Synthesis and Applications of Biodegradable Soy Based Graft

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Synthesis and Applications of Biodegradable Soy Based Graft Copolymers: A Review Manju Kumari Thakur, Vijay Kumar Thakur, Raju Kumar Gupta, and Asokan Pappu ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b01327 • Publication Date (Web): 02 Dec 2015 Downloaded from http://pubs.acs.org on December 9, 2015

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ACS Sustainable Chemistry & Engineering

Synthesis and Applications of Biodegradable Soy Based Graft Copolymers: A Review Manju Kumari Thakur1, Vijay Kumar Thakur2*, Raju Kumar Gupta3 and Asokan Pappu4

1

Division of Chemistry, Govt. Degree College Sarkaghat, Himachal Pradesh University Shimla -

171005, India 2

School of Mechanical and Materials Engineering, Washington State University, United States

3

Department of Chemical Engineering, Indian Institute of Technology Kanpur, 208016, India

4

CSIR- Advanced Materials and Processes Research Institute, Bhopal 462064, India

Email: [email protected]; [email protected]

Phone: 509-335-8491, Fax: 509- 335-4662

ACS Paragon Plus Environment


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ABSTRACT: Different kinds of biorenewable materials are rapidly emerging as the potential alternative to conventional petroleum-based synthetic materials. Among these materials, soy protein and its derivatives are of utmost interest and importance due to their advantages such as low cost, biodegradability, environmental friendliness, biocompatibility, renewability, and wide availability to name few. However, the poor physicochemical/ mechanical properties as well as high moisture sensitivity of different soy based materials limit their successful applications in many fields. Different methodologies to produce new soy based materials with suitable functional groups are highly desired to increase their range of applications. So, in this review article, we have focused on the recent advances in the various graft copolymerization strategies involving soy and its applications. The synthesis, characterization and methodology of graftcopolymers processing and resulting properties of the co-polymers are fully covered. In this article, we have attempted to provide a review of soy protein based different functional materials that will facilitate the development of new generation of multifunctional bio-based materials from biorenewable soy resources.

KEYWORDS: Biorenewable materials,

Graft

copolymerization,

Applications


Soy, Biocomposites,

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INTRODUCTION In everyday life, polymers (natural/ synthetic) are frequently being used in numerous house hold products, industrial products and processes1-4. Indeed, polymers based materials due to their inherent advantages are finding their way into multifunctional applications ranging from aircraft, spacecraft, automotive, marine and biomedical applications5-10. In addition to these, other potential applications of polymer based materials include packaging, chemical equipment, electrical and electronics equipment, energy storage in super capacitors and batteries11-14 . The last few years have seen a swift growth in the interest in using bio-based materials compared to the petro-chemical based materials to prepare a number of green materials15-17. Different kinds of biobased materials ranging from cellulosic fibers, wood to protein based materials are being explored for a number of applications18-21. Biobased materials offer numerous advantages in terms of low cost, better thermal and insulating properties, low density, acceptable specific properties, biodegradability and less energy consumption during their processing in comparison to synthetic high performance materials such as polyamide, polyimide and polyether ether ketone (PEEK)22-24. Indeed, the production of sustainable materials from different biorenewable resources has resulted in vast attention as well as interest in researchers from academic and industrial fields25-26. The prime reason for this interest in sustainable green materials rises from the growing environmental concern as well as the depletion of the fossil fuels all over the world27-29. The use of sustainable materials offers a number of benefits in environmental conservation in comparison to the use of traditional synthetic materials due to their harmful effects especially non biodegradability, nonrenewable nature, presence of persistent organic pollutants, contaminates, and physical effects to name a few

30-31

. Recently, researchers from

different disciplines have reported the use of biorenewable soy based materials as a potential



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green alternative for a number of applications from biomedical to sustainable composites32-35. Among different biobased crops, soybean is an annual crop that is lavishly available all over the world. Due to its huge availability all around the globe, the cost is extremely low36-38. It is an important industrial crop due to its high level of edible oil (about 20%)39-40. It has been used mostly in food industry, thanks to the abundance of essential amino acids in it. Soy protein is generally classified into three types namely soy protein isolate (SPI), soy protein concentrate (SPC) and soy flour (SF), depending upon the protein amount in these materials. These soybean based materials are sustainable, renewable and can be degraded by several natural means36-41. Different manufacturing processes for soy based products have been found to be environmentfriendly. Furthermore, during the processing and procurement of these products, no toxic chemicals are used or toxic gases are released42. Different soy based products contain different amount of protein in them such as soy protein isolate contain the highest percentage of protein (> 90%), soy protein concentrate (SPC) primarily consists of nearly 70% protein, 20% carbohydrates, ash and crude fiber36,41 while soy flour contain nearly 56 % protein and rest of carbohydrate

43

. Recently soy based products (e.g. soy protein) have been used as new green

matrices for the preparation of biodegradable composites and it has been reported that they have the huge potential for several applications such as packaging, computer casings, and panels for auto interior44-45. Soy based materials offer a number of advantages and abundant research work has been reported on the usage of soy protein resin for composites applications. However, still soy based products suffers from few shortcomings such as low chemical resistance, hydrophilic nature and less thermal stability to name a few46-47. The presence of several functional groups such as amino acids (e.g. cysteine, arginine, lysine) and carbohydrates on soy based materials make them suitable for surface modification to improve their inherent properties such as


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mechanical/ thermal properties and moisture resistance23,44,48. Some efforts have been made to modify the surface features of soy based materials using the surface modification techniques49-50. Graft copolymerization is among one of the most rapidly emerging techniques recently being used in the modification of polymers as well as improving their properties. It is a robust technique to tailor the properties and specifications of polymers for desired targeted applications. During any graft-copolymerization technique, selected monomers are covalently bonded onto the studied backbone polymer chain. These monomers are either added as side chains or on the surface depending upon the technique used. Their degree of incorporation is also controllable in most of the cases. Indeed, graft copolymerization of vinyl monomers onto different kinds of polymers ranging from natural to synthetic polymers has proven to be a potential means of altering their inherent characteristics. The graft copolymerization of vinyl monomers is an exciting field of research enriched with huge prospective in the near future. Through the successful use of graft copolymerization techniques, several new properties such as thermal stability, anti-bactericidal/ antistatic properties, improved chemical resistance, flame resistance, soil resistance, stereo regularity, dye ability, cation exchange property, water repellence, viscoelasticity, hygroscopicity and improved adhesion to a variety of substances to name a few can be easily and effectively imparted. Depending upon the applications such as in composites, the graft copolymers can also be used as compatibilizers in polymer blends to stabilize the morphology of immiscible polymers. The graft copolymers prepared using different polymer materials have huge applications in

several industries including automotive, adhesives,

biomedical, coatings, membranes, recognition devices, selective organic-inorganic complex materials and water purification. Different graft copolymerization techniques have opened new ways to design and synthesize innovative materials for a wide range of applications.



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Graft copolymerization using vinyl monomers is one of the most frequently used technique to incorporate new functionalities into the soy based materials. So, in the present article, we review the various graft copolymerization techniques involving vinyl monomers used to modify the soy as still no comprehensive review is available on these used techniques. Different reaction parameters that affect the synthesis and yield of soy based graft copolymers have been discussed in detail. In addition to the synthesis and characterization of soy based graft copolymers, we have also reviewed the different applications of these graft copolymers.

Structure of Soy based Materials Different soy based materials are derived from soybean seeds and these generally contains soy proteins component of 35–40 %. Glycinin (11S globulin) and conglycinin (7S globulin) are the two important constituents of the soy proteins and are mainly present in extracted soy proteins51-52. Soy flour which contain nearly 50 % protein and rest of the materials as carbohydrates is most basic among soybean based products and is frequently processed to get the soy protein and soy protein concentrate (SPC)53. The different constituents of proteins aggregate by different ways during heating. It has also been reported that β-conglycinin and glycinin aggregated via different pathways during heating54. Figure 1 (a) shows the diagrammatic depiction of β-conglycinin and glycinin thermal aggregation behavior while table 1 (a, b,) shows the structural parameters of soy protein and Glycinin/ β-Conglycinin mixtures heated at different temperature derived from small angle X-ray Scattering (SAXS) and Dynamic Light Scattering (DLS). Figure 1 (b) shows the Chromatograms for β-conglycinin and glycinin dispersions that were incubated at different temperatures for 30 min. It was established from the


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study that during the heating, hydrophobic interactions play an important role in the interaction between β-conglycinin and glycinin

54

. For the manufacturers of food, pharmaceutical, and

cosmetic products, the functional properties of proteins are of utmost importance46,55. A number of techniques including enzymatic treatments, physical as well as chemicals have been applied to increase the existing properties of soy products46. The composition, aggregation and emulsification of soy protein has been recently reviewed in an excellent review by Nishinari et al56. It has been reported that on an average dry matter base, the soybean contains approximately 40 % protein and 20 % oil. Soy protein isolate (SPI) is frequently obtained by the removal of oil at lower temperatures and is then used in the food industry.

GRAFTING OF SOY MATERIALS: CHEMISTRY & APPLICATIONS Graft copolymerization is an excellent technique to modify the surface properties of the soy based materials. A number of graft copolymerization techniques have been used to incorporate new functionalities into different types of soy based materials. We have described the graft copolymerization techniques employed to incorporate new functionalities into soy based materials along with their applications in the following section,.

Grafting of Soy Protein Isolate (SPI) Soy protein isolate (SPI) was graft copolymerized with styrene employing ammonium cerous nitrate & potassium persulfate as the reaction initiator57. Effect of different reaction conditions such as time, composite initiator concentration, temperature, monomer concentration and pre-heating time on the percentage grafting/ efficiency was studied in detail. It was observed



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that after the optimization of all the reaction parameters, the highest grafting/ efficiency was 110 and 61 %, respectively. The synthesized graft copolymers were characterized using gravimetric analysis as well as by infra-red (IR) spectroscopy and differential scanning calorimetry (DSC). From the experimental investigation, it was observed that the grafting/ efficiency percentage increased initially and then decreased with the increase in the reaction parameters namely the initiator / monomer concentration, and temperature. The graft copolymerization reaction was found to be completed in 28 hours57. Methacrylic acid (MAA) was also graft copolymerized onto soy protein isolate (SPI) using β-mercaptoethanol as an unfolding and chain-transfer agent for SPI,

58

. In this reaction, ammonium persulphate (APS) was used as an initiator and the

synthesis of copolymers was carried out in 8 mol/ L urea aqueous solution. The effect of reaction parameters such as amount of β-mercaptoethanol, initiator concentration, and temperature was studied by determining the grafting percentage (GP) and grafting efficiency (GE). The grafting percentage and grafting efficiency in this work was described by the following equations:

GP (%) =

GE (%) =

W1 − W0 × 100 W0 W1 − W0 × 100 W2

(1)

(2)

where W0, W1, and W2 denote the weights of the SPI, graft copolymer, and monomer, respectively. The synthesis of graft copolymers was further confirmed by studying the nuclear magnetic resonance (NMR)/ FTIR spectra of pristine SPI and the SPI-grafted MAA copolymer [SPI-g-poly (methacrylic acid) (PMAA)]. The grafting percentage/ efficiency was found to increase with increment in the initiator concentration / temperature up to certain value of the


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initiator and temperature (16 mmol/L & 80°C) and then decreased. The increment in grafting percentage/ efficiency with increment in initiator concentration was attributed to the increase in macro radicals in the reaction system as a result of increased concentration of initiator that attacks more mercaptoes of SPI backbone resulting in more SPI macro radicals and hence higher grafting percentage. However, beyond the optimum concentration of 16 mmol/ L, termination reactions starts taking place due to the formation of excessive free radicals & macro radicals leading to the homopolymerization of the monomer as well as termination of the growing chains. Both these reactions results in a decrease in the grafting percentage/ efficiency. In this study, the influence of temperature on grafting percentage/ grafting efficiency was also studied in the temperature range from 40–100°C and the maximum grafting was obtained at temperature of 80°C. The increase in grafting percentage/ efficiency up to 80°C was attributed to the easier redox reaction between the initiator and the monomer. However, beyond 80°C, the homopolymerization reactions between the monomer and initiator becomes dominant leading to the termination reactions that ultimately decreases the graft yield. Dynamic laser light scattering (DLS) was also used to study the influence of the pH value on the hydrodynamic radius of pristine and grafted SPI in the aqueous solution. From the scattering study it was established that the average hydrodynamic radius of grafted SPI copolymers was lesser compared to the pristine SPI near the isoelectric point of SPI and a high pH value58. Atom transfer radical polymerization (ATRP) was used to synthesize poly (2hydroxylthyl methacrylate) grafted soy protein isolates (SPI-g-PHEMA) in aqueous solutions59. In this study 2-hydroxylthyl methacrylate (HEMA) was used as the reaction monomer because of its specific advantages such as being biocompatible polymer. To prepare the graft copolymers, the soy protein isolate macro initiator (SPI-Br) was synthesized using the condensation reaction



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of the active amino groups and 2-bromoisobutyryl bromide and subsequently used as initiator for the polymerization of HEMA monomer. In this reaction, copper chloride/ bipyridine (CuCl/bpy) was used as the catalyst. The synthesized SPI-g-PHEMA copolymers were then thoroughly characterized using FTIR, transmission electron microscopy (TEM) and C-13-NMR spectra. The molecular weight of the graft chains was also studied using gel permeation chromatography (GPC) and the solution properties of the graft copolymers were investigated using UV and fluorescent spectrophotometer. The hydrophobic character was found to be decreased and the solubility of SPI and SPI-g-PHEMA was found to increase with increase in the pH value. Zetapotentiometer was subsequently used to study the zeta-potential of the pristine SPI and PHEMA grafted SPI. It was found that with the creation of graft copolymers of PHEMA onto the SPI backbone, the static charges on the surface of SPI molecules increased significantly and with the increase in pH values, the zeta potential of SPI / SPI-g-PHEMA solutions decreased significantly59. Ring-opening graft copolymerization reaction was also used to synthesize the biodegradable copolymer, poly (1, 4-dioxan-2-one) (PPDO) grafted soy protein isolate (SPI) (SPI-g-PPDO)60. In this study the ring-opening graft copolymerization of SPI-g-PPDO was carried out using stannous octoate as a co-initiator/catalyst. Figure 2 (a) shows the Sn (Oct) 2 initiated polymerization mechanism of PDO with Soy Protein. In this reaction azeotropic mixture was used as solvent at 80 °C. During the synthesis reaction, pre swelling was found to play an imperative role as it facilitated the graft polymerization reactions. SPI-g-PPDO copolymers with different molecular structures were obtained by varying the SPI/ PDO feed ratio in the reaction system. At the PDO/ soy protein feed ratio of 10:1, the length of the PPDO grafts was found to reach the value of 14.0. The structural changes in the pristine soy after the copolymerization


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were confirmed by characterizing the sample using DSC, Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The copolymerization reaction resulted in the SPI-g-PPDO copolymers with the thermal properties and crystallization significantly different from the pristine soy protein. Figure 2 (b) shows the TG curves of SPI, SPI-g-PPDO, and PPDO with different feed ratios in N2. X-ray diffraction patterns for pristine SPI/ SPI-gPPDOs copolymers were also studied. It was evident from the study that the crystallization ability of pristine SPI increases with increment in the graft chain length and was consistent with the DSC results60. SPI-g-NH-PAMPS copolymers were synthesized using a graft reaction between the free carboxylic acid groups of soy protein isolate (SPI) and the amino groups of poly(2-acrylanmido2-methyl propane sulfonic acid) (H(2)N-PAMPS)61. In this study, 1-(3-(dimethylamino) propyl)3-ethyl-carbodiimide hydrochloride/N-hydroxysuccinimide was used as the condensing agents in a buffer solution. The synthesized graft copolymers were thoroughly characterized using (1) HNMR, FTIR and (13) C-NMR spectroscopies. Subsequently different techniques such as UVVisible spectroscopy, fluorescence spectrometer, zeta potentiometer and dynamic laser light scattering (DLS) were used to investigate the aqueous solution properties of pristine SPI and SPI-g-NH-PAMPS copolymers. It was observed from the study that the charge of SPI-g-NHPAMPS measured by zeta potentiometer was negative within the studied pH range. This behavior was accredited to the ionization of sulfonic groups of grafted chains. The average hydrodynamic radius (< R(h)>) of SPI was found to increase from140 nm to about 200 nm based upon the dynamic laser light scattering (DLS) experiment61. Ultrasonic Treatment was also used to carry out the graft reaction between soy protein isolate (SPI) and gum acacia (GA)62. It was observed that the ultra-sonic treatment facilitated the grafting reaction compared to the



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conventional heating method. The reaction was completed within 60 minutes using ultrasonic treatment in comparison to 48 h of classical heating. Maximum degree of grafting up to 34 % was obtained using the ultrasonic method. Ultrasonic treatment was found to result in significant improvement in the concentration of available free amino groups on the pristine SPI. It was also revealed from the study that in comparison to the pristine SPI, the grafted SPI had higher levels of emulsifying stability index, emulsifying activity index, and surface hydrophobicity62. Soy protein isolate based thermally responsive copolymers were prepared using Nisopropyl acrylamide as the reaction monomer in an aqueous solution63. The synthesis and selfassembly behavior of the graft copolymer (SPI-g-poly (N-isopropylacrylamide) (PNIPA)) and the pristine soy protein isolate was studied in detail. The synthesis reaction was carried out in an 8 mol/ l urea cushioning solution using ammonium persulfate (APS)/ mercaptoacetic acid as an initiator and unfolding agent respectively. Figure 3 (a) shows the synthesis scheme for the graft copolymerization reaction. The synthesized SPI-g-PNIPA copolymers were characterized using FTIR and NMR. Figure 3 (b, c) shows the FTIR and NMR spectra of the pristine and grafted SPI copolymers. It was confirmed from the gravimetric as well as spectroscopic study that the graft copolymers were successfully synthesized. Subsequently other characterization techniques namely transmission electron microscopy, laser light scattering, and fluorescence spectroscopy were also used to study the self-assembly behavior of SPI-g-PNIPA in aqueous solution. Figure 3 (d) shows the TEM images of SPI and SPI-g-PNIPA (GP = 92.86%) with different solution concentrations. It was found that SPI-g-PNIPA assembles into different structures above the critical micelle concentration (cmc). Different structures ranging from the simple spherical structure to spherical core–shell structure/ random coil structure were observed contingent to the copolymer concentration. Different reaction parameters such as the temperature, pH value, graft


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copolymer concentration, and ionic strength were found to significantly influence morphology and the aggregate size of SPI-g-PNIPA copolymers in aqueous solution. The increasing ionic strength was found to increase the aggregate size, while the SPI-g-PNIPA concentration, pH value and temperature were found to have complicated influences on the aggregate size. At pH 8.5, the lower critical solution temperature of the SPI-g-PNIPA was found to be 36 °C. In this study for the first time, the critical micelle concentration (cmc) value of SPI-g-PNIPA was studied in aqueous solution using intrinsic fluorescence spectroscopy and it provided a simple way to determine the cmc value of amphiphilic protein-containing copolymers63. Soy protein isolates have been graft copolymerized with different vinyl monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), butyl methacrylate (BMA) and hexyl methacrylate (HMA) to prepare for their potential applications in composites64. To get the maximum percentage of grafting, a number of reaction conditions including concentration of monomers; grafting temperature and grafting time were optimized. Synthesized graft copolymers were then characterized using different techniques such as nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC) and Fourier transform infrared (FTIR). It was confirmed from these techniques along with the gravimetric analysis that the vinyl monomers were successfully grafted onto the soy protein. The grafted samples were subsequently compression molded into films for their mechanical properties analysis. In this study, effect of the % homopolymer on tensile properties was also investigated. Soy protein grafted with the different acrylates were found to exhibit different tensile properties. These properties were further

found to be dependent on the type of monomer as well as the

homopolymer amount. Table 2 shows the tensile properties of soy based graft copolymer films prepared using different methacrylates along with different amounts of homopolymer. It is



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evident from the table 2 that without any homopolymer, with increase in the size of monomer, the strength as well as the elongation of the prepared films was found to decrease with the exception of HMA grafted soy proteins. It was observed from the study that HMA melts better than other monomers (i.e. MMA, EMA and BMA) due to the good thermoplasticity and lead to the formation of good films. Length of alkyl chains was found to affect the grafting efficiency as well as the thermal behavior. It was concluded from the study that the increase in chain length decreased the grafting efficiency while improved the thermal behavior. The increase in chain length also provided films with better properties.

Grafting of Soy Protein Concentrate (SPC) Soy protein concentrate (SPC) was graft copolymerized under microwave radiations using ethyl methacrylate (EMA) as the reaction monomer and ascorbic acid/ potassium persulphate as redox initiator65. Effect of a number of reaction parameters namely the reaction time, initiator ratio, solvent amount, pH and monomer concentration was studied to get optimum graft yield (78.8 %). The PEMA-g-SPC graft copolymers were then characterized using TGA/ DTA / DTG, XRD, FTIR and SEM techniques. From the TGA/ DTA/ DTG studies it was revealed that the graft copolymerization of EMA onto S-S linkages of SPC lead to the copolymers with enhanced thermal stability. The graft copolymers were also subjected to the study of moisture resistance behavior and it was found that graft copolymer showed higher chemical resistance compared to the pristine SPC65. Same research group has also carried out the graft copolymerization of SPC with ethyl methacrylate in air using ascorbic acid/ potassium persulphate as a redox initiator66. The results obtained in this study were compared with that of


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the graft copolymerization carried out under microwave radiation. Effect of different reaction parameters namely reaction temperature, pH, initiator ratio, reaction time, solvent amount, and monomer concentration on the graft yield was studied in detail. The synthesized PEMA-g-SPC graft copolymers formed were characterized using Fourier transform infrared spectrophotometer, X-ray diffraction and scanning electron microscope techniques. The FTIR spectra of pristine soy protein concentrate/ graft copolymerized soy protein concentrate confirmed the successful graft copolymerization synthesis.

Thermogravimetric analysis was also carried out to study the

thermal characteristics of the pristine / grafted soy protein concentrate. The TGA/ DTA/ DTG of the pristine soy protein concentrate/ graft copolymerized soy protein concentrate confirmed that that graft copolymers were thermally more stable than the pristine soy protein concentrate. From the TGA/ DTA/ DTG, it was clear that the rate of weight loss per minute was higher in case of pristine soy protein concentrate compared to the graft copolymer. These copolymers were also subjected to the chemical resistance study and it was found that the graft copolymers were more resistant toward acid–base attack. The graft copolymers were also found to be more water repellent66.

Grafting of Soy Flour (SOY) Soy protein (and associated carbohydrate) (SOY) commonly known as soy flour was graft copolymerized with poly (methyl methacrylate) (PMMA) to develop novel dielectric materials for advanced applications67. In this study, a simple reflux method was used to carry out the free radical induced graft copolymerization of methyl methacrylate monomer onto preactivated SOY. Figure 4 (a) shows the schematic representation of soy flour (refereed as SOY) and figure 4 (b) shows the mechanism for graft copolymerization reaction (eq. 1-11). The



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reaction was accomplished in three steps namely chain initiation (eq. 4-6), chain propagation (eq. 7-9) and chain termination (eq. 10-11). In this synthesis reaction, along with the graft copolymers there was also formation of the homopolymer which was removed by soxhlet extraction method. The PMMA-g-SOY graft copolymers were then thoroughly characterized using FTIR/ NMR and TGA/ SEM studies (Figure 4 c, d). From FTIR spectra in figure 4c, it is clear that pristine SOY exhibit characteristics bands between 3300 and 3600 cm−1, at 1668 cm−1, and 1551 cm−1 that were attributed to the O–H as well as N–H stretching; C O stretching of the amide group (amide-I) and N–H bending (amide-II). On the other hand, the grafted SOY (i.e. PMMA-g-SOY) showed a new band at 1740 cm−1 due to carbonyl stretching and bands at1155 and 1247 cm−1 due to C–O stretching of poly (MMA) onto the pristine soy. The successful grafting of the monomer onto SOY was also confirmed by gravimetric along with the FTIR. The NMR spectra also supported the FTIR results. From figure 4d, it is evident that pristine Soy exhibit characteristics peaks at 5.19, 4.75, 4.48, 3.83, and 2.49, 1.97, 1.23 ppm. These peaks were attributed to the presence of NH2, SH, and hydroxy groups in the pristine soy flour. However, upon graft copolymerization, the functional group of soy were exposed and reacted with the reaction monomer leading to new NMR peaks with different intensities confirming the successful grafting. All these characterizations confirmed the successful graft copolymerization of the MMA monomer onto pristine SOY. From the TGA/ DTG study, it was also confirmed that the PMMA-g-SOY exhibit the higher thermal stability compared to the pristine SOY. Subsequently after the synthesis of the graft copolymers, the optimized graft copolymers (127 % grafted) were processed into films using a twin screw microcompounder. These films were then subjected to the study of their dynamic mechanical analysis and dielectric properties (Figure 4e). From the dynamic mechanical analysis results, it was found that there was an increase in storage


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modulus and glass transition temperature (Tg) of PMMA-g-SOY copolymers and it was attributed to the successful grafting of PMMA onto SOY that resulted in the covalent bonds formation between the two reaction species. Furthermore, the reinforcement effect of the soy flour was also found to be a contributing factor in the increase in storage modulus. In comparison to PMMA films, the PMMA-g-SOY films were found to exhibit higher storage modulus as well as a low loss tangent along with suitable dielectric properties. The dielectric properties of these graft copolymers were found to be similar to that of the pristine PMMA. This concluded that PMMA-g-SOY can serve as the efficient green dielectric materials. Free radical-induced graft copolymerization of acrylonitrile (AN) onto biorenewable soy flour (SOY) was also carried out to alter the surface characteristics of biorenewable soy flour (SOY) for sustainable polymer composites68. In this study, ammonium persulphate (APS) was used as the reaction initiator to accomplish the graft copolymerization reaction. Equation 1-14 in the figure 5 depicts the mechanism for graft copolymerization of acrylonitrile monomer onto soy flour. Influence of different reaction conditions was studied in detail and subsequently the graft copolymers with optimized degree of grafting were used for the preparation of the composites. Different characterization techniques namely TGA/ SEM/ FTIR were used to confirm the successful synthesis of the graft copolymers. Then composite samples were prepared using both the pristine and grafted SOY as reinforcement using 5 weight percentage loading. Figure 6 (a-c) shows the dynamic mechanical analysis properties of the prepared composites. It is clear from the figure, that the grafted SOY reinforced composites exhibited enhanced storage modulus in comparison to the pristine SOY reinforced composites. This behavior was accredited to the better interactions between both the hydrophobic polymer matrix and the grafted soy. Soy flour (SOY) was also graft copolymerized with ethyl acrylate monomer for diverse applications69. The results



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of

graft

copolymers

were

correlated

with

the

different

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properties

such

as

hydrophilic/hydrophobic/ thermal properties. In addition, the compatibility of the ethyl acrylate grafted soy flour with the polymer matrices was also investigated by preparing the composites using poly (methyl methacrylate) (PMMA) as the model matrix. The prepared composites were subjected to dynamic mechanical properties analysis and it was found that EA-g-SOY/ PMMA composites exhibited enhanced properties compared to the pristine PMMA composites 69.

Grafting of Miscellaneous Forms of Soy (Soy protein, soy protein hydrolysates, Soy protein fibers, Soy peptones) Soy protein was used to prepare the biodegradable polyethylene using free radical polymerization assisted by gamma radiation70. Soy-protein-grafted polyethylene was produced employing benzoyl peroxide as the reaction initiator. The graft copolymerization of soy protein onto polyethylene (PE) was carrying out by first irradiating polyethylene by gamma radiation using Gamma chamber and then copolymerizing using the chemical initiator. Different reaction conditions were optimized (benzoyl peroxide concentration, 2.15 × 10−2 mol/L ; temperature, 70°C; time, 150 min; PE, 0.200 g, soy protein, 0.300 g ; and water 40 mL) to get the maximum percentage of grafting (135%). In this study, the grafted PE (comprising the unreacted PE and soy protein) was named as the PE-g-soy protein composite. While the graft in which the unreacted soy protein/ PE were completely removed was named as the PE-g-soy protein true graft. These graft copolymers were subsequently subjected to the biodegradation study that was determined by a standard soil burial test. The study was completed by investigating the weight-


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loss percentage determined with respect to time in the number of days. The percentage weight loss increased significantly with increase in the number of days. “The effect of the degradation of the grafted samples on the growth of plants (wheat and soybean)” was also studied to see the harmful effect onto the growth of the plants. It was found that there was no harm to the plants under study. These results were confirmed by different studies including the topological morphology as well as thermal stability of the original/ degraded samples. It was concluded from the study that soy protein-grafted PE will be beneficial in making the biodegradable environmental friendly materials 70. Reversible addition fragmentation transfer (RAFT) polymerization reaction was used to synthesize soy protein hydrolysates based graft copolymers71. In this study, the reaction was initiated by installing Benzylthiocarbonate moieties onto the soy protein hydrolysates surface via amidation of free amino groups. This reaction resulted in the creation of a protein macro chain transfer agent (CTA) that was further used for the reversible addition fragmentation transfer (RAFT) polymerization reaction. It was observed from the study that the protein-polymer nanometer-scale particles were formed as a result of the subjection of soy protein macro-CTA (SP-CTA) to RAFT polymerization conditions using acrylate monomers. The solubility of these particles was controlled by the polarity of the monomer used. In this study, authors have used the polyacrylate (e.g. acrylic acid) and polyacrylamide as the reaction monomers. The increasing monomer ratio in the reaction system was found to diminish the particle formation and it was hypothesized that collapse of protein-polymer grafts as result of RAFT polymerization was driven by protein– protein aggregation71. Soy protein was also grafted with diethoxy phosphoryl group via Atherton–Todd reaction72. This study was carried out to overcome the shortcomings in the soy protein



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modification via a minor chemical modification of the soy protein polypeptide chains. The synthesized copolymers were characterized using

31

P NMR, FTIR spectroscopy and solid state

13

C CP/MAS NMR spectroscopy and these characterization confirmed the successful grafting of

diethoxy phosphoryl groups onto soy protein chains. 31P NMR spectroscopy is one of the most convenient and proficient tool to study and analyze the product in any phosphoryl reaction. Figure 7 (a) shows the 31P NMR spectra of pristine and modified soy protein. The new peaks at 12.2 ppm (curves b–e) compared to SPI (curve a) indicated the successfully grafting of the phosphoryl groups onto SPI. From figure 7 (a) it is clear that there were also other peaks in 31P NMR spectra for both SPI as well as modified SPn samples. “These peaks were considered to be coming from phosphatidylcholine (−0.34 ppm), other phospholipids (0.53 ppm), and dimethyl phosphoric acid (20.2 ppm) in raw SPI, respectively”. It was also confirmed in the study that it was not possible to completely remove phosphatidylcholine in spite of the extraction of the raw SPI in a Soxhlet apparatus using anhydrous ethanol and acetone for 24 h. The molar grafting ratio was found to be 0.15–1.18%, and it did not change the nature of soy protein to a significant extent. From the FTIR data, it was also established that the change in the globular structure of soy protein might be due to the increase of β-sheet conformation caused as a result of the slight chemical modification via Atherton–Todd reaction. Figure 7 (b) depicts storage modulus of the pristine SPI and modified SPI. It was observed that with the variation in the grafting ratio, the isoelectric point as well as rheological behavior of the modified soy protein samples also changed. Morphological study of the SPI and modified SPI was also carried out. Figure 8 shows the TEM images of the SPI and modified SPn samples. It was confirmed from the images that functionalization through diethoxy phosphoryl group significantly alters the morphologies as well as globular protein nature. This behavior was attributed to the change in the tertiary


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structure of the protein as a result of phosphoryl modification. The soy protein film prepared after functionalization was found to be robust even without the use of any crosslinking agent and plasticizer. The tensile strength of these films was also investigated and it was found that these properties of the soy protein film in both dry and wet states were good to be used for biomedical applications. The tensile strength of these films in dry and wet state was found to be 35 ± 5 MPa and 3.8 ± 1.5 MPa respectively. It was concluded from the study that the phosphoryl modification of soy protein provides a facile method to improve the mechanical properties of soy protein72. Soy protein fibers based graft copolymers were synthesized using methyl methacrylate as the reaction monomer to develop biodegradable polymer device73. These graft copolymers were then used for petroleum fraction removal from different petroleum-saline emulsion. The graft copolymerization reaction was completed by using sequential experimental design approach. In this study for the process modeling and optimization of graft copolymerization synthesis reaction, fractional factorial design followed by optimal response surface design was successfully used. Different reaction variables were screened for carrying out the synthesis and these were followed by the optimization of six process variables namely monomer concentration, reaction temperature, solvent amount, reaction time, FAS: KPS ratio, and pH at two levels as per Resolution-V design for maximizing graft copolymerization. The graft percentage as high as 272 % was obtained with the optimum reaction conditions. The successful synthesis of graft copolymers was then confirmed using gravimetric analysis as well as using SEM, FTIR, TGA/ DTA/ DTG techniques. These graft copolymers were subsequently subjected to their evaluation against acid–base and moisture resistance behavior. Graft copolymers with maximum percentage of grafting demonstrated higher acid–base and moisture resistance. In addition, the synthesized



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soy protein fiber based polymers were used in the absorption of petroleum from different petroleum-saline emulsions and were found to absorb 76–70 % petroleum fraction. It was concluded from the study that the grafted hydrophobic soy protein fibers can be used in the removal of oil spillage 73. Soy peptones that are obtained by the hydrolysis of proteins were used to prepare soy based graft copolymers using ceric ammonium nitrate (CAN) as free radical initiator under microwave radiation synthesis

74

. In this study, acrylamide monomer (AM) was grafted onto the

peptide backbone (soya peptone) that resulted in the formation of SOYP-g-PAM product. The grafting synthesis was confirmed using physicochemical techniques as well as elemental analysis, FTIR, TGA and SEM. After the preparation of the graft copolymers, these were subjected to the adhesive study for application as water soluble adhesive. “The study was carried out using single lap joint experiment between wooden blocks joined using the graft copolymer as adhesive”. It was observed from the study that the grafted polymer with optimized CAN/ acrylamide concentration of 0.4 g and 7.5 g respectively in the reaction mixture exhibited the enhanced adhesion strength using the graft copolymer as adhesive74. The different types of soy based graft copolymers as discussed in the preceding section have a number of applications. These applications ranges from green composites to biomedical applications. Figure 9 (a) summarizes the applications of soy based graft copolymers. From the above mentioned studies onto different derivatives of soy such as soy protein isolate (SPI); soy protein concentrate (SPC); soy flour (SOY) and other miscellaneous forms using different polymerization reaction mechanism, we can summarize that each reaction has its own advantages and disadvantages. For example, the direct grafting of different vinyl monomers onto soy derivatives using diverse initiators such as ammonium cerous nitrate (CAN), potassium


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persulfate (KPS), ammonium persulfate (APS) using unfolding agents like β-mercaptoethanol /mercaptoacetic acid leads to graft copolymers with desired performances. These reactions via free radical copolymerization were simple and easy to carry out in any laboratory set up and do not need to have stringent reaction conditions such as presence of nitrogen/ argon. These reactions also do not need costly initiators or catalysts system. However, in spite of being simple and facile methods of surface modifications of soy, these methods also exhibit some drawbacks. One of the biggest drawback is no control over the reaction mechanism and molecular weight of the synthesized soy copolymers. During the free radical polymerization of different derivatives of soy in solution, different reactions occurs simultaneously such as chain initiation, propagation, etc., and results in non-defined structures. Furthermore, there is formation of homopolymer in these reactions and that is a non-desired product. Several efforts are currently being made to reduce the formation of homopolymer but it’s still formed in some extent in most of the reactions. Graft copolymerization of soy and its derivatives including SPI with vinyl monomers such as 2-hydroxylthyl methacrylate (HEMA) using atom transfer radical polymerization (ATRP) solves the problem of control of the reaction and the architecture of the final products. During ATRP of SPI, copolymers with well-defined molecular weight as well as narrow molecular weight distribution can be easily obtained which are highly desired for some specific applications. Furthermore, there is no more problem of the homopolymer in the SPI solutions when the reaction is carried out using ATRP. However, this process of controlled synthesis of SPI graft copolymers also suffers from few disadvantages such as it needs some specific reaction conditions. In particular, during the ATRP of SPI, high concentration of the catalyst is usually required and furthermore it is difficult to remove the catalyst from the copolymer product. The



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removal of the catalyst is highly desired for the successful commercialization. Efforts are now being directed to control the amount of catalyst in these reactions. Ring opening graft polymerization is also another potential reaction that facilitates the reaction of SPI with cyclic monomers. The advantage of this reaction is that different cyclic monomers can be polymerized onto SPI as these are commercially available. However, similar to free radical polymerization, it has disadvantages in terms of requirement of high temperature for the polymerization reaction and lack of certain control over the Soy polymer chain length. However, in spite of these disadvantages, by employing the suitable grafting techniques, the desired functional groups can be incorporated into SPI and other materials for better end user applications. Figure 9(b) summarizes the different graft copolymerization techniques, discussed in this work.

CONCLUSION Due to the rising interest in biopolymers, the science and engineering applications of soybean and its derivatives are advancing very rapidly. Indeed, soy based materials are one of the most imperative biorenewable materials available in excess amount mainly as by-product of soybean industry all around the globe. Despite the substantial research effort on the usage of Soy based biorenewable materials, there remains no consensus as to how to maximize their use and incorporate new properties. The presence of amino and hydroxyl groups on the soy based materials are responsible for its physical properties and chemical reactivity. However, in spite of the several advantageous properties of soy based materials, these lack the ease of modification properties of synthetic materials and are not as competent as synthetic materials. To overcome


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the shortcomings of soy based materials, surface functionalization of soy based materials through graft copolymerization to incorporate new suitable functional groups has recently attracted a greater attentions of researchers all around the globe. The graft copolymerization techniques used so far suffers from some disadvantages such as lack of control in free radical graft copolymerization while removal of catalyst and stringent conditions in controlled polymerization. However, these approaches are still expected to result in the new research directions to obtain the sustainable materials with preferred properties.

ACKNOWLEDGEMENTS Authors wish to thanks their parental institutes for providing the necessary facility to accomplish this work.

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TRANSFER

RADICAL

POLYMERIZATION. Acta Polym. Sin. - ACTA POLYM SIN 2008, 008, 424–429. (60) Li, Y.-D.; Chen, S.-C.; Zeng, J.-B.; Wang, Y.-Z. Novel Biodegradable Poly (1, 4-dioxan2-one) Grafted Soy Protein Copolymer: Synthesis and Characterization. Ind. Eng. Chem. Res. 2008, 47, 8233–8238. (61) Xiaoya, L.; Peng, J.; Hua, Z.; Jinqiang, J.; Huiyu, B.; Ming, J. Synthesis and Aqueous Solution Properties of Graft Copolymers Based on Soy Protein Isolate with AminoTerminated Poly(2-Acrylanmido-2-Methyl Propane Sulfonic Acid). Acta Polym. Sin. 2009, 430–436.


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(62) Mu, L.; Zhao, M.; Yang, B.; Zhao, H.; Cui, C.; Zhao, Q. Effect of Ultrasonic Treatment on the Graft Reaction between Soy Protein Isolate and Gum Acacia and on the Physicochemical Properties of Conjugates. J. Agric. Food Chem. 2010, 58, 4494–4499. (63) Li, H.-P.; Ma, B.-G.; Zhou, S.-M.; Zhang, L.-M.; Yi, J.-Z. Thermally responsive graft copolymer of soy protein isolate and N-isopropylacrylamide: synthesis and self-assembly behavior in aqueous solution. Colloid Polym. Sci. 2010, 288, 1419–1426. (64) Shi, Z.; Reddy, N.; Shen, L.; Hou, X.; Yang, Y. Grafting soyprotein isolates with various methacrylates for thermoplastic applications. Ind. Crops Prod. 2014, 60, 168–176. (65) Balbir Singh Kaith, R. J. Evaluation of Thermal Behavior of Microwave Induced Graft Copolymerization of Ethylmethacrylate onto Soy Protein Concentrate. J. Macromol. Sci. 2011, Part A, 299–308. (66) Kaith, B. S.; Jindal, R.; Bhatia, J. K. Morphological and thermal evaluation of soy protein concentrate on graft copolymerization with ethylmethacrylate. J. Appl. Polym. Sci. 2011, 120, 2183–2190. (67) Thakur, V. K.; Thunga, M.; Madbouly, S. A.; Kessler, M. R. PMMA-g-SOY as a sustainable novel dielectric material. RSC Adv. 2014, 4, 18240–18249. (68) Thakur, V. K.; Kessler, M. R. Synthesis and Characterization of AN-g-SOY for Sustainable Polymer Composites. ACS Sustain. Chem. Eng. 2014, 2, 2454–2460. (69) Thakur, V. K.; Kessler, M. R. Free radical induced graft copolymerization of ethyl acrylate onto SOY for multifunctional materials. Mater. Today Commun. 2014, 1 (1–2), 34–41.



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(70) Kaur, I.; Bhalla, T. C.; Deepika, N.; Gautam, N. Study of the biodegradation behavior of soy protein-grafted polyethylene by the soil burial method. J. Appl. Polym. Sci. 2009, 111, 2460–2467. (71) Bhattacharjee, S.; Bong, D. Protein-Polymer Grafts via a Soy Protein Derived MacroRAFT Chain Transfer Agent. J. Polym. Environ. 2011, 19, 203–208. (72) Ma, L.; Yang, Y.; Yao, J.; Shao, Z.; Chen, X. Robust soy protein films obtained by slight chemical modification of polypeptide chains. Polym. Chem. 2013, 4, 5425–5431. (73) Kaith, B. S.; Bhatia, J. K.; Dhiman, J.; Singla, R.; Mehta, P.; Yadav, V.; Bhatti, M. S. Synthesis and optimization of soy protein fiber based graft copolymer through response surface methodology for removal of oil spillage. Polym. Bull. 2013, 70, 3155–3169. (74) D.Mahto; Rani, P.; Mishra, S.; Sen, G. Microwave assisted synthesis of polyacrylamide grafted soya peptone and its application as water soluble adhesive. Ind. Crops Prod. 2014, 58, 251–258.


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Figure 1 (a) Diagrammatic depiction of β-conglycinin and glycinin thermal aggregation behavior at pH 7.0. N, native state; U, unfolded state; Agg, aggregates. Reprinted with permission 54. Copyright 2012 American Chemical Society.



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Figure 1(b). Chromatograms (solid lines) and corresponding Mw/Mmon profiles (dotted lines) for 1.0 wt % β-conglycinin and glycinin dispersions that were incubated at different temperatures for 30 min. (Inset) Protein solubility of β-conglycinin and glycinin dispersions after heating at different temperatures. Reprinted with permission

54

. Copyright 2012 American Chemical

Society.


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Figure 2 (a) Sn (Oct) 2 Initiated Polymerization Mechanism of PDO with Soy Protein. Reprinted with permission 60. Copyright 2008 American Chemical Society.

Figure 2 (b) TG curves of SPI, SPI-g-PPDO, and PPDO with different feed ratios in N2. Reprinted with permission 60. Copyright 2008 American Chemical Society.



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Figure 3 (a) The graft copolymerization mechanism of SPI-g-PNIPA65. Reprinted with permission 63. Copyright 2010 Springer.

Figure 3 (b) FTIR spectra of SPI and SPI-g-PNIPA-2. a SPI, b SPI-g-PNIPA-2 (GP = 92.86%)65 Reprinted with permission 63. Copyright 2010 Springer.


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Figure. 3 (c)

1

H-NMR spectra of SPI and SPI-g-PNIPA-2 (GP = 92.86%) in DMSO65.

Reprinted with permission 63. Copyright 2010 Springer.

Figure. 3 (d) TEM images of SPI and SPI-g-PNIPA (GP = 92.86%) with different solution concentrations63. Reprinted with permission. Copyright 2010 Springer.



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Figure 4 (a) Structural representation of SOY composition. Reprinted with permission

67

.

Copyright 2014 Royal Society of Chemistry.

(Eq. 1)

(Eq. 2)

(Eq. 3)

(Eq. 4)


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(Eq. 5)

(Eq. 6)

(Eq. 7)



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(Eq. 8)


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(Eq. 9) Graft copolymer

(Eq. 10) Homopolymer

Figure 4 (b) Mechanism for graft copolymerization of SOY. Reprinted with permission Copyright 2014 Royal Society of Chemistry.


67

.


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Figure 4 (c) FTIR and 1H NMR spectra of pristine SOY and PMMA-g-SOY. Reprinted with permission 67. Copyright 2014 Royal Society of Chemistry.


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Figure 4 (d) TGA and SEM scanning electron micrographs of pristine SOY and PMMA-g-SOY. Reprinted with permission 67. Copyright 2014The Royal Society of Chemistry.



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Figure 4 (e) Dynamic mechanical analysis and dielectric properties of pristine PMMA and PMMA-g-SOY. Reprinted with permission 67. Copyright 2014 Royal Society of Chemistry.


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 ACS Paragon Plus Environment


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SOY

(M)n-1 M*

*

M (M)n-1

SOY

SOY

(M)n-1-M2-(M)n-1 Graft copolymer

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SOY

(12)

Figure 5 Plausible mechanism for graft copolymerization of acrylonitrile onto SOY 68. Reprinted with permission 68. Copyright 2014 American Chemical Society.


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Figure 6 (a). Storage modulus and tan δ curves of pristine PMMA determined by dynamical– mechanical analysis68. Reprinted with permission

68

. Copyright 2014 American Chemical

Society.



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Figure 6 (b). Storage modulus and tan δ curves of SOY/ PMMA composite determined by dynamical–mechanical analysis68. Reprinted with permission Chemical Society.


68

. Copyright 2014 American

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Figure 6 (c). Storage modulus and tan δ curves of AN-g-SOY/ PMMA composite determined by dynamical–mechanical analysis68. Reprinted with permission Chemical Society.


68

. Copyright 2014 American


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Figure 7 (a) 31P NMR spectra of SPI and modified SPn samples. (a) SPI, (b) SP100, (c) SP200, (d) SP400, and (e) SP600. Sample concentration: 80 mg mL−172. Reprinted with permission 72. Copyright 2013 Royal Society of Chemistry.

Figure 7 (b) Storage modulus G′ and loss modulus G′′ as a function of frequency for SPI and the modified SPn solutions at 1% strain and 25 °C. (a) SPI, (b) SP100, (c) SP200, (d) SP400, and (e) SP600. Sample concentration: 100 mg mL−172. Reprinted with permission 72. Copyright 2013 Royal Society of Chemistry.


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Figure 8 TEM images of SPI and modified SPn samples. (a) SPI, (b) SP100, (c) SP200, (d) SP400, and (e) SP600. The area located as 1 and 2 in (e) represents the SP600 sample and carbon coating, respectively72. Reprinted with permission

72

.

Copyright 2013 Royal Society of

Chemistry.



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Figure 9 (a) Potential applications of soy based graft copolymers.


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Figure 9 (b) Different polymerization methods used to prepare soy based graft copolymers.



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Table 1 (a). Structural Parameters of Soy Protein Heated at Different Temperatures Derived from SAXS and DLS Data54. Reprinted with permission 54. Copyright 2012 American Chemical Society.

soy protein

Rg (SAXS) (nm)

Rh (DLS) (nm) Rg/Rh

I(0)

fractal dimension

7S unheated

4.97 ± 0.14

13.55 ± 0.06

0.37

1.37 ± 0.01

1.24

60 °C

6.11 ± 0.19

14.76 ± 0.24

0.41

1.88 ± 0.02

1.52

80 °C

8.06 ± 0.35

18.39 ± 0.13

0.44

3.38 ± 0.04

2.06

100 °C

8.74 ± 0.37

21.50 ± 0.02

0.41

3.68 ± 0.03

2.16

unheated

5.83 ± 0.03

26.02 ± 0.01

0.22

2.60 ± 0.02

1.32

60 °C

6.36 ± 0.36

36.16 ± 0.70

0.18

2.89 ± 0.02

1.42

80 °C

9.78 ± 0.04

46.43 ± 0.66

0.21

7.30 ± 0.09

2.69

100 °C

10.97 ± 0.05

119.45 ± 0.14

0.09

8.64 ± 0.11

3.24

11S


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Table 1(b). Structural Parameters of Glycinin and β-Conglycinin Mixtures Heated at 100 °C for 30 min Derived from SAXS and DLS Data54. Reprinted with permission 54. Copyright 2012 American Chemical Society.

11S/7S

Rg (SAXS) (nm)

Rh (DLS) (nm)

Rg/Rh

I(0)

fractal dimension

100/25

9.93 ± 0.05

56.05 ± 0.35

0.18

6.53 ± 0.09

2.76

100/50

9.70 ± 0.05

47.25 ± 0.12

0.21

6.05 ± 0.08

2.49

100/100

9.02 ± 0.05

42.10 ± 0.10

0.21

4.78 ± 0.07

2.27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24% Homo25 26polymers 27 28 290 3025 31 3250 3375 34 35100 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Table 2. Dry tensile properties of films made from soy protein grafted with various methacrylates and containing different amounts of homopolymers. Soy proteins were compression molded at 360 °F for 5 minute. In each column, data points with different letters indicate statistically significant difference64. Reprinted with permission 64. Copyright 2014 Elsevier.

Breaking stress (MPa)

Breaking elongation (%)

MMA

EMA

BMA

HMA

MMA

EMA

BMA

HMA

4.9 ± 0.8D 6.0 ± 0.6C 7.0 ± 0.8B 7.5 ± 0.8A 12.8 ± 1.0J

3.2 ± 0.4F 3.9 ± 0.5E 5.2 ± 0.8D 5.9 ± 0.6C 8.5 ± 0.9I

2.5 ± 0.6G 2.9 ± 0.5F,G 3.3 ± 0.9F 5.9 ± 0.6C 5.8 ± 0.6C

1.9 ± 0.8G 2.6 ± 0.6G 2.8 ± 0.7G 2.8 ± 0.9G 3.0 ± 0.8G

1.5 ± 0.5f 1.9 ± 0.5e 2.6 ± 0.5d 2.6 ± 0.7d 2.3 ± 0.3d

1.1 ± 0.3g 1.1 ± 0.3g 1.8 ± 0.5e 1.8 ± 0.7e 3.4 ± 0.6b

1.0 ± 0.3g 1.5 ± 0.2f 3.5 ± 0.6b 4.3 ± 0.7a 71.3±4.2c

1.9 ± 0.9e 9.7 ± 1.0h 10.9 ± 3.7i 38.8 ± 3.7j 111 ± 5.2k


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Table of Contents

Synthesis and Applications of Biodegradable Soy Based Graft Copolymers: A Review

Manju Kumari Thakur1, Vijay Kumar Thakur2*, Raju Kumar Gupta3 and Asokan Pappu4

1

Division of Chemistry, Govt. Degree College Sarkaghat, Himachal Pradesh University Shimla -

171005, India 2

School of Mechanical and Materials Engineering, Washington State University, United States

3

Department of Chemical Engineering, Indian Institute of Technology Kanpur, 208016, India

4

CSIR- Advanced Materials and Processes Research Institute, Bhopal 462064, India

Email: [email protected]; [email protected] Phone: 509-335-8491, Fax: 509- 335-4662



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Synopsis: In this review, recent advances in graft copolymerization approaches towards the synthesis and multifunctional applications of soy based graft copolymers are discussed in detail and highlighted by suitable examples.


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Dr. Manju Kumari Thakur has been working as an Assistant Professor of Chemistry at the Division of Chemistry, Govt. Degree College Sarkaghat, Himachal Pradesh University – Shimla, INDIA since June 2010. She received her B.Sc. in Chemistry, Botany and Zoology; M.Sc., M.Phil. in Organic Chemistry and Ph.D. in Polymer Chemistry from the Chemistry Department at Himachal Pradesh University – Shimla, INDIA. She has rich experience in the field of organic chemistry, biopolymers, composites/ nanocomposites, hydrogels, applications of hydrogels in the removal of toxic heavy metal ions, drug delivery etc. She is the recipient of several fellowships and awards such as GATE, SLET, Merit Certificate holder at college level in Himachal Pradesh University –Shimla, Merit Certificate for SIXTH POSITION in Matriculation (Xth Standard) examination in Himachal Pradesh Board of School Education –Dharamshala and National Scholarship Holder in School and College level at Himachal Pradesh. She has published more than 30 research papers in several international journals, coauthored 10 books and has also published 25 book chapters in the field of chemistry and materials science.



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Dr. Vijay Kumar Thakur has been working as a Staff Scientist in the School of Mechanical and Materials Engineering at Washington State University, USA, since September 2013. His former appointments include being a Research Scientist in Temasek Laboratories at Nanyang Technological University, Singapore, and a visiting research fellow in the Department of Chemical and Materials Engineering at LHU-Taiwan. He did his postdoctorate in Materials Science at Iowa State University and his Ph.D. in Polymer Science (2009) at the National Institute of Technology. In his academic carrier, he has published more than 84 SCI journal research articles in the field of chemical sciences/materials science and holds one United States patent. He has also published 24 books and 33 book chapters on the advanced state-of-the-art of materials science /nanotechnology with numerous publishers. He has been the recipient of several fellowships and awards for his outstanding career in academic and research fields. Vijay is an editorial board member of several international journals as well as member of scientific bodies around the globe. Some of his significant appointments include: Associate Editor for Materials Express (SCI); Advisory Editor for SpringerPlus (SCI); Associate Editor for Current Smart Materials; Regional Editor for Recent Patents on Materials Science (Scopus) and Regional Editor for Current Biochemical Engineering (CAS). He also serves on the Editorial Advisory Board of Polymers for Advanced Technologies (SCI) and is on Editorial Board of Journal of Macromolecular Science, Part A Pure and Applied Chemistry (SCI); International Journal of Industrial Chemistry (SCI) and Energies (SCI).


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Dr Raju Kumar Gupta is an Assistant Professor at the Department of Chemical Engineering, Indian Institute of Technology Kanpur, India. He completed his Ph.D. at the Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore in 2010. His research focuses on the synthesis of quantum dots utilizing greener routes for photocatalysis and solar energy applications, synthesis of water soluble photoluminescent carbon nanodots from biowaste and developing their metal oxide hybrid nanostructures for supercapacitor applications. He is the recipient of several fellowships and awards such as IEI Young Engineer Award (2014– 15) and DST Inspire Faculty Award 2013.



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Dr. Asokan Pappu is a Senior Principal Scientist at the CSIR- Advanced Materials and Processes Research Institute (AMPRI) India. He holds a Ph.D. from IIT Bombay besides Master in Public Health Engineering and B. Tech. in Civil Engineering from India. Dr. Asokan pursued Post doctorate research on GRP waste recycling in cement & concrete composites at the Loughborough University, United Kingdom during 2007-2008. Dr. Asokan has been a Sir CV. Raman Research Fellow and carried out the advanced research on hybrid composites at the University of Waikato, New Zealand in 2010. Dr. Asokan has received six best papers awards and two best and most cited paper awards from Elsevier Sci. publisher. He has published more than 172 research papers and delivered 87 invited / key note lectures and technical presentations and has authored eleven book chapters. He holds membership in eight Professional Societies including Materials Research Society of India and Indian Environmental Association. Dr. Asokan has also executed 17 R&D and Technology demonstration projects value of ~ 110 million INR.


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In this review, recent advances in graft copolymerization approaches towards the synthesis and multifunctional applications of soy based graft copolymers are discussed in detail and highlighted by suitable examples 308x253mm (72 x 72 DPI)


Synthesis and Applications of Biodegradable Soy Based Graft

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