Many are interested in the question of what structure polymers have. The answer to it will be given in this article. Polymer properties (hereinafter - P) are generally divided into several classes depending on the scale at which the property is defined, as well as on its physical basis. The most basic quality of these substances is the identity of their constituent monomers (M). The second set of properties, known as microstructure, essentially denotes the arrangement of these Ms in P on a scale of one Z. These basic structural characteristics play a major role in determining the bulk physical properties of these substances, which show how P behaves as a macroscopic material. Chemical properties at the nanoscale describe how chains interact through various physical forces. On a macro scale, they show how basic P interacts with other chemicals and solvents.
Identity
The identity of the repeating links that make up the P is its first andthe most important attribute. The nomenclature of these substances is usually based on the type of monomer residues that make up the P. Polymers that contain only one type of repeating unit are known as homo-P. At the same time, Ps containing two or more types of repeating units are known as copolymers. Terpolymers contain three types of repeating units.
Polystyrene, for example, consists only of residues of styrene M and is therefore classified as Homo-P. Ethylene vinyl acetate, on the other hand, contains more than one type of repeating unit and is thus a copolymer. Some biological Ps are composed of many different but structurally related monomeric residues; for example, polynucleotides such as DNA are made up of four types of nucleotide subunits.
A polymer molecule containing ionizable subunits is known as a polyelectrolyte or ionomer.
Microstructure
The microstructure of a polymer (sometimes referred to as configuration) is related to the physical arrangement of M residues along the main chain. These are elements of the P structure that require the breaking of a covalent bond in order to change. The structure has a strong influence on other properties of P. For example, two samples of natural rubber can show different durability even if their molecules contain the same monomers.
Structure and properties of polymers
This point is extremely important to clarify. An important microstructural feature of the polymer structure is its architecture and shape, which are related to howbranch points lead to a deviation from a simple linear chain. The branched molecule of this substance consists of a main chain with one or more side chains or substituent branches. Types of branched Ps include star Ps, comb Ps, brush Ps, dendronized Ps, ladder Ps, and dendrimers. There are also two-dimensional polymers that consist of topologically flat repeating units. A variety of techniques can be used to synthesize P-material with various device types, such as living polymerization.
Other qualities
The composition and structure of polymers in polymer science is related to how branching leads to deviation from a strictly linear P-chain. Branching may occur randomly, or reactions may be designed to target specific architectures. This is an important microstructural feature. The architecture of a polymer affects many of its physical properties, including solution and melt viscosity, solubility in various compositions, glass transition temperature, and the size of individual P-coils in solution. This is important for studying the components contained and the structure of polymers.
Branching
Branches can form when the growing end of a polymer molecule attaches either (a) back to itself or (b) to another P-strand, both of which, through hydrogen withdrawal, can create a growth zone for the middle chain.
Branching effect - chemical crosslinking -formation of covalent bonds between chains. Crosslinking tends to increase Tg and increase strength and toughness. Among other uses, this process is used to strengthen rubbers in a process known as vulcanization, which relies on sulfur crosslinking. Car tires, for example, have high strength and crosslinking to reduce air leakage and increase their durability. The rubber, on the other hand, is not cross-linked, which allows the rubber to peel off and prevents damage to the paper. The polymerization of pure sulfur at higher temperatures also explains why it becomes more viscous at higher temperatures in the molten state.
Grid
A highly cross-linked polymer molecule is called a P-network. A sufficiently high crosslink-to-strand ratio (C) can lead to the formation of a so-called infinite network or gel, in which each such branch is linked to at least one other.
With the continuous development of living polymerization, the synthesis of these substances with a specific architecture is becoming easier. Architectures such as star, comb, brush, dendronized, dendrimers and ring polymers are possible. These chemical compounds with complex architecture can be synthesized either using specially selected starting compounds, or first by synthesizing linear chains that undergo further reactions to link with each other. Knotted Ps consist of many intramolecular cyclizationlinks in one P-chain (PC).
Branching
In general, the higher the degree of branching, the more compact the polymer chain. They also affect chain entanglement, the ability to slide past each other, which in turn affects bulk physical properties. Long chain strains can improve polymer strength, toughness, and glass transition temperature (Tg) due to an increase in the number of bonds in the compound. On the other hand, a random and short value of Z can reduce the strength of the material due to a violation of the ability of chains to interact with each other or crystallize, which is due to the structure of polymer molecules.
An example of the effect of branching on physical properties can be found in polyethylene. High density polyethylene (HDPE) has a very low degree of branching, is relatively rigid and is used in the manufacture of, for example, bulletproof vests. On the other hand, low density polyethylene (LDPE) has a significant amount of long and short strands, is relatively flexible, and is used in applications such as plastic films. The chemical structure of polymers favors just such applications.
Dendrimers
Dendrimers are a special case of a branched polymer, where each monomeric unit is also a branch point. This tends to reduce intermolecular chain entanglement and crystallization. A related architecture, the dendritic polymer, is not perfectly branched but has similar properties to dendrimersdue to their high degree of branching.
The degree of structural complexity that occurs during polymerization may depend on the functionality of the monomers used. For example, in the free radical polymerization of styrene, the addition of divinylbenzene, which has a functionality of 2, will lead to the formation of branched P.
Engineering polymers
Engineered polymers include natural materials such as rubber, synthetic materials, plastics and elastomers. They are very useful raw materials because their structures can be changed and adapted to produce materials:
- with a range of mechanical properties;
- in a wide range of colors;
- with different transparency properties.
Molecular structure of polymers
A polymer is made up of many simple molecules that repeat structural units called monomers (M). One molecule of this substance can consist of hundreds to millions of M and have a linear, branched or network structure. Covalent bonds hold the atoms together and secondary bonds then hold the groups of polymer chains together to form the polymaterial. Copolymers are types of this substance, consisting of two or more different types of M.
A polymer is an organic material, and the basis of any such type of substance is a chain of carbon atoms. A carbon atom has four electrons in its outer shell. Each of these valence electrons can form a covalenta bond with another carbon atom or with a foreign atom. The key to understanding the structure of a polymer is that two carbon atoms can have up to three bonds in common and still bond with other atoms. The elements most commonly found in this chemical compound and their valence numbers are: H, F, Cl, Bf and I with 1 valence electron; O and S with 2 valence electrons; n with 3 valence electrons and C and Si with 4 valence electrons.
Example of polyethylene
The ability of molecules to form long chains is vital to making a polymer. Consider the material polyethylene, which is made from ethane gas, C2H6. Ethane gas has two carbon atoms in the chain, and each has two valence electrons with the other. If two ethane molecules are bonded together, one of the carbon bonds in each molecule may be broken, and the two molecules may be joined by a carbon-carbon bond. After two meters are connected, two more free valence electrons remain at each end of the chain to connect other meters or P-strands. The process is able to continue connecting more meters and polymers together until it is stopped by the addition of another chemical (terminator) that fills the available bond at each end of the molecule. This is called a linear polymer and is the building block for thermoplastic compounds.
The polymer chain is often shown in two dimensions, but it should be noted that they have a three-dimensional polymer structure. Each link is at an angle of 109° tonext, and hence the carbon backbone runs through space like a twisted chain of TinkerToys. When voltage is applied, these chains stretch, and the elongation P can be thousands of times greater than in crystalline structures. These are the structural features of polymers.
