Reactive and Functional Polymers (v.74, #C)

We report prediction of selected physical properties (e.g. glass transition temperature, moduli and thermal degradation temperature) using molecular dynamics simulations for a difunctional epoxy monomer (the diglycidyl ether of bisphenol A) when cured with p-3,3′-dimethylcyclohexylamine to form a dielectric polymer suitable for microelectronic applications. Plots of density versus temperature show decreases in density within the same temperature range as experimental values for the thermal degradation and other thermal events determined using e.g. dynamic mechanical thermal analysis. Empirical characterisation data for a commercial example of the same polymer are presented to validate the network constructed. Extremely close agreement with empirical data is obtained: the simulated value for the glass transition temperature for the 60 °C cured epoxy resin (simulated conversion α  = 0.70; experimentally determined α  = 0.67 using Raman spectroscopy) is ca. 70–85 °C, in line with the experimental temperature range of 60–105 °C (peak maximum 85 °C). The simulation is also able to mimic the change in processing temperature: the simulated value for the glass transition temperature for the 130 °C cured epoxy resin (simulated α  = 0.81; experimentally determined α  = 0.73 using Raman and α  = 0.85 using DSC) is ca. 105–130 °C, in line with the experimental temperature range of 110–155 °C (peak maximum 128 °C). This offers the possibility of optimising the processing parameters in silico to achieve the best final properties, reducing labour- and material-intensive empirical testing.
Keywords: Epoxy resins; Molecular simulation; Thermal analysis; Property prediction;

Synthesis and shape memory performance of polyurethane/graphene nanocomposites by J.T. Kim; B.K. Kim; E.Y. Kim; H.C. Park; H.M. Jeong (16-21).
Small amounts of allyl isocyanate modified graphene (iG, 0–2.5 phr) were incorporated into acrylate terminated polyurethane (PU) by UV curing. The effects of this incorporation on the morphological, mechanical, thermal and shape memory properties of the nanocomposites were examined. The iG nanoparticles incorporated into the PU chains acted as both multifunctional crosslinkers and reinforcing fillers, and the effects were most pronounced at 1.5 phr iG. Consequently, the glassy and rubbery state moduli, yield strength, glass transition temperature (Tg ), shape fixity and shape recovery ratios were increased by adding up to 1.5 phr iG. Above the loadings, most of the above properties decreased due to aggregation and the auto-inhibition reaction of allyl compounds.
Keywords: Polyurethanes nanocomposites; UV cure; Graphene oxide; Shape memory;

Synthesis, curing behavior and thermal properties of fluorene-containing benzoxazines based on linear and branched butylamines by Jun Wang; Tian-tian Ren; Yu-dan Wang; Xuan-yu He; Wen-bin Liu; Xian-de Shen (22-30).
A series of fluorene-containing benzoxazine monomers based on linear and branched butylamines were successfully synthesized in high purity and good yield through a facile one-pot procedure by the reaction of 9,9-bis-(4-hydroxyphenyl)-fluorene with paraformaldehyde and isomeric butylamines. The chemical structures of the target monomers were characterized by Fourier transform infrared (FT-IR), Elemental analysis, 1H and 13C nuclear magnetic resonance (NMR). The curing behavior of benzoxazine monomers was studied by differential scanning calorimetry (DSC) and FT-IR. The thermal properties of cured polybenzoxazines were measured by DSC and thermogravimetric analysis (TGA). The results reveal that the polarity of solvent and the basicity of butylamines produce clear effects on the synthesis of the butylamine-based benzoxazine monomers. Also, the basicity and steric effect of butylamines exhibit significant effects on the curing behavior of benzoxazine monomers and the thermal properties of their polymers. The glass transition temperature and thermal stability of branched butylamine-based polybenzoxazines are higher than those of the corresponding linear butylamine-based polybenzoxazine and traditional bisphenol A-based polybenzoxazines.
Keywords: Fluorene-based benzoxazine; Polybenzoxazine; Steric effect; Curing behavior; Thermal properties;

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of various concentrations of PAA. The content of PAA moiety on the surface of the composite films (PANI/PAA films) was estimated by determination of carboxyl groups and found to be controlled by the concentration of PAA in polymerization solution. Acid phosphatase (ACP) was immobilized covalently on the PANI/PAA films by the condensation reaction with the carboxyl groups on the films. It was confirmed that the enzyme activity of the ACP-immobilized PANI/PAA film increased with increasing content of PAA moiety on the surface of the film, accompanying an increase in the amount of the immobilized ACP. The activity of the covalently immobilized ACP was significantly higher than that of the ACP adsorbed on the PANI/PAA film. By use of the ACP-immobilized PANI/PAA film as an enzyme electrode, bioelectrocatalytic oxidation of L-ascorbic acid 2-phosphate (ASA2P) was examined. The enzyme electrode gave the current due to the oxidation of ASA2P in proportion to the content of PAA moiety on the surface of the PANI/PAA film used, which was relevant to the activity of the covalently immobilized ACP.
Keywords: Polyaniline; Poly(acrylic acid); Acid phosphatase; Enzyme electrode; L-Ascorbic acid 2-phosphate;

Polystyrene-supported triazoles for metal ions extraction: Synthesis and evaluation by Abid Ouerghui; Hichem Elamari; Saadia Ghammouri; Riadh Slimi; Faouzi Meganem; Christian Girard (37-45).
In order to prepare substituted polymers bearing functional groups to chelate metals for their application in extraction and/or depollution applications, Merrifield polymer was transformed into the known azidomethyl polystyrene. Click-chemistry based on copper (I)-catalyzed Huisgen’s reaction was then used to form polymer-grafted 1,4-triazoles using a variety of synthesized substituted alkynes. These polymer-supported triazoles were then used to extract metals (Cd, Fe, Mg, Ni and Co) from aqueous solutions. A comparative study of metal extractions by these supported triazoles was made between the starting azidomethyl polystyrene and two natural clays taken from the Gafsa area (South-West Tunisia). Raw and purified clays from two Gafsa sites were found to extract metals quite well with almost no selectivity, except for lower fixations of cadmium and magnesium. The synthesized polymers were found to extract all metals with lower efficiencies than the clays. However, one of the polymer-supported triazole was found to extract selectively cadmium with a high efficiency, reaching the levels of the natural clays.
Keywords: Polystyrene; Clays; Triazole; Click chemistry; Metal extraction;

Highly oleophobic properties are obtained by electrodeposition of original PEDOT derivatives containing F-butyl chains because their surface morphology (spider-web-like structure) favors the “pinning effect”.Original fluorinated (F-butyl, F-hexyl and F-octyl) EDOT derivatives containing thioester connectors are synthesized and used as monomers for the elaboration of liquid-repellent surfaces by electrodeposition. Their surface morphology varies as a function of the fluorinated chain length, due to the increase in the insolubility of the oligomers formed in the first instances. Superhydrophobic surfaces are obtained with F-octyl and F-hexyl chains but only the surfaces produced from the monomer containing F-butyl chains are highly oleophobic. These high contact angles can be explained by their surface morphology (spider-web-like structure) which favors the “pinning effect”. This works allows the decrease in the bioaccumulative potential of fluorinated materials with an increase in their oil-repellent properties.
Keywords: Superhydrophobicity; Oleophobicity; Fiber; Conductive polymers; Electrochemistry;

Assembled diglycolamide for f-element ions sequestration at high acidity by Vivek Chavan; Vasudevan Thekkethil; Ashok K. Pandey; Mudassir Iqbal; Jurriaan Huskens; Sher Singh Meena; Asok Goswami; Willem Verboom (52-57).
Display OmittedDiglycolamides (DGA) form reverse-micellar type of supramolecular aggregates upon equilibration with a nitric acid solution that enhances DGA affinity extraordinary towards f-elements. To mimic DGA aggregates, DGA molecules have been preorganized on chemical platforms to form assemblies having a good affinity towards f-elements. However, the synthetic procedures used are quite laborious that limits their large scale applications. To address this problem, a new DGA-bearing monomer N,N-dioctyl,N′-propyl-2-methylacrylamide diglycolamide has been synthesized. This DGA-methacrylate monomer can be polymerized easily, and shows an interesting affinity towards f-element ions both in monomeric and polymeric forms at high nitric acid concentrations. This makes it very promising for the development of fixed-site membranes, resins, and magnetic assemblies for a variety of applications. DGA-methacrylate monomer has been found to assemble on magnetic nanoparticles Fe3O4. DGA-methacrylate coated Fe3O4 particles capture representative trivalent actinide 241Am with a very high efficiency. However, it has been observed that HNO3 induced preorganization of DGA-methacrylate plays an important role in sorption of f-element ions in the polymeric form and self-assembled molecules on the magnetic nanoparticles.
Keywords: Diglycolamide; Polymer; Magnetic particles; Actinide; High acidity;

In this paper, cross-linked poly (acrylic acid-co-butyl acrylate) microgels were utilized to impart pH-sensitivity to poly (vinylidene fluoride) membranes by phase separation of a casting solution of poly (vinylidene fluoride)/poly (acrylic acid-co-butyl acrylate)/DMF in aqueous solution. The effect of microgels content on morphologies, surface composition, and chemistry of the as-prepared membranes was studied by varieties of spectroscopic and microscopic characterization techniques. By using the filtration of water and protein aqueous solution, the performance of the membrane was evaluated. Results indicated that the as-prepared membrane was pH-sensitive to water flux, bovine serum albumin rejection and antifouling property. Besides, the as-prepared membrane showed an obvious improvement of water flux and proper bovine serum albumin rejection ratio, compared to the pristine PVDF membrane. Meanwhile, dynamic bovine serum albumin fouling resistance and flux recovery property were also greatly enhanced due to the improvement of surface hydrophilicity. Hopefully, the hydrophilic microgels additive would be favorable to fabricate other polymer membranes for water treatment.
Keywords: Poly (vinylidene fluoride); Microgel; pH-sensitivity; Hydrophilicity; Antifouling performance;

The idea to develop hydrophilic lactic acid-based polyelectrolyte was presented. A facile route was utilized to prepare smart hydrogels that contained lactate units and carboxylic groups. The hydrogels were obtained through the radical cross-linking reaction between an unsaturated lactate-contained macromonomer and acrylic acid (AA)/itaconic acid (IA) monomer pair. The structure and performances of the hydrogels were characterized with thermogravimetric analysis, dynamic thermal analysis, scanning electron microscopy, swelling tests and adsorption measurements. The equilibrium swelling ratios of the hydrogels in acidic (pH 3.6) and basic (pH 11.5) media reached 25.3 and 62.3 respectively. The pH-sensitive swelling behaviors of the hydrogel confirmed that the hydrogels contained carboxylic groups and they were hydrophilic. The metal ions including calcium, copper, lead and cerium ions were bound into the hydrogels, which also confirmed the existence of the carboxyl groups. Moreover, the swelling ratio and adsorption capacity of the gel prepared from monomer pair were significantly higher than those obtained in absence of IA, which suggested that the properties of the hydrogels could be controllable by simply adjusting the ratio of AA/IA. In addition, the weight loss percentage of the hydrogel was around 37% after two-week in vitro degradation, which indicated the hydrogel contained lactate units.
Keywords: Lactate units; Carboxyl groups; Hydrogel; pH-sensitive swelling; Absorption; Degradable;

A novel approach was developed for the preparation of the attapulgite/poly(acrylic acid) (ATP/PAA) nanocomposite microgels via the “one-pot” inverse suspension radical polymerization of acrylic acid (AA) with the multi-functionalized attapulgite nanorods (org-ATP) as the sole crosslinker. The parameters of the feeding ratio of the functional attapulgite (org-ATP) nanorods and AA (org-ATP/AA), oil (liquid paraffin)–water ratio, and feeding ratios of dispersing agent (sodium dodecyl benzene sulfonate (SDBS)) and initiator (ammonium persulfate (APS)) were optimized via 4-Variable 3-Level Orthogonal experiments. Under the optimized preparation condition, more than 85% of the monomer AA had been grafted onto the org-ATP nanorods to form the 3-dimensional network of the ATP/PAA nanocomposite microgel. The ATP/PAA nanocomposite microgel exhibited better mechanical stabilities (resistance to pressure and resistance to agitation) and selective adsorption to heavy metal ions, especially to Pb2+. The adsorbed Pb2+ ion could be completely eluted with HCl solution. The better mechanical stability and regeneration make it potential adsorbent for the heavy metal contaminated water.
Keywords: Multi-functionalized ATP; ATP/poly(acrylic acid) nanocomposite microgels; Inverse suspension polymerization; Selective adsorbent; Heavy metal ion;

Synthesis of PEG containing cationic block copolymers and their interaction with human serum albumin by Rakesh Banerjee; Swapnil Gupta; Debabrata Dey; Souvik Maiti; Dibakar Dhara (81-89).
Interaction between PEG containing cationic block copolymers with HSA.In this study, we have demonstrated the synthesis of a new series of cationic homopolymers based on 3-methacrylamidopropyl)-trimethylammonium chloride (MAPTAC) and block copolymers based on MAPTAC and poly(ethylene glycol) methyl ether acrylate (PEGMA), with the aim of studying their interactions with human serum albumin (HSA). The homopolymer (PMAPTAC) and its block copolymers containing 69 and 84 mol% PEGMA (PMAPTAC-b-PPEGMA69 and PMAPTAC-b-PPEGMA84 respectively) were prepared by RAFT technique. Interactions between human serum albumin (HSA) and these cationic polymers were studied using fluorescence spectroscopy, along with isothermal titration calorimetry (ITC) and circular dichroism (CD). The fluorescence spectra of these protein–polymer complexes revealed considerable binding affinity between PMAPTAC and HSA. However, the block copolymers exhibited relatively lower binding affinities with HSA that decreased with increase in PEGMA block length. CD studies corroborated the fluorescence data by suggesting the formation of protein–polymer complex that led to considerable loss in the negative ellipticity of HSA resulting from partial unfolding of the polypeptide chain. However, in case of the block copolymers, the presence of PEG partly prevented the perturbation of the polypeptide chain induced by polymer–protein interactions. ITC data suggested that the binding was an entropy-driven process. GdmCl denaturation curves showed increased stability of native HSA in presence of PMAPTAC, indicating higher conformational stability of HSA in presence of the cationic homopolymer.
Keywords: RAFT polymerization; Protein–polymer interactions; Polyelectrolyte; Fluorescence; Poly(ethylene glycol);

Synthesis and characterization of Aza222-based polymers for the removal of mercury from aqueous solutions by Mikhail Y. Redko; Karrie M. Manes; Julian S. Taurozzi; James E. Jackson; Volodymyr V. Tarabara (90-100).
Polymeric materials for mercury complexation have been prepared by cross-linking 1,4,7,10,13,16,21,24-octaazabicyclo[8.8.8]hexacosane (H6Aza222) with α,α′-dichloro-p-xylene and other multidentate electrophiles. Bulk and microporous p-xylylene-Aza222 were shown to be effective at binding divalent mercury cations from aqueous solutions of HgCl2 or Na2HgI4. The complexants were regenerable using solutions of HCl or Na2S.
Keywords: Polyamine; Mercury adsorption; Peraza[2.2.2]cryptand; Cryptand-metal binding; Mercury–polyamine stability constant;

The structure and mechanical properties of monodisperse pH-responsive poly(2-hydroxyethyl methacrylate/methacrylic acid) (poly(HEMA/MAA)) microgels prepared by inverse microemulsion polymerization were systematically investigated. To facilitate the polymerization, the inverse microemulsion systems were first optimized by generating relevant pseudo-three-component phase diagrams. The reactivity ratios of HEMA (r 1  = 1.001 ± 0.064) and MAA (r 2  = 0.318 ± 0.035) determined by titration method suggested that PHEMA segments preferred to be localized in the core of the synthesized poly(HEMA/MAA)) microgels. The mechanical property studies of the microscopic poly(HEMA/MAA)) microgels from oscillation rheometry revealed that microgel composition, concentration and pH could significantly alter the elastic modulus (G′), and a maximum averaged elastic modulus ( G ave ′ ) value of about 8.2 × 103  Pa was obtained.
Keywords: Microgel; Inverse microemulsion polymerization; Rheology; Mechanical properties;