Reactive and Functional Polymers (v.72, #11)

Synthesis and characterization of telechelic macromers containing fatty acid derivatives by Miroslawa El Fray; Jedrzej Skrobot; Durgadas Bolikal; Joachim Kohn (781-790).
Telechelic macromers end-capped with (meth)acrylic functionalities are the most commonly used materials in rigid, dental formulations. In order to provide higher flexibility to the final product (not necessarily for dental applications), long chain aliphatic fatty acid derivatives may be chosen. Thus, new telechelic macromers comprising methacrylic functionalities and dimer fatty acid derivatives have been synthesized for the first time, and their chemical structure is discussed in detail. Six different systems comprising ester, anhydride and urethane bonds were synthesized from non-toxic raw materials. FTIR spectroscopy and NMR analysis were used to evaluate chemical structure of new systems. Their molecular masses were estimated from GPC measurements and from an analytical method based on iodine value determination. The latter one proved to be very accurate in determining molecular masses of methacrylated telechelics according to a new method developed in this work. We demonstrated that, via simple organic chemistry, different architectures of telechelic macromers comprising commercially available, long chain derivatives of fatty acid, mainly linoleic acid, with α,ω-dihydroxy, α,ω-dicarboxy or α,ω-diamino functionalities were successfully synthesized. These macromers facilitate the development of new reactive (preferably, photocurable) flexible systems for potential biomedical applications.
Keywords: Telechelic macromer; Methacrylates; Fatty acid; Vegetable oil; Renewable resources;

The effects of polymer functional group and solution pH on stability of colloidal Al2O3 water suspension were studied. Both the nonionic polymers: polyethylene glycol (PEG), polyethylene oxide (PEO) and the ionic ones: polyacrylic acid (PAA), polyacrylamide (PAM), polyvinyl alcohol (PVA) were used in the experiments. The following methods were applied: turbidimetry (stability measurements), spectrophotometry (determination of polymer adsorption), viscosimetry (thickness of polymer adsorption layer), potentiometric titration (solid surface charge density) and microelectrophoresis (potential zeta). It was shown that anionic polyacrylic acid is both the most effective stabilizer (at pH 9) and flocculant (at pH 3) of the alumina suspension. Its carboxyl groups have the greatest affinity for the surface active sites (the largest adsorption) of all functional groups present in the other examined polymers. The latter, i.e. hydroxyl (PEG, PEO, and PVA) and acetate (PVA) show a much lower affinity for the Al2O3 surface (negligible adsorption) and minimally affect the stability of the alumina-solution system.
Keywords: Structure of polymer film; Polymer functional groups; Bridging flocculation; Steric stabilization; Macromolecule conformation; Alumina;

Dual-cure hybrid polymer networks were prepared by sequential thiol–ene photopolymerization followed by thermal ring-opening polymerization of benzoxazines with the aim of increasing the glass transition temperature range of thiol–ene based materials and improving the processibility of polybenzoxazines. The hybrid networks are derived from a multifunctional, dually-polymerizable monomer possessing both bis-“ene” and bis-benzoxazine moieties enabling the formation of two networks through a common constituent monomer when combined with a multifunctional thiol. The photopolymerization kinetics of the thiol–ene reaction were investigated by real-time infrared spectroscopy. Sequential thermal ring-opening polymerization of the benzoxazine moieties incorporated into the thiol–ene network was characterized by FTIR and differential scanning calorimetry. The glass transition of the hybrid material was observed at 150 °C; however, competing thiol–ene (radical-mediated) and thiol–benzoxazine (nucleophilic ring-opening) reactions during the UV cure yield a heterogeneous network structure.
Keywords: Thiol–ene; Photopolymerization; Polybenzoxazine; Hybrid network; Dual-cure;

Synthesis of macroporous polymers with radical scavenging properties by immobilization of polyphenolic compounds by R. Dario Arrua; Juan F. Basbus; Miriam C. Strumia; Cecilia I. Alvarez Igarzabal; Mónica A. Nazareno (807-813).
Solid phase radical scavengers have been prepared by the immobilization of antioxidant (AOX) compounds on macroporous polymers. Poly(glycidylmethacrylate-co-trimethylolpropane trimethacrylate) [poly(GMA–TRIM)] and poly(N-acryloyl-tris(hydroxymethyl)aminomethane-co-glycidylmethacrylate-co-N,N′-methylenebisacrylamide) [poly(NAT–GMA–BIS)] were prepared by free radical polymerization using a mixture of dimethylsulfoxide (DMSO)-poly(ethyleneglycol) 6000 (PEG 6000) as a porogenic solvent. The polymers were aminated with ethylenediamine (EDA) and the linkage of the polyphenolic compounds (gallic and caffeic acids) was carried out by two different approaches: through N,N′-dicyclohexylcarbodiimide/4-dimethylaminepyridine (DCC/DMAP) system (one-step method) or through the previous formation of the acyl chloride of the polyphenolic compounds and subsequent amidation reaction (two-step method). The available phenolic groups on the macroporous polymers were determined using the Folin–Ciocalteu method; the radical scavenging properties of the materials prepared were evaluated using the radical species 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2′-azino-bis-[3-ethylbenzothiazoline-6-sulfonic acid] radical cation (ABTS+• ). From the results, higher antiradical capacities were obtained with the polymers in which the immobilization of the antioxidant molecules was performed through the two-step method. The polymeric networks prepared in this work yielded up to 13.2 μmol AOX/g of dry polymer, which allowed a quantitative removal of the radicals tested in less than 30 min.
Keywords: Macroporous polymers; Antioxidants; Phenolic compounds; Polyphenols; Antiradical activity;

Antioxidant capacity of robust polyaniline–ethyl cellulose films by Chyong Fang Hsu; Paul A. Kilmartin (814-822).
Ethyl cellulose films containing up to 17% polyaniline (PANI EC film) were prepared from ethanolic solutions. The antioxidant capacity of the PANI EC films was examined using the oxygen radical absorbance capacity (ORAC) assay, and the films demonstrated very efficient peroxyl free radical scavenging activity. A good correlation was also obtained between the net ORAC curve area and the size of the tested film, indicating the homogenous dispersion of active PANI powder across the film. Reduced PANI presented greater peroxyl radical scavenging activity than more oxidized as-prepared forms. The influence of the PANI EC films on the oxidation of Ropufa oil was determined after incubation at 60 °C for several days. The oil stored in the presence of a PANI EC film was found to exhibit a lower peroxide value than in the absence of PANI, indicating that the conducting polymer can inhibit the oxidation of fish oil.
Keywords: Polyaniline; Ethyl cellulose; Conducting polymer; ORAC assay; Antioxidants;

Polyvinyl alcohol (PVA) microgels were prepared using electron beam irradiation. To improve the PVA microgel functionality and gel fraction, chains of polyacrylic acid (PAA) were incorporated into PVA microgel by radiation grafting technique. The increase in the acrylic acid (AA) content as well as PVA Mwt is accompanied by a mutual increase in the gel fraction and a decrease in the swelling%. Immobilization of different TiO2 concentrations on the surface of the prepared PVA–AA microgel was carried out. The structural changes in the prepared PVA–AA microgel immobilized with TiO2/were investigated using FTIR, EDX and XRD. Photodegradation efficiency of TiO2/PVA–AA microgel against metnil yellow dyes was studied. TiO2/PVA–AA microgel activity increases with the increase of the amount of TiO2 and results in an increase in the rate of the photodegradation reaction. Easily recovery and reusability made TiO2/PVA/AA of great important in practice use as a photocatalytic degradation composite, for dye removal from wastewater.
Keywords: Microgel; Electron beam; Titanium dioxide; Metanil Yellow; Photocatalytic degradation;

Poly(N-propargylamide)s bearing cholesteryl moieties: Preparation and optical activity by Chaohong Zhang; Dong Liu; Bolin Zhou; Jianping Deng; Wantai Yang (832-838).
We synthesized a novel chiral cholesteryl-based N-propargylamide (Mch, HCCCH2NHCOCH2CH2COO―ch, ch = cholesteryl) from which homopolymers [P(Mch)] with different molecular weights (number-average molecular weight: 8600, 14100 and 30000) were prepared. The polymers formed helical structures with a preferential helicity. The three polymers increased in both helix content and specific rotation as the molecular weight increased. P(Mch)-8600 was studied in detail as the model polymer. P(Mch)-8600 adopted helical conformations in toluene, THF, CHCl3 and CH2Cl2, exhibited thermal stability with a decomposition temperature of 273 °C and formed a lyotropic liquid crystal under the studied conditions. Copolymers of different compositions of Mch and an achiral monomer (Met) were prepared. The copolymers formed helices to different degrees depending on the specific composition, indicating an effective approach for controlling the formation of helices in synthetic helical polymers.
Keywords: Helical polymer; Substituted polyacetylene; Optical activity; Cholesteryl group; Liquid crystalline polymer;

Poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membranes were successfully fabricated and activated with glutaraldehyde (GA) to interact with enzyme molecules. A lipase isolated from Candida rugosa was employed as a model biocatalyst and successfully immobilized onto the membrane surfaces via covalent bonds with the aldehyde groups. Scanning electron microscopy images revealed that the membranes retained uniform nanofibrous and open porous structures after the treatments. The results indicated that the increment of the initial glutaraldehyde concentration induced an increase of the enzyme loading on the membrane surfaces but a decrease in the activity of the immobilized enzyme. Under an optimum condition, the glutaraldehyde activated PVA-co-PE nanofibrous membrane reached the highest enzyme activity at 676.19 U/g of the membrane. The pH tolerance, thermal and storage stability of the immobilized lipase were significantly improved. In addition, the immobilized lipase can be easily recovered and retained at 67% of its initial activity after 10 time uses. Therefore, the glutaraldehyde activated PVA-co-PE nanofibrous membrane is a promising solid support media for enzyme immobilization, and the immobilized enzymes could have broad biocatalytic applications.
Keywords: Nanofibrous membrane; Glutaraldehyde activation; Lipase; Enzyme immobilization;

Mixed micelles from methoxy poly(ethylene glycol)–polylactide and methoxy poly(ethylene glycol)–poly(sebacic anhydride) copolymers as drug carriers by Po-Liang Lai; Cheng-Chun Hsu; Tsang-Hao Liu; Ding-Wei Hong; Lih-Huei Chen; Wen-Jer Chen; I-Ming Chu (846-855).
mPEG–PLLA (poly l-lactic acid) is synthesized by ring-opening polymerization of lactide and conjugation with mPEG. Sebacic acid is modified with acetic anhydride and condensed with mPEG to form mPEG–PSA (poly sebacic anhydride). The micelles formed by mPEG–PLLA are characterized by slow degradation and low drug encapsulation efficiency; on the contrary, mPEG–PSA micelles are characterized by rapid degradation but high encapsulation efficiency. They can merge into spherical micelles (Φ  = 140 nm) by self-assembly in water. The mixed micelles can successfully encapsulate a typical hydrophobic drug (curcumin), and significantly improve its solubility. Experimental results show that the mixed micelles have the features of high encapsulation efficiency and slow degradation.
Keywords: Diblock copolymers; Mixed micelles; Drug delivery system; Self-assembly; Polyanhydride;

Molecular architecture and solid-state properties of novel biocompatible PBS-based copolyesters containing sulphur atoms by Michelina Soccio; Nadia Lotti; Massimo Gazzano; Marco Govoni; Emanuele Giordano; Andrea Munari (856-867).
Poly(butylene/thiodiethylene succinate) block copolymers (PBSPTDGS), prepared by reactive blending of the parent homopolymers (PBS and PTDGS) in the presence of Ti(OBu)4, underwent molecular and solid-state characterization, in order to investigate the effects of the transesterification reactions. 13C NMR analysis demonstrated the formation of copolymers whose degree of randomness increased with the mixing time. Thermal measurements showed that all the samples were semicrystalline, with a soft amorphous phase and a rigid crystal phase. WAXD measurements indicated that the copolymers are characterized by the presence of a pure PBS crystal phase, with the exception of physical mixture. The mechanical properties were related to degree of crystallinity. The random copolymer, characterized by the lowest crystallinity degree, exhibits the lowest elastic modulus and the highest deformation at break. When evaluated for indirect cytotoxicity, all the polymers under investigation appeared entirely biocompatible. In addition, positive results from cellular adhesion and proliferation assays carried out with H9c2 cells seeded and grown up to 14 days in culture over films of PBSPTDGS30 and PBSPTDGS240 demonstrated that these new materials might be of interest for tissue engineering applications.
Keywords: Poly(butylene succinate); Thiodiethylene glycol; Reactive blending; Block copolymers; Biocompatibility;

We report cyclo-depolymerizations of solutions of poly(bisphenol-A carbonate) and two poly(alkylene carbonate)s to give, in each case, mixtures of macrocyclic oligomers (MCOs). The aromatic carbonate was less reactive than the aliphatic carbonates. Using various catalysts small-scale entropically-driven ring-opening polymerizations (ED-ROPs) of the MCOs reformed the original polymers. Tetra-n-butylammonium tetraphenylborate was the most generally useful catalyst of those investigated. At 230 °C in the absence of added catalyst the aliphatic carbonate-containing MCOs underwent thermal ED-ROPs. In order to probe the possibility of extending the use of ED-ROP for copolymer synthesis, copolymerizations of the carbonate-containing MCOs, both with each other and with carboxylate ester-containing MCOs were investigated. These afforded a range of copolymers in high yields, several of which were shown by 13C NMR spectroscopy to have the repeat units in random sequences. This approach to the synthesis of copolymers containing carbonate linkages has the potential to be used for the synthesis of polymer libraries.
Keywords: Cyclo-depolymerization; Macrocyclic oligo(bisphenol-A carbonate)s; Macrocyclic oligocarbonates; Entropically-driven ring-opening copolymerization;

A series of diols (diethylene glycol, triethylene glycol, butane-1,4-diol and hexane-1,6-diol) were immobilized onto Merrifield resin and subsequently phosphorylated with dialkyl chlorophosphate (alkyl = Me, Et, Bu). The resins bearing hexane-1,6-diyl groups exhibited very good extraction abilities in regard to precious metal chloro complexes like platinum(IV), palladium(II) and rhodium(III). In batch experiments, more than 98% of Pt(IV) is extracted even when the metal and the hydrochloric acid concentration is enhanced significantly. Elution can be achieved with a solution of 0.5 mol L−1 thiourea in 0.1 mol L−1 hydrochloric acid. In the presence of other noble metals, platinum(IV) is preferentially bound. The extraction yield decreases in slightly acidic solution in the following order: Pt(IV) ≈ Pd(II) > Rh(III) and changes with increasing hydrochloric acid concentration to Pt(IV) > Pd(II) ≫ Rh(III). At different ratios of metal and acid, the temperature has nearly no influence on the platinum extraction. On slightly acidic media, the extraction of rhodium decreases by 30% when the temperature is increased from 10 °C to 40 °C. When the acid and metal concentration is enhanced, the palladium extraction decreases by 7–9%, depending on the resin.
Keywords: Solid-phase extraction; Platinum group metals; Modified polymer resin; Phosphate; Adsorption isotherm;

Three mono-sized poly(glycidyl methacrylate) (PGMA) microspheres of 0.8, 1.8 and 2.5 μm in particle sizes were prepared via dispersion polymerization. Poly(ethylenimine)s (PEIs) of different molecular weights (60 000 and 1200) were coupled to the PGMA bead surface to prepare cationic beads of different charge densities and ligand (cationic group) structures. The cationic microspheres were used to explore the effect of solid phase properties on like-charged lysozyme refolding. The refolding yield increased with increasing bead concentration and charge density. At low bead concentration range, it increased more significantly with bead concentration with the microspheres of higher charge density. This indicates that the microspheres of high charge density are beneficial in facilitating protein refolding. The refolding yield was independent of the cationic group structure. However, PEI of higher molecular weight was favorable in the preparation of microspheres of higher charge density. Smaller-sized particles have higher specific surface area, so they facilitated lysozyme refolding more significantly. By addition of the charged beads, about 90% refolding yield of 4 mg/mL lysozyme could be achieved. The studies provided more insight into the effects of like-charged solids on protein refolding, which would help design more efficient charged media for facilitated protein refolding applications.
Keywords: Mono-sized microsphere; Like-charge; Protein refolding; Charge density; Electrostatic repulsion;

A copolymer based on benzo[1,2-b:4,5-b′]dithiophene and quinoxaline derivative for photovoltaic application by Haimei Wu; Bo Qu; Zhiyuan Cong; Hongli Liu; Di Tian; Bowen Gao; Zhongwei An; Chao Gao; Lixin Xiao; Zhijian Chen; Huanhuan Liu; Qihuang Gong; Wei Wei (897-903).
A D–A–D copolymer (PBDTQx) with a bandgap of 1.78 eV, containing alkoxy-substituted benzo[1,2-b:4,5-b′]dithiophene (BDT) as donor and quinoxaline derivative (Qx) as acceptor, was synthesized by Stille coupling reaction. In order to study the photovoltaic property of PBDTQx, polymer solar cells (PSCs) were fabricated with PBDTQx as the electron donor blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as the electron acceptor. The power conversion efficiency (PCE) of PSC was 1.01% for an optimized PBDTQx: PC61BM ratio of 1:5, under the illumination of AM 1.5, 100 mW/cm2. The results indicated that PBDTQx was a promising donor candidate in the application of polymer solar cells.
Keywords: Polymer solar cell; D–A–D polymers; Heterojunction; Quinoxaline; Thiophene;

Reactions of N-(2,4-dinitrophenyl)-4-arylpyridinium chlorides (aryl = H (1), phenyl (Ph); 2, and 4-pyridyl (Py); 3) with R-(−)-, S-(+)-, or racemic 1,1′-binaphthyl-2,2-diyl sodium phosphates (R-, S-, or rac-BINAP-PO4Na) resulted in anion exchange between Cl and R-, S-, or rac -BINAP- PO 4 - to yield Zincke salts with chiral anions, namely 1R, 2R, 3R, 1S, 2S, 3S, 1rac, 2rac, and 3rac. Reactions of these Zincke salts with 2-methylpiperazine resulted in pyridinium ring opening to yield ionic polymers with 5-(2-methylpiperazinium)-3-aryl-penta-2,4-dienylideneammonium 1,1-binaphthyl-2,2-diyl phosphate units, namely, polymer ( rac - Me ; Ar ; R - BINAP - PO 4 - ) (Ar = H, Ph, and Py), polymer ( rac - Me ; Ar ; S - BINAP - PO 4 - ) (Ar = H, Ph, and Py), and polymer ( rac - Me ; Ar ; rac - BINAP - PO 4 - ) (Ar = H, Ph, and Py). CD measurements revealed a partially helical conformation of the main chain in polymer ( rac - Me ; H ; R - BINAP - PO 4 - ) and polymer ( rac - Me ; H ; S - BINAP - PO 4 - ) . The 2-methylpiperazinium rings of the polymers converted from the boat to the chair form via a half-chair intermediate in solution. This conformational change was accompanied by a decrease in π-conjugation length. This decrease corresponded to a shift in the electrochemical oxidation peaks of the polymers to higher potentials when the polymer solution was left standing in air.
Keywords: Chiral phosphate anion; Conjugated polymer; Zincke salts; Ring-opening copolymerization; Through-space interaction;