Reactive and Functional Polymers (v.69, #2)

Direct introduction of phosphonate by the surface modification of polymers enhances biocompatibility by Cleo Choong; Jon-Paul Griffiths; Mark G. Moloney; James Triffitt; Diane Swallow (77-85).
A novel chemical method for the modification of polystyrene and nylon polymers by the reaction of diaryl carbenes permits the direct and efficient introduction of phosphonate residues upon the polymer surface. The method is simple to execute, involving solution coating to adsorb the reactive coating agent, followed by drying and thermolysis at temperatures not greater than 150 °C. This material can be further modified to the calcium phosphonate derivative, by treatment with aqueous calcium hydroxide. The modified polymers show enhanced biocompatibility of the modified polymer, as evidenced by the improved growth of MG63 human osteosarcoma cell line on the surface. This method is of significance since it offers a simple chemical protocol for the tailoring of the surface properties of materials, it avoids the need to construct ab initio new polymers for a given application, it provides an alternative to existing surface modification protocols, and it extends the range of polymers suitable as biocompatible materials .
Keywords: Surface; Modification; Biocompatibility;

The reduction of silver nitrate with various polyaniline salts to polyaniline–silver composites by J. Stejskal; M. Trchová; J. Kovářová; L. Brožová; J. Prokeš (86-90).
A conducting polymer, emeraldine form of polyaniline (PANI), reduces silver nitrate to metallic silver. The composites of PANI and silver have been prepared at equimolar proportion of reactants. Seven acids, representing inorganic and organic acids, have been used to protonate PANI. The acids were selected with respect to their chemical indifference or the ability to precipitate or reduce silver(I) ions. The PANI–silver composites differed in the conductivity from 1.7 × 10−6  S cm−1 when PANI phosphate was used as a substrate to 22.8 S cm−1 for PANI hydrochloride at comparable silver contents, 24 and 27 wt.%. The protonation state of PANI in PANI–silver composites was analyzed by FTIR spectroscopy. The composites contained spherical silver nanoparticles of 40–80 nm in size and also macroscopic particles, irrespective of PANI entering the reaction.
Keywords: Conducting polymer; Polyaniline; Silver; Silver nanoparticles;

4,4′-Bipyridinium salts (PAS-BPy(R)s) of poly(2-methoxyaniline-5-sulfonic acid) (PAS) were synthesized by the reaction of PAS with N-4-halophenyl-4-(4-pyridyl)pyridinium chlorides (BPy(X)s) or N-2,4-dinitrophenyl-4-(4-pyridyl)pyridinium chloride (BPy(NO2)). The UV–vis, ESR and X-ray photoelectron spectroscopy (XPS) data suggested the occurrence of the self-doping in PAS-BPy(R)s that was based on the electron transfer from the nitrogen atom in the polymer backbone to the 4,4′-bipyridinium unit. PAS-BPy(R)s behaved as polymeric electrolytes in the dilute solutions. Electric conductivity of PAS-BPy(R)s was almost constant when it was measured in the range of 1 ⩽ pH ⩽ 10. Cyclic voltammetry suggested that PAS-BPy(R)s received two-step electrochemical reduction in film, and the electrochemical reaction was accompanied with electrochromism.
Keywords: 4,4′-Bipyridinium salt; Polyaniline; Self-doping; Electron transfer; Electric conductivity;

A star-like amphiphilic copolymer was synthesized via RAFT polymerization by using a pentaerythritol-based compound (PTDBA) as a chain transfer agent with Styrene and DMAEMA as monomers. The polymer structure was characterized by FTIR, 1H NMR, 13C NMR and SEC/MALLS. After the retardation period, the molecular weight of PS-CTA and PMMA-CTA increased linearly with monomer conversion. The amphiphilic copolymer self-assembled into spherical micelles when water was added into its DMF solution. The particle size and polydispersity index (PDI) of the micelles in deionized water were about 406 nm and 0.113, respectively. In a pH 10 buffer solution and low micelle concentration, the micelle size decreased with temperature increase. At higher temperatures and micelle concentrations the size increased, resulting in precipitation among agglomerating micelles. This phenomenon was not observed in deionized water. Furthermore, the copolymer effectively prolonged the release time of chlorambucil (CLB) in deionized water.
Keywords: RAFT; Star block copolymer; Amphiphilic block copolymers; Self-assembly; Chlorambucil; Controlled release;

Adsorption of amino acid derivatives on calixarene carboxylic acid impregnated resins by Tatsuya Oshima; Ryota Saisho; Kaoru Ohe; Yoshinari Baba; Keisuke Ohto (105-110).
Macrocyclic host molecules calixarene carboxylic acid derivatives are found to act as powerful extractants for biologically important amino compounds. A series of adsorbents were prepared from a methacrylate-based polymer Amberlite XAD-7 by impregnation with various calixarene derivatives, for adsorptive recovery of amino acid derivatives. The larger macrocycles calix[6]arene and calix[8]arene carboxylic acid derivatives were more effective for adsorption of amino acid derivatives on the impregnated resin than the calix[4]arene derivative. Since adsorption proceeds mainly via electrostatic interaction, the carboxylic acid groups introduced into the calixarene platform were important for adsorption of cationic amino acid derivatives. The adsorption selectivity for amino compounds using adsorbent impregnated with the calix[6]arene carboxylic acid derivative depends simply on the hydrophobicity of the adsorbates.
Keywords: Calixarene; Extractant impregnated resin; Adsorption; Separation; Amino acid;

Styrene monomers, possessing three kinds of protected quinizarin (Qz) dye precursors such as tBOC, acetyl and tosyl groups, have been prepared and copolymerized with MMA in high yields to obtain protected-Qz precursor polymers (pr-QzP). Thermal and photoinduced acidolytic deprotection behaviors were investigated to confirm the regeneration of the Qz moieties in the polymer films by thermal and spectral analyses. Lithographic fluorescent photoimaging on spin-cast films of pr-QzP containing a photoacid generator resulted in high resolution and sensitivity by a dry process based on chemical amplification. In the dry lithography process, finely resolved sub-0.4-micrometer fluorescent patterns were delineated on the thin precursor polymer films without using a developer.
Keywords: Deprotection by acidolysis; Fluorescent imaging; Lithography; Photogenerated acid; Quinizarin polymers;

A Hagihara–Sonogashira cross-coupling reaction has been used to synthesize a new copolymer consisting of electron-accepting perylene bisimide (PBI) and electron-donating oligo(p-phenylene ethynylene) (OPE) units. Photoinduced singlet energy transfer and charge separation have been studied in solution via steady-state absorption, excitation, fluorescence, and theoretical calculations. The electron transfer from the OPE excited state competes with a singlet energy transfer state to the PBI unit. The results show that the excitation of the OPE unit in the polymer results in energy and electron transfers, while the excitation of the PBI unit in the polymer only result in electron transfer.
Keywords: Perylene bisimide; Oligo(p-phenylene ethynylene); Energy transfer; Charge separation;

A novel reversible addition-fragmentation transfer (RAFT) agent was successfully prepared using aminopropyl-isobutyl polyhedral oligomeric silsesquioxane (POSS). The POSS-containing RAFT agent was successively applied in the RAFT polymerization of styrene to produce the organic/inorganic hybrid homopolymer and block copolymers. The polymerization results showed the POSS-containing RAFT agent is an effective chain transfer agent (CTA) in the RAFT polymerization of styrene. The thermal properties of the organic/inorganic hybrid polymers were also investigated by differential scanning calorimetric (DSC) and thermal gravity analysis (TGA). The results displayed the thermal properties of the hybrid polystyrenes are effectively enhanced by POSS molecules.
Keywords: Reversible addition-fragmentation transfer (RAFT) polymerization; Polyhedral oligomeric silsesquioxane (POSS); Polystyrene;

Facile synthesis of SBA-15/polyaniline nanocomposites with high electrochemical activity under neutral and acidic conditions by Shaohuang Weng; Zhonghua Lin; Yan Zhang; Lixian Chen; Jianzhang Zhou (130-136).
A facile synthesis of SBA-15/polyaniline (PANI) nanocomposites was developed via chemical polymerization in a pH 3 solution based on the electrostatic adsorption of positively charged anilinium ions on negatively charged SBA-15. X-ray diffraction, N2 sorption isotherms, transmission electron microscopy and scanning electron microscopy characteristics indicated that PANI chains were distributed both on the inside and outside surfaces of the SBA-15 pores. A possible synthetic scheme for the creation of nanocomposites has been proposed. The SBA-15/PANI nanocomposites showed high, stable electrochemical activity in neutral and acidic conditions. The preliminary use of the SBA-15/PANI nanocomposites as an electroactive support for the selective detection of uric acid (UA) in the presence of a large excess of ascorbic acid (AA) demonstrates this material’s potential for use in electrochemical biosensors.
Keywords: Electrostatic adsorption; SBA-15/PANI nanocomposites; Electrochemical activity; Biosensor application;

Hollow polyaniline/Fe3O4 microsphere composites with electromagnetic properties were successfully prepared by decorating the surface of hollow polyaniline/sulfonated polystyrene microspheres with various amounts of Fe3O4 magnetic nanoparticles using sulfonated polystyrene (SPS) as hard templates and then removing the templates with tetrahydrofuran (THF). The synthesized hollow microsphere composites were characterized by FT-IR, UV/Vis spectrophotometry, SEM, XRD, elemental analysis, TGA, and measurement of their magnetic parameters. Experimental results indicated that the microspheres were well-defined in size (1.50–1.80 μm) and shape, and that they were superparamagnetic with maximum saturation magnetization values of 3.88 emu/g with a 12.37 wt% content of Fe3O4 magnetic nanoparticles. Measurements of the electromagnetic parameters of the samples showed that the maximum bandwidth was 8.0 GHz over −10 dB of reflection loss in the 2–18 GHz range when the Fe3O4 content in the hollow polyaniline/Fe3O4 microsphere composites was 7.33 wt%.
Keywords: Polyaniline/Fe3O4; Polystyrene/sulfonated polystyrene; Hollow microspheres; Microwave absorption; Electromagnetic parameters;