Copolymers are a kind of important polymer materials, which are prepared by copolymerization. A copolymer consists of two or more monomer units. At present, there are many kinds of copolymers that have been studied and reported, most of which have been commercialized.
- Rubber field: Polymerized styrene butadiene rubber (SBR) is an important copolymer, and the monomers are styrene and butadiene. The processing properties of polymerized styrene butadiene rubber is close to natural rubber, and the properties of wear resistance, heat resistance, aging resistance and vulcanization speed is better than natural rubber. Polymerized styrene butadiene rubber has been widely used in the production of tires, rubber tapes, rubber pipes, electric wires and cables, medical devices and various rubber products, which is the largest general-purposed synthetic rubber specie.
Figure 1. Molecular structure of polymerized styrene butadiene rubber.
- Plastics field: Acrylonitrile butadiene styrene plastic (ABS plastic) is a terpolymer of acrylonitrile (A), butadiene (B) and styrene (S). The relative content of the three monomers can be changed arbitrarily to make various resins. ABS plastic has the common properties of the three components. Acrylonitrile component makes it have high resistance to chemical corrosion and certain surface hardness. Butadiene component makes it be highly elastic and ductile. Styrene makes it have the processing and forming characteristics of thermoplastics and improves the electrical properties. Therefore, taking the advantages of easy access to raw materials, good comprehensive performance and low price, ABS plastic has been widely used in machinery, electrical, textile, automobile, aircraft, ship and other manufacturing industries and chemical industries.
Figure 2. Molecular structure of acrylonitrile butadiene styrene plastic.
- The others: In addition to the above mentioned, copolymers also have a wide range of applications in fiber, coatings, adhesives and other fields.
According to the arrangement of monomers in the molecular chain, copolymers can be divided into alternating copolymers, random copolymers, block copolymers and graft copolymers.
- Alternating copolymers: The structure units in alternating copolymers alternate with each other, and the mole fraction is equal.
- Random copolymers: The structural units of random copolymers appear randomly in which the continuous number of each structural unit is not large. Statistically speaking, the content of a structural unit in one part of polymer chain is equal to its content in the whole polymer.
- Block copolymers: Block copolymers are linear copolymers formed by alternating polymerization of different chain segments with different chemical structures. It can combine the excellent properties of many kinds of polymers together to obtain the functional polymer materials with superior properties. Due to narrow molecular weight distribution and designable molecular structure, block copolymers are one of the most meaningful and challenging researches in the field of polymer research.
- Graft copolymers: Graft copolymers belong to branched polymers in structure. They not only have backbone chains, but also have long branched chains, and the backbone and branched chains are composed of different species structure units. Graft copolymers have some characteristics of physical blends and random copolymers. As a single compound, graft copolymers show the characteristic properties of one component rather than their average properties.
- Zhang J, Jin J, Cooney R, et al. Synthesis of perfectly alternating copolymers for polymers of intrinsic microporosity[J].Polymer Chemistry, 2015, 6.
- Deng Y, Zhang S, Lu G, et al. Constructing well-defined star graft copolymers[J]. Polymer Chemistry, 2013, 4(5):1289-1299..