ABSTRACT:The aim of this study was to investigate the film-forming ability of the hemicellulose O-acetyl-galactoglucomannan (AcGGM) and to evaluate its potential as a barrier material. The polymer film was evaluated by measurement of its oxygen permeability (Ox-Tran® Mocon), thermal properties (differential scanning calorimetry), and dynamic mechanical properties under a humidity scan (humidity-scan DMA). The AcGGM was isolated from industrial process water obtained from mechanical wood pulping. The self-supporting films were formed by solution-casting from water. As expected, a plasticizer was needed to avoid brittleness, and glycerol, sorbitol, and xylitol were compared. However, these additives resulted in higher sensitivity to moisture, which might be less beneficial for some applications. Interesting oxygen barrier and mechanical strength properties were achieved in a film obtained from a physical blend of AcGGM and either alginate or carboxymethylcellulose, both having a substantially higher molecular weight than AcGGM. No phase separation was observed, since all the components used were rich in hydroxyl functionalities. When a plasticizer was also added to the binary mixture, a compromise between (1) low O 2 permeability, (2) high mechanical toughness, and (3) flexibility of an AcGGM-based film was obtained.

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The objective of this study was to create oxygen barrier films based on the hemicellulose O-acetylgalactoglucomannan (AcGGM) that show high resistance toward moisture-rich conditions. We have applied Williamson benzylation, a classic derivatization method of carbohydrates, as well as two different methods for surface grafting, and, finally, lamination of unmodified hemicellulose films with the synthesized hydrophobic benzylgalactoglucomannan (BnGGM). It was found that the thermoplastically behaving BnGGM could form independent transparent and strong films that were easy to handle. As expected, their resistance toward water was very high, and the oxygen barrier properties showed drastically lower sensitivity toward moisture than films from the corresponding unmodified material. The surface grafting and lamination methods were approached in order to try and combine excellent barrier properties with moisture tolerance. It was found that the grafting methods applied had a positive effect in this direction; however, lamination turned out to be an even more promising option.

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Poly(ethyl glyoxylate) (PEtG), a new polyacetal, was synthesized via anionic polymerization in CH 2 Cl 2 . End-capping was achieved using phenyl isocyanate. Average molecular weights in the range of 9000 -216 000 were obtained. 1 H and 13 C NMR characterization highlight the non-stereoregularity of PEtG. The polymer is quasi-atactic and the polymerization almost followed a Bernoulli process. Compared to its homologue poly(methyl glyoxylate), PEtG exhibits enhanced thermal stability (>200°C) and a lower glass transition temperature, T g . Molecular weight influences T g , but does not affect thermal stability.