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In this work, PLA/lignin composite films have been developed for packaging films. The composite films were prepared by a solution casting method. The lignin was prepared from black liquor from the paper industry, by extracting with acetic acids at 50°C. The lignin contents in PLA matrix were 0.5, 1, 3 and 5 phr. Fourier-transformed infrared spectroscopy (FTIR) analysis demonstrated similar structure of lignin precipitation when compared with the standard lignin. The addition of lignin reduced the tensile strength of PLA/lignin films, whereas the composite film at 1 phr of lignin was more elongation than neat PLA. Scanning electron microscopy (SEM) micrographs showed the roughness surface and voids in the composite films, except 1 phr and 5 phr of lignin with a better interface between PLA and lignin. UV-Vis analysis indicated reduced light transmission with increasing lignin contents in UV region.

Circular design and fabrication of PLA nanofiber filters from PLA wastes for effective oil decontamination and oil/water separation.

A process for sizing down and functionalizing commercial polylactide (PLA) resin is developed by alcoholysis with 1,4-butanediol (BDO) and propylene glycol (PG) to medium-sized PLA-based diols, with lower cost than a bottom-up synthesis process. These are subsequently used as polyols in preparing polyurethanes (PU) by reacting with 1,6-diisocyanatohexane (HDI). The PLA-based PU has an excellent elongation at break of 487%. The products are suitable as toughening agents for brittle PLA resin due to their highly elastic properties and high compatibility with PLA. The PU products are blended with PLA resin at various compositions, and their physical and mechanical properties and shape recovery are examined. The tensile tests showed enhancements in elongation at break up to 160% with low modulus. The fracture morphology and FTIR results confirm that the blends show strong interfacial interaction and adhesion between the PLA-based PU disperse phase and the PLA matrix. The PLA/PU blends exhibit a high shape recovery efficiency, and their recovery mechanisms are identified. These flexible PLA/PU blends are promising for various applications where bio-compatibility/degradability and high ductility are required, especially as filaments for 3D bio-printing.

Chitosan (CS) nanoparticles with antibacterial properties have been synthesized by the ionic gelation method using tripolyphosphate (TPP) as a crosslinking agent. Physicochemical properties of the resulting CS-TPP nanoparticles were examined by FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission electron microscopy, and UV-Vis spectroscopy. The antibacterial efficacy of the nanoparticles against S. aureus and E. coli was evaluated by the disc diffusion (DD) method. It was found that the optimum conditions for fabricating the CS-TPP nanoparticles were: pH of 2.85, CS concentration of 1.5 mg/ml, TPP concentration of 0.5 mg/ml, CS:TPP feed ratio of 1:1, mixing speed of 300 rpm, and reaction temperature of 30 °C. The CS-TPP nanoparticles decreased in average particle size with an increase in the CS concentration. Based on the DLS results, the average size of CS-TPP ranged from 79.2 to 114.2 nm, with a polydispersity index of 0.369–0.398. However, slightly larger sizes were observed (150 to 180 nm), based on the TEM and SEM images. The CS-TPP has more regular structures compared to CS, indicated by the increase of crystallinity based on X-ray diffraction patterns. In addition, FTIR spectra confirmed that interactions in tripolyphosphate were predominantly between CS amines and TPP counterions via ionic interactions, as supported by SEM-EDX. CS-TPP exhibited antibacterial activity. The highest inhibition zone radius was 5.0 and 5.5 mm against E. coli and S. aureus, respectively. The bio-based materials have a high potential for use as value-added antibacterial agents.

Biofouling due to biofilm formation is a major problem in ultrafiltration membrane applications. In this work, a potential approach to solve this issue has been developed by functionalization of chitosan-based membranes with benzalkonium chloride (BKC). The chitosan composite membranes consisting of poly(ethylene glycol) (PEG), multiwalled carbon nanotubes (MWCNT), and BKC were synthesized by mixing the membrane precursors and the antibacterial solution, and casting via an inversed phase technique. The effects of the BKC content on the morphology and performance of the membranes are investigated by varying the BKC feed compositions. The composite membranes demonstrate better antibacterial efficacy against Staphylococcus aureus than Escherichia coli. The permeability and selectivity performances of the composites as filter membranes are examined by employing a dead-end filtration system. Interestingly, enhanced toughness of the membranes is observed as a function of the BKC content. Mechanisms of the structural formation are investigated. The results from SEM, XRD, and FTIR spectroscopy revealed that MWCNT/BKC are located as nanoclusters with π–π stacking interactions, and are covered by PEG chains. The shape of the dispersed domains is spherical at low BKC contents, but becomes elongated at high BKC contents. These act as soft domains with an anisotropic shape with toughening of the brittle chitosan matrix, leading to enhanced durability of the membranes, especially in ultrafiltration applications. The composite membranes also demonstrate improved rejection in dead-end ultrafiltration systems due to high porosity, high hydrophilicity, and the positive charges of the membrane surface.

Polymeric nanofibers with superhydrophobic property have attracted vast interest in various applications, especially oil/water separation. In this work, superhydrophobic PLA nanofibers have been fabricated by an electrospinning process and treatment with a hydrophobic agent, alkyl ketene dimer (AKD). AKD consists of a functional group that is specifically reactive toward hydroxyl groups. Glycerol is employed as a template, providing –OH functional groups for the PLA matrix. The electrospun fiber mats were then immersed in AKD solution, in which a grafting reaction took place, leading to an increase in hydrophobicity of the fiber mats. Chemical structures and properties of the materials were then characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), water contact angle (WCA) measurement, and oil absorption ability. Oil/water separation efficiency of the degradable nanofibers was assessed for their use for oil-contaminated water treatment. The fiber mats, after AKD treatment, show super-hydrophobic properties, with oleophilicity. The material possesses high oil absorption rates with absorption capacities higher than 10 g/g fibers and adsorption–desorption cycle abilities of greater than ten cycles. As these materials are derived from a degradable polymer, they are environmentally-friendly and can easily be disposed of after use. These have many advantages over conventional materials.

Alteration of lipid raft organization manifesting as phase separation is important for cellular processes, such as signaling and trafficking. Such behaviors and dynamics of lipid membranes can be affected by external stimuli including both physical and chemical stimuli. In this study, we focused on osmotic-tension-induced phase separation. The effects of osmotic tension on the phase behaviors of vesicles consisting of dioleoylphosphocholine (DOPC)/dipalmitoylphosphocholine (DPPC)/cholesterol (Chol) were quantitatively studied at different temperatures by fluorescence microscopy. We determined the ternary phase diagrams and found that tension leads to a shift in the miscibility temperature. Cholesterol plays a key role in determining the extent of this shift. In addition, we found that osmotic tension can enhance the line tension. The physicochemical mechanism of osmotic-pressure-induced phase separation is discussed.

A process for preparing emulsions of alkyl ketene dimer (AKD) nanoparticles

Microneedle technology has received considerable attention in transdermal drug delivery system research owing to its minimally invasive and convenient self-administration with enhanced transdermal transport. The pre-drug loading microneedle method has been developed for several protein and chemical medicines. However, the protein activity and efficacy are severely affected owing to protein aggregation. Herein, we aim to develop non-degradable hydrogel photocross-linkable microneedles for suppressing protein aggregation. Four-point star-shaped microneedles are fabricated via a photolithography process, and sulfobetaine (SPB) monomer is combined with dextran-glycidyl methacrylate/acrylic acid to form the hydrogel network. Incorporating zwitterionic poly-sulfobetaine (poly-SPB) in the microneedles enables the protection of proteins from denaturation even under external stress, releases the proteins in their native state (without activity loss), and exhibits sufficient mechanical strength to penetrate porcine skin. The microneedles exhibit a high drug loading capacity along with an efficient drug release rate. The rhodamine B drug loading and release model shows that the microneedles can load 8 μg of drugs on one microneedle patch of 41 needles and release nearly 80% of its load within 1 h. We anticipate that this pre-drug loading platform and the advanced features of the microneedles can provide an effective option for administering therapeutic drugs.

Carboxylated magnetic polymeric nanoparticles, having a high magnetic content, and superparamagnetic properties were prepared and applied as effective antiscalants.

A sonochemical approach is widely used as a routine protocol for graphene oxide (GO) preparation prior to adsorption applications, but there is a limited understanding of its effects on the GO sorption ability. Herein, using different types of sorbates, which are cation, cationic and anionic dye, the changes in sorption capacity along with the characteristics of sonicated GO, are shown. The ultrasound treatment unexpectedly removes oxygen functional groups from GO with a concomitant decrease in GO adsorption capacity, rather than an increase in its adsorption as expected from the use of ultrasound in dispersing or exfoliating GO. The C/O ratio increases from 2.1 in pristine GO up to 2.5 in sonicated GO. The loss of oxygen functional groups is also accompanied by an increase in disorder and defects on GO sheets, along with the weakening of π-π interaction. The pathways of GO’s structural and functional groups changed by ultrasound are proposed, based on the generation of OH· radicals from ultrasonic cavitation. These radicals can react with the facile oxygenated groups of GO, such as those of epoxide, hydroxyl, and carboxyl, leading to the partial removal of these groups and the breakage of GO sheets. GO’s adsorption capacities for cation and different dyes can decrease up to 75% after sonication, which is in agreement with the above changes in GO’s characteristics. The effects are readily observed even in mild sonication such as using an ultrasonic bath, signifying their importance in many applications employing ultrasonication to disperse GO.

The design of smart drug delivery carriers has recently attracted great attention in the biomedical field. Smart carriers can specifically respond to physical and chemical changes in their environment, such as temperature, photoirradiation, ultrasound, magnetic field, pH, redox species, and biomolecules. This review summarizes recent advances in the integration of porous particles and stimuli-responsive gatekeepers for effective drug delivery. Their unique structural properties play an important role in facilitating the diffusion of drug molecules and cell attachment. Various techniques for fabricating porous materials, with their major advantages and limitations, are summarized. Smart gatekeepers provide advanced functions such as "open-close" switching by functionalized stimuli-responsive polymers on a particle's pores. These controlled delivery systems enable drugs to be targeted at specific rates, time programs, and sites of the human body. The gate structures, gating mechanisms, and controlled release mechanisms of each trigger are detailed. Current ongoing research and future trends in targeted drug delivery, tissue engineering, and regenerative medicine applications are highlighted.

MXenes, a new family of two-dimensional transition metal carbides or nitrides, have attracted tremendous attention for various applications due to their unique properties such as good electrical conductivity, hydrophilicity, and ion intercalability. In this work, Ti

Biofouling due to biofilm formation is a major problem in ultrafiltration membrane applications. In this work, a potential approach to solve this issue has been developed by functionalization of chitosan-based membranes with benzalkonium chloride (BKC). The chitosan composite membranes consisting of poly(ethylene glycol) (PEG), multiwalled carbon nanotubes (MWCNT), and BKC were synthesized by mixing the membrane precursors and the antibacterial solution, and casting

The authors are grateful for support from the Center of Excellence in Materials and Plasma Technology (CoE M@P Tech), Thammasat University, and Prof. Bernadette Charleux for the supply of P(S27-b-AA120) samples.; International audience

Oxidation reactions of alcohols have been of interest due to their broad applications in different fields. Oxoammonium cation (TEMPO+) of 2,2,6,6-tetramethyl piperidine-1-oxyl (TEMPO) is a high-potential oxidant for the selective oxidation of primary alcohols, with hydroxylamine (TEMPOH) as a side product. TEMPO or TEMPO+ has been widely applied for various reactions. However, the conversion mechanisms among TEMPO, TEMPO+, and TEMPOH are not well understood and remain controversial, due to complications in the direct observation of the reactions. In this work, two-dimensional correlation (2D-COS) UV–visible (UV–Vis) spectroscopy is applied to examine the correlations between the characteristic bands of each species, to obtain insights into the complete reaction mechanisms. Series of dynamic UV–Vis spectra of solutions under different external perturbations (as a function of reaction time) were recorded and used in the generation of 2D-COS synchronous and asynchronous maps. The key UV–Vis band assignments are as follows: 250 nm and 400 nm for TEMPO, 290 nm and 480 nm for TEMPO+, and 200 nm and 315 nm for TEMPOH. The results indicate that the conversion between TEMPO and TEMPOH in acidic solution is a reversible process, which reaches an equilibrium state after two hours. However, the reaction becomes irreversible after three hours, due to a higher degree of irreversible protonation of TEMPOH to form TEMPOH-H+. Fast conversion from TEMPO to TEMPO+ is observed when sodium hypochlorite co-oxidant is added. The synproportionation–disproportionation also reaches an equilibrium. However, there is no evidence of the conversion from TEMPOH to TEMPO+ under the reaction conditions. At high reaction temperature, the formation of TEMPOH occurs first from TEMPO+ decomposition, followed by TEMPO decomposition. These detailed mechanisms are beneficial in designing the optimum process conditions for the oxidation of specific alcohols.

The deposition of scale on membranes or container and pipe surfaces (clogging the system) is a costly issue in water treatment processes or water-cooling systems. To effectively cope with this issue, magnetic polymeric nanoparticles (MPNPs) have been developed and applied as promising scale inhibitors, due to their high surface-area-to-volume ratio, surface modifiability, and magnetic separation ability. Carboxylated MPNPs, having a monodisperse size distribution (236 ± 26 nm) with a high magnetic content of 70 wt% and superparamagnetic properties, were fabricated by using a 2-step process: (i) formation of clusters of hydrophobic magnetic nanoparticles stabilized by oleic acid (OA-MNPs), and (ii) self-assembly of the amphiphilic block copolymer of poly(styrene

Oxoammonium cation (TEMPO+) is a powerful oxidant, generated from nitroxyl radicals (TEMPO). The compound has attracted vast attention as a promising selective oxidant in biology and materials fields. Although TEMPO is regarded as a “green” chemical, its use with halogenated co-oxidants has raised serious environmental concerns. In this study, a halogen-free process has been developed by using ozone as an effective, low-cost, and environmentally-friendly alternative in the generation of TEMPO+. An iodine titration combined with UV–Vis spectroscopy is employed to quantitatively monitor the reaction at a fast speed. The results showed that the conversion of TEMPO reached 70% when the ozone feed content and the reaction time were optimized at 25.60 mM and 45 min, at 4–5 °C, in H2SO4 solution. The TEMPO conversion rate is dependent on the reaction time. A fast reaction rate was observed in the first fifteen-min period and became slower in the subsequent period, depending on the ozone feed contents. The difference in concentrations of the TEMPO and the TEMPO+ decreases in the presence of high ozone feed contents, implying the high selectivity of ozone towards TEMPO oxidation to form TEMPO+ over the disproportionation in acid solutions. The developed “green and mild” process has a high potential for selective oxidation of primary alcohols to other high-value products. The optimized conditions were employed to prepare TEMPO+ for use in the oxidation of Quaternized chitosan (QC). Chemical structures of the resulting Chitosan polyampholyte (CPA) products were characterized, and the Degree of oxidation (DO) was determined. CPA with an OD value as high as 100% was obtained with 1.867 mmol of TEMPO+ per gram of QC.

The significant effects of annealing atmosphere on the thermal reduction of graphene oxide (GO) under different atmospheres, air and nitrogen, have been investigated and their distinct properties shown. Initially thermal annealing of both GO in air and nitrogen leads to elimination of unstable in-plane oxygen containing groups. For GO in air (A-RGO), as the temperature is raised to about 400 °C, oxygen starts to react with carbon atoms along the sheet and defect edges, where carbon atoms are most active, leading to the formation of oxygen functional groups which are carboxyl and epoxide as observed using the infrared absorption and X-ray photoelectron measurements. Raman results also show an increase in the amount of hybridized sp3 carbons and defects in agreement with an increase in the oxygen functional groups. In contrast, thermal reduction of GO in nitrogen (N-RGO) leads mainly to the loss of oxygen functional groups, the decrease in the amount of sp3 carbons, and the increase in the C/O ratio compared to those of A-RGO. The resulting A-RGO and N-RGO possess also very different ion affinities, for instance, A-RGO annealed at 500 °C shows much higher cation sorption capacity compared to that of the N-RGO. Divergent transformation paths between GO undergoing thermal reduction in air and N2 are proposed based on these results.

Poly(l-lactic acid) (PLLA) is a well-known biopolymer, usually synthesized via step-growth or ring-opening polymerization from lactic acid or a lactide monomer, respectively. PLLA microspherical particles are produced by dispersion polymerization with a ring-opening lactide monomer using a particular copolymer chain as a stabilizer. This is not easy to achieve when dehydration is needed. Here, a robust and simple synthesis of a nearly monodisperse, submicron PLLA-based particle/capsule was proposed via radical precipitation polymerization without the use of surfactant. A commercial PLLA was first glycolyzed with ethylene glycol to obtain a low molecular weight glycolyzed PLLA (GPLLA). Then, the GPLLA was copolymerized with methacrylic acid and ethylene glycol dimethacrylate monomers using a benzoyl peroxide initiator. Active sites on the GPLLA backbone were generated by hydrogen abstraction of benzoyloxy radicals that further copolymerized before self-assembly to form the polymer particles. Uniform particle size of about 580 nm with a low polydispersity index (PDI) of 0.012 was obtained. This method was also implemented to produce nearly monodisperse capsules containing linalool. The particle size of PLLA-based capsules was about 280 nm with narrow particle size distribution (PDI of 0.120). The PLLA-based capsules effectively inhibited microbial growth of Staphylococcus aureus, Escherichia coli and Candida albicans and were not toxic to human cells.

In contrast to typical starch esterification in an aqueous solution, which are carried out at elevated to ambient reaction temperatures, a low reaction temperature was applied in this study to minimize the starch chain hydrolysis. The physical properties of the modified starch, obtained from an esterification of cassava starch with long-chain fatty acid chlorides carried out in aqueous media at 4°C, were characterized using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and contact angle measurements. The modified starches show improvement in thermal stability and hydrophobicity, which can be further optimized by varying the types of acid chlorides and the reaction conditions. The starch products have high potential for use as fillers for biodegradable polymers, especially polylactic acid (PLA), as their tunable hydrophobicity can impose strong effect on ...

Effects of UV/photo-initiator treatments on crystal formation and properties of polylactide (PLLA) films are investigated. Camphorquinone and riboflavin photo-initiator solutions in methanol are employed in the treatment of amorphous quenched PLLA films. Results from FTIR, ATR-FTIR, DSC, XRD, and SEM show evidence of crystalline domain formation dispersed throughout the film. 1H NMR and GPC results suggest that the molecular weights of the polymer slightly decrease after the treatment. This indicates that the treatment leads to a diffusion of the photo-initiators molecules through the film matrix, resulting in a low degree of PLLA chain scissions, and formation of carboxylic acid and hydroxyl polar end groups. This, in turn, induces PLLA crystallization, which imposes profound effects on surface wettability and physical and mechanical properties of the samples. The process can be applied in optimizing properties of PLLA films with shorter treatment times, compared to other methods, which is suitable for use in various fields; especially those that require specific characteristics like biomedical, packaging and environmental applications.

Standard techniques for quantitative measurement of polyacrylamide (PAm) contents grafted on polylactide (PLA) film substrates, P(LA- g-Am- co-MBAm), which are commonly used as cell culture substrates or scaffolds, and pH-sensitive absorbents have been developed with X-ray photoelectron (XPS), proton-nuclear magnetic resonance (1H-NMR), and Fourier transform infrared (FT-IR) spectroscopy. The techniques are then applied to examine P(LA- g-Am- co-MBAm) samples prepared from two separate photo-initiator/co-initiator systems. Efficiency and accuracy of the techniques are compared. The results from all techniques are in good agreement, indicating high analysis precisions, although FT-IR technique provides additional advantages, in terms of short analysis time, ease of sample preparation, and accessibility of a machine. The results indicate that the riboflavin (RF) initiator system has higher grafting efficiency than its camphorquinone (CQ) counterpart. These standard techniques can be applied in the analysis of these materials and further modified for quantitative analysis of other grafting systems.