Advanced Materials Research Vols. 55-57

Abstract: Nanocomposite poly(D,L-lactide) (PDLL)-based microparticles containing silk fibroin (SF) nanoparticles were prepared by oil-in-water emulsification solvent evaporation technique of PDLL/SF nanocomposite. The PDLL/SF nanocomposite was obtained from nanoprecipitating SF into PDLL solution in acetone before dried in vacuum oven. The nanocomposite microparticles with PDLL/SF ratios of 20/1, 10/1 and 5/1 (w/w) were prepared and investigated. Interactions between PDLL and SF of microparticles can be observed from FT-IR and thermogravimetric results. Sizes of the SF nanoparticles and the nanocomposite microparticles from SEM micrographs were in the ranges of 50-500 nm and 50-200 µm, respectively. The sizes of SF nanoparticles and nanocomposite microparticles increased as increasing the SF ratio. Surface roughness of the resulted microparticles also increased with the SF ratio.

Abstract: Zwitterionic copolymers were synthesised from N,N-dimethyl-N-(2-acryloylethyl)-N-(3-sulfopropyl) ammonium betaine (SPDA) and 2-hydroxyethyl methacrylate (HEMA) produce a series of polyzwitterion hydrogels. For the synthesis of the charge-balanced copolymer hydrogels, two cationic monomers were selected: 2-(diethylamino) ethyl methacrylate (DMAEMA) and 3-(dimethylamino) propyl methacrylamide (DMAPMA), and an anionic monomer; 2-acrylamido-2-methylpropane sulphonic acid (AMPS). Two series of charge-balanced copolymers were synthesized from stoichiometrically equivalent ratios of DMAEMA or DMAPMA and AMPS with HEMA as a termonomer. All synthesized copolymers produced clear and cohesive hydrogels. The zwitterionic and charge-balanced copolymers displayed similar equilibrium water contents together with similar mechanical and surface energy properties. The swelling of the zwitterionic and the charge-balanced copolymers shows some features of antipolyelectrolyte behavior.

Abstract: Electrospinning has been recognized as an efficient technique for the forming of polymer nanofibers. In this project interest fabricated Soy Protein Isolate (SPI) nanofibers by electrospinning with different supply voltages, positive and negative charge. SPI was dissolved in 80%-95% w/w acetic acid solution and 80%-90% w/w formic acid solution. Only droplet formation of SPI were found instead of fibril formation, and the droplet morphology of SPI is depended on supply voltage, and type of solvent. SPI droplets from the negative supply voltage have smaller and more nodular than droplets from positive supply voltage. Formic acid SPI solution gives smaller size of droplet and more nodular than acetic acid SPI solution. In order to forming SPI nanofibers, zein/SPI blend were performed. The zein/SPI blend was studied at difference blending ratio. The 95/5 Zein/SPI was found to be the best blend composition for electrospun fiber. In addition, the effects of electrostatic distance and electrostatic voltage on electrospun fiber were also investigated. Increasing electrostatic distance or increasing voltage, smaller size of fiber was obtained.

Abstract: A significant number of poly a-ester homologues of poly(L-lactide) (PLLA) have been synthesized and used in miscibility studies together with conventional isomeric diacid-diol polyester variants, poly β-esters (based on β-hydroxybutyrate (HB) and β-hydroxyvalerate (HV)), poly e-caprolactone (PCL), poly e-caprolactone copolymers (e.g. poly(L-lactide-co-caprolactone), and a series of cellulose-based polymers (e.g. cellulose acetate butyrate (CAB), cellulose acetate propionate (CAP)). A combinatorial approach to rapid miscibility screening using 96-well plates and a uv-visible multi-wavelength plate reader has been developed enabling the clarity of PLLA-based multi-component blend films to be observed. Using these techniques and materials, the ternary phase compatibility diagrams of a range of three-component blend films was prepared, illustrating ranges of behavior varying from miscible blends giving rise to clear films to immiscible blends which are opaque. In this way, novel three-component blends of PLLA/CAB/PCL were developed which are miscible when the CAB content is more than 30%, PLLA less than 80% and PCL less than 60%.

Abstract: In this paper, we report innovative gloves that are coated with hydrophobic film such that the outer surface of the gloves is hydrophobic. A coating precursor containing polymethyl hydrogensiloxane, silica nanoparticle, semifluorinated silane and Pt-catalyst was painted onto the gloves. The coated gloves were kept at room temperature for 12 h to make the film dry, and then tested for their chemical resistance with 10 M NaOH, conc. HCl, conc. H2SO4 and conc. HNO3 solutions, as well as the standard buffered solutions (pH = 1, 4, 10, and 12) at 25oC by dropping the chemicals onto the coated gloves. It was found that the nitrile gloves had similar contact angles to the latex gloves when tested with the standard buffered solutions while the nitrile gloves had higher contact angles compared to the latex gloves when tested with different aqueous-based hazardous chemicals. The nitrile gloves coated with the hydrophobic film showed high acid droplet contact angle, leaving behind much lesser damage from hazardous chemicals.

Abstract: onic conductivity, dielectric and thermal properties of (PEO)12LiBF4 solid polymer electrolyte, dispersed with nanoporous Al2O3 have been studied. Out of seven different compositions studied, the (PEO)12LiBF4 polymer-salt complex showed the highest conductivity with σ25 oC = 8.27 × 10-6 S cm-1. Dispersion of different weight ratio of nano-porous alumina fillers to this electrolyte showed that the composite electrolyte composition with 15 wt. % Al2O3 gave the highest conductivity with σ25 oC = 6.05 × 10-5 S cm-1. The glass transition temperature, Tg decreased from -35.3 oC to -43.2 oC and the PEO crystallite melting temperature, Tm decreased from 64.5 oC to 58.8 oC due to the incorporation of 15 wt. % Al2O3 filler, suggesting that the interaction between the PEO backbone and the Al2O3 filler have affected the main chain dynamics of the host polymer. As the presence of the filler results in an increased conductivity mainly due to an increased amount of amorphous phase in the electrolyte above Tm, another mechanism, directly associated with the filler particles, appears to contribute to the observed conductivity enhancement. A possible mechanism for this could be the creation of additional hopping sites and favorable conducting pathways for migrating ionic species though Lewis acid-base type interactions between ionic species and O/OH sites on the filler grain surface. Results of the dielectric relaxation spectroscopy agree with the suggestion that the increased mobility is largely responsible for the obtained conductivity enhancement caused by the nano- porous filler.

Abstract: Hybrid organic-inorganic materials were fabricated using sol-gel technique using poly(methyl methacrylate) and methacrylic acid 3-(trimethoxysilyl)propyl ester (MAMSE) with 90/10, 80/20 and 70/30 (%w/w) ratios with tetrahydrofuran (THF) solvent. The thin films were then characterized using FTIR spectra, SEM, DSC and TGA thermograms. From the preliminary characterization, the hybrid material was found to have nano and ultra scale tight pore ranges. FT-IR spectroscopy uncovered all the signature peaks characteristic of silicate structures in the near-surface regions. Fingerprints of Si-O-Si groups in cyclic and linear molecular substructures are present. The SEM image clearly shows that hybrid materials have homogenous and smooth surface. DSC analysis of the material shows interesting phenomenon regarding glass transition temperature (Tg). The hybrid material was found to have higher Tg than pure PMMA. From TGA analysis, the hybrid materials were observed to have higher thermal stability than pure PMMA.

Abstract: The surface of polystyrene (PS) thin films in argon plasma was modified to study the hydrophilicity properties. An inductively coupled plasma (ICP) system was used to generate the argon plasma. In the experiment, the effect of RF power levels, gas flow rate and treatment time was investigated. The surface morphology of PS films was examined by the atomic force microscopy (AFM), also the contact angle goniometry was used for measuring the wettability of PS films before and after plasma treatment. After the plasma treatment, AFM images of PS revealed the increasing of the surface roughness as increasing the power levels and treatment times. Moreover, after treated with argon plasma, the contact angles of polystyrene films also decrease where the power levels and treatment times were increased. It is clear that the effects of power levels and treatment time improve the wettability of PS films. It can also be observed that by placing the sample in air after plasma treatment, the contact angle gradually increases probably due to moisture absorption in the PS films.

Abstract: Two novel tin(II) alkoxides, namely: tin(II) hexoxide, Sn(OC6H13)2, and tin(II) octoxide, Sn(OC8H17)2, have been synthesized for use as coordination-insertion initiators in the bulk ring-opening polymerization of ε-caprolactone. The kinetics of the polymerization reactions were studied at 140 °C by dilatometry. It was found that both alkoxides were slow to dissolve in the ε-caprolactone monomer due to their molecular aggregation in the solid state. As a result, the slow solubilization of the initiators gave rise to deviations from the expected first-order kinetics. Instead, the kinetic results adhered more closely to zero-order kinetics with apparent zero-order rate constants k0 of 6.58 x 10-2 and 4.63 x 10-2 mol l-1 min-1 for the hexoxide and octoxide respectively

Abstract: The research is aimed to investigate Bauschinger effect and strain hardening by the application of drawbead-tester. Generally, the drawbead is used to control the material flow into the die cavity in sheet metal forming process. When the material is flowing into the drawbead, it may cause the development of strain hardening and/or Bauschinger effect. This work consists of two main equipment particularly developed for the experiments. They are drawbead-tester and three-point bending device. The drawbead-tester provides the possibility to integrate the optical in-process strain analysis system. Whereas the sheet metal was being formed in the drawbead, the local strain of the sheet metal was evaluated. At the same time, the drawbead restraining and holding forces were measured. The three point bending device and numerical simulation method are used to investigate the Bauschinger effect. In the experiment, the cyclic bending forces were measured and compared with the result obtained by numerical simulation.