Chemistry Reference
In-Depth Information
to crystallites with stretched chains (СSС). Such entanglements node pos-
sesses large enough functionality
F
(under node functionality emerging from
it chains number is assumed [29] and it was called cluster. Cluster consists of
different macromolecules segments and each such segment length is postu-
lated equal to statistical segment length
l
st
(“stiffness part” of chain [30]). In
that case the effective (real) molecular weight of chain part between clusters
ef
cl
M
can be calculated as follows [29]:
MF
ef
M
=
cl
,
(1.6)
cl
2
where
M
cl
is molecular weight of the chain part between clusters, calculated
according to the Eq. (1.4).
It is obvious, that at large enough
F
the reasonable values
ef
c
M
, sat-
isfied to Gaussian statistics requirements, can be obtained. Further on for
parameters of entanglements cluster network and macromolecular binary
hooking's network distinction we will used the indices “cl” and “e,” accord-
ingly. Therefore, the offered in Ref. [28] model assumes, that amorphous
polymer structure represents itself local order regions (domains), consisting
of different macromolecules collinear densely packed segments (clusters),
immersed in loosely packed matrix. Simultaneously clusters play the role of
physical entanglements network multifunctional nodes. The value
F
(within
the frameworks of high-elasticity theory) can be estimated as follows [31]:
2
G
F
=
∞
+
2
,
(1.7)
kT
n
cl
where
G
∞
is equilibrium shear modulus,
k
is Boltzmann constant, n
cl
is clus-
ter network density.
(PAr) are adduced. These dependences show n
cl
reduction at
T
growth, that
assumes local order regions (clusters) thermofluctuational nature. Besides,
on the indicated dependences two characteristic temperatures are found eas-
ily. The first from them, glass transition temperature
T
g
, defines clusters full
n
cl
(
T
) and settles down on about 50 K lower
T
g
.
