Linear homo- and co-polycarbonates have been prepared from the sugar-based diols 2,3,4-tri-O-methyl-l-arabinitol and 2,3,4-tri-O-methylxylitol. Statistical co-polycarbonates were obtained from molar feed ratios of sugar:bisphenol A of 1:1 and 2:1. The polycarbonates were stable up to ∼280 °C with maximum decomposition rate above 345 °C. The arabinitol-based homopolymer was found to be semicrystalline whereas the xylitol-based one was amorphous. All the copolymers were amorphous with T g ranging between 60 and 80 °C. Both homo- and co-polycarbonates showed high resistance to chemical hydrolysis; however, they were enzymatically degraded in different degree. The xylitol-based polycarbonates were the more easily degraded by lipase B from Candida antarctica in acetonitrile at 70 °Cthis enzyme showing a high selectivity toward the configuration of the sugar-based moiety.

The synthesis and characterization of a new series of AABB-type polyamides based on l-arabinitol and xylitol are described. These linear polyamides were obtained by reaction of the aldaric acids or aliphatic dicarboxylic acids, with sugar-based diamine or aliphatic diamines. The pentaric diacids were activated as their pentachlorophenyl esters, and the diamino sugars were used as dihydrochlorides. Aliphatic diamines were used either as their activated trimethylsilyl derivatives or as the free bases. All the polyamides were soluble in the usual organic solvents, and those fully sugar-based were also soluble in water. All of them were very hygroscopic, especially those based on xylitol. DSC and X-ray powder diffraction studies showed that l-arabinitol-based polyamides were more crystalline than those derived from xylitol.

The extensive use of oral dosage forms for the treatment of diseases may be linked to deficient pharmacokinetic properties. In some cases the drug is barely soluble; in others, the rapid transit of the formulation through the gastrointestinal tract (GIT) makes it difficult to achieve therapeutic levels in the organism; moreover, some drugs must act locally due to a gastric pathology, but the time they remain in the stomach is short. The use of formulations capable of improving all these parameters, as well as increasing the resident time in the stomach, has been the target of numerous research works, with low-density systems being the most promising and widely explored, however, there is further scope to improve these systems. There are a vast variety of polymeric materials used in low-density gastroretentive systems and a number of methods to improve the bioavailability of the drugs. This works aims to expedite the development of breakthrough approaches by providing an in-depth understanding of the polymeric materials currently used, both natural and synthetic, their properties, advantages, and drawbacks.