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Poly(N-cyclopropylacrylamide) (p-PNCPA) has varied the dispersion state of single-walled carbon nanotubes (SWNTs) in water and it is a thermo-responsive polymer whose conformation has changed with temperature, leading to changes in the nanotube dispersion state. The drying of the p-PNCPA aqueous suspensions have produced composites whose microstructure and electrical conductivity have changed with drying temperature and the stimuli-controlled dispersion of carbon nanotubes have a variety of applications in nanoelectronics.

Synthesis of functional polyacrylates by 4-dimethylaminopyridine (DMAP) catalyzed trans-esterification of poly(pentafluorophenyl acrylate) (polyPFPA) is reported. High fidelity and versatility of this strategy was exemplified by near quantitative conversion with diverse functional alcohols (primary, secondary as well as phenolic) featuring reactive groups like alkene, alkyne or acrylate, enabling further sequential functionalization using click chemistry. Co-integrating an equimolar mixture of allyl and propargyl alcohol produced an orthogonally clickable copolymer by thiol-ene and 1,3-cycloaddition reaction. Base catalyzed ester exchange allowed installation of acid labile Boc-l-serine to create amino acid pendent polymer keeping both NH2- and COOH-group free, thereby providing a facile route toward zwitterionic polymers. Reaction with 2-dimethylaminoethanol conferred dual pH and CO2 responsive polymers from the same reactive precursor. The synthetic strategy was further extended to attach alcohols obtained from natural resources such as geraniol, l-lactic acid or sesamol to engineer new renewable polymers. Even a graft copolymer with very high (93%) grafting density could be achieved utilizing PEG350-OH. The trans-esterification was found to be highly selective for primary alcohols over secondary alcohols and also to the activated PFP-ester over a normal ester such as poly(methyl acrylate). Using such selectivity, fluorescently tagged polymer could be synthesized by replacing only the PFP-ester of a poly(methyl acrylate-co-PFPA) with 1-pyrenemethanol. Further, PFPA was polymerized with 2.0 mol % diacrylate to produce a cross-linked gel network. The PFP-ester groups of the cross-linked gel could be quantitatively replaced with Boc-l-serine, which upon deprotection of the Boc group resulted in a novel zwitterionic hydrogel exhibiting pH-dependent swelling properties. Time-dependent FTIR experiment suggested fast kinetics of the reaction, making this synthetic route practically applicable for postpolymerization modification. Mechanistic investigation exposed involvement of both DMAP and the nucleophilic solvent N,N-dimethylformamide (DMF) in catalyzing the reaction. This also explains the reason as to why near quantitative conversion was achieved in DMF and not in the non-nucleophilic solvent 1,4-dioxane. [ABSTRACT FROM AUTHOR]

RAFT polymerization of 4-acryloxyphenyldimethylsulfoniumtriflate (SR-AEM) using pentafluorophenyl-(4-phenylthiocarbonylthio-4-cyanovalerate)as the chain transfer agent and AIBN as a radical source in acetonitrileat 90 °C yielded poly(4-acryloxyphenyldimethylsulfonium triflate)(poly(SR-AEM))s in high yields with well-controlled molecular weightsand polydispersity indices. The reactive polymer poly(SR-AEM) wasconverted using an excess amount of amines, e.g., isopropylamine yieldingpredominantly poly(N-isopropylacrylamide) with defectsof poly(4-acryloxyphenyl methylsulfide) in a minor ration of lessthan 16%. Furthermore, poly(SR-AEM) could be converted by thermo-triggeredrelease of methyl group at dimethylsulfonium ion group to afford poly(4-acryloxyphenylmethylsulfide) (poly(APM)) as proved by 1H NMR measurements,which did not react with amines anymore. To the best of our knowledge,this represents the first temperature-induced “on–offswitching” of the reactivity of an activated ester by using4-dimethylsulfonim phenol as the stimuli-responsive leaving group. [ABSTRACT FROM AUTHOR]

Herein, the synthesis of polyethylene via an innovative post-polymerization modification (PPM) approach is reported. For this, a block copolymer of poly[ N -(acryloyloxy)phthalimide] (PAP) is synthesized by straightforward reversible addition-fragmentation chain-transfer (RAFT) polymerization using a dedicated macroRAFT transfer agent. Upon decarboxylation of the PAP block, followed by efficient block copolymer cleavage, a polyethylene homopolymer with a predictable degree of polymerization is obtained.

The active color-changing ability of many living species has inspired scientists to replicate the optical property into soft wet and tissue-like hydrogel materials. However, the color-changing processes of most reported examples are controlled by the traditional stimuli ( e.g. , pH, temperature, and ions), which may suffer from the residual chemical product accumulation, and have difficulty in achieving local control and integration into the commercial robots, especially when applied as biomimetic skins. Herein, inspired by the nervous (bioelectricity) control of skin color change in cephalopods, we present an electrically powered multicolor fluorescent hydrogel system with asymmetric configuration that couples thermoresponsive fluorescent hydrogel with stacked graphene assembly (SGA)-based conductive paper through luminous paint as the middle layer. Owing to the highly controllable electrical stimulus in terms of amplitude and duration, the Joule heat supplied by SGA film can be regulated locally and in real time, leading to precise and local emission color control at low voltage. It also avoids the addition of any chemicals. Furthermore, the electrically powered color-changing hydrogel system can be conveniently integrated into the commercial robots as biomimetic skins that help them achieve desirable camouflage, display, or alarming functions.

The development of complex topologies such as macromolecular cages constitutes a fascinating aspect of polymer chemistry. In the present work, a novel strategy involving self-closing bifunctional end-groups, which under specific conditions, are allowed to assemble themselves into a predefined thermodynamically favored macrostructure, was designed to fulfill the topological conversion of star -shaped polymers to their respective cage -shaped polymers. A series of four different well-defined four-arm star -shaped poly(ε-caprolactone) polymers varying in molar masses were successfully synthesized, end-functionalized, and closed into cage -shaped polymers by formation of [3 4 ]triazolophane macrocycle units. The obtained cage -shaped polymers feature interesting properties that depend drastically on the chain length of the arms and seem to differ from previous reported polymer cages.

CO 2 -responsive nanofibers were facilely prepared from photo-cross-linked poly(pentafluorophenyl acrylate) (PPFPA) nanofibers via "amine-active ester" chemical modification. Photo-cross-linked PPFPA nanofibers were modified with histamine under mild conditions to generate cross-linked poly(histamine acrylamide) (PHAAA) nanofibers featuring a CO 2 responsiveness. As expected, the prepared cross-linked PHAAA nanofibers can exhibit a CO 2 -responsive behavior to induce a reversible transition from hydrophobic to hydrophilic upon alternating addition and removal of CO 2 on the surface of nanofibrous membranes. Based on this finding, we could demonstrate that cross-linked PHAAA nanofibers can be employed for reversible absorption and release of protein using bovine serum albumin (BSA) as a model.

Directional dipole-dipole interaction mediated antiparallel dimerization of merocyanine dye (MD) has been explored for maneuvering supramolecular assembly of MD-conjugated flexible macromolecules leading to a cross-linked nanogel. The MD-functionalized copolymer was synthesized by a newly developed organocatalytic transesterification strategy for postpolymerization functionalization of poly(pentafluorophenyl acrylate) (polyPFPA)-based reactive copolymer. Presence of ∼35% pendant MD attached to a coil-like polymer chain leads to spontaneous formation of highly emitting cross-linked nanogel with efficient container property and appreciable stability in toluene owing to strong dimerization propensity among the MD. Considering the significance of MD in the context of nonlinear optics and photovoltaics, these results not only enrich the toolbox for engineering macromolecular assembly, but also open up new possibilities for future organic materials.

In this paper, a template-assisted replication method is demonstrated for the fabrication of hierarchically branched polymeric nanostructures composed of post-modifiable poly(pentafluorophenyl acrylate). Anodic aluminum oxide templates with various shapes of hierarchically branched pores are fabricated by an asymmetric two-step anodization process. The hierarchical polymeric nanostructures are obtained by infiltration of pentafluorophenyl acrylate with a cross-linker and photoinitiator, followed by polymerization and selective removal of the template. Furthermore, the nanostructures containing reactive pentafluorophenyl ester are modified with spiropyran amine via post-polymerization modification to fabricate ultraviolet-responsive nanostructures. This method can be readily extended to other amines and offers a generalized strategy for controlling functionality and wettability of surfaces.

Kabachnik-Fields reaction was employed as a new method for polycondensation. For this purpose, polymers were prepared from a mixture of dialdehydes, diamines, and phosphites. Variation of different starting monomers allowed the synthesis of polymers with tunable properties. It not only allowed the variation of glass transition temperatures but also enabled the synthesis of highly functional polymers including zwitterionic polymers. Further, photodegradable polymers have been realized by utilizing a photolabile dialdehyde monomer, which renders the obtained polymers highly interesting for numerous applications.

Highly ordered block copolymer thin films have been studied extensively during the last years because they afford versatile self-assembled morphologies via a bottom-up approach. They promise to be used in applications such as polymeric membranes or templates for nanostructured materials. Among the block copolymer structures, perpendicular cylinders have received strong attention due to their ability to fabricate highly ordered nanopores and nanowires. Nanopores can be created from a thin block copolymer film upon the removal of one block by selective etching or by dissolution of one polymer block. Here we demonstrate the utilization of polystyrene-block-poly(ethylene oxide) diblock copolymer (PS-hν-PEO) with an ortho-nitrobenzyl ester (ONB) as the photocleavable block-linker to create highly ordered thin films. Removal of the PEO block by choosing an appropriate solvent upon photocleavage is expected to yield arrays of nanopores decorated with functional groups, thus lending itself to adsorption or filtration uses. While the feasibility of this approach has been demonstrated, it is crucial to understand the influence of removal conditions (i.e., efficiency of photocleavage as well as best washing solvent) and to evaluate changes in the surface topology and inner structure upon photocleavage. To this end, the time dependence evolution of the surface morphology of block copolymer thin films was studied using grazing-incidence small-angle X-ray scattering (GISAXS) technique in combination with scanning probe microscopy.

Intrinsic self-healing soft materials such as hydrogels are especially promising for a variety of medical applications. Multistep preparation of starting functional polymer precursors and the expensive stock materials such as tetra-polyethylene glycol are one of the factors that limit the wider use of self-healing hydrogels. Herein, we reported a facile one-pot approach to prepare PEG based self-healing hydrogels from inexpensive commercially available components: polyethylene glycol diacrylate and dithiothreitol. For the first time, borax was used as the catalyst for a thiol-ene Michael-type polyaddition of PEG gels. Borax as the catalyst is quite efficient, allowing rapid gelation (from 40 s to 2 min) under ambient conditions and at room temperature. Essentially, as one catalyst, borax induces the formation of two classes of bonds, covalent thioether and transient boronate ester bonds, were formed at the same time. The storage modulus of the afforded PEG gel (87.5% water) reached up to 10 4 Pa, making the mechanical performance comparable with permanently cross-linked PEG gels. Additionally, the dynamic nature of the boronate ester linkages imparts the gel with self-healing properties, and the obtained gels can be healed within 30 min without external stimulus. Further, the transparent hydrogel is pH and thermal responsive. We believe that the manifold impacts of borax can open a new route to prepare hydrogels with intriguing properties, which find potential application as gel sealant, biosensors, or regenerative medicines.

Activated ester polymers, pioneered by Ferruti and Ringsdorf in the 1970s, are attractive polymeric materials because they can easily be converted into functional polymers by reacting with amine nucleophiles. In the present study, methyl salicylate acrylate, salicyl acrylate, and tert-butyl salicylate acrylate monomers were polymerized yielding three novel reactive precursors suitable for the postpolymerization modification with primary and secondary amines. The reactivities of poly(pentafluorophenyl acrylate), poly(methyl salicylate acrylic ester), and poly(salicyl acrylate) toward amines were compared by kinetic studies and revealed the practical applicability of salicylic acid based derivatives for efficient postpolymerization modifications. In addition, in vitro cytotoxicity of water-soluble leaving groups, pentafluorophenol and salicylic acid, as well as water-soluble polymers containing the respective activated ester groups were investigated using HeLa cells. In short, compared to the frequently used poly(pentafluorophenyl acrylate), poly(salicyl acrylate) activated ester feature a lower reactivity, but exhibit less cytotoxicity. In this respect, poly(salicyl acrylate) as reactive precursor polymers may become alternative routes for the synthesis of functional polyacrylamides when it comes to advanced applications in vivo.

A Kabachnik-Fields postpolymerization modification reaction (KF-PMR) was conducted on poly(4-vinyl benzaldehyde) (poly(St-CHO)) with amines and phosphites. Successful KF-PMR was demonstrated by precise structural analysis of the obtained polymers and kinetic investigation of the KF-PMR processes, making it a powerful tool for postpolymerization modifications that lead to α-amino phosphonates as side groups.

Polystyrene- block -poly(maleimide pentafluorophenyl ester- co -styrene)- block -poly(ethylene oxide) with an o -nitrobenzyl ester junction was synthesized by "one-step" RAFT polymerization. Highly ordered and locally reactive nanoporous thin films were obtained from the photocleavable triblock copolymer after spin coating, solvent annealing, UV exposure, and washing with methanol/water to remove the minor block PEO. The local reactivity in the thin films was demonstrated by fabrication of iron oxide nanotori after post-modification with an amino-functionalized ferrocene and treatment with oxygen plasma.

A Cu-catalyzed multi-component reaction (CuMCR) of terminal alkynes, sulfonyl azides, and amines was employed in a post-polymerization modification process. The reaction was conducted on polystyrene bearing 20 mol % alkyne groups with 4-toluenesulfonyl azide and dihexylamine in the presence of a Cu(PPh 3 ) 3 Br/diisopropylethylamine catalyst. The CuMCR on polymer proceeded efficiently, as confirmed by the obvious gas evolution during the reaction, and the conversion of alkyne moiety reached almost 100%, yielding polymeric N -sulfonylamidine derivatives, as proven by 1 H NMR measurements. In addition, the precise structural assignment was proven by synthesis and analysis of the model monomeric compound (styrene N -sulfonylamidine) and the respective model polymer. We have successfully demonstrated the utiliztation of this new post-modification reaction by employing various amines including dipeptide and 1-aza-15-crown-5-ether.

Scale formation, the deposition of certain minerals such as CaCO3, MgCO3, and CaSO4·2H2O in industrial facilities and household devices, leads to reduced efficiency or severe damage. Therefore, incrustation is a major problem in everyday life. In recent years, double hydrophilic block copolymers (DHBCs) have been the focus of interest in academia with regard to their antiscaling potential. In this work, we synthesized well-defined blocklike PAA-PAMPS copolymers consisting of acrylic acid (AA) and 2-acrylamido-2-methyl-propane sulfonate (AMPS) units in a one-step reaction by RAFT polymerization. The derived copolymers had dispersities of 1.3 and below. The copolymers have then been investigated in detail regarding their impact on the different stages of the crystallization process of CaCO3. Ca(2+) complexation, the first step of a precipitation process, and polyelectrolyte stability in aqueous solution have been investigated by potentiometric measurements, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). A weak Ca(2+) induced copolymer aggregation without concomitant precipitation was observed. Nucleation, early particle growth, and colloidal stability have been monitored in situ with DLS. The copolymers retard or even completely suppress nucleation, most probably by complexation of solution aggregates. In addition, they stabilize existing CaCO3 particles in the nanometer regime. In situ AFM was used as a tool to verify the coordination of the copolymer to the calcite (104) crystal surface and to estimate its potential as a growth inhibitor in a supersaturated CaCO3 environment. All investigated copolymers instantly stopped further crystal growth. The carboxylate richest copolymer as the most promising antiscaling candidate proved its enormous potential in scale inhibition as well in an industrial-filming test (Fresenius standard method).

In nature, mineralization of hard tissues occurs due to the synergistic effect of components present in the organic matrix of these tissues, with templating and catalytic effects. In Suberites domuncula, a well-studied example of the class of demosponges, silica formation is mediated and templated by an axial proteinaceous filament with silicatein-α, one of the main components. But so far, the effect of other organic constituents from the proteinaceous filament on the catalytic effect of silicatein-α has not been studied in detail. Here we describe the synthesis of core-shell TiO(2)@SiO(2) and TiO(2)@ZrO(2) nanofibers via grafting of silicatein-α onto a TiO(2) nanowire backbone followed by a coassembly of silintaphin-1 through its specifically interacting domains. We show for the first time a linker-free, one-step funtionalization of metal oxides with silicatein-α using glutamate tag. In the presence of silintaphin-1 silicatein-α facilitates the formation of a dense layer of SiO(2) or ZrO(2) on the TiO(2)@protein backbone template. The immobilization of silicatein-α onto TiO(2) probes was characterized by atomic force microscopy (AFM), optical light microscopy, and high-resolution transmission electron microscopy (HRTEM). The coassembly of silicatein-α and silintaphin-1 may contribute to biomimetic approaches that pursue a controlled formation of patterned biosilica-based biomaterials.

A poly(oligo(ethylene glycol) monomethyl ether methacrylate)-block-poly(N-isopropyl methacrylamide) (POEGMA-b-PNIPMAM) block copolymer with a biotin end group on the PNIPMAM block as a biotarget was synthesized as a model system for temperature-controlled polymer immobilization. The synthesis was based on RAFT polymerization followed by postpolymerization modification of an activated ester precursor block and an exchange of the dithioester end group within one step. NMR, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and turbidimetry measurements were performed to investigate the stimulus-responsive properties. The double thermoresponsive POEGMA-b-PNIPMAM with biotin end group showed a temperature-dependent multistage assembly behavior as it was completely soluble in water at temperatures below the LCST of both blocks, formed micellar structures above the LCST of PNIPMAM but below the LCST of POEGMA, or precipitated from solution above the LCST of both blocks. At room temperature, the polymer could be immobilized onto a streptavidin surface via its biotin end group, as shown in surface plasmon resonance (SPR) experiments. At 50 °C, at which the block copolymer formed micelles trapping the biotin target within the PNIPMAM core, no immobilization was observed, showing that the biological binding ability of the model could be controlled via external stimuli.

We describe the synthesis and characterization of a cross-linkable siloxane-derivatized tetraphenylbenzidine (DTMS-TPD), which was used for the fabrication of semiconducting highly ordered nanorod arrays on conductive indium tin oxide or Pt-coated substrates. The stepwise process allow fabricating of macroscopic areas of well-ordered free-standing nanorod arrays, which feature a high resistance against organic solvents, semiconducting properties and a good adhesion to the substrate. Thin films of the TPD derivate with good hole-conducting properties could be prepared by cross-linking and covalently attaching to hydroxylated substrates utilizing an initiator-free thermal curing at 160 degrees C. The nanorod arrays composed of cross-linked DTMS-TPD were fabricated by an anodic aluminum oxide (AAO) template approach. Furthermore, the nanorod arrays were investigated by a recently introduced method allowing to probe local conductivity on fragile structures. It revealed that more than 98% of the nanorods exhibit electrical conductance and consequently feature a good electrical contact to the substrate. The prepared nanorod arrays have the potential to find application in the fabrication of multilayered device architectures for building well-ordered bulk-heterojunction solar cells.

A gentle method that combines torsion mode topography imaging with conductive scanning force microscopy is presented. By applying an electrical bias voltage between tip and sample surface, changes in the local sample conductivity can be mapped. The topography and local conductivity variations on fragile free-standing nanopillar arrays were investigated. These samples were fabricated by an anodized aluminum oxide template process using a thermally cross-linked triphenylamine-derivate semiconductor. The nanoscale characterization method is shown to be nondestructive. Individual nanopillars were clearly resolved in topography and current images that were recorded simultaneously. Local current-voltage characteristics suggest a space-charge limited conduction in the semiconducting nanopillars.

We demonstrate that chemically stable, multifunctional polymer thin films can be obtained using the layer-by-layer (LbL) deposition based on covalent bonds between adsorbing chains. Poly(pentafluorophenyl-4-vinylbenzoate) (P1) or poly(pentafluorophenylacrylate) (P2) polymers were assembled with poly(allyl amine) (PAAm) to yield LbL multilayer films through amide bond formation by the reaction between activated esters of P1 or P2 and amine groups in PAAm, which was quantitatively monitored by Fourier transform infrared spectroscopy (FT-IR). It was found that the difference in the solubility of P1 and P2 against ethanol, which was used as the solvent for PAAm, during the LbL deposition yields different reaction conversion for the activated esters in either P1 or P2: the reaction conversion of P2 is higher than the conversion with P1. In addition, free (or unreacted) activated esters and amine groups remaining in the PAAm/P1 LbL film were further utilized for the incorporation of multiple functional materials (5-((2-aminoethyl)amino)naphthalene-1-sulfonic acid (EDANS) and Rhodamine B dyes in the present case) by post-treatments in order to further tailor the film properties. It was also demonstrated that the surface functional groups (activated esters) in the LbL films can also be utilized for surface patterning with one functional material, followed by functionalization with a second functional material during the post-treatment throughout the whole film. Finally, the PAAm/P1 and PAAm/P2 LbL films were shown to be quite stable in the extreme pH range, and free-standing films can easily be obtained by the treatment of the films with mild acidic conditions. The versatility of incorporating multiple functional materials into a single multilayer film as well as the excellent physicochemical stability of the covalently bonded multilayer free-standing films proves to be quite useful to design flexible and multifunctional thin film structures for many chemical and biological applications.

Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize poly[diethylene glycol monomethylether methacrylate] (PDEGMA) (M(n) = 6250 g/mol, PDI = 1.14) with a pentafluorophenyl (PFP) activated ester and a dithioester end group. The hormone thyroxin (T4) was quantitatively attached to the PFP activated ester alpha end group via its amino group. The omega-terminal dithioester was not harmed by this reaction and was subsequently aminolyzed in the presence of N-biotinylaminoethyl methanethiosulfonate, yielding a polymer with a thyroxin and a biotin end group with very high heterotelechelic functionality. The polymer was characterized by (1)H, (13)C, and (19)F NMR, UV-vis, and IR spectroscopy and gel permeation chromatography. The thyroxin transport protein prealbumin with two thyroxin binding sites and streptavidin, which has four biotin binding sites, was conjugated using the biotarget labeled polymer, resulting in the formation of a protein-polymer network, confirming the heterotelechelic nature of the polymer. Polymer-protein microgel formation was observed with dynamic light scattering. To realize a directed protein assembly, prealbumin was immobilized onto a surface, exposing one of its two thyroxin binding groups and thus allowing the conjugation with the thyroxin alpha end group of the heterotelechelic polymer. The biotin omega end group of the attached polymer layer enabled the subsequent immobilization of streptavidin, yielding a defined multilayer system of two proteins connected with the synthetic polymer (efficiency of streptavidin immobilization 81% based on prealbumin). Without the polymer, no streptavidin immobilization occurred. The layer depositions were monitored by surface plasmon resonance. The synthetic approach of combining PFP activated esters with functional MTS reagents presents a powerful method for obtaining well-defined heterotelechelic (bio-) functionalized polymers.

We have investigated a generally applicable protocol for a substrate-independent reactive polymer coating that offers interesting possibilities for further molecular tailoring via simple wet chemical derivatization reactions. Poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylate) hybrid polymers have been synthesized by RAFT polymerization, and stable reactive surface coatings have been prepared by spin-coating on the following substrates: Si, glass, gold, PMMA, PDMS, and steel. These coatings have been used for a defined adjustment of surface wettability by surface-analogous reaction with various amines (e.g., glutamic acid to obtain hydrophilic surfaces (Theta(a) = 18 degrees) or perfluorinated amines to obtain hydrophobic surfaces (Theta(a) = 138 degrees)). Besides the successful covalent attachment of small molecules and polymers, amino-functionalized nanoparticles could also be deposited on the surface, resulting in nanostructured coatings, thereby expanding the accessible contact angle of hydrophobic surfaces further to Theta(a) = 152 degrees. The surface-analogous conversion of the reactive coating with isopropyl amine produced in situ temperature-responsive coatings. Using the presented simple, generally applicable protocol for substrate-independent reactive polymer coatings, the contact angle of water could be switched reversibly by almost 60 degrees.