Thermal Stability of Polycaprolactone Grafted Densely with Maleic Anhydride Analysed Using the Coats-Redfern Equation.

The plastic waste problem has recently attracted unprecedented attention globally. To reduce the adverse eff ects on environments, biodegradable polymers have been studied to solve the problems. Poly(ε-caprolactone) (PCL) is one of the common biodegradable plastics used on its own or blended with natural polymers because of its excellent properties after blending. However, PCL and natural polymers are difficult to blend due to the polymers' properties. Grafted polymerization of maleic anhydride and dibenzoyl peroxide (DBPO) with PCL is one of the improvements used for blending immiscible polymers. In this study, we first focused on the effects of three factors (stirring time, maleic anhydride (MA) amount and benzoyl peroxide amount) on the grafting ratio with a maximum value of 4.16% when applying 3.000 g MA and 1.120 g DBPO to 3.375 g PCL with a stirring time of 18 h. After that, the grafting condition was studied based on the kinetic thermal decomposition and activation energy by the Coats-Redfern method. The optimal fitting model was confirmed by the determination coefficient of nearly 1 to explain the contracting volume mechanism of synthesized PCL-g-MA. Consequently, grafted MA hydrophilically augmented PCL as the reduced contact angle of water suggests, facilitating the creation of a plastic-biomaterial composite.

Preparation of an eco-friendly antibacterial agent for food packaging containing Houttuynia cordata Thunb. extract.

This study aims to develop an antibacterial agent that can be used for food packaging. Essential oils of Houttuynia cordata Thunb., a well-known medical herb, were extracted by two methods: multi-solvent consecutive extraction method and single ethanol extraction with a pre-heating method. Consequently, the extract obtained by the single ethanol extraction with a pre-heating method was more satisfactory from the operational and economic aspects. Afterwards, one of the encapsulation techniques: co-precipitation method using ß-cyclodextrins as wall materials, was applied to form capsules for the protection of the obtained extract. After the capsule synthesis, the results of scanning electron micrographs and X-ray diffraction showed ß-cyclodextrin crystallites in the form of thinner plates became oriented upon co-precipitation. Combining the results of Fourier transform-infrared spectra and an antibacterial assay using Bacillus subtilis as an object microorganism, the extract was confirmed to be successfully encapsulated within hollow cavities of ß-cyclodextrins. A significant inhibitory activity on the growth and breeding of Bacillus subtilis was observed after the addition of fabricated capsules, which suggests the capsules containing the Houttuynia cordata Thunb. extract can be used as eco-friendly antibacterial agents for food packaging.

Characterization of self-assembled silver nanoparticle ink based on nanoemulsion method.

A well-dispersed self-assembled silver nanoparticles (AgNPs) ink with high purity was synthesized via AgNO3 emulsion prepared by blending an AgNO3 aqueous solution and a liquid paraffin solution of both polyoxyethylene (20) sorbitan monooleate (Tween 80) and sorbitan monooleate (Span 80). The ink remained as an emulsion at low temperatures; however, it produced AgNPs after sintering at about 60°C and showed a high stability at nanoscale sizes (with diameters ranging 8.6-13.4 nm) and a high conductivity. During the whole procedure, Tween 80 acted as a surfactant, reductant and stabilizer. Presumably, Tween 80 underwent an autoxidation process, where a free radical of an α-carbon of ether oxygen was formed by hydrogen abstraction. The mean diameter of emulsion droplets could be reduced by decreasing water content and increasing the ratio of surfactant and concentration of AgNO3 aqueous solution. Consequently, the thermogravimetric analysis and X-ray diffraction result clarified the purity of the produced Ag0. Dynamic light scattering and ultraviolet-visible spectroscopy clarified that an increased concentration of AgNO3 decreased the particle size.

Thermal responsive poly(N-isopropylacrylamide) grafted chicken feather keratin prepared via surface initiated aqueous Cu(0)-mediated RDRP: Synthesis and properties.

Poultry chicken feather keratin was extracted and then modified for the fabrication of keratin-graft-PNIPAM copolymers. The keratin was well extracted from feather fiber and powdered. Subsequently, it underwent the surficial functionalization process with initiator groups. After the study conducted full disproportionation of Cu(I)Br/Me6Tren into Cu(0) and Cu(II)Br2 in the solvent, surface initiated aqueous Cu(0)-mediated reversible-deactivation radical polymerization (RDRP) of N-isopropylacrylamide (NIPAM) was performed in a methanol/water mixture solvent. The reaction was performed rapidly and efficiently, during which over 100% graft rate was achieved at 60 min. After 6 h reaction, 200% graft rate could be achieved. High graft rate (up to 287%) was achieved, and graft rate could be regulated by controlling the reaction time and the addition of monomer. The fabricated keratin-g-PNIPAM exhibited a rough surface. As revealed from the results of thermal analysis, the thermal stability of keratin-g-PNIPAM was enhanced noticeably compared with the original keratin. Besides, grafted PNIPAM chains exhibited a higher glass transition temperature. The grafted keratin particles displayed enhanced hydrophilicity. Keratin-g-PNIPAMs exhibit a lower LCST comparing to homopolymer and the flocculation in hot water behavior could be controlled by regulating graft rate.

Robust Sealing of Blood Vessels with Cholesteryl Group-Modified, Alaska Pollock-Derived Gelatin-Based Biodegradable Sealant Under Wet Conditions.

A novel surgical sealant was developed by partially modifying the amino groups of Alaska pollock-derived gelatin derivative with cholesteryl groups (Chol-apGltn), which was combined with the crosslinker, pentaerythritol poly(ethylene glycol) ether tetrasuccinimidyl glutarate (4S-PEG). The burst strength of the resultant sealant was tested using fresh porcine aorta as an adherend. The Chol-apGltn/4S-PEG sealant cured within 25.4 ± 2.0 s. Burst strength increased with increasing degree of Chol modification up to a maximum value of 8.3 mol% (8.3Chol-apGltn). The highest burst strength of the 8.3Chol-apGltn/4S-PEG sealant was 341.3 ± 77.5 mmHg, which was 3.5- and 11.6-fold higher than that of the original apGltn/4S-PEG and commercial fibrin sealants, respectively. The 8.3Chol-apGltn/4S-PEG sealant swelled only slightly in solution (1.1-fold as compared to commercially prepared sealant). Furthermore, tissue migration into the 8.3Chol-apGltn/4S-PEG sealant and subsequent biodegradation was observed following implantation for 4-8 weeks. These results suggest that the 8.3Chol-apGltn/4S-PEG sealant has biomedical applications, including use in cardiovascular and thoracic surgery.