Chemistry Reference
In-Depth Information
2-4 Calculate M
n
and M
w
for a sample of polystyrene with the following com-
position (i
5
degree of polymerization; % is by weight). Calculate the vari-
ance of the number distribution of molecular weights.
i
20
25
30
35
40
45
50
60
80
.80
wt%
30
20
15
11
8
6
4
3
3
0
2-5 What value would M
z
have for a polymer sample for which M
v
5
M
n
?
2-6 Given that homopolymers formed by the following monomers (a
e)
have the following molecular mass distribution:
w
M
i
i
0.05
10,000
0.25
50,000
0.20
80,000
0.20
100,000
0.15
150,000
0.10
200,000
0.05
500,000
(a) CH
2
5
CH(CH
3
)
(b) CH
2
5
CHCl
(c) CF
2
5
CF
2
(d) CH
2
5
CH(OH)
CH
2
Calculate the number average molecular weight M
n
[10 marks] and the
corresponding degree of polymerization of each polymer.
(e) CH
2
5
2-7
If 200 g of polymer A, 300 g of polymer B, 500 g polymer C, and 100 g
of polymer D are mixed, calculate both M
n
and M
w
of the blend.
Polymer A M
n
5
45,000; M
w
5
65,000
Polymer B M
n
5
100,000; M
w
5
200,000
Polymer C M
n
5
80,000; M
w
5
85,000
Polymer D M
n
5
900,000
What are the polydispersity index and the standard deviation of the
number distribution of molecular weight of the mixture?
300,000; M
w
5
2-8 The measured diameters of a series of spherical particles are shown as follows:
Number of particles
Diameter (mm)
1000
2.5
1800
3.0
1700
3.2
1500
3.5
