Natural polymers, hydrogels based

Semisolid Dosage Forms The nature of the base (vehicle) used for the fabrication of semisolid dosage forms affects their hydrolytic stability. Increased degradation of benzylpenicillin sodium in hydrogels of various natural and semisynthetic polymers has been reported [14]. Also at pH 6 in Carbopol hydrogels, the percentage of undecomposed pilocarpine at equilibrium is a function of the apparent viscosity of the medium [15]. 

For many years, it was known that hydrogel adhesives and SIS adhesives were soft to the skin, and that their skin irritation was milder in comparison with common acrylic and natural rubber adhesives. Based on these findings, guiding principles for lowering the skin irritation of adhesives were gradually elucidated. These are the following 1) adhesive matrix should contain lots of liquid substance 2) polymers should... 

The structures of a number of synthetic hydrophilic polymers as a representative range of those commonly used are shown in Fig. 1. Many common hydrophilic polymers are based on methacrylate or acrylate backbones. One of the most common is polyacrylic acid, which forms the basis of many hydrogel materials (Fig. lA). Although simple polyacrylic acid is water soluble, it can be easily cross-linked to form an insoluble network polymer that still, however, retains high affinity for water and is capable of adsorbing large amounts of water to form hydrogels these are discussed later. Polymethacrylic acid-based polymers are similar in nature (Fig. IB). One of the most commonly used polymers for contact lenses, polyhydroxyethyl methacrylate, is based on a similar backbone (Fig. 1C). 

The following sections describe the preparation and characterization of supramolecular polymer networks, particularly emphasizing their physical-chemical features with regard to the type and strength of physical chain cross-linking and the resulting macroscopic material properties. Furthermore, recent work on the formation and characterization of supramolecular hydrogels based on synthetic and natural precursors is summarized with a focus on their application and potential in biomedicine. 

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