polymers – a chemical compound whose name is familiar to all of us. But do you know what polymers really are? Let’s learn the concept, structure, properties and specific applications of this compound in the article below.
What is the term polymer?
polymers are compounds with very large molecular mass, made up of many links linked together. These chains are connected to each other via covalent bonds – two or more molecules will be connected together, sharing a pair of electrons. The molecules that initially make up each link of the polymer are called monomers.
Polyethylene (–CH2–CH2–)n then –CH2–CH2– is the link; n is the coefficient of coincidence.
The index n is called the polymerization coefficient, the higher the degree of polymerization, the higher the molecular mass of the polymer.
Polymers are abundant in nature, typical examples are basic chemicals such as DNA and RNA. There are also other familiar natural polymers around us such as silk, hair, fingernails, toenails, cellulose, protein… In addition, they are also derived from natural gas or coal, petroleum. bumpy.
How to classify polymers?
Currently, polymers are classified into many different types based on origin, synthesis method and structural characteristics.
Based on provenance
Based on origin, people divide polymers into two main categories: polymers of natural origin and synthetic polymers.
Polymers have natural origin like rubber, cellulose…
Synthetic polymers synthetic by man, such as polyethylene, phenol-formaldehyde resin.
In addition, artificial (also known as semi-synthetic) polymers are taken from natural polymers and processed into new polymers such as cellulose trinitrate, viscose silk…
Based on synthesis
Based on the method of synthesis, polymers are classified into two main categories as follows:
Macromolecular polymers synthesized by coincidence reaction: (–CH2–CH2–)n and (–CH2–CHCl–)n.
Condensation polymers are synthesized by condensation reaction:(–HN–[CH2]6–NH–CO–[CH2]4–CO–)n
Based on structure:
However, polymers can also be classified based on structural features.
Polymers have unbranched circuitfor example: PVC, PE, PS, rubber, cellulose, starch…
Polymers have branch circuite.g. amylopectin, glycogen.
Structural Polymers space networkeg resite, vulcanized rubber.
Structural features of polymers
Polymer molecules are made up of many links linked together.
These links are linked together to form a straight or branched chain. The chains of polymer molecules can be linked together by bridges that are groups of atoms, forming a spatial crystal lattice.
Straight circuit (unbranched circuit). For example: polyethylene, amylose…
Branching circuit. For example: amylopectin, glycogen…
Network circuit (space network). For example: vulcanized rubber, bakelite…
Most polymers are solid, non-volatile and insoluble in water or common solvents.
Physical properties of polymers
The most prominent physical properties of polymers are: It exists in the form solid, non-volatile, has no definite melting point (usually melts over a fairly wide range of temperatures). When melted, most polymers form a viscous liquid that solidifies when cooled and is called a thermoplastic. Some other polymers do not melt when heated but decompose immediately, called thermosolids.
Most polymers are insoluble in water or common solvents. Only some solvent-soluble polymers are suitable for viscous solutions, such as benzene-soluble polybutadiene.
Many polymers are flexible (polyethylene, polypropylene…), some are elastic (polybutadiene, polyisoprene…) and some can be spun into durable fibers (nilon-6, cellulose,…). There are polymers that are transparent but not brittle, many are insulating (polyethylene, poly(vinyl chloride), …) or semi-conductive (polianiline, polythiophene, …)
Chemical properties of polymers
Polymers can participate in three reactions: chain cleavage, chain retention reaction and carbon chain increase reaction. These three reactions determine the chemical properties of the polymer.
Separation reaction: Polymers with functional groups in the chain are easily hydrolyzed. The polymerized polymer will be pyrolysis at a certain temperature to produce short segments, which will eventually form a three-terminal monomer. The pyrolysis of polymers into monomers is called depolymerization or depolymerization. Some polymers are oxidized to cut chains.
The reaction keeps the circuit intact: Polymers with double bonds in the chain or the functional group outside the chain can participate directly in the reactions characteristic of the double bond as well as that of the functional group.
Hypervascular reaction: When meeting the right conditions (temperature, catalyst..), polymer chains can link together to form longer chains or form networks, such as vulcanization reactions. rubber into vulcanized rubber, convert rezol into resite, etc. In technology, the reaction connecting polymer chains together to form a spatial network is called polymer crosslinking reaction.
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Polymers are prepared with polymerization or condensation.
Polymerization is the process of linking many similar or similar small molecules (monomers) into very large molecules (polymers). The necessary condition for the structure of the monomer to participate in the polymerization reaction is that the molecule must have multiple bonds or unstable rings that can be opened.
Example: CH2=CH2, CH2=CH–C6H5
Polymerization is the process of linking many small molecules (monomers) into extremely large molecules (polymers), and at the same time releasing other small molecules (such as H2O…). In other words, polymerization is the process of condensing many small molecules into large molecules. For this reaction to occur, the monomer participating in the reaction must have at least 2 functional groups capable of reacting to form bonds.
Applications of polymers in life and production
In life, polymers play an important role in many different fields and professions. This compound is applied in many industries such as textiles, packaging, stationery, plastics, aircraft, construction, toys… The three most prominent applications of polymers in life and production are plastics. , silk and rubber.
Plastic is a flexible material, made from polymers. Besides polymers, its composition may have a number of other substances such as: plasticizers (increasing plasticity, facilitating finished processing), fillers increasing mechanical strength, increasing water resistance, heat resistance . ), additives to color, create odor, increase durability for the environment).
Plastic has many advantages such as lightness, durability, electrical insulation, heat insulation, ease of processing, many colors… Currently, plastics have replaced metal, porcelain and glass in many fields.
Silks are natural or synthetic polymers that have a straight chain structure and can be spun into fibers. Based on origin and production order, silk is classified into natural silk (available in nature such as silk, cotton, jute) and chemical silk – processed from natural polymers or simple substances.
Chemical silk is preferred over natural silk because it has many advantages such as durable, beautiful, easy to wash, and quick to dry.
Rubber is a natural or synthetic polymer with elastic properties. People also divide rubber into 2 types: natural rubber and synthetic rubber. Of which the most popular is Buna rubber. Rubber is widely used in many different sectors of the economy such as tire manufacturing, wire wrapping, raincoats, diving suits, etc.
The outstanding advantages of rubber are elasticity, impermeability, impermeability to gases, abrasion resistance and electrical insulation.
Exercises about polymers in Chemistry textbook 9 have the most specific solutions
Let’s apply the basic theories of polymers above to practice solving some of the following 9th Chemistry textbook exercises.
Exercise 1 (page 165 Chemistry Textbook 9)
Choose the best sentence from the following sentences:
a) Polymers are substances with large molecular masses.
b) Polymers are substances with small molecular masses.
c) Polymers are substances with very large molecular masses made up of many types of atoms bonded together.
d) Polymer is a substance with very large molecular mass made up of many links linked together.
Correct answer: D.
Exercise 2 (page 165 Chemistry Textbook 9)
Choose the correct word or phrase to fill in the blank:
a) Polymers are usually… non-volatile.
b) All polymers are … in water and common solvents.
c) The polymers available in nature are called polymers … while the polymers synthesized by humans from simple substances are called polymers…
d) Polyethylene and poly(vinyl chloride) are polymers… while starch and cellulose are polymers…
The appropriate clusters are:
a) Polymers are usually non-volatile solids.
b) Most polymers are insoluble in water and common solvents.
c) The polymers available in nature are called natural polymers, while the polymers synthesized by man from simple substances are called synthetic polymers.
d) Polyethylene and poly(vinyl chloride) are synthetic polymers, while starch and cellulose are natural polymers.
Exercise 3 (page 165 Chemistry Textbook 9)
In the following polymer molecules: ethylene, cellulose, starch (aminopectin), ppli(vinyl chloride), which polymer molecule has the same chain structure? Specify the chain type of the polymer molecules.
Polymer molecules with straight chain structure: Polyethylene, poly(vinyl chloride), cellulose, polymer molecules with branched chain structure: starch (aminopectin).
Exercise 5 (page 165 Chemistry Textbook 9)
When a polymer is burned, only CO2 and water vapor are obtained with the ratio of moles of CO2: moles of H2O = 1 : 1.
Which of the following polymers: PET, poly(vinyl chloride), starch, protein? Why?
When burning a polymer gives the number of moles of CO2 equal to the number of moles of H2O, the polymer is polyethene.
Poli(vinyl chloride), protein when burned will have other components besides CO2, H2O. Starch burns for the number of moles of CO2 : the number of moles of H2O is not the same.
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