High molecular weight compounds are polymers that have a large molecular weight. They can be organic and inorganic compounds. Distinguish between amorphous and crystalline substances, which consist of monomeric rings. The latter are macromolecules connected by chemical and coordination bonds. In simple terms, a high-molecular compound is a polymer, that is, monomeric substances that do not change their mass when the same "heavy" substance is attached to them. Otherwise, we will talk about the oligomer.
What does the science of macromolecular compounds study?
The chemistry of macromolecular polymers is the study of molecular chains consisting of monomeric subunits. This covers a huge area of research. Many polymers are of significant industrial and commercial importance. In America, along with the discovery of natural gas, a large project was launched to build a plant for the production of polyethylene. Ethane from natural gas is convertedinto ethylene, the monomer from which polyethylene can be made.
A polymer as a macromolecular compound is:
- Any of a class of natural or synthetic substances made up of very large molecules called macromolecules.
- Many simpler chemical units called monomers.
- Polymers make up many materials in living organisms, including, for example, proteins, cellulose, and nucleic acids.
- In addition, they form the basis of minerals such as diamond, quartz and feldspar, as well as man-made materials such as concrete, glass, paper, plastics and rubbers.
The word "polymer" denotes an indefinite number of monomer units. When the amount of monomers is very high, the compound is sometimes referred to as high polymer. It is not limited to monomers with the same chemical composition or molecular weight and structure. Some natural high molecular weight organic compounds are composed of a single type of monomer.
However, most natural and synthetic polymers are formed from two or more different types of monomers; such polymers are known as copolymers.
Natural substances: what is their role in our lives?
Organic high molecular weight organic compounds play a crucial role in people's lives, providing basic structural materials and participating in vital processes.
- For example, the solid parts of all plants are made up of polymers. These include cellulose, lignin and various resins.
- Pulp ispolysaccharide, a polymer made up of sugar molecules.
- Lignin is formed from a complex three-dimensional network of polymers.
- Tree resins are polymers of a simple hydrocarbon, isoprene.
- Another familiar isoprene polymer is rubber.
Other important natural polymers include proteins, which are polymers of amino acids, and nucleic acids. They are types of nucleotides. These are complex molecules composed of nitrogen-containing bases, sugars and phosphoric acid.
Nucleic acids carry the genetic information in the cell. Starches, an important source of dietary energy from plants, are natural polymers made up of glucose.
Chemistry of macromolecular compounds releases inorganic polymers. They are also found in nature, including diamond and graphite. Both are made of carbon. Worth knowing:
- In a diamond, carbon atoms are connected in a three-dimensional network that gives the material its hardness.
- In graphite, used as a lubricant and in pencil "leads", carbon atoms bond in planes that can slide over each other.
Many important polymers contain oxygen or nitrogen atoms as well as carbon atoms in the backbone. Such macromolecular materials with oxygen atoms include polyacetals.
The simplest polyacetal is polyformaldehyde. It has a high melting point, is crystalline, abrasion resistant andthe action of solvents. Acetal resins are more metal-like than any other plastics and are used in the manufacture of machine parts such as gears and bearings.
Substances obtained artificially
Synthetic macromolecular compounds are produced in various types of reactions:
- Many simple hydrocarbons such as ethylene and propylene can be converted into polymers by adding one monomer after another to the growing chain.
- Polyethylene, composed of repeating ethylene monomers, is an additive polymer. It can have up to 10,000 monomers connected in long helical chains. Polyethylene is crystalline, translucent, and thermoplastic, meaning it softens when heated. It is used for coatings, packaging, molded parts, and bottles and containers.
- Polypropylene is also crystalline and thermoplastic, but harder than polyethylene. Its molecules can consist of 50,000-200,000 monomers.
This compound is used in the textile industry and for molding.
Other additive polymers include:
- polybutadiene;
- polyisoprene;
- polychloroprene.
All are important in the production of synthetic rubbers. Some polymers, such as polystyrene, are glassy and transparent at room temperature, and are also thermoplastic:
- Polystyrene can be dyed any shade and is used in the manufacture of toys and other plasticitems.
- When one hydrogen atom in ethylene is replaced by a chlorine atom, vinyl chloride is formed.
- It polymerizes into polyvinyl chloride (PVC), a colorless, hard, rigid, thermoplastic material that can be made into many forms, including foams, films, and fibers.
- Vinyl acetate, produced by the reaction between ethylene and acetic acid, polymerizes into amorphous, soft resins used as coatings and adhesives.
- It copolymerizes with vinyl chloride to form a large family of thermoplastic materials.
A linear polymer characterized by the repetition of ester groups along the main chain is called a polyester. Open chain polyesters are colorless, crystalline, thermoplastic materials. Those synthetic macromolecular compounds that have a high molecular weight (from 10,000 to 15,000 molecules) are used in the production of films.
Rare synthetic polyamides
Polyamides include the naturally occurring casein proteins found in milk and zein found in corn, which are used to make plastics, fibers, adhesives and coatings. Worth noting:
- Synthetic polyamides include urea-formaldehyde resins, which are thermosetting. They are used to make molded objects and as adhesives and coatings for textiles and paper.
- Also important are the polyamide resins known as nylon. They aredurable, resistant to heat and abrasion, non-toxic. They can be dyed. The most famous use is as textile fibres, but they have many other uses.
Another important family of synthetic high molecular weight chemical compounds consists of linear repeats of the urethane group. Polyurethanes are used in the manufacture of elastomeric fibers known as spandex and in the manufacture of base coats.
Another class of polymers are mixed organic-inorganic compounds:
- The most important representatives of this family of polymers are silicones. High molecular weight compounds contain alternating silicon and oxygen atoms with organic groups attached to each of the silicon atoms.
- Low molecular weight silicones are oils and greases.
- Higher molecular weight species are versatile elastic materials that remain soft even at very low temperatures. They are also relatively stable at high temperatures.
Polymer can be three-dimensional, two-dimensional and single. The repeating units are often made up of carbon and hydrogen, and sometimes oxygen, nitrogen, sulfur, chlorine, fluorine, phosphorus, and silicon. To create a chain, many units are chemically linked or polymerized together, thus changing the characteristics of high molecular weight compounds.
What features do macromolecular substances have?
Most of the polymers produced are thermoplastic. Afterthe polymer is formed, it can be heated and reformed again. This property makes it easy to handle. Another group of thermosets cannot be remelted: once the polymers are formed, reheating will decompose but not melt.
Characteristics of macromolecular compounds of polymers on the example of packages:
- Can be very resistant to chemicals. Consider all cleaning fluids in your home that are packaged in plastic. Described all the consequences of contact with the eyes, but the skin. This is a dangerous category of polymers that dissolves everything.
- While solvents easily deform some plastics, other types of plastics are placed in unbreakable packaging for aggressive solvents. They are not dangerous, but can only harm humans.
- Solutions of macromolecular compounds are most often supplied in simple plastic bags to reduce the percentage of their interaction with substances inside the container.
As a general rule, polymers are very light in weight with a significant degree of strength. Consider a range of uses, from toys to the frame structure of space stations, or from thin nylon fiber in tights to Kevlar used in body armor. Some polymers float in water, others sink. Compared to the density of stone, concrete, steel, copper or aluminum, all plastics are lightweight materials.
The properties of macromolecular compounds are different:
- Polymers can serve as thermal and electrical insulators: appliances, cords, electrical outlets and wiring that is made or coated with polymeric materials.
- Heat resistant kitchen appliances with resin pot and pan handles, coffee pot handles, fridge and freezer foam, insulated cups, coolers and microwave-safe utensils.
- The thermal underwear worn by many skiers is made of polypropylene, while the fibers in winter jackets are made of acrylic and polyester.
High molecular weight compounds are substances with an unlimited range of characteristics and colors. They have many properties that can be further improved with a wide range of additives to expand their applications. Polymers can serve as the basis for imitating cotton, silk and wool, porcelain and marble, aluminum and zinc. In the food industry, they are used to give fungi edible properties. For example, expensive blue cheese. It can be eaten safely thanks to polymer processing.
Processing and application of polymer structures
Polymers can be processed in various ways:
- Extrusion allows the production of thin fibers or heavy massive tubes, films, food bottles.
- Injection molding makes it possible to create complex parts, such as large car body parts.
- Plastics can be cast into barrels or mixed with solvents to become adhesive bases or paints.
- Elastomers and some plastics are stretchable and flexible.
- Some plastics expand during processing to hold their shape, such as drinking water bottles.
- Other polymers can be foamed, such as polystyrene, polyurethane and polyethylene.
The properties of macromolecular compounds vary depending on the mechanical action and the method of obtaining the substance. This makes it possible to apply them in various industries. The main macromolecular compounds have a wider range of purposes than those that differ in special properties and methods of preparation. Universal and "whimsical" "find themselves" in the food and construction sectors:
- High molecular weight compounds are made up of oil, but not always.
- Many polymers are made from repeating units previously formed from natural gas, coal or crude oil.
- Some building materials are made from renewable materials such as polylactic acid (from corn or cellulose and cotton linters).
It is also interesting that they are almost impossible to replace:
- Polymers can be used to make items that have no other material alternatives.
- They are made into transparent waterproof films.
- PVC is used to make medical tubing and blood bags that extend the shelf life of the product and its derivatives.
- PVC safely delivers flammable oxygen to non-flammable flexible tubing.
- And an anti-thrombogenic material such as heparin can be included in the category of flexible PVC catheters.
Many medical devices focus on structural features of macromolecular compounds to ensure effective functioning.
Solutions of macromolecular substances and their properties
Because the size of the dispersed phase is difficult to measure and colloids are in the form of solutions, they sometimes identify and characterize physicochemical and transport properties.
| Colloid phase | Hard | Clean solution | Dimensional indicators |
| If the colloid consists of a solid phase dispersed in a liquid, the solid particles will not diffuse through the membrane. | Dissolved ions or molecules will diffuse through the membrane at full diffusion. | Due to size exclusion, colloidal particles cannot pass through UF membrane pores smaller than their own size. | |
| Concentration in the composition of solutions of macromolecular compounds | The exact concentration of the actual solute will depend on the experimental conditions used to separate it from the colloidal particles also dispersed in the liquid. | Depends on the response of macromolecular compounds when conducting solubility studies for easily hydrolyzed substances such as Al, Eu, Am, Cm. | The smaller the pore size of the ultrafiltration membrane, the lower the concentrationdispersed colloidal particles remaining in the ultrafiltered liquid. |
A hydrocolloid is defined as a colloidal system in which particles of macromolecular molecules are hydrophilic polymers dispersed in water.
| Water Addiction | Heat addiction | Dependence on production method |
| Hydrocolloid are colloidal particles dispersed in water. In this case, the ratio of the two components affects the form of the polymer - gel, ash, liquid state. | Hydrocolloids can be irreversible (in one state) or reversible. For example, agar, a reversible hydrocolloid of seaweed extract, can exist in a gel and solid state, or alternate between states with the addition or removal of heat. | Obtaining macromolecular compounds, like hydrocolloids, depends on natural sources. For example, agar-agar and carrageenan are extracted from seaweed, gelatin is obtained by hydrolysis of bovine and fish proteins, and pectin is extracted from citrus peels and apple pomace. |
| Gelatin desserts, made from powder, have a different hydrocolloid in their composition. He is endowed with less fluid. | Hydrocolloids are used in food mainly to affect texture or viscosity (eg sauce). However, the consistency already depends on the method of heat treatment. | Hydrocolloids-based medical dressings are used to treat skin and wounds. ATmanufacturing is based on a completely different technology, and the same polymers are used. |
Other main hydrocolloids are xanthan gum, gum arabic, guar gum, locust bean gum, cellulose derivatives such as carboxymethyl cellulose, alginate and starch.
Interaction of macromolecular substances with other particles
The following forces play an important role in the interaction of colloidal particles:
- Repulsion without regard to volume: this refers to the lack of overlap between solid particles.
- Electrostatic interaction: Colloidal particles often carry an electrical charge and therefore attract or repel each other. The charge of both the continuous and the dispersed phase, as well as the mobility of the phases, are factors that affect this interaction.
- Van der Waals forces: This is due to the interaction between two dipoles, which are either permanent or induced. Even if the particles do not have a permanent dipole, electron density fluctuations result in a temporary dipole in the particle.
- Entropy forces. According to the second law of thermodynamics, the system goes into a state in which entropy is maximized. This can lead to the creation of effective forces even between hard spheres.
- Steric forces between polymer-coated surfaces or in solutions containing a non-adsorbent analog can modulate interparticle forces, creating an additional steric repulsive force thatis predominantly entropic in nature, or a force of depletion in between.
The latter effect is being sought with specially formulated superplasticizers designed to increase the workability of concrete and reduce its water content.
Polymer crystals: where are they found, what do they look like?
High-molecular compounds include even crystals, which are included in the category of colloidal substances. This is a highly ordered array of particles that form at a very large distance (usually on the order of a few millimeters to one centimeter) and look similar to their atomic or molecular counterparts.
| Name of the transformed colloid | Ordering example | Production |
| Precious Opal | One of the best natural examples of this phenomenon is found in the pure spectral color of the stone | This is the result of close-packed niches of amorphous colloidal silicon dioxide (SiO2) spheres |
These spherical particles are deposited in highly silicic reservoirs. They form highly ordered massifs after years of sedimentation and compression under the action of hydrostatic and gravitational forces. Periodic arrays of submicrometer spherical particles provide similar interstitial void arrays that act as a natural diffraction grating for visible light waves, especially when interstitial spacing is of the same order of magnitude as the incident light wave.
Thus, it was found that due to repulsiveCoulomb interactions, electrically charged macromolecules in an aqueous medium can exhibit long-range crystal-like correlations with distances between particles often much larger than the diameter of individual particles.
In all these cases, the crystals of a natural macromolecular compound have the same brilliant iridescence (or play of colors), which can be attributed to diffraction and constructive interference of visible light waves. They satisfy Bragg's law.
A large number of experiments on the study of the so-called "colloidal crystals" arose as a result of relatively simple methods developed over the past 20 years to obtain synthetic monodisperse colloids (both polymeric and mineral). Through various mechanisms, the formation of a long-range order is realized and preserved.
Determination of molecular weight
Molecular weight is a critical property of a chemical, especially for polymers. Depending on the material of the sample, different methods are selected:
- Molecular weight as well as the molecular structure of molecules can be determined using mass spectrometry. Using the direct infusion method, samples can be injected directly into the detector to confirm the value of a known material or provide structural characterization of an unknown.
- The molecular weight information of polymers can be determined using a method such as size exclusion chromatography for viscosity and size.
- ForDetermining the molecular weight of polymers requires understanding the solubility of a given polymer.
The total mass of a compound is equal to the sum of the individual atomic masses of each atom in the molecule. The procedure is carried out according to the formula:
- Determine the molecular formula of the molecule.
- Use the periodic table to find the atomic mass of each element in a molecule.
- Multiply the atomic mass of each element by the number of atoms of that element in the molecule.
- The resulting number is represented by a subscript next to the element symbol in the molecular formula.
- Connect all the values together for every single atom in the molecule.
An example of a simple low molecular weight calculation: To find the molecular weight of NH3, the first step is to find the atomic masses of nitrogen (N) and hydrogen (H). So, H=1, 00794N=14, 0067.
Then multiply the atomic mass of each atom by the number of atoms in the compound. There is one nitrogen atom (no subscript is given for one atom). There are three hydrogen atoms, as indicated by the subscript. So:
- Molecular weight of a substance=(1 x 14.0067) + (3 x 1.00794)
- Molecular weights=14.0067 + 3.02382
- Result=17, 0305
An example of calculating the complex molecular weight Ca3(PO4)2 is more complex calculation option:
From the periodic table, the atomic masses of each element:
- Ca=40, 078.
- P=30, 973761.
- O=15.9994.
The tricky part is figuring out how much of each atom is in the compound. There are three calcium atoms, two phosphorus atoms and eight oxygen atoms. If the join part is in parentheses, multiply the subscript immediately following the element character by the subscript that closes the parentheses. So:
- Molecular weight of a substance=(40.078 x 3) + (30.97361 x 2) + (15.9994 x 8).
- Molecular weight after calculation=120, 234 + 61, 94722 + 127, 9952.
- Result=310, 18.
Complex shapes of elements are calculated by analogy. Some of them consist of hundreds of values, so automated machines are now used with a database of all g/mol values.
