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The Secret of Natural Polymers: Which materials do you know are gifts from nature?
Polymers are large molecules made up of many repeating units derived from one or more monomers. Polymers found in nature and synthetic polymers play an integral role in our daily lives. From familiar synthetic plastics like polystyrene to natural biopolymers like DNA and proteins, which all play important roles in biological structure and function.
Polymers have properties that include high toughness, high elasticity, and a tendency to form amorphous or semi-crystalline structures more readily, making them popular for biological and industrial applications.
The term polymer originates from the Greek words meaning "many" and "part". The term was first proposed by Jöns Jacob Berzelius in 1833, however, in 1920, Hermann Staudinger proposed the concept of modern polymers, emphasizing their large molecular structures as covalently bonded molecules.
Types of natural polymers
Natural polymers can be divided into several types, the common ones are as follows:
Natural polymers
Natural polymers such as hemp, amber and natural rubber have been used for centuries. In addition, cellulose, the main component of wood and paper, is another important natural polymer.
Synthetic polymers
Synthetic polymers include polyethylene, polypropylene, polyvinyl chloride, synthetic rubber, etc. The annual output of these materials exceeds 330 million tons. Common polymers such as polyethylene have the repeating unit or monomer ethylene.
The global demand for natural and synthetic polymers is still increasing, which makes their range of applications continue to expand.
Synthesis and biosynthesis of polymers
Polymerization is the process of combining multiple small molecules (monomers) into a covalent chain or network. During this process, certain chemical groups may be lost from each monomer. Different synthesis methods can be divided into step polymerization and chain polymerization, where step polymerization can be further subdivided into polycondensation and polyaddition.
Biosynthesis
Biological polymers in nature, such as polysaccharides, peptide chains and nucleic acids, are synthesized by enzymatic reactions in cells. For example, the formation of DNA is a process catalyzed by DNA polymerase.
The synthesis of biopolymers plays an important role in today's scientific research, so its applications in various fields have become diversified.
Modification of natural polymers
Many important commercial polymers are synthesized by chemical modification of natural polymers. For example, nitrocellulose is formed by the reaction of nitric acid and cellulose, and vulcanized rubber is formed by the high-temperature reaction of sulfur and natural rubber. These modifications not only improve its performance but also expand its application range.
For synthetic polymers, their microstructure, molecular weight and degree of polymerization are key factors that determine their physical properties.
Structure and arrangement of polymers
The structure of polymers can be described at different length scales, from the subnanometer to the macroscopic level. The structure of each stage provides the basis for the next stage. The different structural forms of polymers affect their physical and chemical properties, especially in terms of crystallization processes and phase separation.
Ultimate Thoughts
Polymers demonstrate their importance both in the natural environment and in contemporary society. Therefore, as we face increasingly complex materials science, should we pay more attention to materials from nature and their potential uses?
