1. ~CH2CHCH2CHCH2CHCH2CHCH2CHCH2CH~
CONCEPTUAL EXAMPLE 10.1
Repeat Units in Polymers
What is the repeat unit in polyvinylidene chloride? A segment of the polymer is represented as
H Cl H Cl H Cl
~C C C C C C~
H Cl H Cl H Cl
Solution
The repeat unit is
H Cl
C C
Joining three of these units forms the segment shown; joining hundreds of the units would form a molecule of the polymer.
What is the repeat unit in polyacrylonitrile? A segment of the polymer is represented as
~CH2CHCH2CHCH2CHCH2CHCH2CHCH2CH~
CN CN CN CN CN CN
Exercise 10.1

2. Structures of Polymers
EXAMPLE 10.2
Structures of Polymers
Give the structure of the polymer made from vinyl fluoride (CH2 CHF). Show at least four repeat units.
Solution
The carbon atoms become bonded in a chain with only single bonds between the carbon atoms. The fluorine atom is a substituent on the chain. (Two of the electrons in the double bond of the monomer are used to join the units.) The polymer is
~CH2CHCH2CHCH2CHCH2CH~
F F F F
Give the structure of the polymer made from methyl vinyl ether (CH CHOCH3). Show at least four
repeat units.
Exercise 10.2A
Give the structure of the polymer made from vinyl acetate (CH CHOCOCH3). Show at least four repeat units.
Exercise 10.2B

3. Condensed Structural Formulas for Polymers
EXAMPLE 10.3
Condensed Structural Formulas for Polymers
Write the condensed structural formula for the polymer formed from dimethylsilanol, (CH3)2Si2(OH)2.
Solution
Let’s start by writing out the structural formula of the monomer.
CH3
HO Si OH
Because there are no double bonds in this molecule, we do not expect addition polymerization. Rather, we expect a condensation reaction in which an OH group of one molecule and an H atom of another combine to form a molecule of water. Moreover, because there are two OH groups per molecule, each monomer can form bonds with the neighbors on both sides. This is a key requirement for polymerization. We can represent the reaction as follows.
CH3 CH3 CH3 CH3
HO Si OH + HO Si OH + HO Si OH + • • •  Si O n H2O
CH3 CH3 CH3 CH3 n

4. Condensed Structural Formulas for Polymers continued
EXAMPLE 10.03
Condensed Structural Formulas for Polymers continued
(a) Write the structural formula for the polymer formed from 3-hydroxypropanoic acid (HOCH2CH2COOH), showing at least four repeat units.
(b) Write a condensed structural formula in which the repeat unit is shown in
brackets.
Exercise 10.3