Amine End Groups Research Articles

Poly(n-butyl methacrylate) with primary amine end groups for supporting cell adhesion and proliferation of renal epithelial cells

ABSTRACTPolymer coatings that support epithelial cell culture have been developed. Ozonolysis and subsequent workup of poly(butyl methacrylate-co-butadiene) copolymers is used to form oligomers with carboxylic acid end groups, which are then further reacted with diamines to provide poly(butyl methacrylate)s with primary amine end groups. The polymers are cast as films and used as cell culture substrates for human dermal fibroblasts and human renal epithelial cells. Fibroblast and epithelial cells adhere and proliferate on acid functional materials but on amine functional films epithelial cells show greater viability than fibroblasts.

A novel route to prepare a multilayer system via the combination of interface-mediated catalytic chain transfer polymerization and thiol-ene click chemistry

Herein, we have designed a novel multilayer system composed of poly(methyl methacrylate) [poly(MMA)] brush, biotin, streptavidin and protein-A on a silicon substrate to attach onanti-immunoglobulin G (anti-IgG). poly(MMA) brush with vinyl end-group was first synthesized by the interface-mediated catalytic chain transfer polymerization. The brush was then modified with cysteamine molecules to generate the polymer chains with amine end-group via a thiol-ene click chemistry. The amine end-groups of poly(MMA) chains were also modified with biotin units to ensure selective connection points for streptavidin molecules. Finally, a multilayer system on the silicon substrate was formed by using streptavidin and protein-A molecules, respectively. This multilayer system was employed to attach anti-IgG molecules in a highly oriented manner and provide anti-IgG molecular functional configuration on the multilayer. High reproducibility of the amount of anti-IgG adsorption and homogeneous anti-IgG adsorption layer on the silicon surface could be provided by this multilayer system. The multilayer system with protein A may be opened the door for designing an efficient immunoassay protein chip.

Stimulus-responsive non-ionic diblock copolymers: protonation of a tertiary amine end-group induces vesicle-to-worm or vesicle-to-sphere transitions

Morpholine-functionalised poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles are transformed into worms or spheres on lowering the solution pH.

Fine-Tuning of the Carbon Dioxide Capture Capability of Diamine-Grafted Metal-Organic Framework Adsorbents Through Amine Functionalization.

A combined sonication and microwave irradiation procedure provides the most effective functionalization of ethylenediamine (en) and branched primary diamines of 1-methylethylenediamine (men) and 1,1-dimethylethylenediamine (den) onto the open metal sites of Mg2 (dobpdc) (1). The CO2 capacities of the advanced adsorbents 1-en and 1-men under simulated flue gas conditions are 19 wt % and 17.4 wt %, respectively, which are the highest values reported among amine-functionalized metal-organic frameworks (MOFs) to date. Moreover, 1-den exhibits both a significant working capacity (12.2 wt %) and superb CO2 uptake (11 wt %) at 3 % CO2 . Additionally, this framework showcases the superior recyclability; ultrahigh stability after exposure to O2 , moisture, and SO2 ; and exceptional CO2 adsorption capacity under humid conditions, which are unprecedented among MOFs. We also elucidate that the performance of CO2 adsorption can be controlled by the structure of the diamine ligands grafted such as the number of amine end groups or the presence of side groups, which provides the first systematic and comprehensive demonstration of fine-tuning of CO2 uptake capability using different amines.

Solid Urea Sulfate Catalyst for Hydrolysis of Cellulose

A new treatment has been demonstrated for urea to synthesis solid-state form of urea sulfate onto silica extracted from rice husk ash via 3-(chloropropyl)triethoxysiline. The 3-(chloropropyl)triethoxysilane was immobilized onto silica at room temperature to functionalize the silica with chloride end groups. The chloride groups were reacted with urea by a nucleophilic substitution reaction. The resulting silica with urea (which had amine end groups) was sulfated with diluted sulfuric acid to produce a novel solid state form catalyst designated RHAUR-SO4H (RHA = rice husk ash). The XPS, EDX and CHNS analysis show that the expected elements were presents in RHAUR-SO4H. The FT-IR spectrum showed the presence of absorption bands attributed to the +NH3 and O=S=O ions groups which confirmed the results were coming from elemental analysis. The TGA\DSC analysis shows that the catalyst is stable at temperatures below 185 °C. Cellulose was hydrolyzed to glucose over RHAUR-SO4H in 2 h, and the glucose was hydrolyzed afterwards to other products within 7 h using a mixture of cyclohexanol\LiCl as a novel solvent system. The catalyst is reusable without a significant loss of catalytic activity.

The role of epoxy matrix occlusions within BaTiO3 nanoparticles on the dielectric properties of functionalized BaTiO3/epoxy nanocomposites

In this work, the effects of controlled nanoparticles aggregations of barium titanate (BaTiO3) on the dielectric properties of epoxy nanocomposites are investigated in detail with respect to different experimental parameters like frequency, ceramic content and temperature. Dispersing silanized BaTiO3 nanopowder under ultrasonic and stir, nanocomposites of epoxy-amine matrix with different morphologies are obtained. The nanoparticles silane functionalization containing amine end groups effectively improve the compatibility of the nano-BaTiO3 and the epoxy matrix. Storage modulus, glass transition temperature, tensile and flexural properties of nanocomposites and dielectric properties are increased until 10% by weight of nano-BaTiO3 loading, well dispersed in the matrix. Above 10wt.% of nano-BaTiO3, scanning electronic microscopy and thermal analysis showed that agglomeration of nanoparticles occurs. Rheological and mechanical nanocomposites properties were evaluated and matrix occlusion behaviors were identified. In light of the specific behavior of the occluded polymer, the dielectric properties, especially dielectric loss are discussed.

Synthesis and properties of allyl terminated renewable non-isocyanate polyurethanes (NIPUs) and polyureas (NIPUreas) and study of their photo-crosslinking

Allyl terminated renewable non-isocyanate polyurethanes (NIPUs) and polyureas (NIPUreas) were synthesized using the transurethanization approach. Dimethyl dicarbamate monomers were prepared by the reaction of a diamine with an excess of dimethyl carbonate (DMC). These monomers were reacted with an excess of a diamine to afford amine terminated polyureas. The amine end-groups were converted into allyl groups by reaction with 10-undecenoic acid. NIPUs were prepared by reaction of an excess of dimethyl dicarbamate monomers with a diol, affording methyl carbamate chain-ends, which were converted into ally groups by reaction with 9-decen-1-ol. All the chemical reactions were conducted under neat conditions, in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. The obtained materials exhibited Tg values varying from −44 to −35°C, Tm values varying from 29 to 201°C, and thermal stabilities above 200°C. The optimal conditions of photo-curing of the prepared materials were determined through a kinetic study of the reaction of the allyl end-groups, in the presence of benzophenone as photoinitiator.

Multidentate Polysarcosine-Based Ligands for Water-Soluble Quantum Dots

We describe the synthesis of heterotelechelic polysarcosine polymers and their use as multidentate ligands in the preparation of stable water-soluble quantum dots (QDs). Orthogonally functionalized polysarcosine with amine and dibenzocyclooctyl (DBCO) end groups is obtained by ring-opening polymerization of N-methylglycine N-carboxyanhydride with DBCO amine as initiator. In a first postpolymerization modification step, the future biological activity of the polymeric ligands is adjusted by modification of the amine terminus. Then, in a second postpolymerization modification step, azide functionalized di- and tridentate anchor compounds are introduced to the DBCO terminus of the polysarcosine via strain-promoted azide–alkyne cycloaddition (SPAAC). Through the separate synthesis of the anchor compounds, it is possible to ensure reproducible introduction of a well-defined number of multiple anchor groups to all polymers studied. Finally, the obtained multidentate polymeric ligands are successfully used in the...

Study of Oxovanadium Polymer Complexes Using Electron Paramagnetic Resonance

The complexes were prepared on the basis of polymer ligands with carboxylic and nitrogen-containing functionalities by complexation with VO2+ cations in aqueous solutions of VOSO4.5H2O. The degree of introduction of VO2+ ions into the polymer matrices depended on the kind of the functional groups in the polymers studied, such as polyacrylic acid, poly-4-vinylpyridine, poly(2-N,N-dimethylaminoethyl) methacrylate, poly(propylene imine) dendrimers such as D8[DAB-dendr-(NH2)8] and D32 [DAB-dendr-(NH2)32], with 8 and 32 primary amine end groups. It was found to be from 31.15 to 69.6 mg metal ions per gram of polymer carrier. An attempt was made to evaluate the structure of the VO2+-containing polymer complexes by electron paramagnetic resonance. The parameters of the electron paramagnetic resonance were determined (gII, g⊥; AII and A⊥) for the complexes studied. The anticipated coordination structure of the compounds was suggested.

Synthesis and photocrosslinking of disulfonated poly(arylene ether sulfone) copolymers for potential reverse osmosis membrane materials

Disulfonated poly(arylene ether sulfone) random copolymers with controlled oligomeric molecular weights were synthesized via nucleophilic aromatic substitution step polymerization. A monofunctional endcapping reagent, meta-aminophenol, was utilized to control the molecular weight of the oligomers and to install telechelic amine endgroups. The meta-aminophenol end-capped oligomers were reacted with acryloyl chloride to obtain novel crosslinkable poly(arylene ether sulfone) oligomers with acrylamide groups on both ends. The chemical compositions of the functional oligomers were characterized by 1H NMR spectroscopy to determine the degree of sulfonation and concentrations of acrylamide endgroups. The acrylamide-terminated oligomers were crosslinked with UV radiation in the presence of a multifunctional acrylate and a UV photoinitiator. Transparent, free-standing, dense films were obtained with high gel fractions. FTIR spectroscopy was utilized to observe the progress of the photo-crosslinking reaction. Thin films were cast from either aqueous or water-methanol solutions. The crosslinked disulfonated poly(arylene ether sulfone) networks exhibited reduced water uptake and swelling relative to their linear counterparts. SEM and AFM showed that the photo-crosslinked thin films had smooth surfaces.

Design and Development of Immunomodulatory Antigen Delivery Systems Based on Peptide/PEG-PLA Conjugate for Tuning Immunity.

Cancer vaccines are considered to be a promising tool for cancer immunotherapy. However, a well-designed cancer vaccine should combine a tumor-associated antigen (TAA) with the most effective immunomodulatory agents and/or delivery system to provoke intense immune responses against the TAA. In the present study, we introduced a new approach by conjugating the immunomodulatory molecule LD-indolicidin to the hydrophilic chain end of the polymeric emulsifier poly(ethylene glycol)-polylactide (PEG-PLA), allowing the molecule to be located close to the surface of the resulting emulsion. A peptide/polymer conjugate, named LD-indolicidin-PEG-PLA, was synthesized by conjugation of the amine end-group of LD-indolicidin to the N-hydroxysuccinimide-activated carboxyl end-group of PEG. As an adjuvant for cancer immunotherapeutic use, TAA vaccine candidate formulated with the LD-indolicidin-PEG-PLA-stabilized squalene-in-water emulsion could effectively help to elicit a T helper (Th)1-dominant antigen-specific immune response as well as antitumor ability, using ovalbumin (OVA) protein/EG7 cells as a TAA/tumor cell model. Taken together, these results open up a new approach to the development of immunomodulatory antigen delivery systems for vaccine adjuvants and cancer immunotherapy technologies.

Strong poly(ethylene oxide) based gel adhesives via oxime cross-linking

There is a demand for materials to replace or augment the use of sutures and staples in surgical procedures. Currently available commercial surgical adhesives provide either high bond strength with biological toxicity or polymer and protein-based products that are biologically acceptable (though with potential sensitizing potential) but have much reduced bond strength. It is desirable to provide novel biocompatible and biodegradable surgical adhesives/sealants capable of high strength with minimal immune or inflammatory response. In this work, we report the end group derivatization of 8-arm star PEOs with aldehyde and amine end groups. Gels were prepared employing the Schiff-base chemistry between the aldehydes and the amines. Gel setting times, swelling behavior and rheological characterization were carried out for these gels. The mechanical-viscoelastic properties were found to be directly proportional to the crosslinking density of the gels, the 10K PEO gel was stiffer in comparison to the 20K PEO gel. The adhesive properties of these gels were tested using porcine skin and showed excellent adhesion properties. Cytotoxicity studies were carried out for the individual gel components using two different methods: (a) Crystal Violet Staining assay (CVS assay) and (b) impedance and cell index measurement by the xCELLigence system at concentrations >5%. Gels prepared by mixing 20% w/w solutions were also tested for cytotoxicity. The results revealed that the individual gel components as well as the prepared gels and their leachables were non-cytotoxic at these concentrations. Statement of SignificanceThis work presents a new type of glue that is aimed at surgery applications using a water soluble star shaped polymer. It show excellent adhesion to skin and is tough and easy to use. We show that it is very biocompatible based on tests on live human cells, and could therefore in principle be used for internal surgery. Comparison with other reported and commercial glues shows that it is stronger than most, and does not swell in water to the same degree as many other water based bioadhesives.

The influence of amino group on PCDTBT-based and P3HT-based polymer solar cells: Hole trapping processes

Polymer solar cells (PSCs) based on aliphatic-amino-functionalized materials presented low performance with negligibly small efficiency, the prime mechanism of which is found to be hole trapping induced by the amine end groups. We propose that such hole trapping behavior depends on the relative energetic position of the hole transport states and the trapping states. Herein, we comparatively study the photovoltaic properties of PSCs based on amino-functionalized fullerene derivative blended with poly [N-9′-heptadecanyl-2, 7-carbazole-alt-5, 5-(4′, 7′-di-2-thienyl-2′, 1′, 3′-benzothiadiazole)] (PCDTBT) or poly (3-hexylthiophene) (P3HT). The former polymer has a lower-positioning highest occupied molecular orbital (HOMO) level, whereas the latter has a comparable HOMO level relative to the ionization state of tertiary aliphatic amine in energy. Our investigation confirms our proposition, revealing an ultrafast trapping process in PCDTBT:amino-group-functionalized fullerene derivative film, which seriously crippled hole transport, consequently results in very poor device performance. In contrast, trapping process is almost negligible in P3HT systems.

The Stability of Amino-Functionalized Polyhedral Oligomeric Silsesquioxanes in Water

Octa(aminopropylsilsesquioxane) Si8O12[(CH2)3NH2]8 is a very important precursor for many other hybrid organic/inorganic polyhedral oligomeric silsesquioxanes (POSS) because of the reactivity of its primary amine groups. Unfortunately, it is unstable in water, which can lead to the cleavage of its siloxane cage. In the present work, such a degradation was confirmed using solid-state (29)Si NMR spectroscopy, and the molecular features at the basis of this instability were studied using molecular dynamics simulations (MD). It was also investigated whether replacing the primary amine end groups by secondary amines or by amides with long aliphatic chains could lead to an improvement in the water stability of the Si/O framework. In the pure bulk models, all POSS interdigitate with their pendant organic arms intertwined. Upon insertion of isolated molecules into water, the dimensions of the primary amine POSS remain close to those of the bulk, while the secondary amine and the amide POSS favor conformations that optimize the intramolecular chain-chain interactions. When there are several POSS molecules in water, they cluster with each other through both intra- and intermolecular chain-chain interactions. This tendency for the organic chains to intertwine whenever possible provides some protection to the siloxane cages from water, but also leaves some of the siloxane O exposed. As such, the latter are accessible to form transient hydrogen bonds with the water molecules, which could be a precursor step to hydrolysis and thus cage breakage. In the molecular models, a better protection was obtained in the amide POSS for two reasons: its chains tended to wrap efficiently around its cage, and its ketone O kept water from getting close to the siloxanes. The molecular modeling characterizations were found to agree very well with experimental evidence.

Molecular weight distribution and endgroup functionality of poly(2-ethyl-2-oxazoline) prepolymers

Control over molecular weight distribution and endgroup functionality is important for prepolymers that are to be further incorporated into block and graft copolymers. Monofunctional, telechelic and heterobifunctional poly(2-ethyl-2-oxazoline) (PEtOx) oligomers were prepared by cationic ring-opening polymerization with different classes of initiators including methyl triflate as the control, activated benzyl and xylyl halides, and non-activated alkyl iodides. Endgroup functionalities and molecular weight distributions were compared by SEC, 1H NMR and titrations. PEtOx oligomers initiated with methyl triflate had polydispersities (PDI's) near 1.1 while those initiated with activated benzyl or xylyl halides had PDI's of 1.30–1.45. The difference was attributed to slower initiation and to covalent species in the activated halide-initiated reactions that were present in addition to the more active cations. 1H NMR showed an approximately 1:1 endgroup functionality in these cases and titrations of the amine endgroups were in good agreement with the NMR endgroup data. Due to the control of functionality and relatively good control over molecular weights and dispersities, it was concluded that these polymers should be suitable as prepolymers for membrane, hydrogel and drug delivery applications. Non-activated alkyl iodides initiated these reactions quite slowly and there was a wider discrepancy between targeted and obtained molecular weights after isolation of the oligomers.

Self-assembled polymeric micelles based on hyaluronic acid-g-poly(D,L-lactide-co-glycolide) copolymer for tumor targeting.

Graft copolymer composed hyaluronic acid (HA) and poly(d,l-lactide-co-glycolide) (PLGA) (HAgLG) was synthesized for antitumor targeting via CD44 receptor of tumor cells. The carboxylic end of PLGA was conjugated with hexamethylenediamine (HMDA) to have amine end group in the end of chain (PLGA-amine). PLGA-amine was coupled with carboxylic acid of HA. Self-assembled polymeric micelles of HAgLG have spherical morphologies and their sizes were around 50–200 nm. Doxorubicin (DOX)-incorporated polymeric micelles were prepared by dialysis procedure. DOX was released over 4 days and its release rate was accelerated by the tumoric enzyme hyaluronidase. To assess targetability of polymeric micelles, CD44-positive HepG2 cells were employed treated with fluorescein isothiocyanate (FITC)-labeled polymeric micelles. HepG2 cells strongly expressed green fluorescence at the cell membrane and cytosol. However, internalization of polymeric micelles were significantly decreased when free HA was pretreated to block the CD44 receptor. Furthermore, the CD44-specific anticancer activity of HAgLG polymeric micelles was confirmed using CD44-negative CT26 cells and CD44-positive HepG2 cells. These results indicated that polymeric micelles of HaLG polymeric micelles have targetability against CD44 receptor of tumor cells. We suggest HAgLG polymeric micelles as a promising candidate for specific drug targeting.

Separation and identification of an oligomeric light stabilizer Chimassorb 944 by gradient elution chromatography coupled with matrix-assisted laser desorption/ionization mass spectrometry

A non-aqueous reversed-phase high-performance liquid chromatographic (HPLC) method has been developed to separate a light stabilizer Chimassorb 944 into individual oligomers, which are further identified using pre-column fluorescent derivatization and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Consistent with previous studies, we find that the Chimassorb 944 product is a complex mixture consisting of a homologous series with the amine end groups and the number of repeat units (n) span from 1 to 26. In addition to the dominant linear species, cyclic oligomers are present at relatively high levels in the low-mass range. Their concentration decreases rapidly with the length of the oligomer backbone and becomes undetectable when n>7. Moreover, comparison of the HPLC and MALDI-MS molar mass distributions of Chimassorb 944 shows that the HPLC analysis produces greater molar mass averages and thus offers an effective means for accurate measure of the relative abundances of the oligomers.

Morphing hydrogel patterns by thermo-reversible fluorescence switching.

Stimuli responsive surfaces that show reversible fluorescence switching behavior in response to temperature changes were fabricated. Oligo(ethylene glycol) methacrylate thermoresponsive polymers with amine end-groups were prepared by atom transfer radical polymerization (ATRP). The polymers were patterned on silicon surfaces by electron beam (e-beam) lithography, followed by conjugation of self-quenching fluorophores. Fluorophore conjugated hydrogel thin films were bright when the gels were swollen; upon temperature-induced collapse of the gels, self-quenching of the fluorophores led to significant attenuation of fluorescence. Importantly, the fluorescence was regained when the temperature was cooled. The fluorescence switching behavior of the hydrogels for up to ten cycles was investigated and the swelling-collapse was verified by atomic force microscopy. Morphing surfaces that change shape several times upon increase in temperature were obtained by patterning multiple stimuli responsive polymers.

Binding of Functionalized Polymers to Surface-Attached Polymer Networks Containing Reactive Groups

To study diffusion and binding of polymers into surface-attached networks containing reactive groups, surface-attached polymer networks bound to oxidized silicon surfaces are generated, which contain succinimide ester groups. The surface-attached polymer layers are brought into contact with poly(ethylene glycol)s (PEG), which carry terminal amine end groups and which have systematically varied molecular weights. The coupling reaction between the active ester groups in the polymer networks and the amine groups in the incoming chains are studied by ellipsometry, surface plasmon spectroscopy, AFM, and Fourier transform infrared spectroscopy (FTIR). The degree of functionalization of the reactive layers by the PEG-NH2 depends strongly on the cross-link density of the network, the active ester content, and the molecular weight of the amine-terminated polymer. A model for the attachment reaction is proposed which suggests that the incoming polymer chains bind only at the outer periphery of the network in a narrow penetration zone. According to this model, when the incoming polymers are rather short, penetration into the layer and binding are prohibited by the high segment density and the anisotropic stretching of the surface-attached networks (“entropic shielding”). For incoming chains with a higher molecular weight and/or networks with a small mesh sizes, size exclusion effects determine diffusion and binding.

Noncovalent functionalization of multi-walled carbon nanotubes with pyrene-linked nylon66 for high performance nylon66/multi-walled carbon nanotube composites

A new interfacial agent, 1-pyrenebutyric chloride (PBC), was synthesized for use in nylon 66 (PA66)/multi-walled carbon nanotube (MWCNT) composites. It has been shown that the pyrene units in PBC adsorb onto the MWCNT surface by physisorption, and the acyl chloride units in PBC react with amine end groups in PA66 during melt extrusion. As a result, PBC that was covalently bonded with PA66 formed at the interface between the MWCNT and PA66 matrix. The PA66/MWCNT composite containing PBC exhibited the best interfacial adhesion between MWCNT and PA66 and the highest level of MWCNT dispersion in the PA66 matrix among the composites examined. It was also found that the PA66/MWCNT composite with the higher interfacial adhesion energy between PA66 and MWCNT exhibited a higher level of reinforcement.