Binding of chlorpheniramine maleate to pharmacologically important alginic acid,carboxymethylcellulose, κ‐carageenan,and ι‐carrageenan as studied by diafiltration

The binding of cationic chlorpheniramine maleate (CPM) to the anionic water‐soluble polymers (WSPs) alginic acid, carboxymethylcellulose, κ‐carageenan, and ι‐carageenan was evaluated by diafiltration at pH 7.5 and in the absence and presence of 0.13M NaCl. CPM interacted with all of the WSPs when no NaCl was present in the solution, with charge‐related formation constants of around 700 M^?1 for all of the polymers, whereas the interactions were cleaved in the presence of 0.13M NaCl, indicating interactions of an electrostatic nature screened by the single electrolyte. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 598–602, 2005     

Natural microshells of alginate-chitosan: Unexpected stability and permeability

We utilized alginate sodium (ALG) and chitosan (CHI) as wall components to construct a natural and biodegradable polyelectrolyte microshell by the electrostatic self-assembly technique. The resultant ALG-CHI shells were found to maintain intact spherical shape in different poly(styrenesulfonate sodium) (PSS) bulk concentrations (maximal detection concentration 20.0 wt%). Compared with the shells composed of PSS and poly(allylamine hydrochloride) (PAH) that collapse or deform at a 4 wt% or more than 4 wt% PSS concentration, the ALG-CHI shells display higher stability. Meanwhile, the permeability of the ALG-CHI shells prior to and after incubation in PSS solutions was directly traced by the fluorescence recovery after photobleaching (FRAP). The composition of the ALG-CHI shells themselves is thought to be responsible for the differences in the stability.     

Hydrogels of polyvinylpyrrolidone (PVP) and poly(acrylic acid) (PAA) synthesized by photoinduced crosslinking of homopolymers

A novel method of covalent crosslinking between polyvinylpyrrolidone (PVP) and poly(acrylic acid) (PAA) resulting in hydrogels has been developed. The hydrogels were formed by photocrosslinking in oxygen-free aqueous solutions containing hydrogen peroxide as a source of hydroxyl radicals. The crosslinking was achieved via irradiation within the broad wavelength range from 200 to 800 nm, as well as by the light cut-off at λ > 300 nm. The obtained PAA-PVP gels were sensitive to pH. Protonation of the PAA carboxylic groups with decreasing pH promoted hydrogen bonding between the PAA and PVP segments within the crosslinked structure and caused the gel to collapse. This property enabled the use of the hydrogels as a simple chemical sensor. When loaded with glucose oxidase, the PAA-PVP gel's opacity and sedimentation due to the clearly observable phase separation were triggered by the presence of glucose due to a drop in pH caused by the enzymatic reaction.     

A study of blending and complexation of poly(acrylic acid)/poly(vinyl pyrrolidone)

Poly(acrylic acid) (PAA) and poly(vinyl pyrrolidone) (PVP) were chosen to prepare polymer complex and blends. The complex was prepared from ethanol solution and the blends were prepared from 1-methyl-2-pyrrolidone solution. DSC results show that the T_gs of the PAA/PVP blends lie between those of the two constituent polymers, whereas T_g of the PAA/PVP complex is higher than both blends and the two constituent polymers. TGA results show that degradation temperature, T_d, of PAA increases upon adding PVP in the blend, but thermal stability of the complex is higher than that of the blends as reflected by the higher T_d. Both FTIR and high-resolution solid state NMR show strong hydrogen bonding between PAA and PVP by showing significant chemical shift. The T_1ρ(H) measurement shows that the homogeneity scale for the blend is at ∼20 Å and that for the complex is ∼15 Å.     

Polyelectrolyte-functionalized multiwalled carbon nanotubes: preparation, characterization and layer-by-layer self-assembly

Two kinds of polyelectrolyte: polyacrylic acid (PAA) and poly(sodium 4-styrenesulfonate) (PSS), were grafted onto the convex surfaces of multiwalled carbon nanotubes (MWNTs) by surface-initiating ATRP (atom transfer radical polymerization) from the initiating sites previously anchored onto the convex surfaces of MWNTs. The grafted polyelectrolyte can be efficiently quantified by the feed ratio of monomer to MWNT-based macroinitiator, and the maximum amount of grafted polymer is higher than 55 wt%. The polyelectrolyte-coated MWNTs resembled core-shell structures justified by the TEM images of the samples obtained, which provided direct evidence for the covalent modification of MWNT. FTIR, ¹H NMR and TGA were used to determine the chemical structure of the resulting products. Comparison of UV-Vis spectra demonstrated that the products were water-soluble, and that PSS was more effective for improving the water solubility of carbon nanotubes. Using the polyelectrolyte- and carboxylic acid-functionalized MWNTs as templates, and poly(2-(N,N-dimethylaminoethyl) methacrylate (PDMAEMA)/hyperbranched polysulfone amine (HPSA) and PSS as polycation and polyanion, respectively, layer-by-layer (LbL) electrostatic self-assembly was conducted in order to explore the application of the functionalized nanotubes. It was found that the functionalized MWNTs have a high efficiency for loading polyelectrolytes by the LbL approach (the adsorbed polymer quantity is higher than 10 wt% in one assembling step). TEM observations showed that the assembled polymer shell on the MWNT surfaces was very even and flat.     

Electric dichroism studies of the bonding of Co(III) chelate with synthetic polyelectrolytes

The interactions of bis-2-(2-pyridylazo)-1-naphthol Co(III), [Co(III) (αPAN)₂⁺], with five kinds of synthetic polyelectrolytes have been studied by spectrophotometric and transient electric dichroism measurements. The polyelectrolytes were: poly(styrene sulphonic acid) (PSS); poly(acrylic acid) (PAA); poly(l-glutamic acid) (PLG); $\text{poly}\text{(N}{}^{\mathrm{<mtext>e</mtext>}}\text{,N}{}^{\mathrm{<mtext>e</mtext>}}\text{-}\text{dicarboxylmethyl-}\text{l}\text{-lysine}$ (PDCML); and poly(l-lysine) (PLL). The equilibrium constant of the reaction:

with P = polyelectrolyte residue was determined spectrophotometrically: K₁ is > 10⁷ M^?1 (PSS); (1.4 ± 0.2) × 10⁴ M^?1 (PAA); (4.0 ± 0.4) × 10³ M^?1 (PLG); (1.4 ± 0.2) × 10⁶ M^?1 (PDCML); and < 10² M^?1 (PLL) at pH 6–8. From transient electric dichroism, the angle (ψ) between the αPAN plane and the polymer axis was determined to be 65° (PSS); 52° (PAA); 55° (PLG); and 52° (PDCML). The large K₁ and ψ values for PSS are ascribed to the hydrophobic interaction between the aromatic αPAN ring and the styrene sulphonate residues of PSS. Using stopped-flow electric dichroism measurements, rapid transfer of a bound Co(III) chelate from the PDCML to PSS chains was shown to occur.     

Interactions of polyelectrolytes bearing carboxylate and/or sulfonate groups with Cu(II) and Ni(II)

The interactions between the water-soluble polyelectrolytes poly(acrylic acid) (PAA) and poly(vinyl sulfonic acid) (PVS), and Cu(II) and Ni(II) are studied by the liquid-phase polymer-based retention (LPR) technique. Assuming a Ni(II)-PVS interaction of electrostatic nature, the nature of the Ni(II)-PAA interaction is found to be electrostatic, while Cu(II)-PAA interactions imply the formation of coordinative bonds. The charge related formation constants for the systems Ni(II)-PAA, Ni(II)-PVS, and Cu(II)-PVS are found to be 57.57×10², 43.4×10², and 60.5×102 M⁻¹, respectively in a 0.010 M NaNO₃ aqueous solution at pH 5, and 1.4×10² for both systems containing Ni(II) and 1.3×10² M⁻¹ for the system Cu(II)-PVS in a 0.10 M NaNO₃ aqueous solution at pH 5.     

Hydrogen bonding interactions and miscibility studies of poly(amide)/poly(vinyl pyrrolidone) blends containing mangiferin

Miscibility studies of amorphous poly(amide)/poly(vinyl pyrrolidone) (PA/PVP) blends containing a crystalline phytochemical called “mangiferin” have been carried out using differential scanning calorimetry, Fourier transformed infrared spectroscopy and polarized optical microscopy. The binary blends of PA/PVP prepared from dimethylsulfoxide solutions were found to be completely miscible showing a systematic movement of a single glass transition temperature over the entire composition range. The FTIR study indicated the occurrence of cross-hydrogen bonding interactions between PA and PVP, which may be responsible for complete miscibility of the PA/PVP pair. Moreover, cross-hydrogen bonding promotes miscibility in binary blends of PA/mangiferin and PVP/mangiferin. However, the addition of mangiferin to PA/PVP blends has resulted in liquid-liquid phase separation between PA/mangiferin and PVP/mangiferin phases due to the preferential affinity of mangiferin to PVP than to PA. With increasing mangiferin concentration, liquid-liquid phase segregations occur between PA + mangiferin and PVP + mangiferin phases in addition to the solid-liquid phase transition of mangiferin crystals. Lastly, a ternary morphology phase diagram of the PA/PVP/mangiferin blends was established, which exhibited various coexistence regions such as isotropic, liquid + liquid, liquid + crystal, liquid + liquid + crystal, and solid crystal regions.     

Novel micelle-forming block copolymer composed of poly (ε-caprolactone) and poly(vinyl pyrrolidone)

The well-defined poly (ε-caprolactone) (PCL)/poly(vinyl pyrrolidone) (PVP) diblock copolymers were synthesized through combining radical polymerization of VP and the controlled coordination-insertion ring-opening polymerization of CL using an aluminum alkoxide macroinitiator formed from the equimolar reaction of triethylaluminum with hydroxy-terminated PVP (PVP-OH). The molecular characterization of PCL/PVP diblock copolymers was confirmed through ¹H NMR spectroscopy and GPC analysis. Polymeric micelles composed of PCL as a hydrophobic core and PVP as a hydrophilic shell were prepared by a diafiltration method. The micellar properties such as sizes, shapes, and critical micelle concentrations (CMC) were investigated with a dynamic light scattering (DLS) spectrometer, transmission electron microscope (TEM) and spectrofluorimeter. The sizes of micelles ranged from 30 to 80 nm in average size. The novel micelles formed from the well-defined PCL/PVP diblock copolymers seem to be feasible as novel promising carriers in biomedical and pharmaceutical applications.     

Tuning the pKa of the antihistaminic drug chlorpheniramine maleate by supramolecular interactions with water-soluble polymers

The interaction of the pharmacologically important chlorpheniramine maleate (CPM) with polyanions containing sulfonate groups such as poly(sodium 4-styrenesulfonate) (PSS), poly(sodium vinylsulfonate) (PVS), and the more hydrophobic poly(sodium 2-(N-acrylamido)-2-methyl-propanesulfonate) (PAMPS) has been studied by ¹H NMR. It was found that the pK_a of the low-molecular weight molecule (LMWM) may be modified by its interaction with the polyanions, changing from 3 to 5, due to electric charge compensation. Interestingly, the interaction of CPM with PSS produces changes in CPM resonances, such as a general broadening and upfield shifts of the signals, and NOE effects between the LMWM and the water-soluble polymer (WSP) that indicate the presence of π-π interactions.     

Synthesis and characterization of pH-sensitivity semi-IPN hydrogel based on hydrogen bond between poly(N-vinylpyrrolidone) and poly(acrylic acid)

A novel spherically shaped semi-interpenetrating network (semi-IPN) hydrogel, which is based on hydrogen bond between chemical crosslinked poly(N-vinylpyrrolidone) (PVP) and linear poly(acrylic acid) (PAA), was prepared. The semi-IPN hydrogel was synthesized by three steps: (1) linear PAA with different molecular weights were obtained by a reaction of free radical polymerization used 2,2′-azo-bis-iso-butyronitrile (AIBN) as an initiator; (2) crosslinked PVP bead was obtained by a reaction of N-vinylpyrrolidone with AIBN used as an initiator and N,N′-methylene-bis-acrylamide (NNMBA) used as a crosslinker by the way of suspension polymerization; (3) complexation occurred between suitable amount of aqueous solution of PAA and the porous PVP bead and was stabilized by multiple frost-defrost, from this step the semi-IPN hydrogel was obtained. Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) proved the presence of the hydrogen bond in the hydrogel. The swelling behaviour of the hydrogel was studied in buffer solution with different pH and NaCl aqueous solution. The results showed that the semi-IPN hydrogel had excellent pH-sensitivity in the range of pH from 2.25 to 4.00 and the small molecule salt had little influence on the swelling behaviour of the semi-IPN hydrogel over the range of concentration of NaCl aqueous solution investigated. The results were confirmed further by scanning electron microscope (SEM). The mechanism of swelling and deswelling was discussed.     

Stability constants and thermodynamic parameters of some intermacromolecular complexes in relation to their specific interaction forces

Summary Intermacromolecular complexes of poly (acrylic acid) (PAA) with poly (ethylene oxide) (PEO), poly (ethylene imine) (PEI) and poly (vinyl pyrrolidon) (PVP) were prepared. The stability constants and thermodynamic parameters (e.g. ΔH⁰ and ΔS⁰) of these complexes were determined at several temperatures. The enthalpy and entropy changes of the systems with temperature have been interpreted in terms of various mode of interaction between the components and compared with each other.     

Efficient white polymer-light-emitting-diodes based on polyfluorene end-capped with yellowish-green fluorescent dye and blended with a red phosphorescent iridium complex

A novel series of blue and yellowish-green light-emitting single polymers were prepared by end-capping of low contents of 4-bromo-7H-benzo [de]naphtha[2′,3′:4,5]imidazo[2,1-a]isoquinolin-7-one (M1) into polyfluorene. Electroluminescence (EL) spectra of these polymers exhibit blue emission (λ_max = 430/460 nm) from the fluorene segments and yellowish-green emission (λ_max = 510/530 nm) from the M1 units. For the polymer (PFNAP-0.06) with the M1 unit content of 0.06 mol-%, its EL spectrum shows balanced intensities of blue emission and yellowish-green emission with Commission Internationale de l'Eclairage (CIE) coordinates of (0.25, 0.34). The maximum brightness of the device prepared from the polymer (PFNAP-0.06) is 6704 cd/m² at 10 V with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) [PEDOT:PSS]/PVK/emission layer/Ca/Ag. A new white polymer-light-emitting-diode (WPLED) can be developed from the single polymer (PFNAP-0.06) system blended with a red phosphorescent iridium complex [Bis(2-[2′-benzothienyl)-pyridinato-N,C^3′] iridium (acetylacetonate) (BtpIr)]. We were able to obtain a white-light-emission device by adjusting the molar ratio of BtpIr to PFNAP-0.06 with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) [PEDOT:PSS]/PVK/emission layer/Ca/Ag. The brightness in such a device configuration is 4030 cd/m² at 9 V with CIE coordinates of (0.32, 0.34).     

Ultra-fine polyelectrolyte fibers from electrospinning of poly(acrylic acid)

Ultra-fine polyelectrolyte fibers have been generated from electrospinning of poly(acrylic acid) in aqueous and DMF solutions. The fiber diameters ranged from 80 to 500 nm and increased with increasing solution concentrations and electrospinning voltages. The fibers generated from the aqueous solutions were more homogeneous in sizes, especially when NaCl or NaOH was added. Higher voltages in electrospinning of the aqueous solutions also resulted in fibers with larger heat capacity in the glass transition region, and higher dehydration temperatures. These polyelectrolyte fibers could be rendered water-insoluble by incorporating β-cyclodextrin (at 20 wt% of PAA) in the aqueous solution, then heat-induced crosslinking was performed at 140 °C for 20 min. The resulting hydrogel fibers showed strongly pH-responsive swelling behaviors.     

Transparent,conductive polymer blend coatings from latex-based dispersions

Flexible, transparent and conductive polymer blend coatings were prepared from aqueous dispersions of poly(3,4-ethylenedixoythiophene)/poly(styrenesulfonate) [PEDOT/PSS] gel particles (∼80 nm) and latex (∼300 nm). The stable dispersions were deposited as wet coatings onto poly(ethylene terephthalate) substrates and dried at 80 °C. Microstructure studies using tapping mode atomic force microscopy (TMAFM) indicate that a network-like microstructure formed during drying at 0.03 volume fraction PEDOT/PSS loading. In this network-like structure, the PEDOT/PSS phase was forced into the boundary regions between latex. In addition, migration of the PEDOT/PSS particles towards coating surface is likely during drying of the aqueous dispersions. The addition of a small amount of dimethyl sulfoxide (DMSO) in dispersions altered the distribution of the PEDOT/PSS phase. As PEDOT/PSS concentration increases to 0.15 volume fraction, the coating surface is dominated by the PEDOT/PSS phase. The effect of DMSO on microstructure becomes less apparent as PEDOT/PSS concentration increases. The conductivity of the polymer blend coatings increases in a percolation-like fashion with a threshold of ∼0.02 volume fraction PEDOT/PSS. The addition of DMSO in dispersions enhanced the coating conductivity beyond the threshold by more than two orders of magnitude. The highest conductivity, ∼3 S/cm, occurs at 0.20 volume fraction PEDOT/PSS concentration. The polymer blend coatings have good transparency with only a weak dependence of transparency on wavelength due to the small refractive index difference between filler and matrix.     

Investigation of the degree of homogeneity and hydrogen bonding in PEG/PVP blends prepared in supercritical CO2: Comparison with ethanol-cast blends and physical mixtures

The degree of homogeneity and H-bond interaction in blends of low-molecular-mass poly(ethylene glycols) (PEG, M_w = 400, 600, 1000) and poly(vinylpyrrolidone) (PVP, M_w = 9 × 10³) prepared in supercritical CO₂, ethanol and as physical mixtures were studied by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and dynamic mechanical analysis (DMA) techniques. Homogeneity of samples prepared in supercritical CO₂ were greater than physically mixed samples, but slightly less than ethanol-cast samples. PEG-PVP H-bond interaction was higher for ethanol-cast blends when compared to blends prepared in supercritical CO₂. This reduced interaction was attributed to a combination of: (1) shielding of PEG-PVP H-bond interactions when CO₂ is dissolved in the blend; (2) rapidly reduced PEG and PVP chain mobility upon CO₂ venting, delaying rearrangement for optimum PEG-PVP H-bond interaction.     

Sensing Cu2+ by controlling the aggregation properties of the fluorescent dye rhodamine 6G with the aid of polyelectrolytes bearing different linear aromatic density

The importance of the linear aromatic density of polyelectrolytes on the ability to bind and influence the state of aggregation of dyes such as rhodamine 6G is highlighted. The corresponding complexes present different interaction patterns with metal ions such as Cu²⁺, undergoing different spectroscopic changes. The chemical bases of these changes are discussed. The different polyelectrolytes studied, poly(sodium 4-styrenesulfonate), poly(sodium 4-styrenesulfonate-co-sodium maleate) at two different comonomer compositions (3:1 and 1:1), and poly(sodium acrylate-co-sodium maleate), bear different linear aromatic density and induce different R6G binding patterns, as seen by diafiltration and UV–vis spectroscopy of absorbance and fluorescence. As the linear aromatic density increases, smaller dye aggregates are induced in the systems. Thus, in the presence of a large excess of the polyelectrolyte showing the highest linear aromatic density, the dyes disperse on the polymer domain and no aggregation is detected. The interaction is less sensitive to the cleaving effect produced by the addition of NaCl 0.1M for the complexes that include the polyelectrolytes with the highest linear aromatic density. In the presence of Cu²⁺, the complexes formed with the polyelectrolytes showing the lowest linear aromatic density tend to cleave, producing the release of the dye from the polymer domain. On the contrary, the complexes formed with the polyelectrolytes showing the highest linear aromatic density effectively retain the dye in the presence of the divalent metal ion. Based on fluorescence changes by the addition of different amounts of Cu²⁺ to the solution, the potential of the polyelectrolyte/R6G complexes in applications as sensing materials is discussed.     

Adsorption of synthetic polyelectrolytes on colloidal spheres

Summary The adsorption of synthetic polyelectrolytes on the surfaces of monodisperse polystyrene spheres and colloidal silica spheres is studied by electrophoretic mobility measurements. Electrolytes used are NaCl, CaCl₂, LaCl₃, Na₂SO₄, sodium poly(ethylenesulfonate) (NaPES), sodium poly(styrenesulfonate) (NaPSS), polybrene^? (PB), poly-4-vinyl-N-ethylpyridinium bromide (C2PVP), poly-4-vinyl-N-benzylpyridinium chloride (BzPVP), and copolymer of 4-vinyl-N-benzylpyridinium chloride (95%) and 4-vinyl-N-n-hexadecylpyridinium bromide (5%) (C16BzPVP). Electrophoretic velocity (u) and the effective charge number (α) of a colloidal sphere increase in the presence of PB, C2PVP, BzPVP, and C16BzPVP, and turn to the positive from the negative values in their absence. Addition of NaPES and NaPSS further decreases u and α values. Adsorption of the polymers on the colloidal spheres are explained by the hydrophobic and/or dipoledipole interactions in addition to the electrostatic forces. Weak adsorption of simple electrolytes on the colloidal spheres is deduced from the electrophoretic measurements.     

Green polymer-light-emitting-diodes based on polyfluorenes containing N-aryl-1,8-naphthalimide and 1,8-naphthoilene-arylimidazole derivatives as color tuner

A novel series of green light emitting single polymers were prepared by end-capping of N-aryl-1,8-naphthalimide and 1,8-naphthoilenearylimidazole derivatives into polyfluorene. The electroluminescence (EL) spectra of polymers (P1 ∼ P5) exhibit greenish-blue, bluish-green, pure green, and yellowish-green emission (λ_max = 465 nm, 490 nm, 500 nm, and 545 nm, respectively) from compounds (M1 ∼ M5). It was found that by the introduction of a small amount of compounds (M1 ∼ M5) (5 mol-%) into polyfluorene, the emission color can be tuned from the blue to green region. The color tuning was found to have gone through charge trapping and Förster energy transfer. The device of P4 emits pure green light with Commission Internationale de l'Eclairage (CIE) coordinates of (0.20, 0.41), and exhibits a maximum brightness of 11500 cd/m² at 12 V with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) [PEDOT:PSS]/PVK/emission layer/Ca/Ag. The device of P5 emits yellowish green light with Commission Internationale de l'Eclairage (CIE) coordinates of (0.36, 0.56), and exhibits a maximum brightness of 6534 cd/m² at 17 V.     

Rheology control by modulating hydrophobic and inclusion associations in modified poly(acrylic acid) solutions

The rheology of modified poly(acrylic acid) (PAA) solutions can be tuned by controlling the inclusion interactions between α-cyclodextrins and alkyl hydrophobes. We demonstrate three modes of control: (1) using free cyclodextrins (CD) to displace hydrophobe-hydrophobe association in hydrophobically modified poly(acrylic acid) (HMPAA) polymers—which reduces fluid viscosity, (2) using competitive inclusion interactions where stronger SDS:CD binding can be used to ‘unmask’ CD:hydropobe inclusion interactions—which increases viscosity, and (3) employing HMPAA inclusion interactions with CD groups grafted to PAA chains (CDPAA)—which produces higher viscosities than purely hydrophobic association systems at the same concentration. The inclusion association between alkyl side-group in HMPAA and CD, either free or grafted onto PAA, obeys a 1-to-1 stoichiometry at low polymer concentrations (<1 wt%). In contrast to purely hydrophobically associating polymers, the CD:hydrophobe interaction is only binary, and, therefore, these associated networks should be ideal model systems to test theoretical predictions for associative fluids.