高分子化学课件

5) The conversion of monomer does not increase with
the reaction time in the polycondensation reactions.
Essentially, the key of polycondensation is the reactions between the function groups. Only with the efficient reaction, the macromolecules can be prepared.
• Great Industrial Value
Examples
Polyester Linear saturated polyester: plasticizer, Linear unsaturated polyester: glass fiber laminate, casting resin, solventless lacquer Network polyester: surface coating
Polymer
Key of Polycondensation – Functionality
functional group：an atomic group in the monomer which participates in reaction in an indicated way.
e.g.： －COOH，－OH，－NH2，－Cl，－NCO， －COOR ， －CHO ，－SO3H
Classification 2
By the reaction mechanism Step-Growth Polymerization Chain Polymerization
Step-Growth Polymerization
－ the middle products can be separated out － the separated middle products can react furthermore
tetramer + monomer
tetramer + tetramer etc.
general reaction： naRa + nbR’b a[R－R’]nb + (2n－1)ab
a，b－ functional group； R’，R－construction unit； ab－ micromolecule
Functionality ( f ) ：
the number of functional groups in the molecule which take part in the reaction. (monomer,oligomer).
How do the functionality influence the polycondensation ? Type 1：System of f = 1，1 CH3COOH+HOC2H5 RCOOH + R’NH2 CH3COOC2H5 + H2O RCONHR’ +H2O
By
monomer ; structure of polymer; thermodynamics
1. By monomer
(1) homogeneous polycondensation, f = 2
a single monomer which two types of func-
tional groups
Most of the Polycondensation reactions are the typical Step-Growth Polymerization.
Polycondensation reactions are taken as examples to illustrate the Step-Growth Polymerization.
Practically, polycondensation should be described by the extent of reaction. (Notes: conversion for the chain polymerization. Chapter 3)
Classifications of Polycondensation
Polycondensation Polycondensation is the abbreviation of condensation polymerization.
many times of repeated condensation
Monomers with functional group
example： polycondensation of amino acids
n H2N －R － COOH → [NH－R － CO]n + (n－1)H2O
(2) mixed polycondensation, f = 2,2
Two kinds of bifunctional monomers. Only one type of functional group in each monomer. Example: diamine / diacid, dihydric alcohol / diacid
According to the active center ： Free Radical Polymerization Cationic Polymerization Anionic Polymerization Coordination Polymerization
Why do we study the Step-Growth Polymerization ?
These reactions involve two different functional groups. One type of the functional group in each monomer.

Forming linear polycondensation polymer
Type 3
Chapter 2
Step-Growth Polymerization
Part 1 An Introduction to Polycondensation
How to Prepare Polymer ?
One way is from monomer Suitable Monomer & Suitable method (polymerization) Another way is from a given polymer
Polymerization ?
The reaction from monomer to polymer
Classification 1
By the change of Composite and Structure between monomer and polymer Polycondensation Adduct polymerization
Adduct polymerization
① No low molecular weight material is produced. The composition of the newly produced material is the same as the monomer.
② There are only reactions between increasing chains and the monomers
Systems of f = 2，2
monomer + monomer dimer + monomer dimer + dimer dimer trimer tetramer
trimer +
tetramer + tetramer +
dimer
dimer trimer
pentamer
pentamer hexamer heptamer octamer
Type 4
systems of f = 2,3；2,4；3,3
Systems of f = 2,3；2,4；3,3 can produce cross linking Polymers.
Summary
1) monomer’s f ≥2； 2) Changeable factors : functional groups (－OH,－COOH,－COOR, －Cl,－NH2，……), f (linear or cross linking polycindensation) R, and R’ Huge sorts of polycondensation polymers 3) The polycondensation polymers are usually the heterochain polymers with N,O,S,P in the backbone and the functional groups in the end. eg.－O－,－CONH－,－COO－etc
What’s the Polycondensation ?
Condensation
A reaction between two different functional groups, losing a molecule
Besides main product, there is a byproduct.
Industrially, polycondensation can be divided into many types according to the group in the polymer chain. polyester, polyamide, polyether reaction