Search results for " solution"

A distorted honeycomb motif in divalent transition metal compounds based on 4-phosphonbenzoic acid and exchange coupled Co(II) and Cu(II): synthesis,…

2013

The first example of a two-dimensional inorganic hybrid material with cobalt as an open-shell transition metal ion and 4-phosphonbenzoic acid as a linker is presented together with its copper analogue. For both metal ions the inorganic part consists of edge-sharing metal–oxygen octahedra leading to a metal honeycomb motif. The magnetic properties of the cobalt compound are reported together with those of the corresponding copper compound based on the remarkably six-coordinated copper(II) ions.

MODIFICATION OF HUMIC SUBSTANCES FOR DEVELOPMENT OF MATERIALS FOR ENVIRONMENTAL TECHNOLOGIES

2019

Humic substances are high molecular weight refractory polycationites formed during decay of living organic matter and through biosynthesis of low molecular weight organic substances (metabolites or decay products of living organisms). Presence of many functional groups in the structure of humic substances determines their ability to interact with metal ions forming stable complexes and influencing metal ion speciation in the environment and mobility, behaviour and speciation forms in the environment. Presently humic substances are a product of industrial scale and quantities in amounts of hundreds of tons are produced. The aim of this study is to analyse derivatization possibilities of humi…

Volumes and heat capacities of the aqueous sodium dodecanoate/sodium perfluorooctanoate mixtures in the presence of β-cyclodextrin

2003

Apparent molar volumes (VΦ) and heat capacities (CΦ) of the sodium dodecanoate (NaL)/sodium perfluorooctanoate (NaPFO) mixtures in the water/β-cyclodextrin (β-CD) solvent as functions of the surfactant total molality (mt) were determined at 25°C. For a given surfactant mixture, VΦ decreases with mt to ca. 0.05 mol kg−1 thereafter it increases tending to a constant value. CΦ displays a behaviour opposite to VΦ. The mt values where the apparent molar properties exhibit extrema are nearly coincident with the critical micellar concentrations determined by conductivity. An equation correlating VΦ to mt was derived by assuming that the equilibria for the 1∶1 surfactant/cyclodextrin complex format…

Polyelectrolytes in dilute solution: viscometric access to coil dimensions and salt effects

2015

Copolymers of acrylamide (AM) and diallyldimethylammonium chloride (DADMAC), differing in molar masses M (52.3 to 227 kDa) and degrees of charging y (0.2 to 0.6), were studied with respect to their viscometric behavior in dilute aqueous solutions containing variable amounts of NaCl. Complementary measurements were performed on a Brookhaven 90 plus particle size analyzer. M dominates the intrinsic viscosities [η]. For the viscometric interaction parameters B this is only true for large concentrations of extra salt. [η] and B as a function of solvent salinity follow Boltzmann laws. Coil dimensions, determined either via dynamic light scattering or viscometry, agree well. For low salt contents…

Consequences of linking charged and uncharged monomers to binary copolymers studied in dilute solution. Part I: Viscometric behavior of the homopolym…

2017

Abstract Intrinsic viscosities, generalized intrinsic viscosities and viscometric interaction parameters were measured for aqueous solutions of poly(ethylene oxide) [PEO], poly(N,N-dimethyl aminoethyl methacrylate) [PR] (uncharged) and for poly{[2-(methacryloyloxy)ethyl] trimethylammonium iodide} [PR+] (charged) within a wide range of molar masses. In this manner it was possible to establish the information required for the study of non-additivity effects upon the formation of binary copolymers from the monomers specified above. The following additional items were of particular interest: The effects of charging PR to PR+ and the composition dependence of the coil overlap in the case of sali…

Intrinsic Viscosities of Polymer Blends: Sensitive Probes of Specific Interactions between the Counterions of Polyelectrolytes and Uncharged Macromol…

2018

In joint dilute aqueous solutions of pullulan (PUL) and poly(sodium 4-styrenesulfonate) (PSS-Na) the Na+ ions of the polyelectrolyte interact so favorably with the monomeric units of PUL that isolated coils containing both types of macromolecules are formed upon dilution. When water is replaced against a 1 M solution of NaCl, this effect dies out because of the large surplus of Na+ ions. On the other hand, if the water contains increasing amounts of the respective counterpolymer instead of NaCl, the formation of mixed isolated coils is fostered, where a further diminution of the intrinsic viscosities is caused by the lower the solvent quality. The molar mass of PSS-Na plays an important rol…

Polymer-polymer interaction, in the presence of a solvent as measured by viscometry

2001

Dilute solution viscometry experiments have been carried out in five ternary polymer systems solvent(1)/polymer(2)/polymer(3). Values of the specific viscosity of polymer (3) in a ‘binary solvent’ formed by polymer(2) + solvent(1) have been used to determine the compatibility of the polymer blends. Krigbaum and Wall formalism has been used to predict compatibility which relies on an interaction parameter that depends on the concentration, weight fraction and molar mass of each polymer. To reduce the dependences and to clarify the criterion of compatibility, a parameter independent of polymer (3) composition and molar mass has been deduced. This parameter shows the same behaviour with polyme…

2017

Abstract In this study, an adsorption-oriented process for the removal of fungicides from polycontaminated aqueous solutions was applied. To remove triazole fungicides from aqueous mixtures of propiconazole (PROPI), tebuconazole (TEBU), epoxiconazole (EPOXI), bromuconazole (BROMU) and difenoconazole (DIFENO), several materials used as adsorbents were compared using batch experiments, namely two conventional activated carbons (ACs) and five nonconventional cross-linked cyclodextrin (CD)-based materials (α-CDP, β-CDP, γ-CDP, αβγ-CDP mixture, and hydroxypropyl-β-CDP). This article presents the abatements obtained. As expected, ACs exhibited the highest levels of triazole fungicide removal: the…

Nanotube Friendly Poly(N-isopropylacrylamide).

2010

Poly(N-ispropylacrylamide) [PNIPAM] is a widely studied polymer for use in biological applications due to its lower critical solution temperature (LCST) being so close to the human body temperature. Unfortunately, attempts to combine carbon nanotubes (CNTs) with PNIPAM have been unsuccessful due to poor interactions between these two materials. In this work, a PNIPAM copolymer with 1 mol-% pyrene side group [p-PNIPAM] was used to produce a thermoresponsive polymer capable of stabilizing both single and multi-walled carbon nanotubes (MWNTs) in water. The presence of pyrene in the polymer chain lowers the LCST less than 4 °C and the interaction with nanotubes does not show any influence on LC…

Tailoring Properties of Carbon Nanotube Dispersions and Nanocomposites Using Temperature-Responsive Copolymers of Pyrene-Modified Poly(N-cyclopropyla…

2010

Despite their immense potential, the ability to control the dispersion and microstructure of carbon nanotubes remains a hurdle for their widespread use. Stimuli-responsive polymers show conformational changes with an applied external stimulus (pH, temperature, light, etc.). The dispersion of carbon nanotubes by thermoresponsive polymers is shown to enable the macroscopic properties of aqueous suspensions to be tailored as a function of temperature. This work presents the synthesis, characterization, and use of temperature-responsive poly(N-cyclopropylacrylamide) (PNCPA) polymers containing 1, 3, and 5 mol % pyrene-bearing repeat units to tailor the dispersion state of single-walled carbon n…