Molecules are much larger than low molecular compounds. Generally, the relative molecular weight of low-molecular-weight organic compounds is below 1000, and that of high-molecular-weight compounds is above 1000, some of which can reach tens of millions.
The basic characteristics of polymer compounds: the relative molecular weight is large, generally above 10000.
Example: the average relative molecular weight of PVC is 50-150000; Natural rubber 400- 1 10,000.
2. Synthesis of polymer compounds:
The chemical reaction of synthesizing polymers from small monomers.
Polymerization is divided into addition polymerization and polycondensation.
(1) addition polymerization: A reaction in which one or more monomers containing unsaturated bonds combine with each other through addition reaction to form polymer compounds.
1) Homopolymerization reaction: it is formed by polymerization of only one monomer, and its molecular chain contains only one monomer link. This polymerization reaction is called homopolymerization. The resulting polymer is called homopolymer.
The common addition polymerization reaction is from vinyl monomer to vinyl polymer compound, and its general formula is:
Such as polyethylene, polyvinyl chloride, polystyrene and other polymers.
2)*** polymerization: When two or more monomers are polymerized at the same time, the resulting polymer contains many monomers, which is called * * * polymerization. The resulting polymer is called * * * polymer. For example, ABS engineering plastics are polymerized from three different monomers: acrylonitrile (CH2=CH-CN), butadiene (CH2=CH-CH=CH2) and styrene (C6H6-CH=CH2).
* * * polymers often have some excellent properties of two or more homopolymers, so the properties of products can be improved by * * * polymerization.
(2) Polycondensation: refers to the condensation of one or more monomers with two or more functional groups to form high polymers, and at the same time react with low molecular substances (such as water, hydrogen halide, ammonia, alcohol, etc.). ) all settled down. The structural features of functional groups left in polycondensates are mostly heterochain polymers. Nylon, polyester, epoxy resin and phenolic resin are all formed by polycondensation. For example, nylon -66 is formed by condensation of adipic acid (HCOO-(CH2)4-COOH) and hexamethylenediamine (H2N-(CH2)6-NH2). Nylon -66 is easily soluble in polar solvents such as formic acid.
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