Membrane Gas Separation

3.3
Results and Discussion 
3.3.1
Physical Properties 
Some physical properties of PTMSN are presented in Table 3.2 . This is an amorphous 
glassy polymer with very high T
g
. Its glass transition is very close to the decomposition 
temperature and can be discerned only by accurate analysis of the TGA curves. Its 
mechanical properties are rather modest, though suffi cient for preparation of stable fi lms 
if the molecular mass of the sample is 400 000 Da or higher.
The density of PTMSN is relatively small, which results in a high value of the fractional 
free volume (FFV) according to Bondi, as will be discussed in more detail later.
3.3.2
Gas Permeability 
A feature of PTMSN is a relatively high gas permeability coeffi cient P , higher than those 
of other addition - type polynorbornenes and comparable with permeability coeffi cients of 

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46
Membrane Gas Separation
Table 3.2  Physical properties of PTMSN
Parameter
Method
Value
Crystallinity
WAXD (Rigaku)
None
Density  
ρ
  , g/cm 
3
Geometric density
0.883
±
0.001
FFV, %
Bondy method
27.5
T
g
, ° C
TMA - 7 (Perkin - Elmer)
293 – 303
T
dec
, ° C (5%)
TGA - 7 (Perkin - Elmer)
In air
330
In Ar
420
Strain strength, MPa
INSTRON - 2111
16.1
Elongation at break, %
INSTRON - 2111
4.1
Table 3.3  Permeability coeffi cients (P, Barrer) of PTMSN and other addition - type 
polynorbornenes (Ni catalysts were used) 
Side group R
He
H 
2
O 
2
N 
2
CO 
2
CH 
4
Ref.
Si(CH 
3
) 
3
840
1800
980
390
4480
990
This work
H
29.4
42
6.9
1.5
34
2.6
This work
CH 
3
88.8
–
–
4.3
81.1
5.6
[9]
CH 
3
*
174
–
–
12.6
202.1
16.9
[9]
* Pd catalyst was used.
Table 3.4  Separation factors
α
(M 
1
 /M 
2
 ) = P (M 
1
 )/ P (M 
2
 ) for some gas pairs 
M 
1
/M 
2
PTMSN
PTMSP [20]
AF2400 [21]
O 
2
/N 
2
2.6
1.7
2.0
H 
2
/N 
2
5.7
2.9
4.3
CO 
2
/N 
2
14.6
10.5
4.7
CO 
2
/CH 
4
5.5
4.4
6.0
PTMP, poly(trimethylsilylpropyne); AF2400, random copolymer of 87 mol% 2.2bis(trifl uoromethyl) - 4,5 - difl uoro - 
1,3 - dioxole and 13 mol% tetrafl uoroethylene.
polyacetylenes and amorphous Tefl ons AF [19] , that is, it is a new member of the family 
of high permeability, high free volume glassy polymers. By the P values it is similar to 
the ‘ polymer of intrinsic microporosity ’ , PIM - 1 (see Chapter 2 by P. M. Budd et al. in 
this book). Table 3.3 presents a survey of permeability coeffi cients of PTMSN, where 
they are compared with those of other addition - type norbornene polymers.
The high permeability of PTMSN is due to the two design peculiarities: the bulkiness 
of the Si(CH 
3
) 
3
group and the rigid character of the main chain (see Tables 3.1 and 3.3 ). 
It can also be concluded that PTMSN is much more permeable that its isomer, ROMP 
polymer containing Si(CH 
3
) 
3
group [17] . It can be noted that these differences are much 
less marked for non - substituted polynorbornenes of addition and ROMP types. 
Permselectivity or separation factors