Grafting of polyacrylonitrile to granular corn starch

Abstract

synopsisAcrylonitrile grafts readily to granular corn starch in aqueous slurry when initiated by hydrogen peroxide plus activator. Prime evidence for grafting lies in the ease of separating PAN from starch in high yield when the initiator is arobisisobutyronitde rather than peroxide. Grafting efficiencies are determined by extraction with appropriate solvents: dimethylformamide for homo-PAN, and Looiling water for ungrafted starch. Grafting efficiencies of PAN range from 78 to 95%, M,, values for grafted PAN are 4,000 to 90,O00, and frequency of attachment of side chains range from 300 to 1100 glucose units per chain. Increasing the monomer level, a t fixed initiator concentration, tends to result in longer rather than more frequent side chains. AN behaves much as has been previously found for MMA, but the somewhat more efficient grafting at more frequent intervals and the more nearly uniform distribution of polymer in the starch granule suggest that AN penetrates the starch granule more readily than MMA. INTRODUCTIONThe grafting of poly(methy1 methacrylate) (PMMA) to granular corn or its unsaturated esters3 by way of free-radical initiation has been described in previous papers from this laboratory. Means of separating ungrafted homopolymer of methyl methacrylate from the graft haye been studied in detaiL4 This paper reports results of similar techniques used to prepare and characterize grafts of PAN (polyacrylonitrile) to granular corn starch.Grafting of PAN to starch has already b&n carried out, but under conditions widely dzerent from those here reported. Walrath et a1.6 prepared grafts to wheat starch by mutual or preirradiation from a ' W o source. Kimura and co-workers grafted by initiation with ceric salt in solutions of potato amylose6 or by use of reprecipitated starch peroxidized with ozone.' Fanta et a1.8 studied the effects of reaction conditions on composition of product obtained by initiation with ceric nitrate in dilute solutions of wheat starch. EXPERIMENTAL MaterialsUnmodified and hypochlorite-oxidized starches were A. E. Staley production materials. The unmodified starch was defatted prior to use as free of nonvolatiles and readily polymerjzable, was used as received. All other reactants were reagent grade or equivalent. PolymerizationThe procedure was the same as previously described for methyl methacrylate.' On addition of the peroxide to the mixture containing all other reactants, the temperature rose from its initial 30°C. to a peak within the next 15 min. Total reaction time was 60-90 min. The product was filtered, washed with water, and dried in air a t room temperature. Conversion of monomer to polymer was 95% or higher in each instance, except for those runs initiated with AIBN (azobisisobutyronitrile). Characterization of RESULTS AND DISCUSSION Qualitative Description of ProductsThe products are recovered in the form of fine white powders, similar in appearance to the original starch. Even the appearance of individual particles is changed hardly a t all by the polymerization, as shown...

Photo‐induced graft copolymerization of acrylonitrile onto sodium salt of partially carboxymethylated guar gum

“…The graft copolymer of Na-PCMGG (DS 5 0.291) containing PAN was hydrolyzed by refluxing for 12 h in 1N HCl as suggested by Brockway and Seaberg. 15 After all the Na-PCMGG went into the solution, a resinous mass was obtained which was characterized with IR spectroscopy.…”

Synthesis and nuclear magnetic resonance analysis of starch‐g‐poly(1,4‐dioxan‐2‐one) copolymers

“…However, starch‐based materials have many disadvantages, such as poor mechanical properties and processability, as well as instability caused by water absorption. To solve these problems, starch has often been modified through blending,1, 2 chemical derivation,3, 4 and graft copolymerization 5, 6…”

“…Starch graft copolymers such as starch‐ g ‐polyacrylonitrile were synthesized 36 years ago by Brockway and Seaberg,5 as reviewed by Athawale and Rathi 6. However, these copolymers with vinyl polymer branches have limited biodegradability, although their properties are acceptable for thickening agents and paper additives, for example.…”

Crosslinking of Starch Xanthate. V. Redox Grafting with Hydrogen Peroxide and Vinyl Monomers in Water

“…There seems to be a hint of carbonyl absorption at 1730 em -l in the IR shown in Figure 4 for the starch-PAN, suggesting that some hydrolysis of nitrile group has ensued possibly. Such hydrolysis would not be expected to alter the solubility character of and deductions for composition and structure in the graft copolymers, since like PAN, 10 The amount of DMF extract obtained from the cross-linked starch-PAN product, which was carried out to find any homopolymers, was meager. The IR spectra of the product, the extract, and the residue left after extraction, all had the same numerical ratio of nitrile group absorption to starch absorption at the 2.9-and 8.5-,um points.…”

“…This product did not dissolve in dimethyl sulfoxide (DMSO) (0.05 g of 60-mesh powder per 5 m/) or in dimethyl formamide (DMF) on standing 1 week at room temperature or upon heating at 100°C for 15 min, but it did acquire a gelatinous appearance on the particle surfaces. According to Brockway and Seaberg,10 copolymer derivative. In contrast, SX of 0.13-0.51 D. S. was found to be readily soluble in roomtemperature DMSO, but insoluble in even hot DMF in our test.…”