SONIC DEGRADATION OF HIGH POLYMERS IN SOLUTION1725 about the pro-hypro peptide linkage sets the hydrogen-bonded configuration which the remainder of the chain may assume. The so-called "collagen fold" is thus directly related t o the trans pro-hypro form.The data presented here cannot answer another important question-whether the proline and hydroxyproline are concentrated in only one of the three collagen peptide chains, as has been suggested in connection with X-ray diffraction data.I6 (16) P. M. Cowan. 5. h9cGarin and A. C. J. North, Nature, 116, 1062 (1955).However, this seems to be unlikely in view of the viscosity data in the 40-100% FA range. On the basis of our data it does appear that there is a decided possibility that long segments of each of the polypeptide chains are essentially free of proline and hydroxyproline. Grassman has found large peptide fragments in gelatin that do not have a full complement of hydroxyproline. This means that other parts of the chain must have more than their average share.17 (17) W. Grassman, K. Hannig, H. Endres and A. Riedel, 2. physiol. Chem., 806, 123 (1956).The rates of sonic degradation of polymethyl methacrylate, polyisobutene polylauryl methacrylate and polystyrene are determined by use of 2,2-diphenyl-l-picryl hydrazyl to measure free radicai fragments. Using fractionated samples it is found (1) that the rate of degradation per polymer backbone bond, under constant conditions of cavitation, is directly proportional to the degree of polymerization; ( 2 ) that large side chains accelerate the rate of degradation; and (3) that a 10-2070 change in the carbon-carbon bond dissociation energy of the polymer chain has little effect upon the rate. A simple model is roposed whereby the rupturing stress arises from the radial velocity gradient surrounding a collapsing cavity. The modef yields a kinetic expression in agreement with the experimental results.

A novel cyclohexane derivatized soybean oil (CSO) is synthesized by Diels–Alder cycloaddition of soybean oil with isoprene. Then, the epoxidized cycloaliphatic soybean oil (ECSO) is prepared via epoxidation of CSO. For comparison purpose, norbornylized soybean oil (NSO) and epoxy norbornane soybean oil (ENSO) are synthesized. The CSO, ECSO, NSO, and ENSO are characterized by1H NMR,13C NMR, gradient heteronuclear single quantum correlation (gHSQC) 2D NMR, and mass spectroscopy. The epoxidized soybean oil (ESO), ECSO, and ENSO are photopolymerized using UV‐light, and the kinetics of the photocuring reactions is evaluated by real‐time Fourier transform infrared (FT‐IR) and photo‐differential scanning calorimetry (DSC). Real‐time FT‐IR and photo‐DSC indicate the improved reactivity of ECSO and ENSO compared to ESO. It is found that the curing rate and final conversion of novel developed ECSO is higher than ESO, but lower than ENSO.

Thermosets and composites were fabricated from the epoxides of norbornane seed oils (linseed oil, soybean oil, high-oleic soybean oil, and non-modified seed oils). The epoxides were cured using a cationic initiator to mold thermosets. Thermosets were characterized for their curing behavior and T g by dynamic scanning calorimetry, crosslinking efficiency by Soxhlet extraction, and thermal stability by thermogravimetric analysis (TGA). Steric hindrance of the norbornylized seed oils had a perturbing effect on the extent of epoxidation. However, the higher ring strain energy of the norbornene moieties played a key role in epoxide curing, resulting in higher T g thermosets with higher crosslinking efficiency. To the epoxide system with the highest optimum balance of T g, crosslinking efficiency, and thermal stability, lignocellulosic sorghum-derived biomass fillers were added. The addition of biomass fillers increased the bio-based content and reduced the cost and weight of the composites. Further, torrefied and carbonized sorghum filler variants were used to study the effect of the extent of thermal treatment on curing and on the final thermoset properties. Fillers were characterized by TGA, IR, elemental analysis, and solid-state NMR. Glass fiber-reinforced composites were molded using the optimum formulation. The mechanical and thermal properties of the novel hybrid biocomposites were investigated using universal testing machine (UTM), impact tester, and TGA. Both the sorghum-filled thermosets and composites showed enhanced thermomechanical property as compared to the non-filled epoxy systems. Carbonized sorghum filler composites exhibited the highest mechanical properties and thermal stability. Elemental differences and biomass precursor differences such as the cellulose, hemicellulose, and lignin content were found to play a critical role toward the composite properties. The SEM images showed good interfacial adhesion between the polymer matrix, fillers, and fiber phase in the biomass-filled composites. Thus, the fabricated composites demonstrate the potential for being used as sustainable, greener, and lightweight composites.

No abstract

Norbornylized seed oils, i.e., norbornylized linseed oil (NLO), norbornylized soybean oil (NSO), and norbornylized high oleic soybean oil (NHOSO), were synthesized via the Diels–Alder reaction of seed oil and dicyclopentadiene (DCPD) at high temperature (∼235 °C) and high pressure (∼80 psi), followed by cationic copolymerization using DCPD with boron trifluoride diethyl etherate catalyst. Norbornylized seed oils were characterized using H1 nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared, and gel permeation chromatography (GPC). Copolymers were formulated with four different DCPD contents, and curing was investigated using dynamic differential scanning calorimetry (DSC) measurements. It was found that the curing followed NLO > NSO > NHOSO with NLO having the highest exotherm, lowest activation energy, and lowest onset temperature. Furthermore, the gelation times were the least for NLO-DCPD copolymers. As anticipated, the degree of unsaturation and norbornene moieties strongly influenced the curing of copolymer thermosets. The copolymer products were compression-molded into thermosets and characterized by DSC, Soxhlet extraction, thermogravimetric analysis (TGA), H1 NMR, solid-state C13 NMR, and GPC. NLO-DCPD thermosets demonstrated high cure, higher thermal stability, glass transition temperature, and cross-linking capability compared to the other seed oil-DCPD counterparts. NMR and GPC results further suggested that bis-allylic and norbornene units concomitantly participated very actively during the cationic curing reaction. Moreover, scanning electron microscopy images of glass fiber-reinforced NLO-DCPD copolymer composites demonstrated good interfacial adhesion between the polymer matrix and fiber phases, imparting enhanced thermo-mechanical properties. This research opens a new venue for higher biobased greener polymer constituent for composite applications.