Multifunctional,pH‐responsive graft copolymer prepared from deproteinized natural rubber and 4‐vinylpyridine via emulsion polymerization

We investigated the synthesis of a pH‐responsive graft copolymer of natural rubber and 4‐vinylpyridine. The grafting reaction was carried out using deproteinized natural rubber (DPNR) latex, with potassium persulfate as a free radical initiator. The pH responsiveness of the graft copolymer was investigated using water swelling and contact angle measurements, and was compared with that of pure DPNR. The graft copolymer was found to become responsive in solution at a pH of around 4. Indigo carmine adsorption studies identified the Langmuir isotherm, suggesting monolayer coverage. The adsorbed indigo carmine, a model anionic drug, and carbon dots, an emerging nanosized fluorophore, could be released from the graft copolymer by lowering the pH of the solution. The graft copolymer was tested as a heavy metal adsorbent, and demonstrated selectivity to copper(II) ions. The graft copolymer of 4‐vinylpyridine and DPNR developed in this study is therefore a multifunctional, pH‐responsive material with a wide range of potential applications, including sensing and catalysis, as a biomedical material and as an adsorbent. © 2017 Society of Chemical Industry     

Synthesis and swelling characteristics of poly(4‐vinylpyridine) gels crosslinked by irradiation

The effect of irradiation under vacuum on thermal properties and swelling behavior on poly(4‐vinylpyridine) (P4VP) was investigated. The gel percentage in the irradiated P4VP films was determined by Soxhlet extraction. UV spectroscopy was also used to determine sol percentage, which decreased as the radiation dose increased. The changes in thermal properties, such as glass‐transition temperature (T_g), were followed by differential scanning calorimetry before and after Soxhlet extraction. The gels prepared after irradiation were characterized with respect to their swelling properties and network structures. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2609–2614, 2001     

A study on compatibility of polymer blends of polystyrene/poly(4‐vinylpyridine)

Blends of polystyrene/poly (4‐vinylpyridine) have been prepared by casting from a common solvent. The compatibility of the blends was studied by using dilute solution viscometry (DSV), differential scanning calorimetery (DSC), Fourier transformation‐infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). The relative viscosity versus composition plots for the blends are not perfect linear. The corresponding intrinsic viscosity values show negative deviation from ideal behavior when plotted against composition. Also, the modified Krigbaum and Wall interaction parameter, Δb, shows small and negative values for all compositions except for the blend PS/P4VP (25 : 75). The results indicate that the polymers are incompatible but small interaction values predict physically miscible blends which eventually show phase separation, as is observed in the present studies. However, the blends as obtained show a single, composition‐dependent, glass transition temperature that fits the Fox equation well, indicating the presence of homogeneous phase. The constant, k obtained from Gordon‐Taylor equation suggests intermolecular attraction between these polymers. FT‐IR and SEM support the results of DSV and DSC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of polypyrrole‐au coated SiO2@poly(4‐vinylpyridine) composites

Microspheres with silica as core and poly(4‐vinylpyridine) (P4VP) as shell were synthesized. AuCl ions were bound by P4VP chains to form the complex, which acted both as an oxidant of pyrrole monomers and as a source of Au atoms. By vapor phase polymerization, the PPy and Au nanoparticles were simultaneously formed on the surfaces of SiO₂@P4VP microspheres. The core‐shell structure was confirmed by transmission electron microscopy. The surface morphologies of the composites were observed by scanning electron microscopy. The molecular structures of composites were characterized in detail by Raman spectra, X‐ray diffraction, and X‐ray photoelectron spectroscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Highly efficient interpenetrating polymerization of styrene and 4‐vinylpyridine with poly(ethylene terephthalate) using benzoyl peroxide

A polymerization method for the preparation of an interpenetrating network polymer with poly(ethylene terephthalate) is reported. Two types of monomer, styrene and 4‐vinylpyridine, were chosen as hydrophobic and hydrophilic representatives, respectively, in order to show the versatility of this polymerization method. The polymer‐immobilized poly(ethylene terephthalate) samples were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy and X‐ray photoelectron spectroscopy. The immobilization efficiency of styrene as a function of reaction temperature, monomer‐to‐initiator molar ratio, reaction time, addition of solvent, surface hydrophilicity and immersion in initiator was studied. The maximum immobilization percentage of styrene reaches 111%. The immobilization efficiency is proportional to polymer molecular weight and sample thickness. Based on these results, this strategy is shown to be an efficient, versatile method for preparing interpenetrating network polymers and can be used as a means to modify the structures and properties of polymeric substrates. © 2013 Society of Chemical Industry     

Proton uptake by poly(2‐vinylpyridine) coatings

A titration technique has been used to directly measure the proton uptake by ion‐exchange poly(2‐vinylpyridine) coatings as a function of solution pH. Contrary to the common assumption that each nitrogen in the pyridine ring is attached to an H⁺ when the polymer film is fully protonated, the use of the titration technique has shown that the portion of the pyridine sites actually protonated does not exceed 25% anywhere in the pH range where the coating is stable. The pK_a value for the poly(2‐vinylpyridine) coating has also been estimated to be 4.5 from the titration curve. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1493–1497, 2001     

Properties and thermal degradation study of blend films with poly(4‐vinylpyridine) and lignin

A series of blend films with different ratio of poly(4‐vinylpyridine) (PVP) to lignin were subjected to dynamic DSC and TGA measurement under nitrogen atmosphere at various heating rates. DSC curves showed that the glass transition temperatures of these blends decreased with the increase of lignin content. TGA studies indicated that the lignin content produced obvious effect on the thermal stability of these blends. The kinetic model function of the thermal decomposition of these blends obeyed the Avrami‐Erofeev model equation, g(α) = [‐ln(1‐α)]^1/m. The degradation kinetic parameters were also obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1875–1879, 2005     

Preparation of fast pH‐responsive ferric carboxymethylcellulose/poly(vinyl alcohol) double‐network microparticles

BACKGROUND: Carboxymethylcellulose (CMC) and poly(vinyl alcohol) (PVA) are biocompatible, and their complex hydrogel shows pH responsiveness. Thus, they are chosen as starting materials to prepare physically dual‐crosslinked Fe‐CMC/PVA microparticles with improved properties. RESULTS: Fe‐CMC/PVA double‐network microparticles were obtained via a facile process under mild conditions. Sodium carboxymethylcellulose was crosslinked with ferric ions to form particles that contained aqueous PVA solution in an emulsion system. The hydrogel particles were then subjected to a freezing–thawing cycle to achieve further crosslinking; the size of the particles formed was in the range 0.2–1.2 µm. The microparticles were capable of maintaining the stability of proteins such as hemoglobin in an acidic environment and exhibited pH‐responsive release behavior. CONCLUSION: The pH responsivity of the Fe‐CMC/PVA physical double‐network microparticles is fast, which is helpful for effectively protecting a loaded bioactive substance. Thus, they may be potential candidates for pH‐sensitive applications. Copyright © 2008 Society of Chemical Industry     

Miscibility study of poly(vinyl chloride)/poly(methyl methacrylate‐co‐4‐vinylpyridine) by viscosimetry,DSC, and FTIR

The miscibility of the poly(vinyl chloride)/poly(methylmethacrylate) system were improved by introducing pyridine units into poly(methylmethacrylate) main. For this purpose, we have synthesized through a radical polymerization a series of methylmethacrylate‐co‐vinyl‐4‐pyridine copolymers of different compositions and carried out a comparative study by viscosimetry, differential scanning calorimetry, and Fourier transform infrared spectroscopic (FTIR) methods. The viscosimetric analysis using the Krigbaum‐Wall, K. K. Chee, and Compos approaches revealed that, the Poly(vinyl chloride)/poly(methylmethactylate‐co‐4‐vinylpyridine)(PVC/MMA4VP‐15) at 15 wt % of 4‐vinylpyridine systems in tetrahydrofuran are completely miscible in all proportions. The differential scanning calorimetry analysis confirmed the miscibility of these systems in all proportions by the appearance of only one glass transition temperature between those of the two pure constituents. The Kwei and Schneider approaches showed also the miscibility of this system, which is due to the specific interactions between the acidic hydrogen atom of PVC and the nitrogen of MMA4VP‐15. The use of FTIR method has confirmed the occurrence of this kind of interactions by broadening and shifting of the involved functional groups vibration bands. In this work, we have also carried out a preliminary test of sorption of THF aqueous solution by PVC and PVC/MMA4VP‐15 blend membranes. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Polymer electrolyte membranes composed of an electrospun poly(vinylidene fluoride) fibrous mat in a poly(4‐vinylpyridine) matrix

Newly proposed polymer electrolyte membranes (PEMs) composed of an electrospun poly(vinylidene fluoride) (PVDF) fibrous mat embedded in a poly(4‐vinylpyridine) (P4VP) matrix were successfully fabricated in order to improve the mechanical and dimensional stabilities and ionic conductivity of membranes in lithium rechargeable batteries. Fourier transform infrared spectroscopic analysis showed that as a result of the use of a high voltage during electrospinning the crystalline structure of PVDF changed partially from α‐phase to β‐phase. Energy‐dispersive X‐ray spectroscopy confirmed the existence of crosslinked P4VP in the PVDF fibrous mat. The electrolyte uptakes of PVDF and PVDF/P4VP composite mats were higher than that of PVDF cast film. The tensile properties of PVDF/P4VP composite mat were considerably improved compared to those of the pristine PVDF fibrous mat under both dry and wet (soaked with electrolyte) conditions. In addition, the mechanical and dimensional stabilities of the PVDF/P4VP composite PEM were further enhanced due to crosslinking between the P4VP chains. Furthermore, the PVDF/P4VP composite PEM exhibited an ionic conductivity that was an order of magnitude higher than that of traditional PVDF film. © 2012 Society of Chemical Industry     

Synthesis of multiblock copolymers of poly(2‐vinylpyridine) and polyoxyethylene

Telechelic dihydroxy poly(2‐vinylpyridine) (THPVP) samples with different molecular weights were synthesized by using lithium α‐methylnaphthalene as an anionic initiator in mixed solvents of benzene and tetrahydrofuran (THF). Then multiblock copolymers of poly(2‐vinylpyridine) (P2VP) and polyoxyethylene (PEO) were obtained by condensing THPVP and PEO with dichloromethane in the presence of potassium hydroxide. The effects of reaction time, molecular weight of PEO and THPVP, and raw meal ratio PEO/THPVP (w/w) were investigated. The best conditions were found. The copolymers can be purified by water and toluene. The purified copolymers were characterized by infrared (IR) and ¹H nuclear magnetic resonance (¹H‐NMR). The PEO segment content was calculated from the integral curve of ¹H‐NMR spectra. The results showed that these multiblock copolymers were connected through oxymethylene. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1632–1636, 2003     

Electrical/mechanical properties and activation energies of some poly(2‐vinylpyridine)‐metal complexes

Poly(2‐vinylpyridine) (P2VP) and its metal‐based complexes have been synthesized and characterized through analytical measurements, such as thermal analysis and IR‐ spectroscopy. The electrical conductivity of these complexes was studied as a function of temperature. The conductivity of P2VP is seen to increase by many orders of magnitude on complexation with some metal chlorides such as BaCl₂, ZnCl₂, NiCl₂, or CoCl₂. The activation energy for electrical conductivity of either of these complexes is found to be lower than that of the host polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3537–3549, 2006     

Studies on polybenzimidazole/poly (4‐vinylpyridine) blends and their proton conductivity after doping with acid

In the present work, polybenzimidazole (PBI) and poly(4‐vinylpyridine) (P4VP) were chosen because they form miscible blends and both materials are suitable for acid doping as a matrix, which can eventually be used as proton conductor. The miscibility and inter‐polymer interactions were studied by infrared (IR) spectroscopy and differential scanning calorimetry (DSC). DSC and IR results suggest that PBI blended with P4VP exhibits good miscibility due to the strong hydrogen bonds formed between PBI's NH groups and P4VP's N: groups. The glass transition temperatures of the blends can be fitted to the Fox equation very well. The blends were also studied by thermogravimetry. Their thermal stability is slightly higher than that of P4VP, but is still lower than that of PBI. Temperature‐dependent conductivity of acid‐doped PBI/P4VP blends was studied. As the temperature increases, the conductivity of PBI/P4VP doped with H₃PO₄ increases. The temperature‐dependent conductivity of the blends follows a simple Arrhenius relationship when the P4VP content is low (less than 15%), while a non‐Arrhenius behaviour of the conductivity of the blends becomes more and more significant with increasing P4VP content. This means that the proton transport in the blends is controlled by both a hopping mechanism and the segmental motion of the polymer. The contribution of these two mechanisms depends on the P4VP content. Copyright © 2003 Society of Chemical Industry     

Preparation and catalytic application of poly 4‐vinylpyridine microspheres

Poly 4‐vinylpyridine (P4VP) microspheres between 170 and 728 nm were synthesized by Emulsifier‐Free Emulsion Polymerization. The monomer concentration, ionic strength, and initiator concentration affected the microsphere size and size distribution. The increasing monomer concentration led to the increase of microsphere size, whereas the size distribution of the resultant P4VP microspheres increased with the increasing ionic strength of the reaction systems. Mo(O₂)₂O·2DMF was successfully anchored onto the P4VP microspheres by ligand exchange, and the heterogeneous catalyst showed high‐catalytic activity for epoxidation of cis‐cyclooctene with environmentally friendly hydrogen peroxide. The size and morphology of the supported microspheres has important influence on the catalytic activity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and characterization of polystyrene/poly(4‐vinylpyridine) triblock copolymers by reversible addition–fragmentation chain transfer polymerization and their self‐assembled aggregates in water

Reversible addition–fragmentation chain transfer polymerization (RAFT) was developed for the controlled preparation of polystyrene (PS)/poly(4‐vinylpyridine) (P4VP) triblock copolymers. First, PS and P4VP homopolymers were prepared using dibenzyl trithiocarbonate as the chain transfer agent (CTA). Then, PS‐b‐P4VP‐b‐PS and P4VP‐b‐PS‐b‐P4VP triblock copolymers were synthesized using as macro‐CTA the obtained homopolymers PS and P4VP, respectively. The synthesized polymers had relatively narrower molecular weight distributions (M_w/M_n < 1.25), and the polymerization was controlled/living. Furthermore, the polymerization rate appeared to be lower when styrene was polymerized using P4VP as the macro‐CTA, compared with polymerizing 4‐vinylpyridine using PS as the macro‐CTA. This was attributed to the different transfer constants of the P4VP and PS macro‐CTAs to the styrene and the 4‐vinylpyridine, respectively. The aggregates of the triblock copolymers with different compositions and chain architectures in water also were investigated, and the results are presented. Reducing the P4VP block length and keeping the PS block constant favored the formation of rod aggregates. Moreover, the chain architecture in which the P4VP block was in the middle of the copolymer chain was rather favorable to the rod assembly because of the entropic penalty associated with the looping of the middle‐block P4VP to form the aggregate corona and tailing of the end‐block PS into the core of the aggregates. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1017–1025, 2003     

Water‐soluble copolymers. I. Biodegradability and functionality of poly[(sodium acrylate)‐co‐(4‐vinylpyridine)]

As a biodegradable functional polymer, poly[(sodium acrylate)‐co‐(4‐vinylpyridine)] [P(SA‐co‐4VP)] containing a small amounts of 4‐vinylpyridine groups were prepared and their biodegradability, dispersity, and complex performance were analyzed. The polymers can be useful as detergent builders and dispersants. It was found that the biodegradation of P(SA‐co‐4VP) was more conspicuous when content of the 4‐vinylpyridine in the copolymer was larger. This indicates that the 4‐vinylpyridine, which acts as biodegradable segments, should be incorporated into the polymer main chain in such a manner that they are digested by activated sludge. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1953–1957, 1999     

Structural effects of type of intercalant in poly (4‐vinylpyridine) nanocomposites: compatible homopolymer or block copolymer

4‐vinylpyridine monomer was mixed with organophilic montmorillonite (MMT) clay and polymerized in the presence of free‐radical initiator. MMT clay was rendered organophilic by means of ion‐exchanging sodium cations for low‐molecular‐weight quaternized poly(4‐vinylpyridine) (P4VP) homopolymer and diblock copolymers of styrene and quaternized 4‐vinylpyridine (SVP) with different sequence lengths. The swelling behaviour of the MMT clay was studied by X‐ray diffraction (XRD). After the cation exchange, the resulting organophilic clays showed an expansion of interlayer distance indicating the nanoscale ordering of intercalant polymer and MMT layers. The nanocomposite materials, when moulded, exhibited improved thermal stability and dynamic mechanical properties compared with neat P4VP. The composite, having longer ionic segments in its organophilic MMT, showed exfoliated nanocomposite structure as well as higher stiffness and damping properties at higher temperatures even for MMT loading as low as 2 wt%. Copyright © 2006 Society of Chemical Industry     

pH‐ and temperature‐induced release of doxorubicin from multilayers of poly(2‐isopropyl‐2‐oxazoline) and tannic acid

We present a simple strategy to prepare doxorubicin (DOX) containing hydrogen‐bonded films of poly(2‐isopropyl‐2‐oxazoline) (PIPOX) and tannic acid (TA) which release DOX in acidic conditions while releasing a minimal amount of DOX at physiological pH. Water soluble complexes of TA and DOX (TA ? DOX) were prepared prior to film construction. PIPOX and TA ? DOX were deposited at the surface at pH 6.5 using the layer‐by‐layer (LbL) technique. We found that multilayers released a minimal amount of DOX at physiological pH due to further ionization of TA with increasing pH and enhanced electrostatic interactions between TA and DOX. In contrast, pH‐induced release of DOX was observed in moderately acidic conditions due to protonation of TA as the acidity increased and electrostatic interactions between TA and DOX decreased. Moreover, we found that raising the temperature from 25 °C to 37.5 °C increased the amount of DOX released from the surface. This can be rationalized with the conformational changes within the multilayers correlated with the lower critical solution temperature behaviour of PIPOX and increased kinetic energy of DOX molecules. Considering the acidic nature of tumour tissues and important biological properties of PIPOX and TA, these multilayers are promising for pH‐ and temperature‐triggered release of DOX from surfaces. © 2017 Society of Chemical Industry     

Morphology and thermal behavior of organo‐bentonite clay/poly(styrene‐co‐methacrylic acid)/poly(isobutyl methacrylate‐co‐4‐vinylpyridine) nanocomposites

Poly(styrene‐co‐methacrylic acid) containing 29 mol % of methacrylic acid (SMA‐29) and poly(isobutyl methacrylate‐co‐4‐vinylpyridine) containing 20 mol % of 4‐vinylpyridine (IBM4VP‐20) were synthesized, characterized, and used to elaborate binary and ternary nanocomposites of different ratios with a 3% by weight hexadecylammonium‐modified bentonite from Maghnia (Algeria) by casting method from tetrahydrofuran (THF) solutions. The morphology and the thermal behavior of these binary and ternary elaborated nanocomposites were investigated by X‐ray diffraction, scanning electron microscopy, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetry. Polymer nanocomposites and nanoblends of different morphologies were obtained. The effect of the organoclay and its dispersion within the blend matrix on the phase behavior of the miscible SMA29/IBM4VP20 blends is discussed. The obtained results showed that increasing the amount of SMA29 in the IBM4VP20/SMA29 blend leads to near exfoliated nanostructure with significantly improved thermal stability. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009