Report On Polymer With Types, Properties, Character, Synthesis And Chain - Pharmacy Polymer Project Report
A polymer is a large molecule (macromolecule) composed of repeating structural units. These subunits are typically connected by covalent chemical. Although the term polymer is sometimes taken to refer to plastics, it actually encompasses a large class comprising both natural and synthetic materials with a wide variety of properties.
Because of the extraordinary range of properties of polymeric materials, they play an essential and ubiquitous role in everyday life. This role ranges from familiar synthetic plastics and elastomers to natural biopolymers such as nucleic acids and proteins that are essential for life.
Polymer Figure Shown:
TYPES OF POLYMERS:1) Natural and synthetic polymers:
Depending on their origin, it is possible to grow polymers as natural or synthetic
(A) Natural polymers:These are the polymers which are isolated from natural materials and also known as biological polymers. Eg; rubber, wool, cellulose, starch, acacia, pectin, chitosan, agar, veegum, gellan gum and proteins.
(B) Synthetic polymers: These are the polymers which are synthesized from low molecular weight compounds. TypicalEg:- polyethylene, PVC, nylon and terylene
2) Organic and inorganic polymers:
A) Organic polymers: An organic polymer may be defined as a polymer whose backbone chain is essentially made of carbon atoms. However the atoms are attached to the valencies of backbone carbon atoms include hydrogen, oxygen, nitrogen, sulphur, etc.
B) Inorganic polymers: An inorganic polymers may be defined as a polymer whose backbone chain is not having carbon atom. Egare : glass, silicon, rubber, etc.
PROPERTIES OF POLYMER:
• Molecular weight and molecular distribution
• Polymer hydrophobicity
• Glass transition temperature
• Crystallity
Characters of Polymer:
• Inert and compatible with the environment
• Non –toxic
• Easily administered
• Easy and inexpensive to fabricate
• Good mechanical strength
Poymer Synthesis:
Polymerization is the process of combining many small molecules known as monomers into a contently bonded chain. During the polymerization process, some chemical groups may be lost from each monomer. This is the case, for example, in the polymerization of PET polyester. The monomers are terephthalic acid (HOOC-C6H4-COOH) and ethylene glycol (HO-CH2-CH2-OH) but the repeating unit is -OC-C6H4-COO-CH2-CH2-O-, which corresponds to the combination of the two monomers with the loss of two water molecules. The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue.
Figure: The repeating unit of the polymer polypropylene
Chain length:
The physical properties of a polymer are strongly dependent on the size or length of the polymer chain. For example, as chain length is increased, melting and boiling temperatures increase quickly. Impact resistance also tends to increase with chain length, as does the viscosity, or resistance to flow, of the polymer in its melt state. Chain length is related to melt viscosity roughly as 1:10, so that a tenfold increase in polymer chain length results in a viscosity increase of over 1000 times. Increasing chain length furthermore tends to decrease chain mobility, increase strength and toughness, and increase the glass transition temperature (Tg). This is a result of the increase in chain interactions such as Van der Waals attractions and entanglements that come with increased chain length. These interactions tend to fix the individual chains more strongly in position and resist deformations and matrix breakup, both at higher stresses andhigher temperatures.
A common means of expressing the length of a chain is the degree of polymerization, which quantifies the number of monomers incorporated into the chain. As with other molecules, a polymer's size may also be expressed in terms of molecular weight. Since synthetic polymerization techniques typically yield a polymer product including a range of molecular weights, the weight is often expressed statistically to describe the distribution of chain lengths present in the same. Common examples are the number average molecular weight and weight average molecular weight. The ratio of these two values is the polydispersity index, commonly used to express the "width" of the molecular weight distribution. A final measurement is contour length, which can be understood as the length of the chain backbone in its fully extended state.The flexibility of an unbranched chain polymer is characterized by its persistence length.
Monomer arrangement in copolymers
Monomers within a copolymer may be organized along the backbone in a variety of ways
• Alternating copolymers possess regularly alternating monomer residues:[AB...]n
• Periodic copolymers have monomer residue types arranged in a repeating sequence: [AnBm...] m being different from n .
• Statistical copolymers have monomer residues arranged according to a known statistical rule. A statistical copolymer in which the probability of finding a particular type of monomer residue at a particular point in the chain is independent of the types of surrounding monomer residue may be referred to as a truly random copolymer.
• Block copolymers have two or more homopolymersubunits linked by covalent bonds Polymers with two or three blocks of two distinct chemical species (e.g., A and B) are called diblock copolymers and triblock copolymers, respectively. Polymers with three blocks, each of a different chemical species (e.g., A, B, and C) are termed triblockterpolymers.
• Graft or grafted copolymers contain side chains that have a different composition or configuration than the main chain.