3.1.1　The development history of biomedical polyme...

3.1.1　The development history of biomedical polymers

Having been developed for about a century，biomedical polymer materials and related devices have become important auxiliary tools and functional materials in the various fields of diagnosis and treatment in modern medicine，hold an irreplaceable important position in modern medicine，and continue to promote the innovation and sustainable development of various diagnosis and treatment technologies.The composition basis of biomedical polymer materials is polymer compounds.Therefore，in order to explain the development history of biomedical polymer materials，we first briefly introduce the basic knowledge of polymer science.

Polymer science and synthetic polymer technology began to sprout in the 1920s and 1930s.So far，it has become an essential part of human daily life and industrial production.Polymer materials，metallic materials，and ceramic materials are the three key materials of modern society.Polymer compounds are generally named as macromolecules，or polymers for short.It is made up of many repeated structural units linked by repeated covalent bonds.Its relative molecular weight can reach thousands or even millions，showing certain mechanical properties of macromolecular compounds.

Each repeated structural unit that makes up a polymer is known as the monomer of the polymer，i.e.，the starting material of the synthetic polymer，capable of forming high molecular weight compounds through the polymerization reactions.

Compared to the small molecular compounds，polymer compounds have the following remarkable characteristics：①The molecular weight is high and the molecule is like a“long chain”.②It has a certain aspect ratio.③If there are branches on the molecular chain，it can form star-shaped，hyperbranched，network and other topological structures.④The molecular weight is not uniform and featured by heterogeneous，i.e.，the polydispersity of polymers.⑤Strong interchain interactions lead to liquid and solid-state polymers，and can't be vaporized.⑥Solid polymers have certain mechanical strength，can be used as load-bearing materials，and can be used to form a clot，draw silk and make film.Among them，biomedical polymer materials are one type of polymer materials used in the fields of artificial organs，tissue engineering and regenerative medicine，physical therapy and rehabilitation，internal and external diagnosis，slow and controlled drug release，blood preparations，and medical devices.(https://www.daowen.com)

In fact，before the concept of“polymer science”and the technology of“man-made polymers”appeared，some natural polymer materials（e.g.，cotton fiber，horsehair）have been used by ancient humans to heal the wounds.Bamboo chips and wooden planks are used for fracture fixation，and these natural polymer products are recognized as the earliest biomedical polymer materials.It is well known that the most important substances in the composition of animal and plant bodies（e.g.，protein，muscle，cellulose，starch，biological enzymes and pectin）are all belong to polymer compounds.Therefore，it is accepted that natural polymers are the basis of life，and the biological world is a huge resource of natural polymers.The ubiquity of polymer compounds in the biological world determines their special status in the medical field.Among various materials，the molecular structure，chemical composition，and physical and chemical properties of man-made polymer materials have important similarities with biological tissues，therefore they can be widely used as biomedical materials.

Modern biomedical polymer materials were born with the concept of“polymer science”and the technology of“man-made polymer”.After that，there have been many significant evolutions in the polymer field，and polymer science and technology have been rapidly developed.As a consequence，new polymer synthetic materials continue to emerge，providing more options for the medical fields，leading to the continuous development of biomedical polymer materials for clinical application，as shown in Table 3-1.