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SYNOPSISA series of new side-chain liquid-crystalline copolymers has been prepared, and the thermal properties of the individual copolymers have been determined. These copolymers are derived from atactic polystyrene and contain both 4-methoxyazobenzene and 4-nitroazobenzene mesogens; these are linked through octyl spacers to the polystyrene backbone. All the copolymers exhibit a smectic phase that has been assigned smectic A on the basis of polarizing microscopy and x-ray diffraction studies. The glass transition temperatures of the polymers exhibit a linear dependence on composition, whereas the clearing temperatures and the associated entropies show significant deviations from such behavior. The smecticisotropic transition temperatures of the copolymers are higher than those of the compositionweighted averages for the corresponding homopolymers, whereas the entropies of transition are lower than expected. X-ray diffraction studies of fiber samples revealed that the director of the mesophase is oriented perpendicular to the fiber axis. The liquid-crystalline polystyrene containing 25 mol % nitro-substituted mesogen shows an unusual &-phase WAXS pattern. The copolymers were investigated further by 13C CP /MAS NMR spectroscopy, and the observed changes in the spectra are analyzed in terms of chemical composition and local electronic environment. The application of the interrupted decoupling technique revealed that the spacer contains a number of gauche defects. These observations lead us to suggest possible microstructural arrangements in the smectic phase. 0 1993 John Wiley & Sons, Inc.

Proteins differentially affect carotenoid bioaccessibility and physicochemical characteristics of the digesta and constituents, depending on carotenoid and protein species/concentration.

Carotenoids are lipophilic phytochemicals; their intake has been associated with reduced chronic diseases. However, their absorption depends on emulsification during digestion and incorporation into mixed micelles, requiring digestive enzymes, gastric peristalsis, bile, and dietary lipids. In this study, we investigated whether whey-protein-isolate (WPI), a commonly consumed protein source, can modulate β-carotene bioaccessibility in vitro, especially under incomplete digestive conditions, i.e. under low digestive enzyme conditions. Thus, pepsin and pancreatin, kinetic energy, gastric digestion time, and amount bile and co-digested lipids were modified, and WPI at concentrations equivalent to 0/25/50% of the protein recommended dietary allowance (approx. 60 g/d) were added to β-carotene dissolved in oil. WPI enhanced bioaccessibility by up to 20% (p<0.001), especially under higher simulated peristalsis or reduced dietary lipids. Conversely, they impaired bioaccessibility to one third (p<0.001) under incomplete digestive conditions. WPI modulated βcarotene bioaccessibility depending on digestive conditions.

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