Solid State Phenomena Vol. 339

Abstract: Poly (N-isopropylacrylamide) (PNIPAAm) is one of the most well-known thermoresponsive polymers that exhibits a reversible coil-to-globule transition in aqueous solution at lower critical solution temperature (LCST) (32°C). PNIPAAm behave as an extended coil form in an aqueous solution below the LCST, meanwhile, above the LCST, it shrinks into a globule form. The LCST of PNIPAAm could be tune when it is chemically modified with hydrophilic and/or hydrophobic compound. In this study, modifications of PNIPAAm end-group with maleimide or phenyl maleimide compounds were prepared and their LCST behaviours were investigated. One end-group of synthesized poly (N-isopropylacrylamide)-chain transfer agent (PNIPAAm-CTA) was modified with maleimide or phenyl maleimide compound through aminolysis reaction to form PNIPAAm-Maleimide (PNIPAAm-M) and PNIPAAm-Phenyl maleimide (PNIPAAm-PhM). Maleimide is a hydrophilic compound, and phenyl maleimide is a slight hydrophobic compound were used in this study. The modification with hydrophilic compound will higher the LCST of PNIPAAm. The slight hydrophobic of phenyl maleimide compound will decrease the LCST. In this study, the successfulness of aminolysis process of PNIPAAm-CTA were determined through the fourier transform infrared (FTIR). Moreover, the LCST behavior of PNIPAAm-CTA, PNIPAAm-M and PNIPAAm-PhM were determined through light scattering intensity analysis. The results indicated that upon heating the solutions of PNIPAAm-CTA, PNIPAAm-M and PNIPAAm-PhM in 10 mM HEPES solution pH 7.4 at 25°C–40°C, PNIPAAm-CTA, and PNIPAAm-PhM solutions started to increase their light intensities at 35°C and PNIPAAm-M at 36°C, respectively. To conclude, modification of PNIPAAm end-group with hydrophobic and/or hydrophilic compound could tune their LCST.

Abstract: This research synthesized natural magnetic particles/chitosan/gold nanoparticles composites (NMP/Chi/AuNPs) using a green method. AuNPs were synthesized using chitosan as a reducing agent and stabilizer in one step. The obtained AuNPs were characterized using UV-Vis spectrophotometer and TEM. Results showed that AuNPs were spherical with an average of 14.9 nm and absorbed at visible light (~530 nm). Then, AuNPs were impregnated on NMP/Chi at room temperature. The impregnation results were characterized using FTIR, XRD, and TEM. In the IR spectra of NMP/Chi and NMP/Chi/AuNPs, the NH bending vibrations of NH₂ are shown at 1604 and 1631 cm^-1. The NMP/Chi/AuNP showed a decrease in intensity and the peak shift to 1395 cm^-1, stretching vibration of C-O from primary alcohol group. Fe-O vibrations of Fe₃O₄ in NMP/Chi and NMP/Chi/AuNPs are shown at 566 and 583 cm^-1. The intensity peak shift and decrease indicate an interaction between AuNPs and NMP/Chi. The results of the XRD NMP/Chi/AuNPs characterization showed that the diffraction peak at 2Ө 35.44° decreased in intensity, resulting in a decrease in crystallinity caused by impregnated AuNPs and the destruction of hydrogen bonds. The new diffraction peak at 2Ө 38.24° indicates the presence of AuNPs. TEM analysis showed an amorphous layer around the NMP, and the average size of AuNP in the NMP/Chi/AuNP composite was 23.01 nm.

Abstract: Natural magnetic particles/chitosan/CuNPs (NMP/Chi/CuNPs) have been successfully synthesized in green chemistry by impregnation of copper nanoparticles (CuNPs) on the composite of natural magnetic particles/chitosan (NMP/Chi). Copper nanoparticles were prepared using Cu(II) solutions with varying concentrations (5, 10, 15, 20, and 25 mM). The synthesis of CuNPs was carried out by chemical reduction with ascorbic acid as a reducing agent and chitosan as a capping agent using microwave heating. The formation of copper nanoparticles was indicated with a peak at 580-590 nm, and the optimum absorbance was obtained at a precursor concentration of 20 mM using a UV-Vis spectrophotometer. The NMP/Chi/CuNP(20) composite material was characterized using Fourier Transform-Infra Red (FTIR) to confirm the interaction between NMP/Chi and CuNP(20). Crystal analysis by X-Ray Diffraction (XRD) showed the highest characteristic peak of Fe₃O₄ at 2θ angle 35° where the peak intensity at NMP/Chi/CuNP(20) decreased compared to NMP and NMP/chi. The mean crystallite sizes of NMP and NMP/Chi were obtained at 8.33 nm and 64.95 nm, respectively. Morphology and elemental composition of composite materials with Scanning Electron Microscopy-Energy Dispersive X-Ray (SEM-EDX) showed that CuNP 20 was successfully impregnated in NMP/Chi and contained the main elements, namely C, N, O, Fe, and Cu. Using TEM analysis, the shape of the NMP/Chi/CuNP(20) particles is similar to that of CuNP(20), which is spherical, and the particle size was 32.95 nm. The material is potential as an easily separable antibacterial agent in water using an external magnet.

Abstract: Heterogeneous metal complex catalyst such as Zinc glutarate (ZnGA) and Zinc-Ferum Double Metal Cyanide (Zn-Fe DMC) have been shown to improve reactivity for alternating copolymerization using CO₂ and epoxides. However, there are not lot of studies that have been done to study the effect of different parameter such as time and temperature on the catalytic activities of ZnGA and Zn-Fe DMC. ZnGA was treated with toluene while Zn-Fe DMC catalyst was treated with (complexing agent) tert-butanol. The main focus of this study is to synthesize ZnGA and Zn-Fe DMC at different parameter where the catalysts were produced at a variety of temperatures (50,60,70 °C) and reaction times (3h & 9h). Three different zinc-ferum ratios (1:4, 1:6, and 1:8) were developed for the Zn-Fe DMC catalyst to compare the effect of iron as metal and zinc on the active site. The catalyst was characterized using Fourier-transform infrared spectroscopy (FTIR) to determine their functional elements and Brunauer–Emmett–Teller analysis (BET) for surface characterization and pore size. The effects of reaction parameters such as time and reaction temperature were investigated using this catalyst in an auxiliary-batch reactor. FTIR result shows that GA was successful incorporation into ZnO and the production of ZnGA catalysts. The presence of typical functional groups in the Zn–Fe DMC catalysts was also confirmed. The surface area and pore volume of ZnGA increases as the temperature and reaction time increases while Zn-Fe DMC the surface area and pore volume decrease as the ratio increases. These surface-modified catalysts can generate high-molecular-weight polymers, which benefits both the environment and industry.

Abstract: This research is about the fabrication and properties study of the alginate bio-composites film for potential use in food sensing applications. A response surface methodology (RSM) was employed to optimize the concentration of sodium alginate (1 to 5% w/v), glycerol (0.4 to 0.8% w/v), and maltodextrin (0.4 to 0.8% w/v) as a function of the tensile strength (TS) and elongation at break (EB) and toughness (T) of the biofilms. The coefficient determination (R²) result obtained for TS against alginate, glycerol and maltodextrin is 81.05%, while for EB and T are 32.07% and 64.70% respectively. It showed that the addition of sodium alginate, glycerol and maltodextrin at different concentrations had significantly affected the TS but no effect on EB and T was observed. The optimization study of the film produces two conditions which are conditions 1 and 2. The optimum conditions parameter for condition 1 is a film with 3.0% alginate concentration, 1.0g/g of glycerol content, and 1.50g/g of maltodextrin content while condition 2 was 1.0% of alginate concentration, 1.0g/g of glycerol content and 0.0g/g maltodextrin content. The values of the TS obtained at the optimized condition were 4.75 MPa and 22.99 MPa which is lower than the predicted value of condition 1 (7.0 MPa) or the maximized TS at condition 2 respectively. The thickness value of edible films in this study had an average of 0.54 mm which was higher than the maximum standard thickness of edible films according to the Japanese Industrial Standard (JIS) which is 0.25 mm. Water Vapour Permeability (WVTR) study indicated that all alginate films in this study had a value higher than the JIS 1975 standard of WVTR for edible films which is at a maximum of 10 g/m²/24 hours. The natural colour from Clitoria Ternatea was successfully immobilized into the alginate-based film and the film become dark purple. Based on the result obtained, prediction equations for responses studied are adequate to describe the experimental data on tensile strength, elongation at break, and toughness. However, further modifications are necessary for improvements in mechanical characteristics in the future.

Abstract: Microcrystalline cellulose (MCC) has been widely used in the production of composite materials because it is inexpensive, easy to process, good mechanical properties and environmentally friendly. Despite its advantages, MCC has disadvantages such as poor thermal stability, hygroscopic and poor compatibility with hydrophobic materials. Understanding the thermal behavior of MCC is important because thermal degradation occurs at different rates and directly affects the final product. In this study, the MCC/ SiO₂ hybrid materials were prepared using in-situ sol-gel synthesis, followed by the investigation of their thermal stability and degradation kinetics using thermogravimetric analysis (TGA). Degradation kinetics were analysed using two model-free analysis (i.e. Flynn-Wall-Ozawa, FWO and modified Coats-Redfern, CRm) to evaluate the degradation behaviour (conversion degree (α) of 0.1 to 0.8) and activation energies (E_a) of MCC, MCC/ sol-gel silica (MCC/SiO₂) and modified MCC (mMCC/SiO₂) at heating rates (β) of 10, 20, 30 and 40 °C/min. Thermal stability results showed that the presence of silica on MCC had no influence on the degradation temperature of the hybrid material however, it slightly shifted the T_onset to higher values. The presence of silica also increased the final residue of the hybrid, especially in mMCC/SiO2 samples. DTG curves clearly show that all samples exhibited one step degradation process. The kinetics study assumed that all samples has single reaction mechanism as the fitted line was parallel in almost all conversion degrees (α) in both FWO and CRm methods. E_a calculated for MCC, MCC/SiO₂ and mMCC/SiO₂ are in good fit with both FWO and CRm model where the R² observed more than 0.97. E_a was increased in both methods, MCC/SiO₂ and mMCC/SiO₂ as compared to MCC, which implied that the addition of sol-gel silica to MCC could promote a stepwise degradation.

Abstract: Currently, packaging especially for food is a significant concern because made of plastic, which is difficult to degrade. Cellulose nanofibers (CNFs) as the composite reinforcement are chosen as a suitable replacement for the fiber. This nanocomposite is made with the main aim of making biodegradable food packaging with other capabilities such as antioxidant, antibacterial, etc. The food packaging was next referred to as bioplastic, consisting of several components. One of the major concerns is selecting cross-linking agents in nanocomposites production. The use of essential oil extracts from plants is widespread because it has an excellent binding ability and good chemical properties. The essential oil of orange peel can be extracted and used because it contains flavonoid compounds that act as antioxidants. The CNFs were made from palm oil empty fruit bunches (EFB) using the acid hydrolysis process in the previous research. The study of this nanocomposites production successfully makes transparent bioplastic. SEM results show a surface with fewer pores filled with cellulose fiber and protein. The addition of essential oil to the film increases the cross-linking bond in the matrix, improving its mechanical properties. The bioplastic was tested its endurance when buried in soil for 6 days and showed a promising results.

Abstract: Yttrium aluminum garnet (YAG) is an important material which require high temperature of 1600°C in its solid-state reaction. To lower this temperature, mechanical activation process has applied to the system which make the crystal arrangement broken thus make it more reactive. This process results in homogeneous and fine particle distribution of Al₂O₃ and Y₂O₃ compared to manually mixed powders. Moreover, milling process also reduce the particle size of the Al₂O₃ and Y₂O₃ from 4694 nm and 349 nm down to 274 nm. This also lessen the crystallite size of Al₂O₃ and Y₂O₃ from 1010 and 164 Å to 310 and 50 Å respectively. Then, after calcination at 1100°C, the milled powders form YAG phase in the opposite of manually mixed powders which form YAM phase. YAG formed have nearly round shape with finer grain compared to manually mixed powders which still has large grain of Al₂O₃ and Y₂O₃. This formation temperature is much lower than the require conventional solid-state reaction.

Abstract: An aging population and lifestyle-related practices increase the incidence of chronic diseases and consequently its costs. The increasing requests for efficient chronic wound care constitute an opportunity for the field of regenerative medicine but, at the same time, it represents a challenge due to the need to limit treatment costs. Calcium-based materials have enormous potential for skin applications, as calcium has an established role in the normal homeostasis of wounded skin and serves as a modulator in keratinocyte proliferation and differentiation. On the other hand, several natural biopolymers, as silk proteins are known for their antioxidant and moisturizing properties as well as a mitogenic influence on mammalian cells. In the present work, a cost-effective method using an oscillatory flow reactor to produce a calcium phosphate/sericin composite system with controlled properties is presented, to be applied in skin wound healing and regeneration. Future perspectives for the produced biomaterials are also addressed.