Volume 16, Issue 1

Poly(lactide), PLA, as one of the most promising biopolymers, has been receiving increasing attention in recent years because of its excellent performances in renewability, mechanical properties, biocompatibility and biodegradability. However, its application is limited by its brittleness and low heat distortion temperatures (HDT). The low HDT mainly results from a low crystallization rate and lack of crystallinity after fast processing, e.g. injection molding. Consequently, considerable attention was paid, in recent years, to achieve fast(er) crystallization of PLA. In here, we briefly review the research progress in the crystallization modification of PLA notably by means of adding nucleating agents and stereocomplexation.

A series of natural composite hydrogels containing a “3-in-1” type triple adsorbent system are designed. For this purpose, Spirulina (Sp) biosorbent is immobilized on/in halloysite nanotubes in different loadings and then physically crosslinked chitosan composite hydrogels are prepared. The water absorbency and Cr (VI) adsorption capacity in neutral pH medium and wet mechanical strength as well as their morphologies are all reported as a function of Sp immobilized nanotube loadings. The use of Sp biosorbent results in composite hydrogels with high water absorbency, wet strength and thermal stability. Spirulina enlarges the metal adsorption windows efficiently and the Freundlich isotherm model can fit the fundamental metal adsorption data well. It is believed that with optimized special composite hydrogel morphologies, all positively charged receptors of the Sp and the nanotubes behave as collector domains for chromate anions.

The aim of the study was to develop hydrogels and investigate the suitability for transdermal delivery of diclofenac sodium (DS) using constant voltage iontophoresis (CVI). Four batches of hydrogels of DS were developed using hydroxylethyl cellulose (HEC) as matrix material and terpenes as penetration enhancers. The hydrogels displayed a viscosity of ~1500 cps at a shear rate of 250 s -1 that was unlikely to change on minute shift in pH or temperature so that the iontophoretic transport would be unaffected. Moreover, the hydrogels were found to possess adequate conductivity at pH 7.4 to enable iontophoretic delivery of DS. In vitro studies indicated that passive transport of DS across porcine skin from hydrogels was comparable (p>0.05) to aqueous solution. The lead hydrogel (F 1 ), containing geraniol was found to enhance the iontophoretic flux of DS by 5.16 fold at 1.5 V compared to passive control. In vivo studies in rats indicated that CVI on application of F 1 significantly suppressed (p<0.001) carrageenan induced edema compared to passive treatment throughout the study.

Polysulfide polymers usually are prepared by the reaction of different dihalide compounds with disodium polysulfides. In this field, dihalides are expensive and produced from halogenation of organic compounds by different methods with harsh conditions. To overcome this problem, in this work, sunflower oil as polyunsaturated oil was used as precursor to produce polyhalide compound. In this field, double bonds of oil were applied as functional groups to halogenate the sunflower via benzoyl peroxide-catalyzed reaction with hydrochloric acid. Also, Na 2 S 3 was synthesized via the reaction between sulfur and sodium hydroxide. Then, halogenated oil was reacted with Na 2 S 3 to produce sunflower oil-based polysulfide polymer. Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance ( 1 H NMR) were used to characterize the structure of sunflower oil and synthesized polysulfide polymer. The content of halogenation was also obtained via energy-dispersive X-ray spectroscopy (EDX). Thermal stability of synthesized polymer was determined by means of thermal gravimetric analysis (TGA) and glass transition temperature was investigated by differential scanning calorimetry (DSC).

The initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) were investigated in microemulsion under light irradiation with ethyl 2-bromoisbutyrate (EBiB) as an ATRP initiator, ferric chloride hexahydrate (FeCl 3 ·6H 2 O) as a catalyst, N,N,N′,N′-tetramethyl-1,2-ethanediamine (TMEDA) as a ligand, and azobisisobutyronitrile (AIBN) as an initiator and reducing agent. The linear dependence of ln([M] 0 /[M]) on polymerization time was observed, indicating that the polymerization was living polymerization. Furthermore, the number-average molecular weights (Mn), gel permeation chromatography (GPC) and molecular weight distributions (MWD) of the PMMA obtained from GPC were controlled. The product was characterized by 1 H nuclear magnetic resonance (NMR) and GPC. The living features were verified by chain-extended with MMA with the obtained PMMA as macroinitiator.

Chitin was ultrasonically treated to improve its dye adsorption characteristics. The effects of ultrasound cycle and amplitude on the chitin Sauter diameter (D Sauter ), deacetylation degree (DD), crystallinity index (CI) and specific surface area (S BET ) were evaluated. The untreated and treated chitin samples were applied to remove Methylene Blue (MB) and Ponceau 4R (P4R) dyes from aqueous solutions. Chitin D Sauter decreased from 625 to 250 μm after the ultrasonic treatment. Chitin DD was not influenced by the ultrasound treatment, remaining in the range of 42.3–45.8%. For all ultrasonic conditions, the chitin CI values decreased from 86.3% (untreated chitin) to 70.0%. The specific surface area (S BET ) increased from 2.2 to 38.5 m 2 g -1 . After ultrasonic treatment, the dye removal percentage increased from 53.2 to 74.3% for MB and from 3.3 to 20.2% for P4R, at initial dye concentration of 50 mg l -1 . Treated chitin can be used seven times maintaining the same performance. The ultrasound-assisted treatment is an alternative to improve the chitin dye adsorption characteristics.

Ag 2 O nanoparticles (NPs) were synthesized using colloidal solution of spherical polyelectrolyte brushes (SPB) as nano-reactors. In this work, the average diameter of Ag 2 O NPs was around 10 nm as determined by transmission electron microscopy (TEM). The composite NPs of Ag 2 O immobilized in SPB (Ag 2 O-SPB) showed significant absorption in the visible light region as confirmed by UV-Vis diffuse reflectance spectra (DRS), and their photoluminescence (PL) exhibited emission peak in the visible range. Ag 2 O-SPB has shown outstanding photocatalytic activity during degradation of methyl blue (MB) in the visible light. This work will open up a new way to prepare ideal Ag 2 O nano-catalyst for the remediation of wastewater using visible light.

Thermoplastic polyurethane/organically-modified montmorillonite (TPU/OMMT) nanocomposites were synthesized by the pre-polymer polymerization method using Cloisite ® 30B organoclay, 1,6-hexamethylene diisocyanate (HDI), polycaprolactone diol (PCL diol, 2000 g/mol) and 1,4-butanediol (BDO). The hard segment content of the TPU was maintained at ~25.5% while the role of clay content was investigated at 1, 3 and 5 wt.% of clay concentration. The aim of this work was to obtain a high-performance polyurethane system while reaching a general microstructure-property relationship for TPU/OMMT nanocomposites. Clay exfoliation was achieved at 1 and 3 wt.% of clay loadings while some agglomerated clay sheets were observed in samples containing 5 wt.% OMMT. Significant hydrogen bonding occurred between the urethane linkages with unreacted -CH 2 CH 2 OH groups of the OMMT particles which resulted in strong matrix-filler interactions. Consequently, the values of tensile modulus were enhanced with clay content; namely a 177% improvement was observed for samples containing 5 wt.% OMMT. On the other hand, samples exhibited more thermoplastic behavior with the increase of clay content which resulted in lower deformability and lower values of tensile strength.

A poly(phenoxy-imine)/p-silicon rectifying device was fabricated and the current-voltage characteristics of the device were examined as a function of temperature in the 40–300 K range. The temperature dependence of the main parameters, namely, the barrier height (Φ b ), ideality factor ( η ), reverse current ( I 0 ) and series resistance ( R s ), were investigated. It was seen that the Φ b and the I 0 values of the device increased with increasing temperature, while the η and the R s values decreased. The temperature dependences of the Φ b and the η were interpreted by the assumption of a Gaussian distribution of the barrier heights arising from barrier inhomogeneities that prevailed at the interface of the poly(phenoxyimine)/p-silicon. From ln( I 0 /T 2 ) vs. 1/ ηT plot, the values of the activation energy ( E a ) and Richardson constant ( A *) were calculated as 0.324 eV and 2.84×10 -7 A cm -2 K -2 , respectively. The experimental value of the R s from the forward current-voltage plots decreased with an increase in the temperature.

The aims of this paper are to investigate the inherent relationship between the structures of the polyacrylates and release behaviors as drug carriers in the transdermal drug delivery systems. Three model polyacrylates compounds were synthesized by radical polymerization. Three polymer materials were characterized by Fourier transform infrared, differential scanning calorimeter and cytotoxicity, and the release behaviors of drug molecules transporting through the polymers membranes were tested. Moreover, the effects of the polymers’ structures on the permeability were studied by molecular dynamic simulation. The simulation results showed that higher chains mobility and larger fractional free volume of the polymer membranes resulted in higher permeation rates. By comparing the monomers’ structure in the polymer materials, it was found that the polymer chains’ mobility decreases, and permeation rate correspondingly decreases with the increase in the amount and volume of side groups on the double bonds.