Natural polymers carbohydrates

Natural polymers Carbohydrates Dextran Hydrophilic Drug delivery [190]... 

The remainder of this chapter will deal with natural polymers. These are large molecules, produced by plants and animals, that carry out the many life-sustaining processes in a living cell. The cell membranes of plants and the woody structure of trees are composed in large part of cellulose, a polymeric carbohydrate. We will look at the structures of a variety of different carbohydrates in Section 23.3. Another class of natural polymers are the proteins. Section 23.4 deals with these polymeric materials that make up our tissues, bone, blood, and even hair. ... 

Development of biodegradable laminate films derived from naturally occurring carbohydrate polymers. Carbohydrate polymers, 60, 39-42. 

Polymers are substances whose molecules are very large, formed by the combination of many small and simpler molecules usually referred to as monomers. The chemical reaction by which single and relatively small monomers react with each other to form polymers is known as polymerization (Young and Lovell 1991). Polymers may be of natural origin or, since the twentieth century, synthesized by humans. Natural polymers, usually referred to as biopolymers, are made by living organisms. Common examples of biopolymers are cellulose, a carbohydrate made only by plants (see Textbox 53) collagen, a protein made solely by animals (see Textbox 61), and the nucleic acid DNA, which is made by both plants and animals (see Textbox 64). 

BakeUte Polymer produced by the condensation of phenol and formaldehyde, cellulose Naturally occurring carbohydrate polymer, elastomer Rubber. 

In the rapidly expanding area of nanochemistry, chemists often use Nature as inspiration to create their systems and in trying to mimic Nature, both in the efficiency and the perfection of the structures a number of natural building blocks have already been incorporated into synthetic materials. We have already reviewed how structurally simple natural building blocks (such as lipids, amino acids, peptides, carbohydrates and natural polymers)... 

Polymers are very large molecules made up of repeating units. A majority of the compounds produced by the chemical industry are ultimately used to prepare polymers. These human-made or synthetic polymers are the plastics (polyethylene, polystyrene), the adhesives (epoxy glue), the paints (acrylics), and the fibers (polyester, nylon) that we encounter many times each day. It is difficult to picture our lives without these materials. In addition to these synthetic polymers, natural polymers such as wood, rubber, cotton, and wool are all around us. And, of course, life itself depends on polymers such as carbohydrates, proteins, and DNA. This chapter discusses synthetic polymers. Naturally occurring polymers are presented in Chapters 25, 26, and 27. 

To start, let s divide natural polymers into two major categories. Homologous biopolymers consist of only one type of monomer unit—for example, proteins (amino acid units). Heterologous biopolymers, as their name implies, contain more than one class of monomer units. An example would be glycoproteins, which contain both carbohydrate and protein portions. Heterologous polymers are often block or graft copolymers. We will focus our attention on homologous biopolymers. 

The development of useful adhesive compositions based on the interaction of isocyanate resins with natural polymers such as lignin, proteins, and carbohydrates. 

Modification of Diisocyanate-Based Particleboard and Plywood Glues with Natural Polymers Polyphenols, Carbohydrates, and Proteins... 

Adhesives from Diisocyanates and Starch. Reactions between diisocyanates and carbohydrates are possible, resulting in polyurethane-like polymers. Starch as a most abundant natural polymeric carbohydrate is, without additives, an inefficient wood adhesive, giving weak and nonwater-resistant bonds. Another disadvantage of starch is that, even at low concentrations, the viscosity of the starch solution is too high for application. In our tests, maize starch was used as an extender for diisocyanates. The potlife of formulations of three parts starch powder and seven parts diisocyanate was more than 24 hours. 

Fang, J.M., Fowler, P.A., Escrig, C., Gonzalez, R., Costa, J.A., and Chamudis, L. (2005). Development of biodegradable laminate films derived from naturally occurring carbohydrate polymers. Carbohydrate Polymers. 60(1), 39 2. 

Chemists have devoted much effort to exploring this natural world of chemistry as well as to determining structures the natural world has stimulated the extension of the chemical world into models and analogs of the natural chemicals. The field of organic chemistry was influenced heavily by the types of chemical structures found in natural products many medicinal compounds are still invented by using natural products as models for analogs. Chemists have also invented important polymers once nature showed us the natural polymeric carbohydrates, polypeptides, nucleic acids, and the polymers such as rubber that are produced from natural materials. 

Natural polymers such as proteins, carbohydrates, fats, and waxes constitute an important group of encapsulation materials however, microparticles for the controlled drug delivery purpose have been prepared... 

In natural polymer chemistry a vast number of derivatives and technologies involving cellulose including the process for rayon the chromatographic material diethylaminoethylcellulose and numerous esters such as the triacetate indicate both the historical and present-day role of this important polymeric carbohydrate. 

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