Effect of surface‐grafted ionic groups on the performance of cellulose‐fiber‐reinforced thermoplastic composites

The influence of the surface chemistry of the cellulose fiber and polymer matrix on the mechanical and thermal dynamic mechanical properties of cellulose‐fiber‐reinforced polymer composites was investigated. The cellulose fiber was treated either with a coupling agent or with a coupling‐agent treatment followed by the introduction of quaternary ammonium groups onto the fiber surface, whereas the polymer matrix, with opposite polar groups such as polystyrene incorporated with sulfonated polystyrene and poly(ethylene‐co‐methacrylic acid), was compounded with the fiber. The grafting of the fiber surface was investigated with Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Experimental results showed that an obvious improvement in the mechanical strength could be achieved for composites with an ionic interface between the fiber and the polymer matrix because of the adhesion enhancement of the fiber and the matrix. The improved adhesion could be ascribed to the grafted ionic groups at the cellulose‐fiber surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2022–2032, 2003     

Thermodynamics of miscible polymer blends using a concentration-dependent χ parameter

The Flory equation-of-state theory, as expressed by Patterson and co-workers, has been applied to two miscible polymer blends: poly(vinyl chloride)/poly(ε-caprolactone) and poly(methyl methacrylate)/poly(vinylidene chloride). For both blends, the variation of the polymer-polymer interaction parameter, χ, as a function of composition, is mostly small and can be accounted for by the Flory theory. However, for poly(vinyl chloride)/poly(ε-caprolactone) blends, at high poly(ε-caprolactone content), the large variation of χ as a function of concentration can be explained by a variation of the surface-to-volume ratio of the polymers in the mixture with blend composition. The variations of the surface-to-volume ratios determined in this study agree with those reported in the literature using small-angle x-ray scattering.     

The photoelectron spectra of methyl-substituted allenes and of tetramethyl-bisallenyl

The split Δ = 0.6 eV of the first band at 10.5 eV in the photoelectron spectrum of allene (1) has been ascribed to a Jahn—Teller distortion by Baker and Turner. The influence of alkyl substitution on Δ and on the band position has been investigated by recording the photoelectron spectra of all methyl-substituted allenes 2 to 6, of 1,1-di-tert. butyl-allene (7) and of 1,2-cyclononadiene (8). It is shown that the dependence of Δ on substitution can be rationalized by assuming that it is due to a (pseudo) Jahn—Teller effect in 1 and in the symmetrically substituted derivatives and to the combined influence of this effect and a differential, inductive destabilization in the other cases.The photoelectron spectrum of tetramethyl-bisallenyl 9 can be explained on the basis of known parameters for semi-localized π-orbitals and for their through-space and through-bond coupling.     

Die Photoelektron-Spektren der Dihalogen-acetylene

The photoelectron-spectra of the six dihaloacetylenes XC?CY with X, Y ? Cl, Br, I have been recorded. The first five bands of these spectra can be assigned (in order of increasing ionization potentials) to the states ²∏_(u)(1), ²∏_(g)(2), ²∏_(u)(3), ²∑_(g)⁺(4), ²∑_(u)⁺(5) where the lower indices g, u are valid only for the centro-symmetric molecules I(X, X). The first three states correspond to π-ionization, the last two to σ-ionization of the axially symmetrical lone pairs. The ²∏-states split under the influence of spin-orbit-coupling into components ²∏_3/2 and ²∏_1/2, the former having the lower energy. The assignment of states and components to the individual bands is confirmed by the size of the split due to spin-orbit-coupling, the vibrational fine structure of the bands and by a simple parametrization of the ZDO. molecular orbital model assumed as a basis for the qualitative discussion.     

The photoelectron spectra of methyl-substituted allenes and of tetramethyl-bisallenyl

The split Δ = 0.6 eV of the first band at 10.5 eV in the photoelectron spectrum of allene (1) has been ascribed to a Jahn—Teller distortion by Baker and Turner. The influence of alkyl substitution on Δ and on the band position has been investigated by recording the photoelectron spectra of all methyl-substituted allenes 2 to 6, of 1,1-di-tert. butyl-allene (7) and of 1,2-cyclononadiene (8). It is shown that the dependence of Δ on substitution can be rationalized by assuming that it is due to a (pseudo) Jahn—Teller effect in 1 and in the symmetrically substituted derivatives and to the combined influence of this effect and a differential, inductive destabilization in the other cases.The photoelectron spectrum of tetramethyl-bisallenyl 9 can be explained on the basis of known parameters for semi-localized π-orbitals and for their through-space and through-bond coupling.     

Microencapsulation of nisin in alginate-cellulose nanocrystal (CNC) microbeads for prolonged efficacy against Listeria monocytogenes

The present study was undertaken to develop edible nisin-microencapsulated beads in order to inhibit growth of Listeria monocytogenes in ready-to-eat (RTE) ham. Different concentrations of nisin (16, 31, and 63 μg/ml) were microencapsulated into alginate-cellulose nanocrystal beads. Microencapsulation kept the available nisin (63 μg/ml) content 20 times greater compared with free nisin (63 μg/ml) during 28 days of storage at 4 °C. Results showed that 63 μg/ml microencapsulated nisin exhibited 31.26 μg/ml available nisin content after 28 days of storage at 4 °C, whereas there was no available nisin content left for free nisin. Cooked ham slices were then coated by the microencapsulated nisin beads, inoculated with L. monocytogenes [~3 log colony-forming units (CFU)/g], and stored at 4 °C under vacuum packaging for 28 days. The beads containing 16, 31, and 63 μg/ml nisin significantly (P ≤ 0.05) reduced the L. monocytogenes counts by 2.65, 1.50, and 3.04 log CFU/g after 28 days of storage compared with free nisin. Furthermore, microencapsulated nisin beads did not change the physicochemical properties (pH and color) of RTE ham during storage.