Controlled release of polymer conjugated agrochemicals. System based on poly(methyl vinyl ether‐alt‐maleic anhydride)

Controlled release formulations were prepared by using commercially available poly(methyl vinyl ether‐alt‐maleic anhydride) (I) and 2,4‐dichlorophenoxy acetic acid herbicide (2,4‐D). The copolymer (I) was reacted with various diamines to produce amido‐amine containing carboxylate copolymers. The produced copolymers were reacted with the acid chloride of herbicide 2,4‐D as model herbicide for carboxylic group functionalized herbicides. The formulations produced were characterized by IR and elemental analyses. The release of the herbicide 2,4‐D from the formulations was studied under different aqueous medium conditions and the effect of copolymer microstructure on release profiles was investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 415–421, 2001     

Controlled release of 2‐methyl‐4‐chlorophenoxy acetic acid herbicide from waste gelatin–based blends and composites

The volume of plastic waste is becoming a serious problem for waste management. Waste management is based on four hierarchical approaches: reduction, reuse, recycling, and energy recovery. We now report on recycling of gelatin scraps that are derived during the production of pharmaceutical capsules, by using the gelatin scraps in the production of controlled‐release systems. This may help to minimize the side effects that often accompany the conventional application of pesticides. More important, the gelatins themselves, when degraded, might be useful to soil solarization and crop growth. Using and recycling these waste materials in the proposed application would save natural resources and consequently would be economically useful. The synthesis of gelatin films, and composites incorporating 2‐methyl‐4‐chlorophenoxy acetic acid (MCPA) as herbicide, will be described. Morphology and mechanical properties of the films were investigated by scanning electron microscopy and tensile tests, respectively. The release of the MCPA herbicide from the prepared blends and composites was investigated. The prepared formulation proved to be useful for agricultural applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1420–1427, 2004     

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.     

Synthesis,characterization and application of poly[(1‐vinyl‐2‐pyrrolidone)‐co‐(2‐hydroxyethyl methacrylate)] as controlled‐release polymeric system for 2,4‐dichlorophenoxyacetic chloride using an ultrafiltration technique

BACKGROUND: Polymers supporting chemicals used in agriculture have recently been developed to overcome the serious environmental problems of conventional agrochemicals. The success of these formulations is based on a suitable choice of polymer support. Degradable polymeric hydrogels are of particular interest. The gradual release of the bioactive agent can be achieved by hydrolytic or enzymatic cleavage of the linking bond. RESULTS: In this context, poly[(1‐vinyl‐2‐pyrrolidone)‐co‐(2‐hydroxyethyl methacrylate)] [poly(NVP‐co‐HEMA)] has been used as a bioactive carrier reagent. Herein, we report a controlled‐release system with the herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D) using an ultrafiltration system. Hydrolysis was studied by testing the release at various pH values. A high release with poly(NVP‐co‐HEMA)–2,4‐D was observed at pH = 7 and 10 after two days (Z = 2). The release percentage of copolymer–herbicide increased at pH = 10. It showed release values between 79.0 and 94.5%. Poly(NVP‐co‐HEMA)–herbicide can release a bioactive compound in aqueous solution at pH = 3, 7 and 10. CONCLUSION: Based on the results of homogeneous hydrolysis, it is argued that the herbicide release rate depends on the pH of the reaction environment. This functional polymer could be employed as a biodegradable material for applications in agrichemical release. Copyright © 2008 Society of Chemical Industry     

Preparation and optimization of 2,4‐D loaded cellulose derivatives microspheres by solvent evaporation technique

Controlled release herbicide formulations were prepared by microencapsulation using solvent evaporation technique. 2,4‐D was chosen as core material, which was microencapsulated in two cellulose derivatives as matrices: cellulose acetate butyrate butyryl (CAB) and ethylcellulose (EC). The work is intended to produce systems containing the herbicide to reduce its risks by dermal contact, evaporation, or degradation and to control the release of the active agent. The microspheres loaded by 2,4‐D were characterized by scanning electron microscopy and infrared spectroscopy. We have obtained microparticles in the range of D₃₂ of 42–277 μm with CAB and 88–744 μm with EC by varying the process parameters. The drug entrapment was improved by controlling certain factors such as polymer/solvent ratio, pH of continuous phase, and organic phase solvent. The drug release was established in deionized water at pH = 5.5 and 25°C and the 2,4‐D concentrations were estimated by UV analysis. The release data were analyzed according to Fick's law and the results demonstrate that the release rate can be controlled by modifying the process parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2742–2751, 2007     

Effect of natural polyphenols on physicochemical properties of crosslinked gelatin‐based polymeric biocomposite

This work was aimed to study the effect of natural polyphenols extract (Acacia nilotica bark) on physicochemical properties of crosslinked gelatin‐poly(acrylamide‐co‐acrylic acid), Gel‐poly(AAm‐co‐Ac), polymeric biocomposite film. Gelatin‐based composite films have extensive application as biocompatible biomaterial as drug carriers, cosmetics, and agricultural food packaging. The prepared composite films were characterized using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), in addition to the swelling and degradation behavior. UV‐Vis absorption spectra and scanning electron microscopy (SEM) were also applied to observe the interaction between Gel‐poly(AAm‐co‐Ac) and natural polyphenol (catechin). The study has demonstrated that the involvement of hydrogen bonding and hydrophobic interactions as the major forces involved in the stabilization of gelatin‐based polymeric biocomposite film by the plant polyphenols (catechin and gallic acid derivatives). Thermal stability studies of crosslinked gelatin‐based composite film revealed that A. nilotica bark extract stabilizes the gelatin molecules and leads to moderate increase of the denaturation temperatures relative to the uncrosslinked one. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and Mechanical Characterization of Gelatin-Based Films Using 2-Hydroxyethyl Methacrylate Cured by UV Radiation

Gelatin films were prepared from gelatin granules in aqueous medium by casting. Tensile strength, tensile modulus and elongation at break of the gelatin films were found to be 27 MPa, 100 MPa and 4%, respectively. Gelatin films were soaked in five different formulations containing 2-hydroxyethyl methacrylate (HEMA) (10–50%, by wt), methanol and photoinitiator and then cured under UV radiation. Again, a series of gelatin solutions was prepared by blending varying percentages (10–50% by wt) of HEMA and then films were prepared and UV cured. It was found that tensile properties of gelatin films improved significantly.     

Controlled release of carboxylic‐containing herbicides by starch‐g‐poly(butyl acrylate)

The use of starch‐g‐poly(butyl acrylate) as a new material for encapsulating carboxylic‐containing herbicides such as 2,4‐dichlorophenoxyacetic acid and 2,4,5‐trichlorophenoxyacetic acid for controlled release was studied. The herbicides were individually encapsulated within the modified starch substrate, which was graft‐copolymerized with a small amount of butyl acrylate. The modification of starch induced a hydrophobic behavior in the matrix, made it swell less, and caused the release rate to slow, especially for herbicides with higher water solubility. Therefore, the survival life of the starch products for controlled release could be expected to extend to some extent compared with that of natural starch. In addition, the effects of the molecular weight, herbicide content, and particle size on the swellability and release behavior were also investigated. Scanning electron microscopy revealed that the herbicides encapsulated within the starch matrix were dispersed in the form of tiny cell. Consequently, the herbicides encapsulated were released through diffusion. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1535–1543, 2001     

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     

Physical and thermal characterization of graphene oxide modified gelatin‐based thin films

The incorporation of graphene oxide (GO) nanosheets into fish gelatin‐based films and the resulting effect on the structural, mechanical, and thermal properties of the film was investigated. Gelatin films were prepared using a casting method with d ‐sorbitol as the plasticizer and carrageenan as the stabilizer. GO nanofillers were dispersed into the gelatin network in different weight percentages. FTIR spectroscopy was used to characterize the molecular structure of gelatin films and revealed that there were no major changes in the functional groups of fish gelatin films after addition of GO and carrageenan. Tensile, differential scanning calorimetery (DSC), and thermo gravimetric analysis (TGA) tests were performed to study the effectiveness of GO nanofillers and the effect of sorbitol and carrageenan on the film properties. Addition of 1 wt% of GO significantly increased the tensile strength and the elongation modulus of the gelatin films (to 44 and 1320 MPa, respectively). This was attributed to the strong interfacial interactions between GO sheets and gelatine molecules. However, increasing the GO percentage to 2 wt% resulted in a considerable decrease in both properties (to 11 and 224 MPa, respectively). This might be due to the agglomeration of GO sheets in the gelatin network. DSC results showed a substantial increase in the T_m of the films as a result of adding carrageenan and GO to the gelatin network. This might be due to the strong combination of helical structure of carrageenan and oxygen containing groups of GO. POLYM. COMPOS., 35:2043–2049, 2014. © 2014 Society of Plastics Engineers     

A comparative study of gamma and ultraviolet radiation on gelatin film with 2-ethylhexyl acrylate

Gelatin films were prepared from gelatin granules in an aqueous medium by casting. Tensile strength (TS) and elongation at break (Eb%) of the films were found to be 29.2?MPa and 4.9%, respectively. Gelatin films were irradiated under gamma and UV radiation with different doses. Gamma treated gelatin films showed higher TS and Eb% over untreated ones, and even higher than that of the UV treated films. A series of gelatin solutions (formulations) was prepared by blending varying percentages (2–10% by wt) of 2-ethylhexyl acrylate (EHA) and then the films were prepared. Some EHA-blended gelatin films were irradiated under gamma radiation at various doses (50–500?krad) and other films were cured under UV radiation at different intensities (10–30 UV passes). EHA-blended?+?gamma treated gelatin films showed the highest mechanical properties than that of the EHA-blended?+?UV treated films. The degradation properties present in the soil were determined for the pure and treated films. It was observed that EHA-blended?+?gamma treated gelatin film degrades more than that of the EHA-blended?+?UV treated films.     

Lignin‐polyethylene glycol matrices and ethylcellulose to encapsulate highly soluble herbicides

The blending of lignin with polyethylene glycol (PEG) allowed us to obtain formulations with controlled release properties in which metribuzin have been successfully trapped with encapsulation efficiency higher than 85%. Moreover, the modification of the lignin's viscoelastic properties by the addition of PEG led to obtain herbicide formulations with active ingredient contents lower than 15%, suitable for its application in soil. Fourier transformed infrared spectroscopy and differential scanning calorimetry studies indicated the compatibility between polymers and metribuzin in lignin‐based controlled release formulations (CRFs). Lignin‐based formulations were coated in a Wurster‐type fluidized‐bed equipment using ethylcellulose and dibutylsebacate. Scanning electron microscope pictures showed a homogeneous film in ethylcellulose‐coated CRFs. The kinetic release studies showed that the release rate of metribuzin was mainly controlled either by selecting the granule size of controlled release lignin‐PEG matrixes, or by changing the thickness of coating film for ethylcellulose coated CRFs. These results could help to increase the efficiency of delivery of the highly soluble herbicide metribuzin and prevent the environmental pollution derived from its use. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41422.     

Preparation of gelatin-based films modified with nanocrystalline cellulose

Gelatin is a natural biological macromolecule derived from the collagen in the connective tissue of the skin, bone and other tissues. It has been widely used in medicine, food and industrial production and other fields for easy molding, excellent compatibility and biodegradability. However, physical and chemical disadvantages impede its further application, seriously. Therefore, modification of the gelatin films becomes more and more important. In this study, the gelatin/nanocrystalline cellulose (NCC) composite films were prepared by casting method with 4% glycerol as plasticizer. The effect of NCC on the properties of the composite films was investigated by the characterization of its morphology and mechanical, thermal, and optical properties and water adsorption. The results showed that mechanical, thermal stability and water absorption properties of the gelatin/NCC composite film were obviously improved. The composite films showed the highest tensile strength (13.56?±?0.25 MPa) when the mass concentration of NCC was 0.6%. Adding NCC to gelatin benefited the thermal stability of composite films. The gelatin/NCC composite film of 0.4% NCC had the highest melting transition temperature (138.9 °C). The composite films exhibited the lower water absorption (271.1%) when mass concentration of NCC was 1.0%. Thus, these results indicated that NCC could affect the properties of gelatin-based composite films, and showed it has potential for application in food packing.     

Evaluation of Some Nonionic Surfactants Derived from Tannic Acid as Additives for Water‐Based Mud

Water‐based mud is the most‐used mud for oil and gas exploration and is generally considered to be more environmentally friendly than oil‐based or synthetic‐based mud. Therefore in this study we focused on water‐based mud and a series of nonionic surfactants derived from tannic acid was evaluated as additives for water‐based muds. The rheological properties for formulated water‐based muds contain nonionic additives at different temperatures were investigated including: apparent viscosity, plastic viscosity, yield point, gel strength, thixotropy and filtration properties. In addition to the relation between shear stress and shear rate were presented at different temperatures. The results of the studied nonionic surfactant showed improvements in the rheological properties when used as additives for water‐based mud formulation.     

Dry‐peelable temporary protective coatings from waterborne self‐crosslinkable sulfourethane–silanol dispersions

Novel temporary protective coatings were prepared by the addition of release additives to waterborne polyurethane dispersions. New types of self‐crosslinkable sulfourethane–silanol (SUS) dispersions were utilized as the peelable coatings. These dispersions are stable, low‐volatility organic chemical (VOC) waterborne dispersions that spontaneously crosslink upon drying without extra additives or processing steps. Tensile strengths up to 6000 psi with elongations between 300–600% were obtained for the crosslinked films. The adhesion of the films to a variety of substrates can be controlled by the addition of hydrophilic additives, including glycerol, oligomers of glycerol, and poly(ethylene glycol) derivatives. Alternatively, hydrophobic additives that are water dispersible, such as paraffin waxes and sulfated castor oil, can also be used to control adhesion. In addition, this technique can be utilized for the release of films derived from a wide variety of waterborne urethane dispersions, including carboxylated polyurethane ureas. The removable coatings are useful for the temporary protection of plastic surfaces during thermoforming processes. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1443–1449, 2004     

Preparation of bioactive glycosylated glial cell‐line derived neurotrophic factor‐loaded microspheres for medical applications

Poly (lactic‐co‐glycolic acid) (PLGA)‐coated gelatin microspheres containing glial cell‐line derived neurotrophic factor (GDNF) were developed by thermal gelation through a water‐in‐oil emulsion technique. Gelatin types (A and B) at four different pH levels were investigated for their influences on the morphology, the microsphere size, the zeta potential, and the swelling ability. The encapsulation of GDNF and the release characteristics of GDNF were also determined using enzyme‐linked immunosorbent assay (ELISA). The maximum cumulative released amounts of GDNF from the microspheres were increased from 50 to 90% after 4 d (based on the actual amount of the GDNF). Thus, the release of the GDNF contents in the microspheres depends on the amount of GDNF. Trigeminal ganglion cells (TGCs) were used to study the bioactivity of GDNF released from the microspheres, which was proven to retain its bioactivity in promoting the TGCs' neurite outgrowth. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40167.     

Poly(ε‐caprolactone) composites containing gentamicin‐loaded β‐tricalcium phosphate/gelatin microspheres as bone tissue supports

In this work, novel antibacterial composites were prepared by using poly(ε‐caprolactone) (PCL) as the main matrix material, and gentamicin‐loaded microspheres composed of β‐tricalcium phosphate (β‐TCP) and gelatin. The purpose is to use this biodegradable material as a support for bone tissue. This composite system is expected to enhance bone regeneration by the presence of β‐TCP and prevent a possible infection that might occur around the defected bone region by the release of gentamicin. The effects of the ratio of the β‐TCP/gelatin microspheres on the morphological, mechanical, and degradation properties of composite films as well as in vitro antibiotic release and antibacterial activities against Escherichia coli and Staphylococcus aureus were investigated. The results showed that the composites of PCL and β‐TCP/gelatin microspheres had antibacterial activities for both bacteria. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Electrospinning of heated gelatin‐sodium alginate‐water solutions

Most polymers that are electrospun are dissolved in a solvent and are spun at ambient temperature. Gelatin, a natural polymer, has excellent potential in medical applications as a biodegradable polymer, especially when combined with sodium alginate. Unfortunately, gelatin/water or gelatin/sodium alginate/water solutions cannot be electrospun at ambient temperature without the incorporation of substances that are considered potentially toxic to the human body, such as acetic acid. In this study, gelatin/water solutions with and without sodium alginate were successfully electrospun without the use of additional solvents by using heated water solutions. The effect of electrospinning parameters such as solution concentration and applied voltage on the nanofiber morphology of these solutions was studied. These nanofibers from heated gelatin/water solutions exhibited good morphology with an average size of 291 ± 67 nm at 18% concentration to 414 ± 52 nm at 20% concentration. Similar sizes were observed when sodium alginate was incorporated into the gelatin/water solutions, although the relationship was dependent upon the amount of sodium alginate in the solution as well as the total concentration. Typically, these nanofibers containing sodium alginate were produced at a lower gelatin concentration compared with the gelatin/water nanofibers because of the increase of viscosity and conductivity of the solutions due to the addition of the highly viscous and conductivity sodium alginate. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Improving the physical and chemical functionality of starch‐derived films with biopolymers

The physical and chemical properties of composite starch‐based films containing cellulosic fiber, chitosan, and gelatin were investigated. Films containing both cellulosic fibers and chitosan demonstrated tremendous enhancements in film strength and gas permeation. The water absorbency of composite films could be greatly reduced in film composites containing cellulosic fibers and gelatin, but the inclusion of chitosan into these films provided a higher hydrophilicity, increasing water absorbency. Film transparency was not noticeably affected in the composite films that were made. These films may have wide application in the food packaging, agricultural mulching, and the medical industries. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2542–2548, 2006     

Transformation of 2,4‐dichlorophenoxy‐ethanoic acid (2,4‐D) by a photoassisted ferrous oxalate/H2O2 system

The kinetics of the dependence of pH, oxalate, and hydrogen peroxide concentrations on the degradation performance of the herbicide 2,4‐dichlorophenoxyethanoic acid (2,4‐D) was studied in a novel ferrous oxalate/H₂O₂/UV system. The formation and destruction of the primary intermediate, 2,4‐dichlorophenol (2,4‐DCP), was also monitored in the study. A rate enhancement of about 2.9 times was found when 1.2 mM of oxalate was added to the conventional Fe²⁺/H₂O₂/UV process. However, excess oxalate suppressed the reaction due to the scavenging and light attenuation effects. The 2,4‐D transformation at a lower initial pH was faster than that at a higher pH, and the different reaction mechanisms were investigated. In addition to the decay rates, the yield of the intermediate 2,4‐DCP was also affected by the initial solution pH. The increment of hydrogen peroxide concentration did not increase the initial decay rates of 2,4‐D, yet it improved the overall removal of 2,4‐D and elevated the formation of the corresponding intermediate (2,4‐DCP). Copyright © 2004 Society of Chemical Industry