Antibacterial activities of polystyrene-block-poly(4-vinyl pyridine) and poly(styrene-random-4-vinyl pyridine)

Styrene was polymerized in the presence of benzoyl peroxide (BPO) and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) to yield polystyrene-TEMPO (PS-TEMPO) macroinitiator. The PS-TEMPO macroinitiator with different molecular weight was reacted with 4-vinyl pyridine (4-VP) to synthesize polystyrene-block-poly(4-vinyl pyridine) (PS-b-PVP), which was then quaternized with n-octyl iodide. Antibacterial activity of the quaternized copolymers was assessed against a gram negative bacterium (Pseudomonas aeruginosa) and a gram positive one (Staphylococcus aureus) by using the shake flask test method, and the results were compared with those of poly(styrene-random-4-vinyl pyridine) (P(ST-r--VP)). The quaternized copolymers inhibited greatly the growth of the bacteria, and PS-b-PVP was more active than P(ST-r-VP), which was ascribed to the fact that the content of quaternized 4-VP units on the surface of the particles of the former copolymer was higher than that corresponding to the latter one.     

Hybridization of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine) aggregates in dioxane/water solution

Self-assembly of binary blends of two triblock copolymers of poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine), i.e., P4VP₄₃-b-PS₂₆₀-b-P4VP₄₃ (P1) and P4VP₄₃-b-PS₃₆₆-b-P4VP₄₃ (P2), in dioxane/water solution was studied. These two triblock copolymers individually tend to form vesicles (P2) and cylindrical micelles (P1) in dilute solution. It was found that copolymer components in the blend, sample preparation method, and annealing time had significant effect on hybridization aggregate morphology. By increasing P1 content in the copolymer blends, fraction of looped and stretched cylinders increased, while fraction of bilayers decreased. Nearly no bilayer was observed when P1 content was above 85 wt%. On the other hand, fraction of cylinders decreased while fraction of bilayers increased with the increase of P2 content in copolymer blends. Lamellar structures were obtained, when P2 content was 60 wt% in the copolymer blends, whereas cylinders were seldom found when P2 content was above 80 wt%. These results indicate that P1 and P2 copolymer molecules cooperatively participate in the formation of cylinders and vesicles. Some exotic structures, such as lamellae with protruding cylinders (LPC), incomplete vesicles with protruding cylinders (VPC), and cylindrical bilayers, have been kinetically trapped. These structures may result from intramicellar fusion processes in cylindrical micelles. The striking structures represent a compromise between bilayer and cylindrical geometries.     

Ionic miscibility enhancement in poly(tetrafluoroethylene)/poly(ethyl acrylate) blends. I. Dynamic mechanical studies

It is shown that ion-ion interactions resulting from a proton transfer induce considerable miscibility in blends of functionalized poly(tetrafluoroethylene) with ethyl acrylate copolymers containing 4-vinyl pyridine. Dynamic mechanical measurements, in conjunction with transparency of the samples, are used to evaluate miscibility. It is shown that mixing conditions exert a profound effect on the properties of the final blend. The glass transition of the blend is shown to be strong function of the blend composition, as is characteristic of highly miscible systems.     

Specific interactions and miscibility of blends of poly(ε-caprolactam) and sulfonated PEEK ionomer

Sulfonation of poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), PEEK, improves its miscibility with poly(ϵ-caprolactam), Nylon-6 (N6). This article describes the thermal transitions and the specific interactions that occur for blends of the free acid derivative (H-SPEEK) and the lithium (Li-SPEEK) and zinc salts (Zn-SPEEK) of sulfonated PEEK (19.2 mol % sulfonation) with N6. The interactions responsible for miscibility were characterized by Fourier transform infrared (FTIR) spectroscopy. For blends of H-SPEEK and N6, miscibility is due to hydrogen bonding between the sulfonic acid and the amide group. For blends of N6 with the salts of SPEEK the specific interaction involves an ion-dipole complex of Li⁺ with the amide carbonyl or Zn²⁺ with the amide nitrogen. The relative strengths of the intermolecular interactions for the three types of blends increased as the cation was varied in the order: H⁺ < Li⁺ < Zn²⁺, and the T_gs of the mixtures increased in the same order. © 1996 John Wiley & Sons, Inc.     

Surface-enhanced raman scattering from poly(4-vinyl pyridine)

Surface-enhanced Raman scattering (SERS) has been observed for poly(4-vinyl pyridine) absorbed onto silver island films. Bands near 1219 and 1613 cm^?1, which are weak in normal Raman spectra of PVP, are strong in SERS spectra, and the band near 1020 cm^?1, which is the strongest band in the normal spectra, is relatively weak in SERS. The strongest bands in the SERS spectra all belong to the same symmetry species as α_ZZ, implying that the pyridine moieties are adsorbed through the nitrogen atoms with a vertical conformation. The ring breathing mode of the pyridine rings is observed near 1020 cm^?1, a frequency characteristic of pyridinium ions or coordinated pyridine, providing further evidence for adsorption through the nitrogen atoms. Silver catalyzed photooxidation, which can lead to the appearance of artifacts in SERS spectra, particularly of polymers, can be reduced by overcoating SERS samples with thin films of polymers such as poly(methyl methacrylate) that have low Raman scattering cross sections.     

Photoactive proton conductor: poly(4-vinyl pyridine) gel

We describe a hydrogen-bonded poly(4-vinyl pyridine)-based dielectric material, in which conductivity can be induced due to the presence of side-chain protonated species that form spontaneously when the polymer is dissolved in pyridine. The conductivity of the proton conductive gel can be controlled by direct irradiation at the proton-transfer center: a reversible change of conductivity was observed in response to the on/off switching of 385 nm wavelength radiation. Over most of the range of intensities used, the proton conductivity exhibited a bimolecular character. We present a model of the protonated pyridine side-chain unit in the ground and excited states (DFT level). In the ground state, the protonated pyridine moiety has a cyclic, conjugated structure.     

The effects of some transition-metal compounds on the flame retardance of poly(styrene-co-4-vinyl pyridine) and poly(methyl methacrylate-co-4-vinyl pyridine)

Several copolymers of both styrene and methyl methacrylate with 4-vinyl pyridine have been prepared and modified by coordination with the transition-metal compounds vanadium acetylacetonate (VO[acac]₂), vanadyl dichloride (VOCl₂) and ferric chloride. The flame-retardant effects of these modifications have been assessed by measurements of limiting oxygen indices, by thermogravimetric analysis, and by examination of chars by scanning electron microscopy. Effects on mechanical properties have been assessed by dynamic mechanical thermal analysis. The limiting oxygen indices of the modified polymers are significantly higher than those of the parent polymers, and the production of considerable amounts of rigid, intumescent chars suggests predominantly condensed-phase mechanisms of flame retardance.     

Surface-enhanced Raman scattering from bilayers of polystyrene,diglycidyl ether of bisphenol-A,poly(4-vinyl pyridine), and poly(4-styrene sulfonate)

Surface-enhanced Raman scattering (SERS) has been observed from thin films of polystyrene (PS), diglycidyl ether of bisphenol-A (DGEBA), and poly(4-vinyl pyridine) (PVP) deposited on silver island films Degradation of the polymers occurred rapidly during laser irradiation and was accompanied by the appearance of strong bands near 1375 and 1575 cm-1. These bands were attributed to the formation of graphite-like species by the silver-catalyzed thermal oxidation of the polymers induced by localized laser heating of the substrate. When the thin films of PS, DGEBA, or PVP were overcoated with much thicker films of a second polymer such as polystyrene sulfonate (PSS), the degradation was greatly reduced, and excellent SERS spectra of the PS, DGEBA, and PVP films were obtained. Overlayers reduced degradation within the first films deposited on silver island films by restricting the availability of oxygen at the interface to its solubility in the overlayer polymer or by altering the adsorption of oxygen onto the substrate. SERS was observed for the PS, DGEBA, and PVP films and the PSS overlayers when the films were deposited from relatively dilute solutions. When the PS, DGEBA, and PVP films were deposited from more concentrated solutions, SERS was not observed from the PSS overlayers. It was suggested that most of the SERS was due to a short-range, charge-transfer mechanism associated with sites of atomic scale roughness and that SERS was observed from the overlayer when the first film failed to occupy all of the sites.     

Molecular interpretation of miscibility in polyamide-6 blends with alkali ionomers of sulfonated polystyrene

Blends of polyamide-6 with lithium ionomers of 9.8 and 5.4 mole percent sulfonated polystyrene, formed by combining solutions of these polymers, are miscible over a wide compositional range, but those with the equivalent sodium ionomers are not. The molecular origin of this difference is addressed by studying the far infared and infrared spectra of the blends and pure materials to follow changes in the interactions between the cations and their surroundings, and changes in the interactions between functional groups. Based on analysis of these spectra, a molecular level interpretation of the blending is proposed. The initial step involves both the interaction of one amide carbonyl with an Li⁺ ion and simultaneous hydrogen bonding between an amide N? H and a sulfonate group. This eventually leads to formation of an Li(>CO)⁺_n(n ～ 4) entity while the sulfonates are converted to the acid form through hydrogen bonding to the amide N? H groups. The Na⁺ ion does not interact strongly enough with the amide groups to leave its sulfonate environment to a significant extent. © 1995 John Wiley & Sons, Inc.     

Ion-specific swelling behaviors of partially quaternized poly(4-vinyl pyridine) gel

Swelling degrees of partially quaternized poly(4-vinyl pyridine) (p.q.P4VP) were measured as functions of the degree of quaternization (D.Q.: 5, 10, 15, 30, and 50 mol%), salt concentration (0–4 M), and salt species (KF, LiCl, NaCl, KCl, CsCl, MgCl₂, KBr, LiSCN, KSCN, Na₂SO₄, and MgSO₄) to study ion effects on the three kinds of interactions involved with p.q.P4VP in aqueous systems, i.e., electrostatic interaction, hydrogen bonding to the nitrogen of the pyridine ring, and hydrophobic interaction, as well as to estimate the relative contributions of the respective ion effects to gel swelling. Upon addition of salts at the lowest salt concentration studied (0.01 M), p.q.P4VP gels, except for one with D.Q.=10%, significantly deswelled depending on the counterion species; the lowest swelling degree was observed for the thiocyanates and the highest one for KF. In the higher salt concentration region (≧1 M) where electrostatic interactions might well be screened, however, some salt systems (e.g., LiCl, KSCN) showed swelling with increased salt concentration, contrary to the common behavior of usual ionic gels. These ion-specific swelling behaviors were interpreted as being caused by additive ionic effects on the three kinds of interactions.     

Miscible blends of zinc-neutralized sulfonated polystyrene and poly(2,6-dimethyl 1,4-phenylene oxide)

Zinc-neutralized sulfonated polystyrene ionomers (ZnSPS) and poly(2,6-dimethyl 1,4-phenylene oxide) homopolymer (PXE) form miscible blends up to at least 7.8 mol % sulfonation, as measured by thermal and mechanical criteria. The addition of an equal weight of PXE raises the glass transition temperature of ZnSPS by 40–50°C. However, this miscibility is not achieved by eradicating the microdomain structure present in ZnSPS, even though the PXE coils are considerably larger than the spacings between ionic aggregates. Small-angle x-ray scattering indicates that while the average interaggregate spacing is roughly the same in ZnSPS and its 50/50 blend with PXE at a given sulfonation level, the extent of phase separation is reduced upon PXE addition, indicating that more ionic groups are dispersed in the matrix. Factors influencing miscibility in the ZnSPS/PXE materials and related blends are discussed.     

Miscibility of poly(vinyl chloride) with ethyl acrylate 4-vinyl pyridine copolymers

Blends (50:50, w:w) of poly(vinyl chloride) (PVC) and poly(ethyl acrylate-co-4-vinyl pyridine) (PEA–4-VP) of different 4-VP contents (2–14 mol %) were prepared. These were found to be partially miscible as evidenced by the presence of a single, through broad, tangent δ peak obtained from torsion pendulum experiments. Several possible types of interactions which might exist between PVC and PEA-4-VP, such as ion-dipole, crosslinking, charge transfer, hydrogen bonding, and dipole–dipole interactions, were explored. From ultraviolet, conductance, infrared, and solubility studies, it was shown that hydrogen bonding or dipole–dipole (or possibly a combination of the two) interactions were the most likely in this system. These interactions have been suggested previously for other systems by various investigators.     

Phase behavior of poly(ethylene oxide) and sulfonated polystyrene blends with and without solvent

The phase behavior of poly (ethylene oxide) (PEO) and poly(styrene-co-sodium sulfonated styrene) (SPS) blends has been examined as a function of copolymer composition. The mixtures show complex coacervation in dilute benzene/methanol (9/1, v/v) solution. The presence of intermolecular interactions between PEO and SPS in solution is verified by viscometry. Interaction between PEO and SPS in the solid state was supported by small-angle x-ray scattering; however, binary blends containing low PEO content show high miscibility, whereas the blends with high PEO content show phase separation.     

Antibacterial behaviour of quaternized poly(vinyl chloride)-g-poly(4-vinyl pyridine) graft copolymers

Amphiphilic graft copolymers consisting of poly(vinyl chloride)(PVC) main chains and poly(4-vinyl pyridine)(P4VP) side chains were synthesized via atom transfer radical polymerization(ATRP) using direct initiation of chlorine atoms. The successful synthesis of PVC-g-P4 VP graft copolymers was confirmed by Fourier transform infrared spectroscopy(FTIR) and proton nuclear magnetic resonance(1H-NMR). Transmission electron microscope(TEM) and small angle X-ray scattering(SAXS) analysis showed that PVC-g-P4 VP exhibited microphase-separated, ordered structure with 37.6 nm of domain spacing, which was not observed in neat PVC. For antibacterial applications, the tertiary nitrogen atoms of PVC-gP4 VP was quaternized using 1-bromohexane, as confirmed by FTIR measurements. Bacteria including Escherichia coli(E. coli), Staphylococcus aureus(S. aureus), Bacillus cereus(B. cereus), and Pseudomonas aeruginosa(P. aeruginosa) were completely killed in 24 h on the quaternized PVC-g-P4VP(46% grafting) surface, indicating its excellent antibacterial behavior while it showed to be cytotoxic to mammalian cell.     

Effect of styrene-4-vinyl pyridine diblock copolymer on morphological,thermal, and mechanical properties of poly(2,6-dimethyl-1,4-phenylene ether)/polyethylene ionomer blends

The compatibilizing effects of a styrene-4-vinyl pyridine diblock copolymer on the properties of immiscible poly(2,6-dimethyl-1,4-phenylene ether) (PPE)/polyethylene ionomer (Surlyn) blends are investigated by examining the phase morphology and the thermal and mechanical properties. The block copolymer is synthesized by sequential anionic polymerization at ?78°C and melt-mixed with PPE and Surlyn at 290°C. When a small amount of block copolymer is present, the domain size of the dispersed phase becomes smaller. The tensile strength and elongation at break increase with addition of the block copolymer for PPE-rich matrix blends, whereas the tensile strength increases but the elongation at break decreases for Surlyn-rich matrix blends. These effects are interpreted in terms of the interfacial activity and the reinforcing effect of the block copolymer. From the experimental results, it is concluded that the block copolymer plays a role as an effective compatibilizer for PPE/Surlyn blends. © 1994 John Wiley & Sons, Inc.     

Block copolymer compatibilizers for polystyrene/poly(dimethylsiloxane) blends

Symmetric polystyrene (PS)–poly(dimethylsiloxane) (PDMS) diblock copolymers were mixed into a 20% dispersion of PDMS in PS. The effect of adding the block copolymer on the blend morphology was examined as a function of the block copolymer molecular weight (M_n,bcp), concentration, and viscosity ratio (η_r). When blended together with the PS and PDMS homopolymers, most of the block copolymer appeared as micelles in the PS matrix. Even when the copolymer was preblended into the PDMS dispersed phase, block copolymer micelles in the PS matrix phase were observed with transmission electron microscopy after mixing. Adding 16 kg/mol PS–PDMS block copolymer dramatically reduced the PDMS particle size, but the morphology, as examined by scanning electron microscopy, was unstable upon thermal annealing. Adding 156 kg/mol block copolymer yielded particle sizes similar to those of blends with 40 or 83 kg/mol block copolymers, but only blends with 83 kg/mol block copolymer were stable after annealing. For a given value of M_n,bcp, a minimum PDMS particle size was observed when η_r ～ 1. When η_r = 2.6, thermally stable, submicrometer particles as small as 0.6 μm were observed after the addition of only 3% PS–PDMS diblock (number‐average molecular weight = 83 kg/mol) to the blend. As little as 1% 83 kg/mol block copolymer was sufficient to stabilize a 20% dispersion of 1.1‐μm PDMS particles in PS. Droplet size reduction was attributed to the prevention of coalescence caused by small amounts of block copolymer at the interface. The conditions under which block copolymer interfacial adsorption and interpenetration were facilitated were explained with Leibler's brush theory. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 346–357, 2002; DOI 10.1002/polb.10098     

The synthesis and properties of adducts between poly(4-vinyl pyridine) and metal alkyls

Poly(4-vinyl pyridine) is used as a polymeric ligand to react with metal alkyls, Me_nM (n = 3, M = Al, Ga or In; n = 2, M = Cd or Zn) to form adducts. The adducts are characterized by solid state ¹³C NMR, infrared spectroscopy, microanalyses and differential scanning calorimetry (DSC). All the adducts are nonpyrophoric and thermally dissociable, so they may have potential both for use in adduct purification processes or for use as safer metal alkyl sources for Metal–Organic Chemical Vapor Deposition.     

Grafting of 4-vinyl pyridine onto poly(vinyl alcohol) initiated by potassium diperiodatocuprate(III)

In this article, the graft copolymerization of 4-vinyl pyridine onto poly(vinyl alcohol) via the potassium diperiodatocuprate(III)-poly(vinyl alcohol) redox system as an initiator was investigated in an alkaline medium. The graft copolymer was characterized with Fourier-transform infrared spectra analysis. A mechanism is proposed to explain the generation of radicals and the initiation. The effects of reaction variables, such as the initiator concentration, the ratio of monomer to poly(vinyl alcohol), pH, and reaction temperature and time, are investigated, and the grafting conditions are optimized. Graft copolymers with high grafting efficiency are obtained, thus indicating that potassium diperiodatocuprate(III)-PVA redox system is an efficient initiator for this graft copolymerization. Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. B, 2006, Vol. 48, No. 7, pp. 1190–1194. This text was submitted by the authors in English.