Thermoresponsive hydrogels based on renewable resources

This work aims to synthesize novel thermoresponsive hydrogels from renewable resources, bacterial cellulose (BC), and castor oil (CO), and to investigate the effect of CO on physical and thermal behaviors of BC/Poly(N-isopropylacrylamide) (PNIPAM) hydrogels. The structural properties of the hydrogels are analyzed by Fourier-transform infrared (FTIR) spectroscopy. Differential scanning calorimeter (DSC) technique and thermogravimetric analysis (TGA) are also performed to examine the thermal properties of the hydrogels. The morphological differences of the hydrogels are analyzed by scanning electron microscope (SEM). The thermoresponsive performances of the hydrogels are examined by swelling and deswelling behaviors. The hydrogel with CO is found to be more sensitive to temperature changes than the one without CO. Deswelling study demonstrates 91 and 25% of water loss for hydrogels with and without CO, respectively. The present study shows a novel approach to synthesize thermoresponsive hydrogels with renewable resources for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48861.     

Highly toughened polylactide by renewable Eucommia ulmoides gum

Polylactide (PLA) derived from natural sources has attracted increasing interest and has provided a promising alternative to traditional plastics derived from petroleum sources. With no loss of environmental friendly features, PLA was highly toughened by Eucommia ulmoides gum (EUG) derived from Eucommia ulmoides oliv. The dynamic mechanical analysis, scanning electron microscopy (SEM), and differential scanning calorimetry results show that the PLA–EUG blends were immiscible systems. SEM micrographs revealed that EUG particles were well dispersed in the PLA matrix with number‐average particle diameters of 2–4 μm. The mechanical properties indicated that the tensile strength decreased with increasing EUG contents, but the elongation at break and the impact strength were enhanced. The notched impact strength of the blends improved by 5.9‐fold compared to that of neat PLA. The PLA–EUG blends exhibited distinct shear‐thinning behavior; this indicated good processability, and the storage modulus and loss modulus of the PLA–EUG blends increased with EUG content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46017.     

Morphology,mechanical, and physical properties of wet-spun cellulose acetate fiber in different solvent-coagulant systems and in-situ crosslinked environment

Wet spinning is a popular fiber manufacturing process where the effects of solvent and coagulant on the wet-spun fiber are significant. In this study, we have explored the effect of solvent-coagulant interaction and in-situ crosslinking on the wet-spun cellulose acetate (CA) fiber. Investigation on 12 different solvent-coagulant systems revealed that variation in the systems resulted in significant variance in morphology and mechanical property of the fiber. Remarkable increase in mechanical property was observed after in-situ crosslinking with citric acid and polyethylene glycol (PEG). Inclusion of sodium hypophosphite (NaH₂PO₂) as catalyst further increased tensile modulus (~407%) and crystallinity index (~46%) compared to CA fiber crosslinked with only citric acid. It was established that fiber from CA-DMSO solution crosslinked with 10% citric acid and 10% PEG extruded in ethanol showed the highest tensile modulus (~30 MPa). This in-depth study found an appropriate combination of solvent-coagulant for forming stable CA fiber, with the addition of crosslinkers and catalyst further increasing the strength and usability of the fiber.     

Natural resources derived biocomposites as potential carriers of green pesticides in agricultural field: Designing and fabrication of a pot-like device

Hemp fibers (HF) are used as filler in pectin to produce biocomposites. To improve the compatibility of the filler with the polymeric matrix, HF are treated through mechanochemically assisted alkaline attack. The effect of the treatment time on the morphology of HF is investigated through atomic force microscopy and infrared spectroscopy. Cinnamic acid, a green pesticide, is added to the composites in order to test the capability of such materials to act as potential devices in the agricultural field. Analysis of thermal, mechanical, barrier properties and surface energy are evaluated on biocomposites and compared either to unfilled pectin or to composites filled with untreated HF. The release of cinnamic acid is evaluated and found to be dependent on the fibers' treatment time. The design and the fabrication of a pot prototype is also reported. The manufacture appears promising as green functional container for plants to be implanted in the ground.     

Recent synthetic approaches and emerging bio‐inspired strategies for the development of sustainable pressure‐sensitive adhesives derived from renewable building blocks

In this review, we provide a bird's eye view of recent developments in the field of pressure‐sensitive adhesives (PSAs) derived from renewable monomeric building blocks. This emerging research field has been driven by increasing sustainability requirements in the adhesive industry and bridges the gap existing between highly optimized petroleum‐based synthetic PSA systems, which display superior performance but lack biobased content, and historical PSAs derived from naturally occurring biopolymers (e.g., starch and natural rubber), which provide more environmentally friendly bonding solutions but have inherent technical limitations that prevent their more widespread implementation in today's technically demanding applications. We critically reviewed a representative (and exhaustive) survey of recent synthetic approaches to the development of biobased PSAs from the academic (articles) and industrial (patents) literature categorized in two families: chain‐growth and step‐growth polymerization routes. Finally, we draw a parallel between renewable synthetic PSAs and nature's self‐adhesive glues, highlighting how the synergy between green chemistry and biomimetic concepts could inspire the emergence of a new generation of smart, synthetic, biobased PSAs with differentiated properties that approach the ones that are found in the natural world and with a wide spectrum of potential applications in the industrial and medical sectors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40669.     

Fully bio‐based poly(ɛ‐capolactone)/poly(lactide) alternating multiblock supramolecular polymers: Synthesis,crystallization behavior,and properties

Supramolecular poly(?‐capolactone)/poly(lactide) alternating multiblock copolymers were prepared by UPy‐functionalized poly(lactide)‐b‐ poly(?‐capolactone)‐b‐ poly(lactide) copolymers. The prepared supramolecular polymers (SMPs) exhibit the characteristic properties of thermoplastic elastomers. The stereo multiblock SMPs (sc‐SMPs) were formed by blending UPy‐functionalized poly(l ‐lactide)‐b‐ PCL‐b‐ poly(l ‐lactide) (l ‐SMPs) and UPy‐functionalized poly(d ‐lactide)‐b‐ PCL‐b‐ poly(d ‐lactide) (d ‐SMPs) due to stereocomplexation of the PLLA and PDLA blocks. Sc‐SMPs with low content of d ‐SMPs (≤20%) are transparent, elastic solids, while those having high d ‐SMPs content are opaque, brittle solids. The effects of l ‐SMPs/d ‐SMPs mixing ratios on thermal, crystallization behaviors, crystal structure, mechanical and hydrophilic properties of sc‐SMPs were deeply investigated. The incorporation of UPy groups depresses the crystallization of polymer, and the stereocomplex formation accelerates the crystallization rate. The used initiator functionalized polyhedral oligomeric silsesquioxanes causes a different effect on the crystallization of PLA and PCL blocks. The tensile strength and elongation at break of l _d /d _d ‐SMPs (d represents the initiator diethylene glycol) are significantly larger than that of l _p /d _p ‐SMPs (p represents the initiator polyhedral oligomeric silsesquioxanes), and their heat resistance and hydrophilicity can be also modulated by the l ‐SMPs/d ‐SMPs mixing ratios and the different initiators. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45575.     

Protein‐based bioplastics and their antibacterial potential

The use of conventional petroleum‐based plastics in many applications poses the risk of contamination, potentially causing infection when used in medical applications, and contamination when used in food packaging. Nontraditional materials such as protein are being examined for their potential use in the production of bioplastics for applications that require uncontaminated materials. The proteins of albumin, soy, and whey provide possible sources of raw material for bioplastic production, as they have already been utilized in the area of edible films and low‐stress applications. We conducted this study to investigate the thermal, viscoelastic, and antibacterial properties of the albumin, soy, and whey bioplastics with the use of three plasticizers—water, glycerol, and natural rubber latex (NRL). Bacillus subtilis and Escherichia coli were utilized as Gram (+) and Gram (?) species, respectively, for antimicrobial analysis. Albumin and whey bioplastics exhibited similar thermal and viscoelastic properties, whereas soy bioplastics had varied viscoelastic properties based on the plasticizer used. In terms of antibacterial activity, the albumin–glycerol and whey–glycerol were the best bioplastics, as no bacterial growth was observed on the plastics after 24 h of inoculation. In terms of the future impact of this research, the aim will be to scale up production of the bioplastics for use in food packaging as well as biomedical applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41931.     

Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

Poly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41856.     

Ion‐transport study in nanocomposite solid polymer electrolytes based on chitosan: Electrical and dielectric analysis

In this study, (1.1111 ? x)(0.9CS–0.1NaTf)? xAl₂O₃(0.02 ≤ x ≤ 0.1) [where CS is chitosan, NaTf is sodium triflate (NaCF₃SO₃), and Al₂O₃ is aluminum oxide] nanocomposite solid polymer electrolyte (SPE) films based on CS were prepared by a solution casting technique. X‐ray diffraction and scanning electron microscopy analysis revealed that the alumina nanoparticles had a great effect on the structural and morphological behavior of the CS–NaTf (90:10) polymer electrolyte. An investigation of the electrical and dielectric parameters of the nanocomposite SPE films was conducted. Electrical impedance spectroscopy was carried out for this purpose. The relationships between the electrical and dielectric parameters were used to interpret and understand the ion‐conduction mechanism. We observed that the direct‐current conductivity (σ_dc) and dielectric constant followed the same trend with salt concentration. σ_dc versus temperature showed the Arrhenius and Vogel‐Fulcher‐Tammann (VTF) regions. The drops of σ_dc at high temperatures were observed for all of the samples. The ion relaxation dynamics were studied from Argand plots. For the first time, we confirmed the existence of a strong experimental relationship between the high‐frequency semicircle of the impedance plots and the high‐frequency dispersion regions of the alternating‐current conductivity (σ_ac). The dispersion regions of σ_ac were used to study the ion‐conduction mechanism. The behavior of the frequency exponent as a function of the temperature was used to interpret σ_dc versus the temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41774.     

Rheological study of the incorporation of grape seed extract in chitosan and gelatin coatings

This study aims to evaluate the incorporation, addition order and concentration of grape seed extract (Vitis vinifera L.) in chitosan and gelatin solutions, candidates as food coatings due to their excellent antioxidant and barrier properties. This study originally assesses how such variables can affect the rheological parameters of this particular combination of materials. Initially, 1% (w/w) solutions of chitosan (C) and gelatin (G) are mixed at a 1:1 ratio (CG). For grape seed extract addition, ethanolic solutions (50%, v/v) are prepared in different concentrations, with two incorporation orders: 1) addition to CG and 2) addition to the chitosan gel (C), followed by G mixing. The addition order reveals a direct influence on the rheological properties, and low extract concentrations leads to solutions with adequate viscosity for coating applications. The findings of this study confirm that it is essential to standardize the addition procedures during the preparation of the materials.     

Synthesis and characterization of polysaccharide hydrogel based on hydrophobic interactions

Hydrogels based on hydrophobic, or micellar interactions, are physically crosslinked hydrogels which are an attempt to overcome the poor mechanical properties of traditional, chemically crosslinked gels, such as low shear strength. We have prepared a polysaccharide-based hydrogel with physical crosslinks via hydrophobic interactions. In this work, we have synthesized hydrogel by grafting a hydrophobic moiety dioctylamine onto hydrophilic precursor carboxymethyl cellulose (CMC) through an amide bond formation, where ~33% of the carboxyl group in CMC was reacted with dioctylamine. The thermosensitive hydrogel can arrest 100 mL of deionized water per gram of gelator within few seconds. It showed the moderate rheological property. The hydrogel is nontoxic and does not show any adverse to human hemoglobin. It is a CMC based a unique gelator with high biocompatibility represent to be useful materials for biomedical application. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47665.     

Synergistic reinforcing of poly(lactic acid) by poly(butylene adipate-co-terephthalate) and alumina nanoparticles

Biodegradable poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends and PLA/PBAT/Al₂O₃ nanocomposites were fabricated via solution blending. The influence of PBAT and Al₂O₃ content on the thermal stability, flexural properties, impact strength, and morphology of both the PLA/PBAT blends and the PLA/PBAT/Al₂O₃ nanocomposites were investigated. The impact strength of the PLA/PBAT/Al₂O₃ nanocomposites containing 5 wt% PBAT increased from 4.3 to 5.2 kJ/m² when the Al₂O₃ content increased from 0 to 1 wt%. This represents a 62% increase compared to the impact strength of pristine PLA and a 20% increase compared to the impact strength of PLA/PBAT blends containing 5 wt% PBAT. Scanning electron microscopy imaging revealed that the Al₂O₃ nanoparticles in the PLA/PBAT/Al₂O₃ nanocomposites function as a compatibilizer to improve the interfacial interaction between the PBAT and the PLA matrix.     

Construction of gold nanoparticles by tubular polysaccharide from black fungus and their apoptosis-inducing activities in HepG2 cells

Gold nanoparticles (AuNPs) with size of 12 ~ 25 nm were loaded on the dendritic nanotubes (DNTs), which were self-assembled by the triple-helix polysaccharides from black fungus (AF1). The characterization results proved that the AuNPs were dispersed on the surface of DNTs without affecting their tubular structure. Due to the dendritic structure, the loading content of AuNPs could arrived at 46.4%. Moreover, the potential anticancer activities of the complex (DNT-Au) were evaluated by the induction of apoptosis in HepG2 cells. It was found DNT-Au could be taken up by cells and enter into lysosomes, further inducing apoptosis in HepG2 cells by ROS-mediated mitochondrial dysfunction. This work was benefit for the development of natural polysaccharide as a substrate to stabilize nanoparticles in biomedical fields.     

Thermal degradation of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) in drying treatment

This study examines the isothermal treatment of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) powders and films. The PHB and PHBV crystallinities were determined using X‐ray diffractometry, and shown to increase with temperature (130–150°C) and then decreased from 55% to 45% at 180°C. The crystal morphology of crystal planes (101) and (111) became sharp at a high temperature. The weight average molecular weight (M_w) of PHB decreased from 1,028,000 to 41,800 g/mol when heated at 180°C for 30 min. The molecular weight of PHB decreased more rapidly than that of PHBV with time. No peak signal was observed in gel permeation chromatography after heating at 150°C because the solubility of PHB changed with crystallinity. The thermal behaviors of PHB and PHBV were analyzed by differential scanning calorimetry and thermogravimetric analysis. The roughness, contact angle, and surface morphology of PHB and PHBV films were also measured to determine the surface properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3659–3667, 2013     

Comparison of bacterial cellulose production by Gluconacetobacter xylinus on bagasse acid and enzymatic hydrolysates

To fulfill the comprehensive utilization of cellulose and hemicellulose components in bagasse for bacterial cellulose (BC) production, both bagasse acid and enzymatic hydrolysates were used for BC production by Gluconacetobacter xylinus. Although the BC accumulation rate was slower during the early period of fermentation in the bagasse acid hydrolysate than in the enzymatic hydrolysate, the highest BC yield (1.09 vs. 0.42 g/L) was higher in the bagasse acid hydrolysate. The substrate utilization was evaluated in both bagasse acid and enzymatic hydrolysates, and glucose, xylose, and acetic acid were better carbon sources than arabinose and cellobiose for G. xylinus. The structure of the BC samples obtained from bagasse acid and enzymatic hydrolysates, including the microscopic morphology, functional groups, and crystals, was similar especially in the later phase of fermentation, which was analyzed by field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray diffraction. Thus, both bagasse acid and enzymatic hydrolysates could be promising substrates for BC production. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45066.     

Graft modification of methyl acrylate onto chicken feather via surface initiated Cu(0)-mediated reversible-deactivation radical polymerization

In this study, chicken feather was functionalized with 2-Bromoisobutyryl bromide (BIBB) where methyl acrylate (MA) was grafted through Cu(0)-mediated reversible-deactivation radical polymerization (RDRP) catalyzed by copper wire. Feather-g-PMAs with three different target degrees of polymerization (Dp) were prepared fast. Besides, molecular mass of PMA was closely associated with the theoretical value; PMA also exhibited relatively low polydispersity (~1.17). The catalyst was removed through simple washing, and thus a colorless product was yielded. However, Cu(0)-mediated RDRP in the presence of the unmodified chicken feather caused the loss of control. Feather-g-PMA with a short graft chain exhibited a uniform interface coated on the feather fiber. Because the grafted PMA and the feather substrate had a strong interaction, and the graft ratio was less, there was only one stage of decomposition, and no glass transition temperature was detected. We detected a rough surface on feather-g-PMA with a longer graft chain and observed the glass transition of PMA and obviously two stages of decomposition. After densely graft, the hydrophilicity of chicken feather decreased. These feather-g-PMAs exhibited better compatibility in organic solvents (e.g., acetone and toluene). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48246.     

Tung oil‐based thermosetting polymers for self‐healing applications

Several bio‐renewable thermosetting polymers were successfully prepared from tung oil through cationic polymerization for the use as the healing agent in self‐healing microencapsulated applications. The tung oil triglyceride was blended with its methyl ester, which was produced by saponification followed by esterification. The changes in storage modulus, loss modulus, and glass transition temperature as functions of the methyl ester content were measured using dynamic mechanical analysis. In addition, the fraction of cross‐linked material in the polymer was calculated by Soxhlet extraction, while proton nuclear magnetic resonance, Fourier transform infrared spectroscopy and TEM were used to investigate the structure of the copolymer networks. The thermal stability of the thermosets as a function of their methyl ester blend contents was determined by thermogravimetric analysis. Finally, the adhesive properties of the thermosets were studied using compressive lap shear and the fracture surfaces were analyzed using SEM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40406.     

In situ chemically crosslinked chitosan membrane by adipic acid

Adipic acid, which is nontoxic, was used to dissolve chitosan. The chitosan/adipic acid solution was used to prepare chitosan membrane. After being heated at 80–100°C, the membrane was in situ chemically crosslinked by adipic acid, as verified by Fourier transform infrared and wide‐angle X‐ray diffractometer analysis. The crosslinked membrane did not collapse even without treatment in alkaline solution. In addition, the in situ crosslinking reaction was studied. The crosslinking degree (CLD) was quantitatively calculated based on the mass of water produced. The results showed that CLD was positively related to both heating temperature and time. Results of kinetic of crosslinking reaction suggested that the amidation was in agreement with the first‐order rate equation and that the temperature effect could be described with the Arrhenius equation. The results of weight loss of chitosan membrane in phosphate‐buffered solution (pH = 7.4) indicated that the best water resistance of chitosan membrane was obtained at 90°C. In brief, a straightforward, nontoxic, environment‐friendly, and economical chemically crosslinking approach has been developed for chitosan materials. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of five saturated fatty acids on the properties of sweet‐potato‐starch‐based films

To fully explore the influences of saturated fatty acids (SFAs) on the properties of sweet‐potato‐starch (SPS)‐based films, five SFAs were chosen to add to SPS. The SPS‐based films were prepared by casting. The microstructure, mechanical, optical, water vapor barrier, and thermal properties of the films were investigated. The 2.0% (w/w, on the basis of starch) SFA significantly changed the SPS pasting characteristics in the peak viscosity, breakdown, and other feature point viscosity values as determined by a Rapid Visco Analyser. The amylose molecular weights decreased as measured by high‐performance size exclusion chromatography. A thermal study with differential scanning calorimetry suggested that the addition of SFA increased the onset temperature and peak temperature. Scanning electronic microscope (SEM) images showed a continuous and uniform structure in the films with SFA. The SPS–SFA composite films showed lower light transmission and elongation at break than the control. Compared with the control films, the addition of SFA increased the tensile strength and decreased the water vapor permeability of the films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41380.     

Preparation of polyurethane foams using fractionated products in liquefied wood

Liquefaction of sawdust was studied using glycerol and methanol as mix solvents. A new bio‐polyol product consisting of high purity multi‐hydroxy compounds was obtained by precipitation of the hydrophobic organics from the liquefied product in an aqueous solution. As identified by GC‐MS, the dominate components in bio‐polyol were glycerol, glycerol derivatives, and multiple types of sugar derivatives. By using the mass ratio of m (sawdust) : m (glycerol) = 1 : 1, the total content of multi‐hydroxy compounds reached 90.84%. The hydroxyl number of the bio‐polyol was 1287 mgKOH/g with a rotational viscosity of 1270 cP. Preparation of polyurethane foams using bio‐polyol and isocyanate was also studied. Water was used as an environmental friendly blowing agent. The factors that influence the cell structure of foams (i.e., catalyst, dosage of blowing agent, and mass ratio of bio‐polyol to PEG‐400 were studied. The compressive strength of the synthesized foam was 150 Kpa, which met the requirement of Chinese specification for rigid foams. The synthesized foams were characterized by FTIR, SEM, and TG. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40096.