Advances in Chemical Engineering and Science, 2012, 2, 435-443
http://dx.doi.org/10.4236/aces.2012.24053 Published Online October 2012 (http://www.SciRP.org/journal/aces)
Effects of Side-Chain on Conformational Characteristics of
Poly(3,5-Dimethyl-Phenyl-Acrylate) in Toluene at 40˚C
Nasrollah Hamidi1*, Stanley Ihekweazu2, Christopher A. Wiredu3, Onize H. Isa4,
Kevin Watley4, Christopher Rowe3, Briante’ Nimmons3, Alexis Prezzy4,5,
Shane Scoville4, Quentin Hills4,5, Judith Salley1
1Department of Biological and Physical Sciences, South Carolina State University, Orangeburg, SC, USA
2Department of Civil and Mechanical Engineering Technology, South Carolina State University, Orangeburg, SC, USA
3North High School, North, SC, USA
4Orangeburg Wilkinson High School, Orangeburg, SC, USA
5Claflin University, Orangeburg, SC, USA
Email: *Nhamidi@scsu.edu
Received August 11, 2012; revised September 13, 2012; accepted September 22, 2012
ABSTRACT
The intrinsic viscosity [η] of poly(3,5-dimethyl-phenyl-acrylate) (35PDMPA) solutions were evaluated throughout the
measurements of the flow times of toluene and polymer solutions by classical Huggins, and Kraemer’s methods using a
Cannon-Ubbelohde semi-micro-dilution capillary viscometer in a Cannon thermostated water bath at 40˚C ± 0.02˚C.
The values of Huggins’ constant estimated ranged from 0.2 to 0.4 which were within expectations. The intrinsic viscosities
and molecular weight relationship was established with the two-parameter classical models of Staudinger-Mark-Houwink-
Sakurada and Stockmayer-Fixman. Conformational parameter C and σ indicated 35PDMPA be semi flexible. Also, the
rigidity of 35PDMPA was confirmed by Yamakawa-Fuji wormlike theory modified by Bohdanecký. The molecular
parameters were estimated and compared. The results showed that 35PDMPA behaves like a semi-rigid polymer in
toluene at 40˚C rather than a random coil flexible macromolecule.
Keywords: Intrinsic Viscosity; Poly(3,5-Dimethyl-Phenyl-Acrylate); Conformational Parameters; Rigidity Factor;
Kuhn Statistical Length
1. Introduction
The influence of temperature and side chain groups on
the physical properties of polyethylene chains is well
documented [1]. In the case of polyacrylates, interests
have focused on the changes induced by altering the
length of alkyl ester group [2] or identity of the ester
linkage such as phenyl with alkyl substituent in various
positions [3]. One way to evaluate and analyze the prop-
erties of such polymers is at least to correlate the depend-
ence of their equilibrium configuration to their structure.
Among the methods of evaluating configurational prop-
erties are the application of matrix methods in the form
of rotational isomeric state (RIS) model to calculate
conformational properties such as Flory’s characteristic
ratio (C) [4] and or application of the wormlike model
based on Yamakawa-Fujiitheory [5] and its simplified
form byBohdanecký [6]. Neither the RIS nor the worm-
like model has been applied to evaluate the influence of
side chain on unperturbed dimensions of 35PDMPA. This
paper presents experimental findings pertaining to dilute
solution properties of 35PDMPA in toluene at 40˚C.
The intrinsic viscosity of a macromolecule in a dilute
solution is a measure of its hydrodynamic average size,
form, and shape in the solution. Many studies were found
that explored the empirical relationships between coil
dimensions of synthetic polymers with their intrinsic
viscosity [1-7]. The most frequently used relationship
between intrinsic viscosity, [η], and the weight-average
molecularmass, Mw, is the Mark-Houwink-Kuhn-Saku-
rada (MH) Equation:
w
K
M; (1)
where, the parameter α is a measure of the thermody-
namic power of solvent and Kα is a measure of coil vol-
ume for an unperturbed condition or ideal solvent called
θ-condition for random coil polymers. Numerous re-
searchers [1-8] have demonstrated the validity of the MH
equation applied to random coiled polymers for molecu-
lar weights ranging in several orders of magnitude. By
increasing thermodynamic strengths of solvents, the
magnitude of coefficient α would increase while the
magnitude of Kα would decrease. Generally, for the ran-
*Corresponding author.
C
opyright © 2012 SciRes. ACES
N. HAMIDI ET AL.
436
dom coil flexible polymer molecules, the value of α
would be between 0.50 and 0.80. For non-flexible and
rigid (worm-like or rod-like) macromolecules higher
values of α larger than or equal to unity have been ob-
served. Thus, the numerical value of α provides informa-
tion concerning polymer conformation as well.
In this work, the viscosity of 35PDMPA samples are
treated according to the Huggins’ [9] and Kraemer’s [10]
relationship to evaluate the intrinsic viscosity of the
polymer samples; the constant of each method has been
determined and related to the nature of the polymer sol-
vent system. The intrinsic viscosity, in conjunction with
the molecular mass data of 35PDMPA solutions, is
treated according to the theories of intrinsic viscosity of
random flexible and worm-like polymers developed by
Yamakawa-Fuji and simplified by Bohdanecký.
2. Experimental
2.1. Monomer
3,5-dimethyl-phenyl-acrylate (35DMPA) was obtained
by the reaction of corresponding phenol and acryloyl
chlorideat low temperature (in an ice bath)using triethyl-
amineas a base to trap HCl produced and hexanes as sol-
vent (Scheme 1). Acryloly chloride and 3,5-dimethyl-
phenol are slightly soluble in hexanes but 35DMPA is
miscible in hexanes. It was purified by re-distillation
under reduced pressure (~7 torr). The monomer was
is very
2


3
322
2012 12
0
3
322
20
12
0
3
34 2π
3
34.
2π
K
K
R
A
AC KnBMKM
M
R
KMCK nBM
M
 


 













Copyright © 2012 SciRes. ACES
N. HAMIDI ET AL. 441
y=0.173x‐ 19.77
=0.999
y=5.691E06x
2
+1.620E01x
1.564E+01
=9.992E01
20
30
80
130
180
230
280
330
05001000 1500 2000
[](cm
3
g
–1
)
Mw
1/2
Figure 5. Plot of [η] versus Mw1/2 for 35PDMPA in toluene
at 40˚C.
low such as in the case of 35PDMPA in toluene at 40˚C,
Equation (24E). In this case, the ratio
2
0
RM
is
very high which represent stiff chains. Since 35PDMPA
is composed of the unit -CH2-CHR- the backbone of the
polymer does not introduce rigidity. Then the rigidity
must be caused by the side chains effects. Hence, the
excluded-volume effect also is not negligible with the
lowest molecular weights.
As Figure 5 shows, also, the plot of [η] vs 12
Mw for
35PDMPA homologues series fits to a straight line with
r2 = 0.9986.
112
0.1729 w
2
019.663AKM
M
  (26A)
32 0.173M
2
00
, 0
KF R
(26B)
The value of Kθ calculated in this manner is only 6.4%
higher than the former polynomial adjustment. Table 4
summarizes the molecular parameters of 35PDMPA in
toluene at 40˚C. The molecular weight of the Kuhn sta-
tistical segment MK is about 15 times higher than that of
the chain repeating unit. This is an indication of chain
stiffness of the 35DMPA in toluene at 40˚C.
Most of the vinyl polymers and derivatives of poly
(acrylic acid) and poly (methacrylic acid) with various
side groups showed the proportionality of [η] and 12
M
over a broad span of molecular weights as reported in
reference [25]. However, they do not show semi-rigid
characteristics as in the case of 35PDMPA. In the case of
35PDMPA, large size side chains increases the cross-
sectional chain diameter and the orientation of side chains
produce a high impediment around the polymer chain.
To verify the value of Kθ, a plot of
12
w
M
vs
12
M
w such as shown in Figure 6 will be useful. The
intercept of the plot Kθ, = 0.170 obtained at infinite Mw.
Table 4. Characteristics parameters of 35PDMPA. Data of
other polymer also is gathering to compare PHE [25] and
PDiPF [24].
Polymer 35PDMPA PHE PDiPF
Characteristics LinealPolynom Ref 25 Ref 24
ML (cm) × 10–8 57 57 20 134
K0 (cm) 0.173 0.163 0.150 -
2
0
R
M × 1016 0.782 0.751 0.711 -
lK (cm) × 10–8 45 43 14 220
MK 2560 2456 278 29,480
Mk/M0 15 14 1 294
-A 19.77 15.64 0.000 -
-A0 2.259 1.942 0.000 -
dbr 0.120 0.179 0.540 -
db (cm) × 108 5.36 7.68 7.60 14.00
0.1
0.13
0.16
00.001 0.002 0.003 0.004
[]Mw
–1 /2
(Mw)
–1 /2
Figure 6. Plot of [η]/Mw–1/2 versus M–1/2. Extrapolation to
infant Mw gave account for Kθ,.
Kθ, is very close to the value of the slope of [η] and
12
M
02.95.36 br
w
According to the Yoshizaki-Nitta-Yamakawa theory
[23], the hydrodynamic interaction depends on the re-
duced bead diameter dbr which, in the range 0.3 dbr
0.8, is related to the A0 parameter by [33]
which is the value of K0, of Equation (26B).
A
d (27)

Table 4 shows the characteristic parameters of
35PDMPA. Also, for the sake of comparison, character-
istics parameter of a very flexible chain such as bisphe-
nol-A based poly(hydroxyethers) (PHE) from reference
[25] and an stiff polymer, Poly(disopropylfumarate),
(PDiPF) from reference [24] are sited. The high values of
lK and MK of 35PDMPA suggests a semi flexible mac-
romolecule.
3.6.2. Comments on 12
M
vs 12
M
(SF) plot [34,35]
12
w
M
Based on Equation (24), the plot of versus
Copyright © 2012 SciRes. ACES
N. HAMIDI ET AL.
442
12
M
should be linear only for long enough chains (n <
103) where the absolute value of Aη is much lower than
12
K
0w
M and the function K(nK) approaches its limit. As
Figure 4 illustrates the two low-molecular-weight sam-
ples are not met in this condition. Thus precaution is nec-
essary to evaluate dimensional parameters based on BSF.
In the case of Aη = 0, the BSF plot can be modified to
12
M
vs

12
Kn M
K which should be linear and
can be extrapolated to M = 0. This, however, is not the
case of 35PDMPA in toluene that has a negative Aη value.
If Aη is not equal to zero, both the original and modified
SF plots are non-linear as shown in Figure 4. They can
have a minimum if Aη > 0 or bend downward with de-
creasing molecular weight if Aη < 0 (such asin the case of
35PDMPA, Figure 4). In either case, the extrapolation to
M = 0 based on BSF is not justified [36].
3.7. Conclusions and Remarks
As previously mentioned, the nature of the main chain of
a 35PDMPA polymer may not contribute to the high
value of C and σ as much as the 3,5-dimethyl-phenyl
ester side chains. The 3,5-dimethyl-phenyl lateral chains
occupy a larger volume (thus posing steric hindrances)
and more importantly, they may hinder the backbone
internal rotations by establishing orientational correla-
tions between themselves. The stiffening of the polymer
chain due to the presence of large aromatic groups and
long n-alkyl pendant groups has already been reported
for some other polymers by several researchers. Also, it
is known that the interaction of elements of polymer
chains with solvent molecules could affect the probabil-
ity distribution of the angles of internal rotation in the
chain [37]. This observation was confirmed both theo-
retically and experimentally by a number of researchers
[38,39] and here is confirmed by application of wormlike
cylinder model.
The values of C of 35PDMPA (21 - 23) are much
higher than values observed for other polyacrylates. For
example, the value of C for polyphenylmethacrylate,
PPMA, both theta solvents and good solvents (12.2 and
13.3) are larger than ones for many atactic vinyl polymers,
which are in the range of 5 < C <10 usually found in the
literature. It should also be remarked that the value of C
in good solvents probably has been underestimated as
they were obtained by extrapolating to M = 0 the mo-
lecular weight region of the Stockmayer-Fixman plot in
which the effect of stiffness is coupled with excluded
volume. And, also, it is overestimated by extrapolation to
M = . However, chain rigidity may be contributing to
the slope so that the results obtained for Kθ and C could
be inaccurate. An indication that the positive slope in this
plot may include the effect of chain stiffness comes from
the convergent trend observed in the curves at high mo-
lecular weights. This leveling of the slope cannot be ac-
counted for by the theory of flexible coils perturbed by
excluded volume but has been predicted by wormlike
models of stiff chains.
The value of C of 35PDMPA (29) obtained by ex-
trapolating to M = using SFthe molecular weight region
in which the effect of excluded volume levels is much
higher than values observed for the same polymer by SF
extrapolation to M = 0. The same effect was observed for
other polymers. An example is polyphenylmethacrylate,
PPMA, both theta solvents and good solvents.
4. Acknowledgements
We appreciate the financial support of 1890 Research at
South Carolina State University, and the U.S. Air Force
Laboratory/Clarkson Aerospace/Minority Leadership Pro-
gram to financially support teachers and high school stu-
dents involved in this project. Also, many thanks to the
Department of Biological and Physical Sciences for pro-
viding lab space, materials, supplies and instrumentation
in conjunction with 1890-Reserch Grant Project SCX-
420-24-04 and the USDA Evans-Allen Research pro-
gram. Many thanks to MS. P. Laursen for the helps in
technical writings.
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