All issues / Volume 11 (2017) / Issue 8 (August)
Biomimetic dopamine-conjugated polyaspartamides as novel adhesive materials were synthesized and characterized. These modified polyaspartamides contain three different groups combined with dopamine (DOPA), i.e., γ-amino butyric acid (GABA), ethanolamine (EA) and octylamine (OA), which are referred to as PolyAspAm (DOPA/GABA), PolyAspAm(DOPA/EA) and PolyAspAm(DOPA/OA), respectively. These three water-swollen polymer glues show good adhesion (0.1~0.4 MPa) with various daily-life materials (aluminum foil, glass and paper) as well as some plastic substrates (PET and PMMA). Compared to the polymers with more hydrophilic groups (GABA and EA), the polymer glue with the hydrophobic alkyl group (OA) exhibited higher adhesive strength values on most substrates. In addition, when applied to biological porcine skin, these glues demonstrated adhesion of values of 15~20 kPa with EA- and OA-conjugated polymers. These results suggest the great potential of dopamine-modified polyaspartamides as versatile and efficient polymeric glues for industrial and biomedical applications.
A new bio-based elastomer, poly(butylene 2,5-furandicarboxylate-ε-caprolactone) (PBFCL), has been synthesized from 2,5-furandicarboxylic acid, 1,4-butanediol, and ε-caprolactone successfully for the first time. The obtained copolyester was characterized in terms of chemical structure, thermal and mechanical properties, and enzymatic degradability. In PBFCL elastomer, butylene-2,5-furandiacrboxylate units (hard segments) crystallize to serve as physical crosslinks while ε-caprolactone polyester diol (soft segments) provide flexibility. PBFCL is a multi-blocked copolyester with randomly distributed rigid and soft segments. It possesses original feature of high strength and biodegradability stemming from the uses of aromatic and aliphatic monomers respectively. An important aspect of this new furanic-aliphatic polyester is its tailor-made properties simply achieved by changing the content of hard or soft segments. Typically, PBFCL-40 of optimal composition has Young’s modulus as low as 15.4 MPa, tensile strength as high 24.8 MPa, and elongation as long as 885%.
Black PE100 compounds were prepared using a co-rotating twin screw extruder by addition of carbon black masterbatches containing 35–40 wt% carbon black and different polymer carriers to a pipe grade PE100 material with bimodal molecular weight distribution. Different properties of carbon black masterbatches and PE100 black compounds were evaluated using thermal, rheological and mechanical tests. Rheological results indicated an inverse correlation between melt flow index (MFI) of masterbatch samples and storage modulus, complex viscosity and shear viscosity of black compounds, while flow instabilities of compounds were also postponed to higher shear rates. TGA indicated that masterbatch with highest value of MFI contained highest amount of low molecular weight lubricants which resulted in inhibition of strain hardening behavior in tensile test of its respective black compound unlike all other samples, reflecting possible suppressing of its long term resistance to slow crack growth. This behavior is attributable to facilitated crystallization and chain folding of longer chains in the presence of low molecular weight lubricants in this sample and consequently formation of thicker lamellas as confirmed by DSC, hence lowering density of entanglements in amorphous area and inhibition of strain hardening.
In this work, an electroactive polyimide (EPI) coating with biomimetic surface structure of rose petal used in anticorrosion application was first presented. First of all, amino-capped aniline trimer (ACAT) was synthesized by oxidative coupling reaction, followed by characterized through Fourier transform infrared spectroscooy (FTIR), liquid chromatography – mass spcerometry (LC-MS) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. Subsequently, as-prepared ACAT was reacted with isopropylidenediphenoxy-bis(phthalic anhydride) (BPADA) to give electroactive poly(amic acid) (EPAA). Moreover, poly(dimethylsiloxane) (PDMS) was used to be the soft negative template for pattern transfer from the surface of rose petal to the surface of polymer coating. The EPI coating with biomimetic structure was obtained by programmed heating the EPAA slurry casting onto the negative PDMS template. The anticorrosive performance of as-prepared biomimetic EPI coating was demonstrated by performing a series of electrochemical measurements (Tafel, Nyquist, and Bode plots) upon cold-rolled steel (CRS) electrode in a NaCl aqueous solution. It should be noted that the biomimetic EPI coating with <Í>rose petal-like structure was found to exhibit better anticorrosion than that of EPI without biomimetic structure. Moreover, the surface contact angle of water droplets for biomimetic EPI coating was found to be ~150°, which is significantly higher than that of EPI coating with smooth structure (~87°), indicating that the EPI coating with biomimetic structure reveals better hydrophobicity. The apparent mechanism for improved anticorrosive properties is twofold: (1) the biomimetic structure of EPI coating can repel water droplets. (2) electroactivity of EPI coating promotes the formation of densely passive layer of metal oxide on metallic surface.
Networks of polyacrylamide were studied for the possibility of imprinting of the oligomeric form of human growth hormone. The tetrameric molecular form of human growth hormone was molecularly imprinted for the first time. The results show that approximately 50–70% (w/w) of the templates (depending on polymerization conditions) could be extracted from the molecularly imprinted acrylamide polymers. The resulting ‘gel antibodies’ against this form of human growth hormone in the form of granules of polyacrylamide were compared with granules of non-imprinted polymer. The selectivity of the artificial gel antibodies was studied. Investigation of the binding to imprinted polymer of the template hormone, other molecular forms of the hormone and other proteins shows the selectivity of the developed artificial gel antibodies.
This paper reports on the potential of electrospun alginate nanofibre membranes to be used for the bio-sorption of heavy metals from aqueous solutions. Poly(ethylene oxide) (PEO) and its blends were electrospun at an applied voltage of 1–1.3 kV/cm and a solution flow rate of 0.8 mL·hr–1. The electrospinnability of the nanofibre blends was enhanced by storing the blend solutions in a controlled environmental chamber. The electrospun nanofibre membranes were washed with calcium chloride to remove PEO. Beadless nanofibres with average diameters of 114 nm and a surface area of 18.03 m2·g–1 were obtained. Fourier transform infra-red (FTIR) spectroscopy and thermogravimetric analysis (TGA) confirmed the removal of PEO after washing with calcium chloride. The adsorption behaviour of the nanofibrous membranes was investigated using Cu(II) as model metalloid at different concentrations (0–1000 mg·L–1), temperatures (25, 40, and 60 °C) and pH values (2–6). The Langmuir isotherm better presented the equilibrium experimental data than the Freundlich model. The electrospun alginate membranes displayed a maximum monolayer sorption capacity (Q0) of 15.6 mg·g–1 at a pH of 4. In a competitive adsoption experiment the removal of metal ions in a mixture followed the order Cu > Ni > Cd > Co.
In this research, theoretical CO2 diffusivity coefficients in amorphous polymers were calculated from dielectric constant changes during CO2 desorption. These values showed agreement with experimental diffusivity coefficients from a gravimetric method. Three amorphous polymer films made from Polystyrene (PS), Polycarbonate (PC), and Cyclic Olefin Polymer (COP) resins were saturated with supercritical CO2 at 5.5 MPa and 25 °C for 24 hours in a pressure chamber. The CO2 infused films were removed from the chamber for gas desorption experiments. The capacitance of the samples were recorded with an Inductance, Capacitance and Resistance (LCR) meter. These values were used to calculate the change in dielectric constants. CO2 weight percentages measured by a scale was used to calculate experimental diffusivity and solubility coefficients. It was found that the trend of dielectric constant changes was similar to that of the CO2 weight percentage changes during gas desorption. A mathematical model was built to predict the CO2 weight percentages during desorption from the measured dielectric constants. Theoretical diffusivity coefficients from this work agree well with literature data.