N-vinylcaprolactam) (PVCL) microgels without addition of reducing agent and surfactant. It has been shown that only in the case of α-CD modified microgels metal particles were immobilized inside the colloidal gels, which is due to a coordination of the cyclodextrin molecules to the surface of Au nanoparticles. The PVCL-α-CD-Au composite particles can work efficiently as catalyst for the reduction of aromatic nitro-compounds by using the reduction of 4-nitrophenol (Nip) and 2,6-dimethyl-4-nitrophenol (DMNip) as model reactions. Most importantly, due to the selective binding ability of α-CDs to certain reagents, the synthesized hybrid microgels show different catalytic activity for the target compounds during the catalytic reactions: a significant enhancement in the catalytic activity has been observed for the reduction of Nip, while no obvious effect has been found for the reduction of DMNip.
Co-reporter:Karla Doermbach and Andrij Pich
Nanoscale 2015 vol. 7(Issue 20) pp:9169-9173
Publication Date(Web):22 Apr 2015
DOI:10.1039/C5NR00924C
In this article we report on the controlled synthesis of asymmetric lemon-shaped and dumbbell-shaped multi-compartment nanoparticles (MCPs) with a reactive surface and interesting morphology. In our approach we utilize partial coating of hematite ellipsoids with a hydrophobic polymer layer followed by selective silica deposition on the non-coated surface. Ellipsoidal hematite particles provide a non-centric asymmetry, which is strongly enhanced during the seeded emulsion polymerization. The asymmetric growth of polymers on the hematite particle surface is driven by phase separation phenomena, which lead to a reduction of the interfacial tension. We found the tips of the hematite ellipsoids to be uncovered after polymerization. A selective deposition of silica onto the free tips leads to dumbbell-shaped particles with hydrophilic and hydrophobic parts.
Co-reporter:Huan Peng, Michael Kather, Kristin Rübsam, Felix Jakob, Ulrich Schwaneberg, and Andrij Pich
Macromolecules 2015 Volume 48(Issue 13) pp:4256-4268
Publication Date(Web):July 2, 2015
DOI:10.1021/acs.macromol.5b00947
Reversible addition–fragmentation chain transfer (RAFT) copolymerizations of methacrylic acid N-hydroxysuccinimide ester and cyclic N-vinylamide derivatives (N-vinylpyrrolidone, N-vinylpiperidone, and N-vinylcaprolactam) were successfully performed with methyl 2-(ethoxycarbonothioylthio)propanoate as chain transfer agent (CTA). Effects of different reaction parameters, such as solvent type, temperature, and CTA-to-initiator (C/I) ratio, were studied to optimize the polymerization conditions in order to obtain copolymers with variable chemical composition, controlled molecular weight, and narrow polydispersity index (PDI). The solvent type has a high impact on the polymerization reaction, and a high C/I ratio decreases polydispersity as well as conversion. Increased steric hindrance through an enlarged lactam ring offsets the monomer reactivity. The controlled character of RAFT polymerization was evidenced by the low PDI of the copolymers and a linear relationship between conversion and molecular weight. Biohybrid nanogels were synthesized by direct coupling between reactive copolymers and enhanced green fluorescent protein (EGFP) or cellulase (CelA2_M2) at room temperature in a water-in-oil emulsion. The EGFP-conjugated nanogels were fluorescent, while the CelA2_M2 encapsulated in nanogels retained its catalytic activity, as demonstrated by the hydrolysis of 4-methylumbelliferyl-β-d-cellobioside.
Co-reporter:Ricarda Schroeder, Andrey A. Rudov, L. Andrew Lyon, Walter Richtering, Andrij Pich, and Igor I. Potemkin
Macromolecules 2015 Volume 48(Issue 16) pp:5914-5927
Publication Date(Web):August 7, 2015
DOI:10.1021/acs.macromol.5b01305
In this work, different systems of colloidally stable, ampholytic microgels (μGs) based on poly(N-vinylcaprolactam) and poly(N-isopropylacrylamide), wherein the anionic and cationic groups are randomly distributed, were investigated. Fourier transmission infrared spectroscopy and transmission electron microscopy confirmed the quantitative incorporation and random distribution of ionizable groups in μGs, respectively. The control of hydrodynamic radii and mechanical properties of polyampholyte μGs at different pH values was studied with dynamic light scattering and in situ atomic force microscopy. We have proposed a model of pH-dependent polyampholyte μG, which correctly describes the experimental data and explains physical reasons for the swelling and collapse of the μG at different pHs. In the case of a balanced μG (equal numbers of cationic and anionic groups), the size as a function of pH has a symmetric, V-like shape. Swelling of purely cationic μG at low pH or purely anionic μG at high pH is due to electrostatic repulsion of similarly charged groups, which appears as a result of partial escape of counterions. Also, osmotically active counterions (the counterions that are trapped within the μG) contribute to the swelling of the μG. In contrast, electrostatic interactions are responsible for the collapse of the μG at intermediate pH when the numbers of anionic and cationic groups are equal (stoichiometric ratio). The multipole attraction of the charged groups is caused by thermodynamic fluctuations, similar to the those observed in Debye–Hückel plasma. We have demonstrated that the higher the fraction of cationic and anionic groups, the more pronounced the swelling and collapse of the μG at different pHs.
Co-reporter:Philipp Wilke, Vincent Coger, Milen Nachev, Susann Schachschal, Nina Million, Stephan Barcikowski, Bernd Sures, Kerstin Reimers, Peter M. Vogt, Andrij Pich
Polymer 2015 Volume 61() pp:163-173
Publication Date(Web):20 March 2015
DOI:10.1016/j.polymer.2015.01.078
•Novel functional, biocompatible microfibers have been developed.•Microfiber surface was modified by microgels, loaded with ZnO NPs, during electrospinning process.•Microfiber pads are capable of zinc ion release under physiological conditions.We present a novel and facile method for the design of biocompatible microgel-modified microfibers loaded with ZnO nanoparticles capable of zinc ion release under physiological conditions. The microfibers consist of three materials hierarchically assembled in a controlled and reproducible way. We synthesized poly(N-vinylcaprolactam-co-itaconic acid) aqueous microgels with carboxylic groups located in the microgel core. The obtained microgels can be loaded with various amounts of ZnO nanoparticles by in-situ growth of ZnO in microgels. As shown by electrophoretic mobility and TEM measurements, ZnO nanoparticles are selectively loaded in the microgel core and stabilized by itaconic acid groups bearing strong negative charges. ZnO-loaded microgels were used as functional additive to produce poly(ε-caprolactone) (PCL) microfibers using the electrospinning process. The resulting microfibers consist of a PCL core coated with the microgels located at the surface of the fibers. The variation of the ZnO amount loaded into microgels allows regulating the ZnO content in microfibers and gives the possibility to tune the released amount of zinc ions in aqueous medium at pH 7.5 and 37 °C. We demonstrate that the obtained functional microfibers are biocompatible and non-toxic, thus being good candidates for biomedical applications like scaffolds for tissue engineering, biointerface coatings or wound closing dressings.
Co-reporter:C. Scherzinger, A. Balaceanu, C.H. Hofmann, A. Schwarz, K. Leonhard, A. Pich, W. Richtering
Polymer 2015 Volume 62() pp:50-59
Publication Date(Web):7 April 2015
DOI:10.1016/j.polymer.2015.02.007
•Polymers from secondary and tertiary amides are compared.•Thermoresponsive polyacrylamides with amide proton show cononsolvency.•Thermoresponsive polyacrylamides without amide proton do not show cononsolvency.•Tertiary poly(N-vinylcaprolactam) behaves like tertiary polyacrylamides.•Calculations reproduce the experimental results.In this comparative study we investigate the influence of the side chain substitution pattern on the volume phase transition temperature (VPTT) of thermo-sensitive polymer microgels. We especially focus on cononsolvency of water and methanol. We compare literature data for poly(N-isopropylacrylamide) (PNIPAM) that shows cononsolvency to experimental data for secondary amide poly(N-n-propylacrylamide) (PNNPAM) as well as tertiary poly(N,N-diethylacrylamide) (PDEAAM) and poly(N-vinyl-caprolactam) (PVCL). As methods we apply size determination by dynamic light scattering (DLS) as well as differential scanning calorimetry(DSC) and theoretical calculations using COSMO-RS (conductor-like screening model for real solvents). Clear differences are found for PDEAAM and PVCL in comparison to PNIPAM and PNNPAM. We ascribe the significant differences between PNIPAM and PNNPAM on the one hand and PDEAAM and PVCL on the other hand to the amide proton, which is present in PNIPAM and PNNPAM but not in the other two polymers.
Co-reporter:Garima Agrawal, Andreas Ülpenich, Xiaomin Zhu, Martin Möller, and Andrij Pich
Chemistry of Materials 2014 Volume 26(Issue 20) pp:5882
Publication Date(Web):September 23, 2014
DOI:10.1021/cm502358s
In the present work, we demonstrate the preparation of adaptive hybrid capsules with microgel/SiO2 composite walls. During the first stage of the capsule synthesis process, microgel particles stabilize the oil droplets in water and become self-assembled on the oil/water interface. At the second stage, microgels are subsequently glued by the sol–gel reaction of a silica precursor-hyperbranched polyethoxysiloxane (PEOS) which occurs at the oil/water interface. Consequently, hybrid capsules consisting of silica shell with embedded microgels are obtained. Responsive microgels present in the capsule wall act as transportation channels for different encapsulated materials. The use of smart microgels allows us to design capsules with controlled size, morphology, and wall permeability able to operate in both water and organic solvents.
Co-reporter:Sudha J. Devaki, Neethu K. Sadanandhan, Renjith Sasi, Hans-Juergen P. Adler and Andrij Pich
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:6991-7000
Publication Date(Web):19 Jun 2014
DOI:10.1039/C4TC01010H
In this work, we demonstrate an inimitable liquid crystalline template strategy for the preparation of water dispersible electrically conducting poly(3,4-ethylenedioxythiophene) nanospindles (PEDOTSs). PEDOTSs were formed during the polymerization of the spindle shaped liquid crystalline phase of “EDOT–PDPSA” which was formed by the specific interactions of 3,4-ethylenedioxythiophene (EDOT) with 3-pentadecyl phenol-4-sulphonic acid (PDPSA). Liquid crystalline phases were characterized by Polarized Light Microscopic (PLM) analyses, rheology and XRD. Morphology and solid state ordering of conducting nanospindles were characterized by SEM, TEM and XRD. PEDOTSs exhibited an electrical conductivity of ∼2.79 S cm−1 and a good thermal stability (∼300 °C), which suggests their applicability in fabricating high temperature electronic devices. Furthermore, electrochemical studies of PEDOTS modified glassy carbon electrodes (GCEs) showed an oxidation peak of ascorbic acid at a lower potential of 0.046 V with a peak current about 10 times (91.68 μA) higher than that of the bare GCE with excellent electrode stability, proposing that it can be used as a steady electrode for the electro-catalytic oxidation of similar molecules.
Co-reporter:Dominic Kehren, Astrid Catalina Molano Lopez, Andrij Pich
Polymer 2014 Volume 55(Issue 9) pp:2153-2162
Publication Date(Web):25 April 2014
DOI:10.1016/j.polymer.2014.03.025
In this work we prepared composite poly(caprolactone) (PCL) microfibres decorated with temperature-sensitive poly(N-vinylcaprolactam) nanogels by an one-step electropsinning process. Microfibres with variable internal structure were prepared by using two different solvent systems: methanol/toluene (Me/Tol) and chloroform/dimethylformamide (Ch/DMF). Our experimental data shows that the nature of the solvent mixtures allows obtaining microfibres with different morphologies: Microfibres with nanogels on the fibre surface (Me/Tol) and microfibres with nanogels in the fibre interior (Ch/DMF). The morphology of composite fibres was visualized by scanning electron microscopy (SEM) and their properties investigated by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and contact angle measurements. The results show that combining hydrophobic poly(caprolactone) with hydrophilic nanogels leads to microfibres exhibiting controlled swelling in water. Additionally, the thermo-sensitive properties of the nanogels are maintained whether they are on the surface or inside of the fibres. The presence of nanogels in the fibre structure also allows regulating their degradability.
Co-reporter:Yaodong Wu, Susanne Wiese, Andreea Balaceanu, Walter Richtering, and Andrij Pich
Langmuir 2014 Volume 30(Issue 26) pp:7660-7669
Publication Date(Web):2017-2-22
DOI:10.1021/la501181k
Herein, we investigate the interfacial behavior of temperature-sensitive aqueous microgels on the toluene/water interface. Copolymer microgels based on N-vinylcaprolactam (VCL) and two acrylamides, N-isopropylacrylamide (NIPAm) and N-isopropylmethacrylamide (NIPMAm), with various copolymer compositions were used in this study. It is revealed that these copolymer microgels have the similar internal structure, regardless of the chemical composition. A classic kinetics of interfacial tension with three distinct regimes is found in the dynamic interfacial tension plots of copolymer microgels, which is similar to inorganic nanoparticles and proteins. The influences of the copolymer composition and the temperature on the interfacial behavior of microgels are investigated. The results show that the interfacial behavior of copolymer microgels at the toluene/water interface follows exactly the trend of the volume phase behavior of microgels but, on the other hand, strongly depends upon the chemical compositions of copolymer microgels. In contrast, with respect to the size range of microgels studied here (50–500 nm), the size of the microgel has no influence on the interfacial tension. Below the volume phase transition temperature (VPTT), the equilibrium interfacial tensions of all microgel systems decrease as the temperature increases. Above VPTT, the equilibrium interfacial tension remains at a certain level for poly(N-vinylcaprolactam) (PVCL)- and poly(N-isopropylmethacrylamide) (PNIPMAm)-rich microgel systems and increases slightly for poly(N-isopropylacrylamide) (PNIPAm)-rich microgel systems. The evolution of dynamic interfacial tension for microgel solutions against toluene at T < VPTT is faster than that at T > VPTT, because of the reduced deformability of the microgel with the increase of the temperature. The softer microgels with lower cross-linking degrees exhibit faster kinetics of reduction of interfacial tension compared to those with more cross-linked degrees, which strongly supports the deformation-controlled interfacial behavior of microgels.
Co-reporter:Jens Köhler;Sebastian Kühl;Helmut Keul;Martin Möller
Journal of Polymer Science Part A: Polymer Chemistry 2014 Volume 52( Issue 4) pp:527-536
Publication Date(Web):
DOI:10.1002/pola.27028
ABSTRACT
Starting with hexachlorocyclotriphosphazene (HCCP) and branched polyethylenimine (bPEI) crosslinked cyclomatrix polyphosphazene poly(HCCP-co-bPEI) microspheres are prepared by precipitation polymerization in acetonitrile at 50 °C under ultrasound irradiation. The influence of varying reagent ratios on the chemical composition, morphology, and physical and chemical properties of the microspheres is investigated. Furthermore, the microspheres are characterized by Fourier-transform infrared spectroscopy, dynamic light scattering (DLS), X-ray photoelectron spectroscopy, elemental analysis, as well as 31P MAS NMR. FESEM and DLS analysis show microspheres of smooth and spherical shape which swell both in water and acetonitrile. The particle diameters in the dry state range from 0.4 to 0.9 μm, but due to swelling a size increase between 45 and 140% is observed depending on the chemical composition and the solvent medium. The thermal stability of the microspheres ranges from 262 to 351 °C. The presence of reactive amine groups on the surface is proven by electrophoretic mobility measurements and chemical modification with two model compounds. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 527–536
Co-reporter:Garima Agrawal, Marco Philipp Schürings, Patrick van Rijn and Andrij Pich
Journal of Materials Chemistry A 2013 vol. 1(Issue 42) pp:13244-13251
Publication Date(Web):02 Sep 2013
DOI:10.1039/C3TA12370G
A newly developed N-vinylcaprolactam/acetoacetoxyethyl methacrylate/acrylic acid based microgel displays in situ reductive reactivity towards HAuCl4, forming hybrid polymer–gold nanostructures at ambient temperature without additional reducing agents. The colloidal gold nanostructure is selectively formed in the core of the microgel and the composite structure is used as a noble metal catalyst, the activity of which can be tuned depending on the size of the formed core. The hybrid particles can easily be isolated after catalysis via centrifugation and re-used with retention of the catalytic activity.
Co-reporter:Garima Agrawal, Jingbo Wang, Berit Brüster, Xiaomin Zhu, Martin Möller and Andrij Pich
Soft Matter 2013 vol. 9(Issue 22) pp:5380-5390
Publication Date(Web):19 Apr 2013
DOI:10.1039/C3SM50248A
In the present work we demonstrate the synthesis of degradable thermo-sensitive poly(N-vinylcaprolactam) microgels via precipitation polymerization using reactive polyvinylalkoxysiloxanes as crosslinkers (Cross-PAOS). These compounds were synthesized by co-condensation of vinyltriethoxysilane and tetraethoxysilane followed by transesterification with poly(ethylene glycol) monomethyl ether (PEG) to increase their water solubility. Experimental results showed that the microgels synthesized using Cross-PAOS exhibited excellent colloidal stability in water. These microgels are thermo-responsive and their size can be tuned depending upon the ratio of vinyl and PEG groups in Cross-PAOS. The size of microgel particles increases with increasing vinyl groups in Cross-PAOS while it decreases with increasing PEG groups. The presence of silicon dioxide in the microgel structure was confirmed by X-ray photoelectron spectroscopy and elemental analysis. Additionally, the microgels prepared in this way contain crosslinking sites which can be degraded under alkaline conditions.
Co-reporter:Dominic Kehren
Macromolecular Materials and Engineering 2013 Volume 298( Issue 12) pp:1282-1293
Publication Date(Web):
DOI:10.1002/mame.201300024
Abstract
In this work microgel-PVA composite fibres are prepared by means of an electrospinning process using aqueous solutions of poly(vinyl alcohol) (PVA) and poly(N-vinylcaprolactam)-based microgels. The optimal parameters are defined to fabricate homogenous composite fibres in which the microgels are embedded into a PVA matrix. It is demonstrated that the fibres can be physically and chemically crosslinked. The fibre morphology is visualised and its properties investigated by differential scanning calorimetry, DSC, thermo-gravimetric analysis, TGA, and isothermal moisture sorption analysis. The results show that the thermo-sensitive properties of the microgels are retained inside the fibres and that the degree of swelling and the moisture sorption kinetics can be tuned by changing the temperature.
Co-reporter:Andreea Balaceanu, Yaroslav Verkh, Dan E. Demco, Martin Möller, and Andrij Pich
Macromolecules 2013 Volume 46(Issue 12) pp:4882-4891
Publication Date(Web):June 4, 2013
DOI:10.1021/ma400495y
PVCL and PNIPMAAm core–shell components in microgel particles are shown to have different volume phase temperature transition behavior than the respective homopolymer microgel particles due to confinement effects. A combination of dynamic light scattering (DLS) data that gives access to the temperature dependence of hydrodynamic radius and modified Flory–Rehner theory in the presence of networks confinement allowed obtaining information about correlated morphological changes of components inside of core–shell microgels. The core–shell components individual temperature behavior is analyzed by modifying the Flory–Rehner transition theory in order to account for core–shell morphology and the existence of an interaction force between core and shell. Describing the dependence on temperature of the radial scale parameter, the ratio between the radius of the core and the hydrodynamic radius, we gain access to the swelling behavior of the core and shell components irrespective of the swelling behavior of the total hydrodynamic radius. Furthermore, the theoretical description of volume phase temperature transition permits the development of scenarios for the correlated changes in the core and shell radial dimensions for the two microgels with reversed morphologies. The fact that the theoretical model is appropriate for the treatment of core–shell microgels is proved a posteriori by obtaining a temperature dependence of the components that is in accordance with the expected physical behavior. Novel core–shell microgel systems of PVCL (poly(N-vinylcaprolactam))-core/PNIPMAAm (poly(N-isopropylmethacrylamide))-shell and PNIPMAAm-core/PVCL-shell, with a double volume phase temperature transition due to the thermoresponsive components, were used for this study.
Co-reporter:Smriti Singh;Martin Möller
Journal of Polymer Science Part A: Polymer Chemistry 2013 Volume 51( Issue 14) pp:3044-3057
Publication Date(Web):
DOI:10.1002/pola.26719
ABSTRACT
Biohybrid nanogels are crosslinked colloidal networks that consist of biological and synthetic polymers as building blocks. Such polymer colloidal particles attracted much attention in recent years mainly due to their outstanding properties and huge application potential that by far overcome classical nanogels or microgels prepared from water-soluble synthetic polymers. In this report, we review recent developments on the synthesis and properties of biohybrid nanogels. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3044–3057
Co-reporter:Andreea Balaceanu;Veronica Mayorga;Wanjuan Lin
Colloid and Polymer Science 2013 Volume 291( Issue 1) pp:21-31
Publication Date(Web):2013 January
DOI:10.1007/s00396-012-2659-1
In this work, we designed copolymer microgels by the copolymerisation of N-vinylcaprolactam (VCL) and two acrylamides (N-isopropylacrylamide (NIPAAm) and N-isopropylmethacrylamide (NIPMAAm)) under precipitation conditions in aqueous phase. In synthesis protocols, the ratio between monomers was varied from 1:5 to 5:1 mol/mol. By NMR and Raman spectroscopy, we determined the chemical composition of PVCL/NIPAAm and PVCL/NIPMAAm copolymer microgels reflecting the initial monomer ratio in the reaction mixture. The hydrodynamic radii of PVCL/NIPAAm microgels are around 375 nm (at 25 °C) and do not vary with the copolymer composition. On the contrary, for PVCL/NIPMAAm microgels, the size decreases from 450 to 250 nm with an increase of the VCL amount in copolymer structure. The heterogeneity of the microgel structure in terms of the distribution of the monomer units was probed by 1H transverse magnetization relaxation NMR, showing that the VCL, NIPAAm and NIPMAAm units are unorderly distributed in the colloidal networks. The investigation of volume phase transition temperature (VPTT) for copolymer microgels was performed using dynamic light scattering, NMR and differential scanning calorimetry. It has been found that PVCL/NIPAAm microgels show VPTT around 35 °C independently from the copolymer composition; however, PVCL/NIPMAAm particles exhibit a nonlinear increase of VPTT from 34 to 45 °C as the NIPMAAm fraction in copolymer structure increases.
Co-reporter:Garima Agrawal, Marco Schürings, Xiaomin Zhu, Andrij Pich
Polymer 2012 Volume 53(Issue 6) pp:1189-1197
Publication Date(Web):9 March 2012
DOI:10.1016/j.polymer.2012.01.051
In the present work we demonstrate that functional polymer microgels may act as smart self-catalyzing system inducing controlled formation of silica nanoparticles inside the polymer network and formation of hybrid colloids. We synthesized a water soluble silica precursor PEG-PEOS via post-modification of hyperbranched poly(ethoxysiloxane) (PEOS) with poly(ethylene glycol) monomethyl ether. We used poly(N-vinylcaprolactam)-based microgel functionalized with imidazole and β-diketone groups as a matrix for biomimetic deposition of silica. Composite microgel particles containing silica nanoparticles (up to 20 wt.-%) have been prepared by simultaneous PEG-PEOS conversion and silica deposition in the microgels. TEM studies indicate the infiltration of silica nanoparticles (∼10 nm) inside the corona region of the microgels due to the strong acid–base interaction between the acidic silica and basic imidazole groups. The resulting composite particles were found to be colloidally stable and no aggregation was observed even after months of storage. The incorporation of silica nanoparticles increased the rigidity of the microgel particles and reduced their thermal sensitivity.
Co-reporter:Smriti Singh;Julia Blöhbaum;Martin Möller
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 20) pp:4288-4299
Publication Date(Web):
DOI:10.1002/pola.26236
Abstract
This article reports the synthesis of biohybrid nanogels by crosslinking six-arm acrylate functionalized star shaped P(EO-stat-PO) with the amine groups of various amino acids of a hen egg ovalbumin in W/O emulsion. PEG Poly(ethylene glycol)-diamines of different molecular weights (368.5 g/mol, 897.1 g/mol, 3000 g/mol, and 6000 g/mol) were used to optimize the crosslinking reactions in aqueous droplets. The increase of molecular weight of the PEG-diamine led to decrease of the nanogel size due to better stabilization by longer PEG chains. The size of the ovalbumin nanogels was independent of the acrylate-sP(EO-stat-PO):ovalbumin ratio in the reaction mixture. The bicinchoninic acid (BCA) assay proved that the ovalbumin has been effectively crosslinked by reactive prepolymers. From the results of BCA assay, it can also be established that there exists a limiting amount of ovalbumin which can be incorporated into the nanogels. Both Diamine and ovalbumin-based nanogels exhibit amphoteric behavior and display a positive charge in acidic and a negative charge in basic environment. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Lei Li, Cheng Cheng, Marco P. Schürings, Xiaomin Zhu, Andrij Pich
Polymer 2012 Volume 53(Issue 15) pp:3117-3123
Publication Date(Web):6 July 2012
DOI:10.1016/j.polymer.2012.05.021
We report on the synthesis and properties of aqueous poly(N-vinylcaprolactam-co-acetoacetylethylmethacrylate-co-vinylimidazole) microgels with controlled degree of hydrophobic modification. Water-insoluble wedge-shaped sulfonic acid molecules with alkyl chains of different lengths were integrated into microgels via acid–base interaction. Hydrophobized microgels retain their colloidal stability in water. The length of the alkyl chain in the wedge-shaped molecules has a significant influence on their size, loading capacity and environmental sensitivity (thermochromic effect of the dye-loaded microgels). Furthermore, the incorporation into the hydrophobized microgels of dexamethasone, an important anti-inflammatory corticoid medicine, as well as its in vitro release profiles was investigated.Graphical abstract
Co-reporter:Sascha Pargen, Christian Willems, Helmut Keul, Andrij Pich, and Martin Möller
Macromolecules 2012 Volume 45(Issue 3) pp:1230-1240
Publication Date(Web):January 17, 2012
DOI:10.1021/ma2021437
We investigate the synthesis of functional polystyrene/oligoglycidol particles by surfactant-free emulsion polymerization. Oligoglycidol macromonomers with linear and branched oligoglycidol structure and variable oligoglycidol chain lengths were synthesized. These macromonomers were used as surfmers (surfactants and comonomers) in emulsion polymerization of styrene. Monodisperse colloidally stable polystyrene particles were obtained, decorated with oligoglycidol chains with diameters between 100 and 600 nm. The increase of the macromonomer concentration induced a decrease of the particle size and broadening of the particle size distribution. The macromonomers with branched architecture were more effective and produced monodisperse particles even at low concentrations. Due to the steric stabilization provided by the hydrophilic oligoglycidol layer on the particle surface, the emulsion of polystyrene/oligoglycidol particles obtained exhibited very good resistance against electrolytes. The chemical and enzyme catalyzed grafting polymerization of ε-caprolactone from the polystyrene/oligoglycidol particle surface was demonstrated along with formation of composite particles.
Co-reporter:Hailin Wang, Karola Schaefer, Andrij Pich, and Martin Moeller
Chemistry of Materials 2011 Volume 23(Issue 21) pp:4748
Publication Date(Web):October 6, 2011
DOI:10.1021/cm2017328
Silica encapsulated perylenediimide (PDI) nanoellipsoids with core–shell structure have been synthesized in solution by a combination of precipitation method and sol–gel chemistry. Electron energy loss spectrum (EELS) analysis proves that the obtained composite particles consist of a PDI core and a silica shell. The UV–vis and fluorescence spectra show the strong π–π stacking state of PDI molecules in the composite colloids. The silica deposition process on the PDI surface can be well controlled allowing variation of the shell thickness from 10 to 50 nm. Thermogravimetrical analysis data indicate that the thermal stability of PDI increases after deposition of a silica shell. The photostability of PDI is enhanced by the introduction of silica shell. The silica coating improves the dispersibility of PDI in different solvents and in polymer films.Keywords: core−shell; encapsulation; nanoparticle; perylene diimide; silica;
Co-reporter:Stephanie Hiltl, Marco-Philipp Schürings, Andreea Balaceanu, Veronika Mayorga, Clemens Liedel, Andrij Pich and Alexander Böker
Soft Matter 2011 vol. 7(Issue 18) pp:8231-8238
Publication Date(Web):01 Aug 2011
DOI:10.1039/C1SM05675A
We investigate the guided large scale self-assembly of microgels consisting of N-vinylcaprolactam (VCL), N-isopropylacrylamide (NiPAAm) and acetoacetoxyethyl methacrylate (AAEM) using nanostructured substrates fabricated via controlled wrinkling. Depending on the type of microgel, the arrangement in the grooves of the substrates influences the particle shape and the overall pattern formation. Thus we obtain straight lines composed of single particles as well as zigzag-structures. In an additional processing step, we use the nanostructured substrates as stamps to transfer the formed microgel patterns onto a planar support. Subsequent UV-crosslinking of the microgel strings yields anisotropic particles.
Co-reporter:Andreea Balaceanu;Dan E. Demco;Martin Möller
Macromolecular Chemistry and Physics 2011 Volume 212( Issue 22) pp:2467-2477
Publication Date(Web):
DOI:10.1002/macp.201100340
Abstract
The Flory temperature-induced volume transition theory for copolymer microgels is generalized for the case of a bimodal heterogeneity of the crosslink density in the microgel particles and applied to PVCL–PNIPAAm and PVCL–PNIPMAAm systems. The most probable morphological parameters are selected from the microscopic and thermodynamic constraints imposed by 1H transverse relaxation NMR data and the Flory equation of state in the approximation of a homogeneous morphology. NMR proves the existence of a bimodal heterogeneous morphology of the copolymer microgel particles. Although the systems are different in chemical structure, the heterogeneity parameters obtained from Flory transition theory and NMR transverse relaxation are not essentially different.
Co-reporter:Andreea Balaceanu, Dan E. Demco, Martin Möller, and Andrij Pich
Macromolecules 2011 Volume 44(Issue 7) pp:2161-2169
Publication Date(Web):March 10, 2011
DOI:10.1021/ma200103y
The Flory temperature-induced volume transition theory for homopolymer microgels was generalized for the case of bimodal heterogeneous morphology. The most probable morphological parameters were selected from the microscopic and thermodynamic constraints imposed by 1H transverse relaxation NMR and Flory equation of state in the approximation of a homogeneous morphology. Proton transverse magnetization relaxation NMR proved directly the existence of a bimodal heterogeneous morphology of the PVCL microgel particle. The volume polymer fractions in the deswollen state and the number of subchains for the core and corona were obtained from size−temperature data for a series of differently cross-linked microgels made of poly(N-vinylcaprolactam) (PVCL) in water. The cross-link density effect given by the different amounts of cross-linker used was investigated using dynamic light scattering. From the combination of Flory heterogeneous theory and NMR transverse relaxation, the number of polymer subchains in core and corona was shown to increase with the amount of cross-linker. Moreover, the ratio of the cross-link density in core and corona could be evaluated from the transverse relaxation times T2 of each decay components. The quantitative characterization of PVCL microgels by size−temperature data and 1H transverse relaxation NMR shows the consistency of the assumptions made in the generalization of Flory theory of microgels for heterogeneous morphology.
Co-reporter:Markus J. Kettel, Fiete Dierkes, Karola Schaefer, Martin Moeller, Andrij Pich
Polymer 2011 Volume 52(Issue 9) pp:1917-1924
Publication Date(Web):19 April 2011
DOI:10.1016/j.polymer.2011.02.037
Co-reporter:Sebastian Berger, Olga Ornatsky, Vladimir Baranov, Mitchell A. Winnik and Andrij Pich
Journal of Materials Chemistry A 2010 vol. 20(Issue 24) pp:5141-5150
Publication Date(Web):12 Apr 2010
DOI:10.1039/C0JM00075B
In this article we demonstrate that hybrid nanogels can be prepared by encapsulation of reactive nanoparticles (NPs) directly during nanogel synthesis. Nanogels investigated in present study consist of poly(N-vinylcaprolactam-co-(2-acetoacetoxyethyl) methacrylate) copolymer. The modification of the LaF3:Eu nanoparticle surface with reactive double bonds allows effective incorporation of the NPs into the nanogel structure. This approach ensures effective encapsulation of varying amounts of NPs into the nanogel interior with a loading efficiency close to 95%. The NPs are covalently bound to the nanogel core, and no NP leakage occurs. Reactive NPs act as multifunctional cross-linking agents and increase the cross-linking degree of the nanogels. We demonstrate the possibility of the incorporation of LaF3 nanoparticles doped with different ions (Eu, Tb, Pr, Gd) or nanoparticle mixtures into nanogels. These nanogels exhibit temperature-sensitive properties and superior colloidal stability in water and other aqueous media.
Co-reporter:Alexander Türke, Wolf-Joachim Fischer, Hans-Juergen Adler, Andrij Pich
Polymer 2010 Volume 51(Issue 21) pp:4706-4712
Publication Date(Web):1 October 2010
DOI:10.1016/j.polymer.2010.08.027
We report synthesis of colloids with polymer core and inorganic shell consisting of silver nanoparticles (AgNPs) which can be used as building blocks for the preparation of conducting composite films. Polymer colloids based on copolymer of styrene and butyl acrylate with variable film formation temperature and functional surface have been prepared by surfactant-free emulsion polymerization. Polymer particles with average size between 140 nm and 220 nm and narrow size distribution were used as templates for deposition of AgNPs by microwave-assisted reduction of silver precursors in aqueous medium. The loading of the AgNPs on the polymer particle surface has been increased up to 60 wt.-%. Obtained hybrid colloids were used for preparation of composite films. The electrical conductivity of the composite films starts to increase if the AgNPs loading on the polymer particle surface is above 20 wt.-%.
Co-reporter:Sebastian Berger, Rekha Singh, Janardhanannair D. Sudha, Hans-Juergen Adler, Andrij Pich
Polymer 2010 Volume 51(Issue 17) pp:3829-3835
Publication Date(Web):4 August 2010
DOI:10.1016/j.polymer.2010.06.039
Microgel–clay composite particles were prepared by one-step surfactant–free precipitation polymerization. Laponite nanoparticles present in the reaction mixture become encapsulated during the microgel formation process. Microgel–clay composites based on poly(N-vinylcaprolactam-co-acetoacetoxyethyl methacrylate) containing different amount of incorporated clay nanoparticles were synthesized. The clay content was varied from 2 wt% to 18 wt%. The extremely high incorporation efficiency of the clay nanoparticles into microgels was detected. The size of the hybrid microgels was decreased from 700 nm to 100 nm by increase of the clay concentration in the reaction mixture. Obtained hybrid microgels exhibit negative surface charge and excellent colloidal stability. Microgel–clay composite particles display temperature-sensitive behaviour in water. The swelling degree of the hybrid microgels decreases with increase of the clay loading. Microgel–clay composite particles exhibit temperature-controlled uptake of the cationic dye, Methylene blue, and can be used as scavenger systems in aqueous media.
Co-reporter:Cheng Cheng, Xiaomin Zhu, Andrij Pich and Martin Möller
Langmuir 2010 Volume 26(Issue 7) pp:4709-4716
Publication Date(Web):December 4, 2009
DOI:10.1021/la903588p
A simple route for the design of hydrophilic microgels comprising inner hydrophobic nanodomains has been developed based on postmodification of microgels by complexation of wedge-shaped amphiphilic molecules with complementary functional groups. Aqueous microgels functionalized with imidazole groups were transferred into an organic medium, where imidazole groups were neutralized by water-insoluble wedge-shaped molecules bearing a sulfonic acid group at the tip of the wedge and a large hydrocarbon body. After redispersion of the modified microgel particles into the aqueous phase, wedge-shaped amphiphiles ionically attached to the polymer chains self-assembled into discrete nanodomains in the interior of the polymer colloids due to the hydrophobic attraction force. The loading of the wedge-shaped molecules into microgels can be controlled by variation of the amount of imidazole groups integrated into the microgel network as well as the neutralization degree. The experimental results suggested that incorporation of hydrophobic domains into hydrophilic colloids induced dramatic changes of their properties such as swelling degree, surface charge, and responsiveness toward temperature and pH. Finally, we demonstrated that internally hydrophobized microgel particles are very effective in uptake of hydrophobic molecules in aqueous media.
Co-reporter:Sebastian Berger;Haiping Zhang
Advanced Functional Materials 2009 Volume 19( Issue 4) pp:554-559
Publication Date(Web):
DOI:10.1002/adfm.200801203
Abstract
In this paper, a preparation of stimuli-responsive capsules based on aqueous microgels is described. Microgel particles act as stabilizers for oil-in-water emulsion and organize themselves on the surface of chloroform droplets containing the biodegradable polymer poly(4-hydroxybutyrate-co-4-hydroxyvalerate) (PHBV). After chloroform evaporation, composite capsules consisting of a thin PHBV wall with integrated microgels are obtained. Due to the presence of microgels acting as sensitive building blocks, the capsules respond to different stimuli (temperature, solvent concentration). Preliminary results indicate that the capsule dimensions and morphology can be tuned by microgel and PHBV concentration in water and chloroform, respectively.
Co-reporter:Nadine Häntzschel;Rolf-Dieter Hund;Heike Hund;Marc Schrinner;Christian Lück
Macromolecular Bioscience 2009 Volume 9( Issue 5) pp:444-449
Publication Date(Web):
DOI:10.1002/mabi.200800219
Co-reporter:Andrij Pich;Sebastian Berger;Olga Ornatsky
Colloid and Polymer Science 2009 Volume 287( Issue 3) pp:269-275
Publication Date(Web):2009/03/01
DOI:10.1007/s00396-008-1972-1
We describe the preparation and thermal response of aqueous microgels based on poly(N-vinyl caprolactam) containing grafted poly(ethylene glycol) (PEG) chains. These microgels were synthesized by free radical copolymerization of vinyl caprolactam and acetoacetoxyethyl methacrylate in the presence of methoxy-capped poly(ethylene glycol)methacrylate macromonomers. We show that variation of the amount of PEG macromonomer or the length of the PEG chain provides effective control of the microgel diameter in the range 60–220 nm. The presence of the grafted PEG chains improves the colloidal stability of the microgels. The incorporation of the PEG macromonomers into microgel structure decreases the swelling degree and induces a shift of the volume phase transition to higher temperatures.
Co-reporter:Huan Peng, Xiaobin Huang, Alex Oppermann, Andrea Melle, Lindsey Weger, Marcel Karperien, Dominik Wöll and Andrij Pich
Journal of Materials Chemistry A 2016 - vol. 4(Issue 47) pp:NaN7583-7583
Publication Date(Web):2016/11/01
DOI:10.1039/C6TB01285J
In this study, thermal and redox dual sensitive nanogels based on N-vinylcaprolactam (VCL) and N-succinimidyl methacrylate (Suma) crosslinked with diallyl disulfide were synthesized via a facile and straightforward method. The reactive succinimide groups were mainly located in the nanogel shell which increases considerably their accessibility for conjugation reactions. Doxorubicin (DOX) was successfully loaded into the nanogel through two different routes. Approximately 91.3% of DOX molecules were covalently bound to the nanogel network via coupling with succinimide groups under mild conditions to obtain prodrug nanogels, while 8.7% of DOX molecules were captured into the nanogels via electrostatic interactions with the –COOH group from the hydrolyzed ester groups of the nanogels. The DOX-loaded nanogels demonstrated volume phase transition temperature (VPTT) near human physiological temperature. The nanogels shrink near body temperature, which could help lock the drug molecules stably in blood circulation. The conjugation of DOX molecules in nanogels avoided premature unspecific drug release under physiological conditions. The small amount of physically loaded DOX (due to electrostatic interactions) could be partially released as free DOX due to the increasing acidic conditions in the endosome/lysosome pathway. The chemically conjugated DOX was released in the form of a prodrug polymer triggered by the high concentration of glutathione in the cytosol that induced nanogel degradation. The present drug delivery system exhibits a sustainable delivery profile in the intracellular release study and high antitumor activity. We are convinced that the thermal and reduction dual-responsive prodrug nanogels have tremendous potential in controlled drug release.
Co-reporter:K. Wiemer, K. Dörmbach, I. Slabu, G. Agrawal, F. Schrader, T. Caumanns, S. D. M. Bourone, J. Mayer, J. Steitz, U. Simon and A. Pich
Journal of Materials Chemistry A 2017 - vol. 5(Issue 6) pp:NaN1292-1292
Publication Date(Web):2016/12/13
DOI:10.1039/C6TB02342H
We report the synthesis of a new multifunctional colloidal hybrid system consisting of thermoresponsive amphiphilic biocompatible poly(N-vinylcaprolactam) microgels loaded with hydrophobic superparamagnetic FePt nanoparticles (NPs). In the first step, water swellable poly(N-vinylcaprolactam) microgels were mixed with hydrophobically coated sub-10 nm superparamagnetic FePt NPs in a tetrahydrofuran (THF) solution. In the second step, changing the surrounding solvent from THF to water forces the FePt NPs to migrate into the amphiphilic microgels. These new hybrid microgels (i) are colloidally stable in water and their thermo-responsive properties in terms of volume phase transition are retained, (ii) exhibit superparamagnetic characteristics introduced by FePt NPs, (iii) show a drastically reduced cytotoxicity compared to water-soluble FePt NPs of similar size, as known from the literature. This makes the new hybrid microgels suitable e.g. as biocompatible containers for drug delivery or for imaging.
Co-reporter:Sebastian Berger, Olga Ornatsky, Vladimir Baranov, Mitchell A. Winnik and Andrij Pich
Journal of Materials Chemistry A 2010 - vol. 20(Issue 24) pp:NaN5150-5150
Publication Date(Web):2010/04/12
DOI:10.1039/C0JM00075B
In this article we demonstrate that hybrid nanogels can be prepared by encapsulation of reactive nanoparticles (NPs) directly during nanogel synthesis. Nanogels investigated in present study consist of poly(N-vinylcaprolactam-co-(2-acetoacetoxyethyl) methacrylate) copolymer. The modification of the LaF3:Eu nanoparticle surface with reactive double bonds allows effective incorporation of the NPs into the nanogel structure. This approach ensures effective encapsulation of varying amounts of NPs into the nanogel interior with a loading efficiency close to 95%. The NPs are covalently bound to the nanogel core, and no NP leakage occurs. Reactive NPs act as multifunctional cross-linking agents and increase the cross-linking degree of the nanogels. We demonstrate the possibility of the incorporation of LaF3 nanoparticles doped with different ions (Eu, Tb, Pr, Gd) or nanoparticle mixtures into nanogels. These nanogels exhibit temperature-sensitive properties and superior colloidal stability in water and other aqueous media.
Co-reporter:Garima Agrawal, Marco Philipp Schürings, Patrick van Rijn and Andrij Pich
Journal of Materials Chemistry A 2013 - vol. 1(Issue 42) pp:NaN13251-13251
Publication Date(Web):2013/09/02
DOI:10.1039/C3TA12370G
A newly developed N-vinylcaprolactam/acetoacetoxyethyl methacrylate/acrylic acid based microgel displays in situ reductive reactivity towards HAuCl4, forming hybrid polymer–gold nanostructures at ambient temperature without additional reducing agents. The colloidal gold nanostructure is selectively formed in the core of the microgel and the composite structure is used as a noble metal catalyst, the activity of which can be tuned depending on the size of the formed core. The hybrid particles can easily be isolated after catalysis via centrifugation and re-used with retention of the catalytic activity.
Co-reporter:He Jia, Dominik Schmitz, Andreas Ott, Andrij Pich and Yan Lu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 11) pp:NaN6195-6195
Publication Date(Web):2015/02/13
DOI:10.1039/C5TA00197H
We report a facile and green method for the fabrication of hybrid microgels by the immobilization of catalytically active Au nanoparticles in α-cyclodextrin (α-CD) modified poly(N-vinylcaprolactam) (PVCL) microgels without addition of reducing agent and surfactant. It has been shown that only in the case of α-CD modified microgels metal particles were immobilized inside the colloidal gels, which is due to a coordination of the cyclodextrin molecules to the surface of Au nanoparticles. The PVCL-α-CD-Au composite particles can work efficiently as catalyst for the reduction of aromatic nitro-compounds by using the reduction of 4-nitrophenol (Nip) and 2,6-dimethyl-4-nitrophenol (DMNip) as model reactions. Most importantly, due to the selective binding ability of α-CDs to certain reagents, the synthesized hybrid microgels show different catalytic activity for the target compounds during the catalytic reactions: a significant enhancement in the catalytic activity has been observed for the reduction of Nip, while no obvious effect has been found for the reduction of DMNip.
Co-reporter:Andrea Melle, Andreea Balaceanu, Michael Kather, Yaodong Wu, Elisabeth Gau, Wenjie Sun, Xiaobin Huang, Xiangyang Shi, Marcel Karperien and Andrij Pich
Journal of Materials Chemistry A 2016 - vol. 4(Issue 30) pp:NaN5137-5137
Publication Date(Web):2016/07/05
DOI:10.1039/C6TB01196A
Herein we report the synthesis of biocompatible stimuli-responsive core–shell microgels consisting of a poly(N-vinylcaprolactam) (PVCL) core and a poly(2-methoxyethyl acrylate) (PMEA) corona via one-step surfactant-free precipitation copolymerization. The copolymerization process was investigated by reaction calorimetry, microgel growth was monitored by in situ dynamic light scattering and the chemical structure of core–shell microgels was characterized by Raman spectroscopy. It was possible to incorporate up to 32 mol% MEA into the PVCL/MEA microgels without loss of colloidal stability and broadening of the size distribution. The core–shell morphology of microgels was confirmed by transverse magnetization relaxation 1H-NMR, dynamic light scattering (DLS), atomic force microscopy (AFM) and viscosimetry. By means of the NMR data, calorimetry and viscosity measurements it could be shown that MEA is mainly located in the microgel shell. This leads to hindered temperature-induced swelling and collapsing of the PVCL-core, as demonstrated by DLS measurements, due to the fact that the PMEA-shell exhibits a very low LCST around 5 °C. These results could also be confirmed by AFM: an increasing MEA-content leads to the formation of dense and compact core–shell microgels and results in a loss of their softness and deformability. Due to the presence of the PMEA-shell these microgels can be endocytosed much faster by HeLa cells maintaining their viability and can be suitable candidates for the design of drug carriers or imaging/diagnostic systems.
Co-reporter:Sudha J. Devaki, Neethu K. Sadanandhan, Renjith Sasi, Hans-Juergen P. Adler and Andrij Pich
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN7000-7000
Publication Date(Web):2014/06/19
DOI:10.1039/C4TC01010H
In this work, we demonstrate an inimitable liquid crystalline template strategy for the preparation of water dispersible electrically conducting poly(3,4-ethylenedioxythiophene) nanospindles (PEDOTSs). PEDOTSs were formed during the polymerization of the spindle shaped liquid crystalline phase of “EDOT–PDPSA” which was formed by the specific interactions of 3,4-ethylenedioxythiophene (EDOT) with 3-pentadecyl phenol-4-sulphonic acid (PDPSA). Liquid crystalline phases were characterized by Polarized Light Microscopic (PLM) analyses, rheology and XRD. Morphology and solid state ordering of conducting nanospindles were characterized by SEM, TEM and XRD. PEDOTSs exhibited an electrical conductivity of ∼2.79 S cm−1 and a good thermal stability (∼300 °C), which suggests their applicability in fabricating high temperature electronic devices. Furthermore, electrochemical studies of PEDOTS modified glassy carbon electrodes (GCEs) showed an oxidation peak of ascorbic acid at a lower potential of 0.046 V with a peak current about 10 times (91.68 μA) higher than that of the bare GCE with excellent electrode stability, proposing that it can be used as a steady electrode for the electro-catalytic oxidation of similar molecules.
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