Chemistry Reference
In-Depth Information
The dependence tgd (
D
ch
), obtained for the considered copolymers at two
dence exists within the clearly determined limits. At
D
ch
= 1.0 it tries to attain
tgd = 0, that was to be expected from the made above assumptions. At
D
ch
=
2.0 the value tgd is approximately equal to its maximum value. Therefore,
the linear dependence tgd(
D
ch
) can be used for this parameter prediction in
different
D
ch
ranges.
Similar linear dependences for SP - OPD with various
C
form
were ob-
tained in Ref. [7] and they testify to molecular mobility level reduction at
d
f
decrease and extrapolate to various (nonintegral)
d
f
values at
D
ch
= 1.0.
The comparison of these data with the Eq. (1.5) appreciation shows, that
D
ch
reduction is due to local order level enhancement and the condition
D
ch
= 1.0 is realized at
d
f
values, differing from 2.0 (as it was supposed earlier
in Ref. [23]). This is defined by polymers structure quasiequilibrium state
achievement, which can be described as follows [24]. Actually, tendency of
thermodynamically nonequilibrium solid body, which is a glassy polymer, to
equilibrium state is classified within the frameworks of cluster model as lo-
cal order level enhancement or j
cl
increase [24-26]. However, this tendency
is balanced by entropic essence straightening and tauting effect of polymeric
medium macromolecules, that makes impossible the condition j
cl
= 1.0 at-
tainment. At fully tauted macromolecular chains (
D
ch
= 1.0) j
cl
increase is
ceased and polymer structure achieves its quasiequilibrium state at
d
f
vari-
ous values depending on copolymer type, that is defined by their macromol-
ecules different flexibility, characterized by parameter
C
∞
.
Let us consider within the frameworks of irreversible aggregation mod-
el one more possible interpretation of polymers structure features - the so
called diffusion-limited aggregation (DLA) [27, 28].
According to the Ref. [29] for DLA the value
d
f
≈ 2.5. The spatial distri-
bution of DLA elements (in our case - statistical segments) can be character-
ized with the aid of two dimensions:
d
f
and chemical dimension
d
l
, which are
defined as follows:
,
(2.6)
d
N
~
r
f
,
(2.7)
d
N
~
l
l
where
N
is particles number in cluster between two arbitrary points of clus-
ter,
r
and
l
are distances between these points [30]. The value
r
is the piece
length, connecting these points and
l
is defined as the shortest way over
