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as a consequence of small errors in the measurements of (/ii2) /nm2 that can affect in a significant way the value of the temperature coefficient. References and Notes(1) Flory, P.

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SynopsisA detailed assignment of the 13C chemical shifts of K -and i-carrageenans in their Na+ and K+ forms in DzO and dimethylsulfoxide is given. Evidence of the conformational transition induced by temperature variation in the absence of any gel formation on K-carrageenans is also presented. This evidence is based on 13C-nmr and optical rotation experiments.

Blends of bacterial poly(hydroxybutyrate) (PHB) with poly(hydroxyoctanoate) (PHO) were prepared by co-dissolving the two polyesters in chloroform and casting the mixture. To probe the question of blend miscibility, scanning electron microscopy (SEM) observations and differential scanning calorimetry (DSC) spectra were collected for the blends and blend components as well. It has been observed that PHB shows no miscibility at all with PHO, resulting in two-phase systems in which the nature of the continuous phase is composition-dependent. Dynamic mechanical analysis and tensile properties of these materials were also investigated. The morphology of the blend strongly influences the mechanical behavior. The mechanical properties of these materials have been predicted from a model involving the percolation concept. It takes both linear and nonlinear mechanical behaviors into account and allows for the effect of the lack of adhesion between material domains and/or breakage of one of the component.

The l3C NMR spectra of N-acetyl-D-glucosamine (1) and chitobiose (2), monomer and dimer of chitin, were assigned and used to assign the I3C NMR spectra of chitin in lithium thiocyanate and in LiCl/dimethylacetamide solutions. The dissolution of chitin in formic acid was studied.IR, I3C and 'H NMR spectra show that dissolution occurs by a reaction of formic acid with chitin with the formation of formyl chitin as a statistical derivative of chitin. I3C NMR spectra of diformyl-and diacetylchitin were also assigned to characterize these regular polymers.