Current application of controlled degradation processes in polymer modification and functionalization

Ecological concerns over the accumulation of polymeric waste material and the demand for functionalized polymers in specialty applications have promoted extensive research on different controlled degradation processes and their use. The production of functionalized or modified polymers by conventional synthetic routes is expensive and time consuming. However, advances in degradation technology have become an enabling factor in the production of modified polymers and their functionalization. Mild irradiation, ozonization, and enzymatic routes are among the processes that have been explored for polymer modification. Biopolymers, such as chitosan, hyaluronic acids, and polyhydroxyalkanoates, are known to be suitable for a diverse number of applications, ranging from biomedical to organic‐electronics. At the same time, their high molecular weight, crystallinity, and shelf degradability limit their utility. Controlled degradation processes can be used to prepare these types of polymers with reasonably low molecular weights and to generate radical species that help to stabilize these polymers or to initiate further beneficial reactions. In this article, we review the application of controlled degradation processes for polymer modification and functionalization. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biodegradable superabsorbent hydrogel for water holding in soil and controlled-release fertilizer

The bio-based environment-friendly functional polymers are the most desired materials for the society. Thus, a superabsorbent hydrogel (SAH) of starch-modified poly(acrylic acid) was reported and the concentrations of reactants, initiators, and crosslinkers were optimized to achieve the highest water absorption (>700 g/g). The chemical structure of SAH was supported by solid-state ¹³C nuclear magnetic resonance and Fourier-transform infrared spectroscopic studies. The hydrogels were found to be biodegradable and possess high water absorption capacity. After the addition of 0.25% of the hydrogel, water-holding capacity of the soil was enhanced by 120%. Significant effect was also observed on bulk density and porosity of the soil after the addition of SAH. Furthermore, urea-encapsulated SAH can be used as a controlled release fertilizer for crops, as indicated by a preliminary study on the growth rate of chick pea (Cicer arietinum) plant. Thus, SAH has the potential to be used as a controlled-release carrier and water-conserving agent in different fields. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48495.     

Self‐driven graft polymerization of vinyl monomers on poultry chicken feathers in the absence of initiator/catalyst

An efficient and simple method for graft copolymerization of powdered chicken feather (CF) with vinyl monomers without any free radical initiator is reported. Various vinyl monomers such as glycidyl methacrylate (GMA), styrene (S), and methyl methacrylate (MMA); (20–60 wt % with respect to CF) were successfully grafted to chicken feather (CF) by using sodium dodecyl sulfate (SDS, 0.086–0.5 mmol) in the absence of any catalyst or initiator. Most likely, the hydrophilicity, hydrophobicity, and complex forming properties of chicken feather keratin with surfactant molecules were responsible for efficient grafting of polymers on CF surface. The effect of polymerization conditions, such as monomer concentration, temperature, and time of reaction, on the grafting parameters such as monomer conversion, grafting efficiency, and molar grafting ratio were studied. The described method showed a good potential of using low cost, easily accessible poultry chicken feathers as grafting material and self catalyzing agent for graft copolymerization with vinyl monomers to produce low cost commodity plastic for various end uses. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44645.     

Field performance on lettuce crops of poly(butylene adipate-co-terephthalate)/polylactic acid as alternative biodegradable composites mulching films

This work developed biodegradable poly(butylene adipate-co-terephthalate)/polylactic acid (PBAT/PLA) composites with different fillers to improve their physicochemical properties and biodegradability. The films were tested considering mechanical, morphological, thermal, crystalline, biodegradability, and ecotoxicity tests. Mechanical and morphological results indicated that the fillers' nature influences mechanical performance; all composites showed high-tensile strength (~30 MPa) than the pristine films (~12 MPa). The use of both fillers resulted in an interface, improving the matrix compatibility, reflecting in good thermal performance, low-water absorption, and high hydrophobicity. The WA (water absorption) and hydrophobicity are essential to maintain the crop's moisture since the water lost through plant transpiration will be condensed and returned to the soil. Films showed biodegradability and absence of toxicity, which allows the substitution of polyethylene commodity films as mulching films. Biodegradation and ecotoxicity tests indicate that the developed films are beneficial for lettuce crops and contribute to the development of seedlings.     

Structural,topographical, and mechanical characteristics of purified polyhydroxyoctanoate polymer

Insight into the topographic and mechanical properties of biomaterials allows for efficient selection of a material for a specific application. Here, atomic force microscopy (AFM) and force spectroscopy were exploited to reveal the topographic and mechanical characteristics of charcoal-purified, solvent-cast polyhydroxyoctanoate (PHO) film. The root mean square surface roughness of a PHO surface derived from ethyl acetate, acetone, or chloroform solution was 13.2, 11.5, or 30.9 nm, respectively, for 100 μm² AFM images. The distribution of the local Young's modulus had a maximum of 25.4, 14.1, and 12.6 MPa for PHO films obtained from ethyl acetate, acetone, and chloroform solution, respectively. The positron annihilation spectroscopy measurements allowed us to determine the free volume in the polymer film structure (9.38%). Moreover, a number of additional techniques (X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, gel permeation chromatography, NMR, infrared spectroscopy, and polarized light microscopy) were used to reveal PHO features. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47192.     

Polyhydroxybutyrate and hydroxyvalerate production by Bacillus megaterium strain A1 isolated from hydrocarbon‐contaminated soil

In this study, we attempted to find an alternative microbial resource as a bioplastic producer. Among all of the isolates, the A1 strain produced 44% poly(β‐hydroxybutyrate) (PHB) in proportion to its dry cell weight. The molecular identification of the 16S RNA gene showed that this bacterium was a strain of Bacillus megaterium with the accession number KC579390. The optimization studies led us to the conclusion that the highest poly(β‐hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) production was 78% when 5% molasses was used as the carbon source at pH 6 and 35°C after 60 h of incubation. Attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy and H‐NMR were used for chemical characterization. Differential scanning calorimetry was used to determine the thermal properties of the PHB and PHBV that were synthesized with sucrose and molasses as carbon sources, respectively. The FTIR spectra of the polymers were characterized by typical absorption bands at 1715–1720 cm^?1 for amide‐bound C?O bands and 1261–1279 cm^?1 for an ester‐bound C? O band. The molecular weights of PHB and PHBV synthesized with sucrose and molasses were calculated as 428 and 498 kDa, respectively, according to the viscometric method. This study indicated that the B. megaterium strain A1 is an alternative microbial resource as a bioplastic producer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40530.     

In vitro comparative biodegradation analysis of salt‐leached porous polymer scaffolds

This study presents a comprehensive, side‐by‐side analysis of chemical, thermal, mechanical, and morphological changes in four polymers used in tissue engineering: poly(glycerol‐sebacate) (PGS), poly(lactic acid) (PLA)/poly(ε‐caprolactone) (PCL) blend, poly(lactic‐co‐glycolic acid) (PLGA), and Texin 950, a segmented polyurethane resin (PUR). Polymer foams were created using a salt‐leaching technique and then analyzed over a 16‐week period. Biodegradation was analyzed by examining the morphology, thermal properties, molecular weight, chemical, and mechanical properties using scanning electron microscopy, differential scanning calorimetry, gel permeation chromatography, attenuated total reflectance‐Fourier transform infrared spectroscopy, thermogravimetric analysis, and compression testing. PGS underwent the most rapid degradation and was hallmarked by a decrease in compressive modulus. PLA/PCL blend and PLGA both had rapid initial decreases in compressive modulus, coupled with large decreases in molecular weight. Surface cracks were observed in the PUR samples, accompanied by a slight decrease in compressive modulus. However, as expected, the molecular weight did not decrease. These results confirm that PUR does not undergo significant degradation but may not be suitable for long‐term implants. The biodegradation rates of porous PGS, PLA/PCL blend, and PLGA found in this study can guide their use in tissue engineering and other biomedical applications. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Biobased miktoarm star copolymer from soybean oil,isosorbide, and caprolactone

Soybean oil-based macroinitiator was prepared from epoxidized soybean oil. A ¹H NMR quantitative method was utilized for the characterization of this macroinitiator. A kind of renewable carbohydrate derivate, 1,4: 3,6-Dianhydro-D-glucitol 2-acrylate 5-acetate (AAI) was prepared as the substitute monomer of styrene. Series of renewable miktoarm star copolymers initiated by soybean oil macroinitiator were obtained by atom transfer radical polymerization (ATRP) of AAI and ring-opening polymerization (ROP) of ε-caprolactone sequentially. The obtained miktoarm star block copolymers were characterized by ¹H NMR, FTIR, and DSC. The DSC results show well dependence of the thermal behaviors of these miktoarm star block copolymers on the component of the two kinds of segments. A new strategy of renewable resource utilization has been provided on polymeric materials. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48281.     

Biodegradable composites with improved barrier properties and transparency from the impregnation of PLA to bacterial cellulose membranes

Poly(lactic acid) (PLA) was impregnated in bacterial cellulose (BC) membranes. BC/PLA films were prepared by solvent casting and mechanical, optical and barrier properties, and biodegradation process were investigated. The transparency of processed films was higher than that of neat BC and increased with PLA content. Moreover, the incorporation of PLA to BC enhanced significantly the water vapor barrier properties of the BC membranes. The bionanocomposites contained a high percentage of cellulose due to the impregnation method that leads to the film with a BC content of 94%, which practically maintains the excellent mechanical properties of BC. However, when increasing the PLA content in the bionanocomposites the mechanical properties decreased slightly with respect to BC. Biodegradation under real soil conditions was determined indirectly through the study of the visual degradation and disintegration, demonstrating that the bionanocomposites were degraded faster than the neat PLA. The successful production of BC/PLA bionanocomposites suggested the possible application of them for active food packaging. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43669.     

Rheology,injectability, and bioactivity of bioactive glass containing chitosan/gelatin,nano pastes

Bioactive pastes containing bioactive sol–gel derived glass (BG) and various amounts of chitosan (Cn) and gelatin (Gel) were prepared in this study. To be exact, three pastes were prepared by mixing 25 parts by weight of glass powder with (a) 100 parts by weight of a 3 wt% acetic acid-based chitosan solution, (b) 100 parts by weight of a 3 wt% water-based gelatin solution, and (c) 100 parts by weight of a solution containing equal amounts of the above-mentioned solutions. The bioactivity of the composite samples was evaluated by the immersion of the prepared pastes into the simulated body fluid (SBF) solution. The samples were also analyzed by X-ray diffractometry (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and atomic absorption spectroscopy (AAS). The results indicated better apatite formation capacity on the glass-/chitosan-/gelatin-injected paste after 14 days. Furthermore, unlike the chitosan containing paste, the gelatin-containing sample was injectable and displayed viscoelastic behavior as determined by conducting the rheology test in oscillation mode. In addition, while chitosan made the paste more viscous, it improved the washout resistance when compared to the gelatin-containing sample. The experimental results also indicate the formation of spherical calcites in the pastes prior to immersion into the SBF solution.     

Green synthesis and characterization of poly(glycerol-azelaic acid) and its nanocomposites for applications in regenerative medicine

A series of novel bio-polyester nanocomposites based on glycerin and azelaic acid as monomers incorporating hydroxyapatite (HA) nanoparticles were fabricated via in situ polymerization method. Chemical structure of the samples was investigated by ¹H-NMR, ¹³C-NMR, and Fourier-transform infrared spectroscopy (FTIR). Energy dispersive X-ray-mapping analysis illustrated that the nanoparticles were well dispersed in the poly (glycerol azelaic acid) (PGAZ) matrix. Viscoelastic properties of the samples under various frequencies were examined in which the PGAZ specimen containing 1.0 wt% of HA nanoparticles (PGAZH1.0) exhibited superlative properties. Furthermore, the alterations in the glass transition temperature of the samples were comprehensively discussed. Thermal gravimetric analysis displayed that nanocomposites generally have a difference in degradation patterns from that of the pristine sample. Dynamic contact angle demonstrated that the presence of HA nanoparticles imposed a significant influence on hydrophilicity. The hydrolytic degradation values at pH = 7 and pH = 11 were measured and determined that the degradation rate for the PGAZ sample containing 1.5 wt% HA (PGAZH1.5) was higher than those of the other samples. Moreover, in vitro studies elucidated that cell attachment on PGAZH1.0 and PAZH1.5 surfaces were acceptable.     

Highly permeable biomimetic reverse osmosis membrane with amphiphilic peptide stabilized aquaporin as water filtering agent

The shortage of fresh water is one of the most critical problems our society must address. The most commonly accepted method to produce fresh water is by membrane systems. Since the discovery of aquaporins (AQPs) (water channel proteins), researchers have been trying to incorporate them as functional units in biomimetic membranes to achieve superior water permeability and solute rejection. However, it still remains challenging due to the lack of an effective strategy to stabilize AQPs and fabricate robust membranes. Here, we report the utilization of an amphiphilic peptide (BP1) to stabilize AQPs and use the resulting protein–BP1 complex for desalination purposes. We demonstrated the secondary structure and stability of protein–BP1 complex in aqueous solution using circular dichroism and transmission electron microscopy. The resulting membrane with aquaporin incorporation showed water permeability of 12.33 LMH, improved 28% compared to mutant control membrane, and 83.6% compared to traditional polyamide membrane, while maintaining the high sale rejection (96%). These results demonstrate a great potential of this new incorporating technique for desalination applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46169.     

Preparation of a biodegradable poly(vinyl alcohol)–starch composite film and its application in pesticide controlled release

With the herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D) as a model drug, a series of poly(vinyl alcohol)–starch (PVA–ST) composite films for controlled drug release were prepared by a casting method. The morphology, structure, and release properties were systematically investigated. The results show that when the PVA–ST composite film containing 2,4‐D (PSD) was immersed in water, the drug‐release rate was high, whereas the introduction of sodium montmorillonite (Na‐MMT) and an alginate ion‐crosslinking structure to PSD significantly reduced the release rate and maintained the sustained release of the model drug for a longer period. A leaching experiment through the soil layer showed that the PSD drug‐loaded film with Na‐MMT and the alginate ion‐crosslinking structure (PSDMA) possessed good release properties. The cumulative leached amount of the herbicide 2,4‐D after eight irrigations was reduced to 57.6% from 100%. In addition, the PSDMA film showed favorable mechanical and thermal properties. This composite film is expected to have potential applications in the fields of agriculture, drug delivery, and more. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45051.     

Pullulan‐based films and coatings for food packaging: Present applications,emerging opportunities,and future challenges

Societal and industrial demands for lower environmental impact, cost effectiveness, and high‐performance goods and services are increasingly impacting the choice of technologies which are developed and deployed in consumer products. Like many other sectors, food packaging is moving to new technologies; the use of biopolymers is one of the most promising strategies toward an optimized use of traditional packaging materials (e.g., oil‐based plastics) without impairing the goal of extending shelf life. Among other food packaging materials, pullulan is attracting much attention due to its unique features. The goal of this review is to provide an overview of current and emerging applications of pullulan within the food packaging sector. In particular, the functional properties of interest for the food packaging industry will be discussed in light of the physicochemical attributes of this exopolysaccharide. Future challenges that may dictate the successful penetration of pullulan in the food packaging market are also outlined. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40539.     

Morphology,physical properties,silver release,and antimicrobial capacity of ionic silver‐loaded poly(l‐lactide) films of interest in food‐coating applications

In the present study, silver ions were incorporated into a poly‐(l ‐lactide) (PLA) matrix by a solvent casting technique using different solvents and glycerol as plasticizer. The effect of the different formulations on the morphology, thermal, mechanical and color properties were first evaluated. Additionally, a thorough study of the silver ions release to an aqueous environment was also monitored over time by anodic stripping voltammetry and correlated with the antimicrobial performance against S. enterica. The incorporation of silver contents of up to 1 wt % did not affect morphology, thermal or mechanical properties of the films. A sustainable, antibacterial effectiveness was found for the films in liquid medium and a breakpoint of 10–20 μg L^?1 silver was established under the stated conditions, evincing silver ion releasing technologies may be applied to liquid environments while complying with current legislation. This study provides insight into the structure properties relationship of these antibacterial polylactide materials of significant potential in coating applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41001.     

Simultaneous removal of Cd,Co, Cu,Mn, Ni,and Zn from synthetic solutions on a hemp-based felt. III. Real discharge waters

Two hemp-based materials were used as nonconventional adsorbents for the final treatment of industrial discharge waters (DWs) from a metal-finishing plant. The first adsorbent, referred as HEMP, was a felt made of 100% hemp fiber. The second was the same felt coated with a maltodextrin-1,2,3,4-butanetetracarboxylic crosslinked polymer (HEMPM) in order to provide ion-exchange properties to the material by introducing carboxylic groups. The batch experiments showed that both materials exhibited high adsorption capacities toward metal ions present in 12 DWs, leading to concentrations well below those allowed by the French regulation. Measurements of the germination rate of Lactuca sativa seeds and of mobility inhibition of Daphnia magna, used as ecotoxicological tests, were carried out on DWs before and after hemp treatment. The average germination rate before and after treatment were 47.2 ± 4.1 for untreated DWs, 71.2 ± 6.3 for DWs treated by HEMP, and 89.3 ± 4.7 for DWs treated by HEMPM. The EC50 values for four DWs were between 2.1 and 10.4% of DW, indicating high toxicity. After HEMPM treatment, exposure to the DW for 24 h did not cause immobilization (EC50 > 90%). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48823.     

Synthesis and characterization of PMMA composites activated with starch for immobilization of L‐asparaginase

Poly (methyl methacrylate) (PMMA)–starch composites were prepared by emulsion polymerization technique for L‐asparaginase (L‐ASNase) immobilization as highly activated support. The hydroxide groups on the prepared composites offer a very simple, mild and firm combination for enzyme immobilization. The pure PMMA and PMMA‐starch composites were characterized as structural, thermal and morphological. PMMA‐starch composites were found to have better thermal stability and more hydrophilic character than pure PMMA. L‐ASNase was immobilized onto PMMA‐starch composites contained the different ratio of starch (1, 3, 5, and 10 wt %). Immobilized L‐ASNase showed better performance as compared to the native enzyme in terms of thermal stability and pH. K_m value of immobilized enzyme decreased approximately eightfold compared with the native enzyme. In addition to, immobilized L‐ASNase was found to retain 60% of activity after 1‐month storage period at 4 °C. Therefore, PMMA‐starch composites can be provided more advantageous in terms of enzymatic affinity, thermal, pH and storage stability as L‐ASNase immobilization matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43421.     

Preparation,characterization, and release behavior of ceftiofur‐loaded gelatin‐based microspheres

Drug‐loaded microspheres prepared from biomacromolecules have received considerable interest. In this article, we report a facile method for preparing ceftiofur‐loaded gelatin‐based microspheres for controlled release. We investigated the effects of factors, including the rotational speed, concentration of surfactant, concentration of gelatin, and ratio of water to oil (W/O), on the morphologies of gelatin microspheres and obtained the optimized conditions; for a typical average diameter of about 15 μm, these were 1000 rpm, a concentration of span 80 of 2.0%, a gelatin concentration of 20%, and a W/O of 1:20. Gelatin microspheres loaded with ceftiofur, ceftiofur‐Na, and ceftiofur‐HCl were prepared and characterized by scanning electron microscopy and laser light scattering. In vitro release studies were carefully performed for microspheres prepared with different crosslinker contents, loaded with different drugs, and blended with chitosan. The loaded ceftiofur showed an obviously longer release time compared with pure ceftiofur powder. A higher content of crosslinker led to a longer release time, but when the content reached 5%, the microspheres had a significantly cracked surface. The results also indicate that the blending of a small amount of chitosan could greatly prolong the release time. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2369–2376, 2013     

Sustainable biodegradable coffee grounds filler and its effect on the hydrophobicity,mechanical and thermal properties of biodegradable PBAT composites

Poly(butylene adipate‐co‐terephthalate) (PBAT) and coffee grounds (CG) wastes are biodegradable materials. The high cost of PBAT restricts its marketability; the lignocellulosic CG were used as a reinforcing agent for PBAT. Thus, the present work focuses mainly on the preparation and characterization of bio‐based PBAT composites filled with CG bio‐additives with affordable cost, and with potential use in a variety of eco‐friendly fields such as packaging, biomedical devices, and composting. The PBAT polymer was melt blended with various contents of CG powder using twin screw extrusion. The compatibility and dispersion state of investigated biocomposites in presence or absence of PEG as plasticizer were investigated by using scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The effect of the addition of PEG on PBAT/CG was characterized by differential scanning calorimetry (DSC), tensile properties, contact angle measurements, and thermogravimetric analysis. The chemical interaction between hydroxyl groups of CG particles and PEG plasticizer was achieved by these techniques. A pyrolysis kinetic model was proposed to identify the kinetic parameters of the thermal degradation of PBAT and CG powder. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44498.     

Preparation,characterization and antioxidant activity of acetylated garlic polysaccharide,and garlic polysaccharide-Zn (II) complex

Garlic polysaccharide (PS) was extracted from garlic by hot-water extraction. Acetylated garlic polysaccharide (AcPS) and garlic polysaccharide-zinc complex (ZnPS) were synthesized. The results of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy analysis showed that the modifications were successful. The antioxidant activities of PS, AcPS, and ZnPS were further investigated in vitro, including scavenging superoxide anion and hydroxyl radicals, antilipid peroxidation capacity, and reducing power. The results showed that the scavenging abilities of AcPS and ZnPS on hydroxyl radical (The IC₅₀ of PS, AcPS, and ZnPS were 2.86, 1.62 and, 1.49 mg/ml, respectively,) and superoxide anion radical (The scavenging rate of PS, AcPS, and ZnPS were 1.5% and 1.8%, and 2.3%, respectively, when concentration was at 1.0 mg/ml.) were stronger than that of PS, and the inhibitory effect of AcPS on lipid peroxidation was significantly stronger than that of PS (The IC₅₀ of PS and AcPS were 1.05 and 0.53 mg/ml, respectively.). It indicated that the acetylation was a favorable way to enhance the antioxidant activity of garlic PS; ZnPS complex could be applied as potential candidate for antioxidant and Zn supplement.