Reaction Of Poly Research Articles

A new type of raspberry-like polymer composite sub-microspheres with tunable gold nanoparticles coverage and their enhanced catalytic properties

A new type of gold nanoparticles-coated composite spheres with chemically reactive poly(glycidyl methacrylate) colloids as cores is synthesized in raspberry-like fashion via a controlled assembly method. The surface coverage of the immobilized gold nanoparticles, which is controlled by the surface charge density of the poly(allylamine hydrochloride)-modified polymer spheres and the conformation of the adsorbed polyelectrolyte chains on the spheres, can be tuned with polyelectrolyte concentration, ratio of polymer spheres to gold nanoparticles, and the pH value of the solution. A double-conformation poly(allylamine hydrochloride) film structure: inner collapsed and outer extended, is proposed to explain how the polyelectrolyte concentration, ratio of polymer spheres to gold nanoparticles, and the pH value of the solution affect the adsorption amount of the gold nanoparticles on the modified polymer spheres. The obtained composite particles are stable without loss of the gold nanoparticle coatings even after applying ultrasonication, cleaning or long term nanopure water storage. These composites exhibit an excellent catalytic activity with an average turnover frequency of 250.5 mol mol−1 s−1 and the fastest reported reduction of 4-nitrophenol with sodium borohydride is achieved within 76 s.

Electro-optical and Electrochemical Properties of Poly(N-Benzoyl-2-ethynylpyridinium tetraphenylborate)

A new conjugated ionic polyacetylene with bulky tetraphenylborate as counter ion was prepared by the ion-exchange reaction of poly(N-benzoyl-2-ethynylpyridium chloride) using sodium tetraphenylborate. Poly(N-benzoyl-2-ethynylpyridium chloride) was prepared in high yield by the activated polymerization of 2-ethynylpyridine with benzoyl chloride without any additional initiator or catalyst. Such instrumental methods as NMR, IR, and UV-visible spectroscopies revealed that the present polymer has a conjugated polymer backbone system having N-benzoylpyridinium tetraphenylborate as substituents. This polymer showed characteristic wide UV-visible absorption band and green PL maximum value at 620 nm, which is corresponding photon energy of 2.00 eV. The oxidation of polymer was slightly started at 0.05 V, where the vinylene unit of the conjugated polymer backbone could be oxidized in the scan and the redox process was irreversible. The kinetics of the redox process of polymer was controlled by the diffusion process.

Photopatterning Based on a Chemically Amplified Mechanism Nano-Sheet Films

In the paper, an approach for introducing a photoacid generator (PAG) into Langmuir- Blodgett (LB) films to draw photopatterns is described. The chemically amplified positive-tone resist system used here consisted of two components: a copolymer, poly(iso-pentylmethacrylamide- co-4-t-butyloxylvinylphenylcarbonate) [poly(iPMA-t-BVPC39)] and a photoacid generator (PAG), tri(2,3-dibrompropyl)iso-cyanvrate (TDBPIC). In the two-component system, the acid generated by the photoacid generator (PAG) catalyzes the deprotection reaction of poly(iPMA-t-BVPC39) to re- move the tert-butoxycarbonyl group (t-BOC) in the exposed region during the post exposure baking process, thus rendering the exposure region soluble to alkali aqueous to form a positive tone. Phhot- olithographic properties of the LB films have been evaluated. The patterns can be resolved with a resolution of 1 μm line width by UV irradiation,followed by development with an alkali solution. Quantum yield is determined to be 0.065 and catalytic chain length is also calculated to be 2460. The LB films used above can be used to generate etched gold patterns on a glass substrate using an aqueous iodide, ammonium iodide in alcohol /water，as the etchant. The etch resistance of such LB films is sufficiently good, allowing patterning of a gold film suitable for photomask fabrication.

The influence of biomimetic topographical features and the extracellular matrix peptide RGD on human corneal epithelial contact guidance

A major focus in the field of tissue engineering is the regulation of essential cell behaviors through biophysical and biochemical cues from the local extracellular environment. The impact of nanotopographical cues on human corneal epithelial cell (HCEC) contact guidance, proliferation, migration and adhesion have previously been demonstrated. In the current report we have expanded our study of HCEC responses to include both biophysical and controlled biochemical extracellular cues. By exploiting methods for the layer-by-layer coating of substrates with reactive poly(ethylene imine)/poly(2-vinyl-4,4-dimethylazlactone)-based multilayer thin films we have incorporated a single adhesion peptide motif, Arg–Gly–Asp (RGD), on topographically patterned substrates. This strategy eliminates protein adsorption onto the surface, thus decoupling the effects of the HCEC response to topographical cues from adsorbed proteins and soluble media proteins. The direction of cell alignment was dependent on the scale of the topographical cues and, to less of an extent, the culture medium. In EpiLife® medium cell alignment to unmodified-NOA81 topographical features, which allowed protein adsorption, differed significantly from cell alignment on RGD-modified features. These results demonstrate that the surface chemical composition significantly affects how HCECs respond to topographical cues. In summary, we have demonstrated modulation of the HCEC response to environmental cues through critical substrate and soluble parameters.

Explosion-like reactions in poly(vinyl chloride) on impact

To date, solving the issues of the safety of produc� tion and use of poly(vinyl chloride) [–CH2–CHCl–]n (PVC) has been limited to studying its flammability and combustibility, whereas the issue of the possibility of its explosive decomposition under mechanical actions has been sidestepped. Thermodynamically, as most of the saturated polymers of the vinyl series, PVC is a nonequilibrium system. Calculations show that, in particular, the decomposition of the PVC monomer to yield HCl + C + CH 4 + H 2 is accompanied by significant (80 kJ/mol) heat release. However, actually, primary reactions of ther� mal decomposition of PVC are endothermic and PVC is stable even at higher (>100°С) temperatures. We

A new single-ion polymer electrolyte based on polyvinyl alcohol for lithium ion batteries

In this study, a novel single-ion conducting polymer electrolyte, lithium polyvinyl alcohol oxalate borate (LiPVAOB), from the reaction of poly(vinyl alcohol) (PVA) with different molar ratio of boric acid, oxalic acid and lithium carbonate was prepared. The prepared materials were characterized by Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG), differential thermal analysis (DTA), electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry. Ionic conductivity of these polymer electrolytes from adding an assistant (about 20wt.% propylene carbonate) is dependent on molar ratio of the reactants and can up to 6.11×10−6Scm−1 at ambient temperature. Their electrochemical window can be stable up to 7V (vs. Li+/Li), which is of great attraction for high voltage lithium ion batteries with high energy density.

N-sulfonic acid poly(4-vinylpyridinium) chloride: an efficient and reusable solid acid catalyst in N-Boc protection of amines

N-sulfonic acid poly(4-vinylpyridinium) chloride is easily prepared by the reaction of poly(4-vinylpyridine) with neat chlorosulfonic acid. This reagent can be used as an efficient catalyst for the N-Boc protection of amines at room temperature and neat conditions. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be reused and recovered for several times.

Quantum Chemical Investigation of Secondary Reactions in Poly(vinyl chloride) Free‐Radical Polymerization

AbstractFree‐radical polymerization of vinyl chloride is investigated computationally with special attention to the secondary reactions involving mid‐chain radicals (MCRs). Namely, the rate constants of backbiting, chain scission, chain transfer, and propagation reactions are evaluated using a density functional theory method. The rate coefficients of such reactions are estimated taking into account the position of the radical along the chain as well as its distance from the chain‐end. In particular 1:5, 5:1, and 5:9 backbiting are the most relevant secondary reactions, followed by the slower propagation of MCRs. Finally, a kinetic model of suspension polymerization including the investigated reactions is developed, in order to determine their impact on the quality of the final polymer. magnified image

Synthesis and characterisation of sterically stabilised polypyrrole particles using a chemically reactive poly(vinyl amine)-based stabiliser

Poly(vinyl amine) (PVAm) was derivatised using 2-thiophenecarboxaldehyde via Michael addition to prepare a statistical copolymer stabiliser for the synthesis of primary amine-functionalised polypyrrole (PPy) particles. A minimum stabiliser concentration of around 20 % (w/v) relative to pyrrole was required for well-defined PPy particles of approximately 100–200 nm, as judged by transmission electron microscopy (TEM) and dynamic light scattering (DLS). FTIR spectroscopy confirmed that stabiliser grafting had occurred, while x-ray photoelectron spectroscopy (XPS) studies indicated a stabiliser surface coverage on the PPy particles of around 53 %. PPy particles prepared at stabiliser concentrations below 20 % (w/v) were not colloidally stable above pH 6. However, higher stabiliser concentrations (e.g., 50 % (w/v) based on pyrrole) led to a significant improvement, with colloidal stability being retained above pH 7. Long-term colloidal stability studies of PPy particles stored at pH 7.5 confirmed that the amine-based stabiliser produced more stable aqueous dispersions than the imine-based stabiliser, since the latter bond is hydrolytically unstable.

Reactive mono- and di-epoxy-functionalized poly(3-hydroxybutyrate)s. Synthesis and characterization

This work describes universal transformation method of low molar mass crotonate-terminated poly(3-hydroxybutyrate)s (PHB), obtained by anionic ROP of β-butyrolactone and controlled degradation of high-molar mass bacterial PHB, into mono- and di-epoxy-functionalized reactive poly(3-hydroxybutyrate)s via oxidation of crotonate end groups to α-3-methyloxirane-2-carboxylates, while carboxylate terminal groups were functionalized by simple alkylation with epibromohydrin. Combining these two methods resulted in telechelic structures: α-3-methyloxirane-2-carboxylate-ω-glicydyl PHB. Moreover, the reactivity of 3-methyloxirane groups of a functional aPHB, was confirmed in experiment with primary amine and primary alcohol, revealing very high yield in reaction with alcohol, while degradation of polymer backbone was noticed during reaction with amine.

Reactivity of Poly-, Di-, and monosaccharides in their hydrolysis in subcritical water

The reactivity of the water-soluble sodium salt of carboxymethyl cellulose (CMC), sucrose, glucose, and fructose in subcritical water at 120–320°C is reported. A mathematical model is suggested to describe the variation of the CMC molar mass during hydrolysis at various temperatures and reaction times. Kinetic parameters of the conversions of CMC, sucrose, glucose, and fructose in subcritical water are presented. High temperatures and short reaction times are favorable for the formation of monosaccharides from CMC.

Introduction of N-sulfonic acid poly(4-vinylpyridinum) chloride as an efficient and reusable catalyst for the chemoselective 1,1-diacetate protection and deprotection of aldehydes

N-sulfonic acid poly(4-vinylpyridinium) chloride is easily prepared by the reaction of poly(4-vinylpyridine) with neat chlorosulfonic acid. This reagent can be used as an efficient catalyst for the preparation of 1,1-diacetates at room temperature and neat condition. Deprotection of the resulting 1,1-diacetates can also be achieved using the same catalyst in methanol. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be reused and recovered for several times.

Effect of polymerization and preheating processes on poly(ethylene terephthalate) depolymerization

The depolymerization reaction of poly(ethylene terephthalate) (PET) was analyzed on the basis of experimental and numerical data obtained from molecular orbital calculations. Various types of PETs polymerized by different methods and preheated by microwave irradiation were used to investigate the depolymerization mechanism. The activation energies obtained from the optimized structures of the ground state and the transition state were compared with the experimental data. On the basis of these comparisons, it was found that not only the crystallinity but also configuration changes caused by preheating were essential for realizing a high rate of transesterification reactions, such as depolymerization. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrochemical sensing by surface-immobilized poly(ferrocenylsilane) grafts

Chemically modified electrodes, decorated with covalently tethered poly(ferrocenylsilane) – PFS chains, are fabricated. Robust, relatively dense redox-active films with a height of around 10 nm are successfully formed by reaction of poly(ferrocenyl(3-iodopropyl)methylsilane) with amine-terminated monolayers on silicon or gold surfaces. The electrochemical properties of the surface-immobilized PFS chains are studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), both in aqueous and organic media. Information on the properties of these films as a function of redox state is gained using quantitative adherence measurements between the films and AFM tips. An ascorbic acid electrochemical sensor based on these surface-anchored PFS chains, exhibiting a high sensitivity and stability, was fabricated. The PFS layers described are easily derivatized, thus forming a platform for creating highly tailorable redox-active interfaces.

Poly(dopamine acrylamide)-co-poly(propargyl acrylamide)-modified titanium surfaces for ‘click’ functionalization

Poly(dopamine acrylamide)-co-poly(propargyl acrylamide) (PDA-co-PPA) copolymers, containing alkyne- and catechol-functionalities, were prepared from reactive poly(pentafluorophenyl acrylate) (PPFA) via functionalization of the pentafluorophenyl-activated ester groups with dopamine hydrochloride and propargylamine. The bifunctional PDA-co-PPA copolymers were then coupled to the titanium (Ti) surface via coordination interaction of the catechol moieties, yielding a functionalizable Ti platform containing ‘clickable’ alkyne groups on the surface for the copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC) of azide-labeled fluorescein, rhodamine, β-cyclodextrin, poly(ethylene glycol) (PEG), mannose and biotin. The functionalized Ti surfaces from the CuAAC reactions were characterized by fluorescence microscopy (for the rhodamine- and fluorescein-functionalized Ti surfaces), non-specific protein adsorption (for the PEG-grafted Ti surface), specific protein adsorption (for the mannose- and biotin-functionalized Ti surfaces) and host–guest interaction with antibiotics (for the β-cyclodextrin-functionalized Ti surface).

Dynamic covalent polymer brushes: reversible surface modification of reactive polymer brushes with alkoxyamine-based dynamic covalent bonds

Reactive poly(methacrylate)-based polymer brushes with radically exchangeable alkoxyamine units in the side chains were prepared on flat silicon substrates and their reactivity and surface properties were investigated. The reactive polymer brushes were prepared by surface-initiated atom transfer radical polymerization (ATRP) and the graft density of the brushes was estimated to be approximately 0.36 chains per nm2. Radical crossover reactions among the alkoxyamine units in the side chains of the polymer brushes and at the ends of the fluorinated polymer chains were carried out to produce polymer brushes with low surface free energies. Angular-dependent X-ray photoelectron spectroscopy (XPS) measurement suggested that the fluorinated polymer chains were predominantly attached to the outermost surface because of the size exclusion from the high graft density. In addition, the de-grafting reaction of the fluorinated polymer chains was also performed to confirm the reversibility of the radical crossover reactions. The surface properties of the polymer brushes after the grafting and de-grafting processes were characterized by XPS and contact angle measurements. The composition calculated from the XPS indicated that the reversible grafting of the fluorinated polymer chains proceeded successfully. The surface wettability of the polymer brushes also changed after the grafting of the fluorinated polymers. Furthermore, after the de-grafting of the fluorinated polymer chains, the peaks attributed to fluorine atoms completely disappeared from the XPS spectrum and the wettability of the surface after the de-grafting returned to that obtained before grafting.

Reactive triblock polymers from tandem ring-opening polymerization for nanostructured vinyl thermosets

Multiply functional hydroxyl telechelic poly(cyclooctene-s-5-norbornene-2-methylene methacrylate) was synthesized by ring opening metathesis (co)polymerization of cis-cyclooctene and 5-norbornene-2-methylene methacrylate using the second generation Grubbs catalyst in combination with a symmetric chain transfer agent bearing hydroxyl functionality. The resulting hydroxyl-telechelic polymer was used as a macroinitiator for the ring opening transesterification polymerization of d,l-lactide to form reactive poly(lactide)-b-poly(cyclooctene-s-5-norbornene-2-methylene methacrylate)-b-poly(lactide) triblock polymers. Subsequently, the triblocks were crosslinked by free radical copolymerization with several vinyl monomers including styrene, divinylbenzene, methyl methacrylate, and ethyleneglycol dimethacrylate. Certain conditions led to optically transparent thermosets with mesoscale phase separation as evidenced by small angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. Disordered, bicontinuous structures with nanoscopic domains were generated in several cases, rendering the samples attractive for size-selective membrane applications.

Tunable Morphologies From Bulk Self‐Assemblies of Poly(acryloxypropyl triethoxysilane)‐b‐poly(styrene)‐b‐poly(acryloxypropyl triethoxysilane) Triblock Copolymers

AbstractReactive poly(acryloxypropyl triethoxysilane)‐b‐poly(styrene)‐b‐poly(acryloxypropyl triethoxysilane) (PAPTES‐b‐PS‐b‐PAPTES) triblock copolymers are prepared through nitroxide‐mediated polymerization (NMP). The bulk morphologies formed by this class of copolymers cast into films are examined by small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). The films morphology can be tuned from spherical structures to lamellar structures by increasing the volume fraction of PS in the copolymer. Thermal annealing at temperatures above 100 °C provides sufficient PS mobility to improve ordering.

Nanostructured Membranes for Enzyme Catalysis and Green Synthesis of Nanoparticles

Macroporous membranes functionalized with ionizable macromolecules provide promising applications in high capacity toxic metal capture, nanoparticle syntheses, and catalysis. Our low-pressure membrane approach has good reaction and separation selectivities, which are tunable by varying pH, ionic strength, or pressure. The sustainable green chemistry approach under ambient conditions and the evaluation of a reactive poly(acrylic acid) (PAA)-modified polyvinylidene fluoride (PVDF) membrane is described. Two distinct membrane types were obtained through different methods: 1) a stacked membrane through layer-by-layer assembly for the incorporation of enzymes (catalase and glucose oxidase), providing tunable product yields and 2) Fe/Pd nanoparticles for degradation of pollutants, obtained through an in situ green synthesis. Bioreactor-nanodomain interactions and mixed matrix nanocomposite membranes provide remarkable versatility compared to conventional membranes.

Effect of reactive poly(ethylene glycol) flexible chains on curing kinetics and impact properties of bisphenol‐a glycidyl ether epoxy

AbstractBisphenol‐A glycidyl ether epoxy resin was modified using reactive poly(ethylene glycol) (PEO). Dynamic mechanical analysis showed that introducing PEO chains into the structure of the epoxy resin increased the mobility of the molecular segments of the epoxy network. Impact strength was improved with the addition of PEO at both room (RT) and cryogenic (CT, 77 K) temperature. The curing kinetics of the modified epoxy resin with polyoxypropylene diamines was examined by differential scanning calorimetry (DSC). Curing kinetic parameters were determined from nonisothermal DSC curves. Kinetic analysis suggested that the two‐parameter autocatalytic model suitably describes the kinetics of the curing reaction. Increasing the reactive PEO content decreased the heat flow of curing with little effect on activation energy (Ea), pre‐exponential factor (A), or reaction order (m and n). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012