Polymer:- May be defined as the high molecular weight compound, formed by using monomers. Therefore polymer possesses specific structural units (i.e. monomers), repenting several times.
Monomer: May be defined as the low molecular weight chemical substance possesses multiple bonds as reactive sites.The Chemical conversion process of monomers into polymer is known as polymerization reaction. Monomer must possess multiple bonds as reactive sites.
1) Hydrocarbon monomers:-
Hydrocarbon monomers contain only hydrogen & carbon elements in their structure. Hydrocarbon monomers contain C = C, this pi-bond can be broken easily homolytically or heterolytically by the use of heat, light, free radicals or by cat ions, anions. E.g.:- ethylene can form polymer in such way- nCH2 = CH2 ethylene – polymerization → (-CH2-CH2-CH2-CH2-)n-
2)What is co-polymer? -- i. When two or more different types of monomers arc used in making a polymer, the polymer is known as co-polymer. II. Homopolymer is the polymer consists of one type of monomer only, iii. Co-polymerization has unique importance in the industry. Beez product formed by copolymerization possesses specific properties. iv. Properties of copolymer depend on the chemical nature of monomers, relative amount of monomers & arrangement of the monomers. E.g. useful commercial polymer : Butadiene + styrene
vi) In copolymerization different monomers can be arranged in four ways: a)Alternating -c-d-c-d-c-d-c-d-c-d-c-d b) Random -d-d-d-c-c-d-d-c-d- c) Block -c-c-c-c-c-d-d-d-d-d-c-c-c-c-c-c d) Graft -c-c-c-c-c-c-c-c-c
3) Weight average molecular weight (Mn) — 3
- Molecular weight of the polymer decides the properties of that polymer; therefore molecular is important factor to understand the quality of polymer.
- Let polymer bulk comprises of N number of polymer molecule of which N1 molecule have molecular weight M1 , N2 molecule have molecular weight M2 & N3 molecules have molecular weight M3 ------ & so on.
- Then total number of molecules--- Numbers of fractions of N I species
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