Polymers

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All about Polymers for Class XII CBSE
Ganesh Ramkumar
Mapa Mental por Ganesh Ramkumar, atualizado more than 1 year ago
Ganesh Ramkumar
Criado por Ganesh Ramkumar mais de 9 anos atrás
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Resumo de Recurso

Polymers
  1. very large molecules having high molecular mass
    1. alias MACROMOLECULES
      1. formed by joining repeating structural units
        1. These rep. str. units are derived from simple & reactive molecules called MONOMERS
          1. linked to each other by COVALENT BONDS
            1. formation of polymers from resp. monomers is called POLYMERISATION
      2. CLASSIFICATION
        1. Source
          1. Natural
            1. Semi Synthetic
              1. Synthetic
              2. Structure
                1. Linear
                  1. Cross Linked alias Network
                    1. Branched
                    2. Intermolecular Forces
                      1. Elastomers
                        1. weakest int. mol. forces
                          1. thus stretchable
                            1. have few "crosslinks" which help restore shape
                        2. Thermoplastics
                          1. int. mol. forces b/w Elastomers, Fibres
                            1. linear or slightly branched
                              1. rept.ly softens on heating, hardens on cooling
                          2. Fibres
                            1. strong int. mol. forces like H bonding
                              1. thus has close packing of chains
                                1. thread forming solids
                                  1. with high tensile strength, modulus
                                  2. hence impart crystalline nature
                              2. Thermosetting Polymers
                                1. cross linked or heavily branched
                                  1. on heating undergoes EXTENSIVE CROSSLINKING in moulds
                                    1. thus become infusible
                                      1. can't be reused
                              3. Mode of Polymerisation
                                1. Addition
                                  1. alias Chain Growth Polymerisation
                                    1. Free radical mechanism
                                      1. Chain Initiation
                                        1. a free radical from a catalyst initiates the process
                                          1. Catalysts: benzoyl or acetyl or tert - butyl peroxide
                                        2. Chain Propogation
                                          1. the radical grows bigger by reacting with unsaturated monomers
                                          2. Chain Termination
                                            1. one big radical reacts with other to form a polymer
                                              1. can have different terminations
                                            2. Ionic
                                            3. formed by rept. add. of monomers having double / triple bonds
                                              1. like alkenes, alkadienes and their derivatives
                                              2. Homopolymers
                                                1. formed from single monomeric species
                                                2. Copolymers
                                                  1. formed from two diff. monomer species
                                                  2. Important Polymers
                                                  3. Condensation
                                                    1. rep. condensation b/w two diff. bifunctional or trifunctional monomers
                                                      1. elimination of small molecules like water, -OH, HCl takes place
                                                        1. alias Step Growth Polymerisation
                                                          1. product of each step is again bifunctional
                                                            1. CLASSIFICATION based on linkages
                                                              1. amide linkages
                                                                1. es

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