Journal of Biomaterials and Nanobiotechnology, 2011, 2, 114-124
doi:10.4236/jbnb.2011.22015 Published Online April 2011 (
Copyright © 2011 SciRes. JBNB
Surface Properties and Compatibility with Blood
of New Quaternized Polysulfones
Raluca Marinica Albu, Ecaterina Avram, Iuliana Stoica, Emil Ghiocel Ioanid,
Dumitru Popovici, Silvia Ioan
Institute of Macromolecular Chemistry, Iasi, Romania.
Received January 13th, 2011; revised January 16th, 2011; accepted January 21st, 2011.
The paper describes some properties of new quaternized polysulfones obtained by quaternization of chloromethylated
polysulfone with different tertiary amines-N,N-dimethylethylamine and N,N-dimethyloctylamine. Hydrophilic/hydropho-
bic properties, morphological aspects and interface properties with red blood cells and platelets are affected by the
alkyl radicals and by history of the formed films from solutions in N,N-dimethylformamide/methanol and N,N-dimethyl-
formamide/water solvent/nonsolvent mixtures. The results obtained are useful in biomedical applications, including
evaluation of bacterial adhesion to the surfaces, or utilization of modified polysulfones as semipermeable membranes.
Keywords: Quaternized Po lysulfones, Surface Properties, Blood Compatibility
In recent decades, considerable attention has been de-
voted to the investigation of new applications of poly-
sulfones, and also, of chloromethylated and quaternized
polysulfones, which was mainly due to their specific
properties. Literature showed that polysulfones and their
derivatives were widely used as new functional materials
in biochemical, industrial and medical fields, due to their
structure and physical characteristics, such as good opti-
cal properties, high thermal and chemical stability, me-
chanical strength, resistance to extreme pH values and
low creep [1-4]. Chain rigidity is derived from the rela-
tively inflexible and immobile phenyl and SO2 groups,
while toughness - from the connecting ether oxygen [4].
The polysulfone can be modified to improve its per-
formance for specific applications [4,5], by chloro-
methylation, a reaction of considerab le interest from both
theoretical and practical points of view, such as obtaining
of precursors for functional membranes, coatings, ion
exchange resins, ion exchange fibers and selectively
permeable membranes [6,7]. Also, quaternization with
ammonium groups is an efficient method to obtain some
properties recommended in various applications, e.g. as
biomaterials and semipermeable membranes. These
groups can modify hydrophilicity (of special interest for
biomedical applications) [8], the antimicrobial action
[9,10], solubility characteristics [11,12], allowing water
permeability and separation [13,14]. In addition, the
functional groups are an intrinsic requirement for affinity,
ion exchange and other specialy membranes [15]. More-
over, the bioapplication of polysulfones can be divided in
two categories, namely blood contacting devices – for
example, hemodialysis, hemodiafiltration and hemofil-
tration as membrane, and cell or tissue contacting devices
for example, bioreactor made by hollow fibre membrane,
nerve generation through polysulfone semipermeable
hollow membrane, et c [5].
In previous publications, the synthesis [16-18] and
some solution properties [11,19-23] of modified polysul-
fones have been presented. Studies have been carried out
on the quaternization reaction of chloromethylated poly-
sulfones, for obtaining water soluble polymers with
various amounts of ionic chlorine. The conformational
behavior in solution and the experimental and theoretical
results on the preferential adsorption coefficients versus
solvent composition have been discussed in correlation
with the interaction parameters of quaternized polysul-
fones/mixed solvents [10,20,23]. Surface wettability and
hydrophilicity trends, as well as the morphological char-
acteristics of some modified polysulfones were also ana-
lyzed, for biomaterials and semipermeable membrane
applications [10,12,22,24]. On the other hand, it is well-
known that surface-induced blood coagulation is one of
the main problems in the development of blood- contact-
ing materials. From a clinical point of view, literature
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones 115
shows that a biomaterial can be considered as hemo-
compatible only when its interaction with blood does no t
provoke da mage of blood cells or chang e in the structure
of plasma proteins [25-27]. The surface free energy of
biomaterials and the corresponding values of the work of
spreading can be used as characterization parameters for
predicting cell spreading onto their surfaces and hence,
for establishing their blood compatibilit y.
The objective of the present study was to investigate
the morphological characteristics of quaternized poly-
sulfones obtained from chloromethylated polysulfones
with tertiary amines, N,N-dimethylethylamine and N,
N-dimethyl-octylamine. The corresponding films, ob-
tained from solutions in N,N-dimethylformamide (DMF)
/methanol (MeOH) and DMF/water mixtures, were ana-
lyzed by atomic force microscopy, to emphasize the in-
fluence of casting solutions on the morphological proper-
ties. The results were correlated with the hydrophilic/
hydrophobic properties and red blood cells and platelets
compatibility. Influence of the alkyl radical sizes from
the side groups was evidenced comparatively with the
modified polysulfones with N-dimethyloc-tylammonium
chloride pendant groups [27]. In this context, such inves-
tigations were discussed in correlation with the comput-
erized chemical structure, which provides a generalized
view on the chemical conformations of the repeating
units, realized by the HyperChem professional program
(Demo version). This representation helps to identify
aspects of molecular structure which may be relevant to
the structure-property problem here under consideration,
blood compatibility inclu ded.
2. Materials and Methods
2.1. Materials
UDEL-3500 polysulfone (PSF) (Union Carbide, Mn =
39000; Mw/Mn = 1.625), a commercial p roduct, was puri-
fied by repeated reprecipitations from chloroform and
dried for 24 h in vacuum, at 40˚C, before being used in
the synthesis of chloromethylated polysulfon e. A mixture
of commercial paraformaldehyde with an equimolar
amount of chlorotrimethylsilane (Me3SiCl) as a chloro-
methylation agent, and stannic tetrachloride (SnCl4) as a
catalyst, was used for the chloromethylation reaction of
polysulfone, at 50˚C. The reaction time necessary to ob-
tain chloromethylated polysulfones with 6.58% chlorine
content (CMPSF) was 72 h [7]. Finally, the samples were
dried under vacuum at 40˚C.
Polysulfones with different alkyl side groups, PSF-
DMEA and PSF-DMOA, were synthesized by reacting
chloromethylated polysulfone with different tertiary
amines-N,N-dimethylethylamine (DMEA) and N, N-
dimethyloctylamine (DMOA), respectively. The quarter-
nization reaction was performed in DMF, using a CMPSF/
tertiary amine molar ratio of 1:1.5, for 24 h. The quater-
nary polymers were isolated from the reaction medium
by precipitation in diethylether, washed three times with
diethylether, and dried for 48 h under vacuum, at room
temperature. The contents of ionic chlorine of 2.89 and
3.23, and total chlorine of 3.10 and 3.29 for PSF- DMEA
and PSF-DMOA, respectively, were determined b y S cho n-
inger’s method followed by potentiometric titration with
AgNO3, using an automatic TitraLab Radiometer 840.
The ratios between ionic chlorine and the total chlo-
rine contents show that the quaternization reaction of
CMPSF occurs at a transformation degree close to 98%.
Thus, one may consider that almost all chloromethylenic
groups were quaternized. Scheme 1 presents the general
chemical structures and conformational structures - ob-
tained by a computerized method using the HyperChem
professional program (Demo version) considering four
structural units, of PSF-DMEA and PSF-DMOA.
2.2. Contact Angle
Contact angle analysis for surface tension investigations
and atomic force microscopy (AFM) measurements were
realized on quaternized polysulfones films. PSF-DMEA
and PSF-DMOA were dissolved in DMF, DMF/MeOH
(over the 75/25% - 25/75% v/v and 75/25% - 45/55% v/v
composition range, respectively), and DMF/Water (over
the 75/25% - 40/60% v/v and 75/25% - 50/50% v/v
composition range, respectively), to reach the concentra-
tions of approximatively 7 g/dL. The solutions were cast
on a glass plate and initially solidified by slow drying in
saturated atmosphere with the used solvent, and finally
by drying at 50˚C under vacuum. Uniform drops of the
test liquid were deposited on the film surface and
the contact angles were measured after 30 s, with a vid-
eo-based optical contact angle measuring device, in a
temperature of 25˚C. The used test liquids are water,
methylene iodide (CH2I2), and 1-brom-naphtalin (1-Bn).
2.3. Atomic Force Microscopy
Atomic force microscopy (AFM) measurements were
performed in air, at room temperature (23˚C), in the tap-
ping mode using a Scanning Probe Microscope (Solver
PRO-M, NT-MDT, Russia) with commercially available
NSGI0 cantilevers. The manufactu re’s value for the p rob e
tip radius was l0 nm and for the typical force constant
was 11.5 N/m. In the tapping mode, the cantilever was
oscillated at a frequency of 286 kHz, over a 20 × 20 µm2
scan area for each sample.
3. Results and Discussion
3.1. Surface Tension Parameters
The geometric mean method (GM ) (Equati ons (1) and (2))
opyright © 2011 SciRes. JBNB
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones
Copyright © 2011 SciRes. JBNB
Scheme 1. Chemical structures and conformational structures with minimized energies, considering four repeating units of
polysulfones with quaternary groups.
[28,29] and the acid/base method (LW/AB) (equation (3)
and (4) [30,31] were utilized for calculating the surface
tension parameters of PSF-DMEA and PSF-DMOA, with
surface properties of test liquids [32] from Table 1, and
the contact angles measured between these solvents and
quaternized polysulfone films from Table 2. The contact
angles between these solvents and PSF-DMOA films are
presented in previous paper [27] .
lv lv
 (1)
 (2)
is the contact angle determined for test liquids,
subscripts “lv” and “sv” denote the liquid-vapor and sur-
face-vapor interfacial tension, respectively, while super-
scripts “p” and “d” denote the polar and disperse com-
ponents, respectively, of total surface tension,
1cos LW LW
v lvsvlvsvlv
 
 
  (3)
 (4)
where 2
 , superscript “LW/AB” indi-
cates the total surface tension, and also , superscript “AB
and “LW” represent the polar component obtained from
the electron-donor,
, and the electron-acceptor,
interactions, and the disperse component, respectively.
Table 3 shows the results for the surface tension com-
ponents, evaluated with both methods. The surface ten-
sion parameters are influenced by the solvent/nonsolvent
composition from which the films had been prepared.
Some studies have reported that the chain shape of a po-
lymer in solution could affect the morphology of the po-
lymer in bulk. In this context, the conformations of both
PSF-DMEA and PSF-DMOA are affected by the charged
groups from different alkyl radicals of the studied qua-
ternized samples, and also by the compositition of the
solvent mixtures. Thus, Figure 1 depicts the variation of
intrinsic viscosity with the volume fraction of DMF, in
DMF/MeOH and DMF/water mixtures, for PSF-DMEA
Table 1. Surface tension parameters (mN/m) of the liquids
used for contact angle measurements, red blood cells and
Liquid lv
Water [32] 72.80 21.80 51.00 25.5025.50
Methylene iodide
(CH2I2) [32] 50.80 50.80 0 0.720
(1-Bn) [32] 44.40 44.40 0 0 0
Red blood cell [35]36.56 35.20 1.36 0.0146.2
Platelet [35] 118.2499.14 19.10 12.267.44
Table 2. Contact angle (°) of different liquids on films pre-
pared from solutions of PSF-DMEA in DMF/MeOH and
DMF/water (% v/v) (column 1).
Contact angle
Solvent mixtures W MI 1-Bn
100/0 DMF/MeOH 71 28 17
75/25 DMF/MeOH 70 31 22
50/50 DMF/MeOH 61 30 20
25/75 DMF/MeOH 63 31 24
75/25 DMF/water 59 35 21
50/50 DMF/water 60 33 18
40/60 DMF/water 56 33 16
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones 117
Table 3. Surface tension parameters (mN/m) and contribution of the polar component to the total surface tension (%) for
quaternized polysulfone films PSF-DMEA and PSF-DMOA prepared from solutions in DMF/MeOH and DMF/water (v/v %),
according to the geometrical mean method and the acid/base method (equations (1) - (4)).
Geometrical mean method Acid/base method
Solvent mixtures d
sv sv
100/0 43.7 5.9 49.7 11.9 42.5 3.6 2.6 6.2 48.7 12.6
75/25 42.5 6.6 49.2 13.5 41.3 4.3 2.8 6.9 48.1 14.3
50/50 42.9 10.7 53.7 20.0 41.8 9.9 2.5 9.9 51.7 19.2
25/75 42.1 10.0 52.1 19.1 40.6 6.5 4.1 10.4 51.0 20.4
75/25 41.8 12.2 54.0 22.7 41.5 21.4 0.1 3.18 44.68 7.1
50/50 42.6 11.4 54.0 21.1 42.3 19.0 0.2 3.83 46.08 8.3
40/60 42.8 13.4 56.3 23.9 42.7 25.4 0.2 4.15 46.85 8.9
100/0 40.9 5.1 46.0 11.0 42.4 0.4 1.4 1.5 43.9 3.4
75/25 39.6 3.0 42.6 6.9 42.7 0.2 0.8 0.8 43.5 1.8
50/50 43.6 1.9 45.2 4.1 43.1 1.5 2.0 1.8 44.9 3.9
45/55 39.1 3.6 42.7 8.5 41.3 1.0 0.5 1.4 42.7 3.3
PSF-DMOA, DMF/water [27]
75/25 38.4 7.5 46.0 16.4 41.4 0.5 1.2 1.5 42.9 3.5
60.40 38.5 8.6 47.1 18.3 40.2 0.8 3.5 3.3 43.6 7.6
50/50 41.4 5.9 47.4 12.5 42.8 0.5 1.3 1.6 44.4 3.6
Figure 1. Influence of DMF volume fraction, , on intrinsic viscosity,
, and on the experimental values of the preferen-
tial adsorption coefficient, , in DMF/MeOH and DMF/water, at 25˚C, for PSF-DMEA and PSF-DMOA samples.
and PSF-DMOA, respectively [23]. For the PSF-DMEA
in the DMF/MeOH system, one may observe that the
polymer coil dimension decreases with increasing the
DMF content in the 0.25 - 1 volume fraction domain;
below a 0.25 volume fraction of D MF, the polymer pre-
cipitates. For the same polymer, but in a DMF/water
solvent mixture, the dimension s increase with in creasing
the DMF content, starting from approximately the same
volume fraction of DMF. The PSF-DMOA coil dime-
sions possess maximum values in DMF/MeOH and DMF/
opyright © 2011 SciRes. JBNB
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones
water, around 0.6 and 0.8 DMF volume fractions, resp e c-
tively. For volume fractions of DMF below 0.25 in
DMF/MeOH and 0.5 in DMF/water, the PSF-DMOA
precipitates due to the nature of the alkyl radicals and
content of nonsolvent in the system. Also, the values of
intrinsic viscosity are h igh er for PSF-DMOA-with bulky
carbon atoms in the alkyl side chain, compared with
PSF-DMEA, where the alkyl side chain possesses two
carbon atoms. Therefore, for a given composition of the
DMF/MeOH and DMF/water solvent mixtures, one of
the components is preferentially adsorbed by the quater-
nized polysulfone molecules in the direction of a ther-
modynamically most effective mixture.
These aspects influence the surface properties of the
polymer. Moreover, according to previous data [27], it
was found out that PSF evidences the lowest hydro-
philicity, induced by the aromatic rings connected by on e
carbon and two methyl groups, oxygen elements, and
sulfonic groups, while chlorometh ylation of PSF with the
functional group -CH2Cl increases hydrophilicity (see the
values of surface tension for PSF and CMPSF in Table 3
from reference [27]). On the other hand, PSF-DMEA
films possess low polar surface tension parameters, but
slightly higher than those for PSF-DMOA. The hydro-
phobic character is given by the ethyl radical from the
N-dimethylethylammonium chloride pendant group and
by the octyl radical from the N-dimethyloctylammonium
chloride pendant group, respectively, as visualized in the
conformational structures from Scheme 1. Furthermore,
the electron donor interactions,
, are smaller than the
electron acceptor ones,
, for PSF-DMEA, and elec-
tron donor in teractions,
, exceed the electron acceptor
, for PSF-DMOA, caused by the induc-
tive phenomena from alkyl radical. The results reflect the
capacity of the N-dimethylethylammonium chloride or
N-dimethyloctylammonium chloride pendant groups to
determine the acceptor or donor character of the polar
terms, generated by these inductive phenomena.
3.2. Surface and Interfacial Free Energy
The effect of alkyl radicals of quaternized polysulfones
and of the history of the films formed from solutions on
surface properties was analyzed by surface free energy,
w - expressing the balance between surface hydro-
phobicity and hydrophilicity (equation (5)) [32], by in-
terfacial free energy between two particles of quaternized
polysulfones in water phase,
G (equations (6) and
(7)), and by the work of spreading of water,
W (equa-
tion (8)).
wlv water
where lv
and water
are given in Tables 1 and 2, re-
ws sl
  (6)
pp dd
sllv svlv sv
 
 (7)
12 12 12
LW d
v lvsvlvsvlvlv
 
  
According to literature [33,34] which specifies that
GmJ/ m2 for more hydrophobic materials,
evidences a high hydrophobicity for both samples,
depending on the conditions of films preparation (Table
4). Moreover, the interfacial free energy, GM
G evalu-
ated from solid-liquid interfacial tension,
, (equation
(7)) has negative values (Table 4). Therefore, an attrac-
tion occurs between the two polymer surfaces, s, im-
mersed in water, w, confirming the hydrophobic charac-
teristics of both polymers, with higher hydrophobicity for
PSF-DMOA films. Also, the hydrophobicity of these
polymers was described by the work of spreading of wa-
W, over the surface, which represents the differ-
ence between the work of water adhesn, a
W, and the
work of water cohen, c
W. According to the negative
values of the interfacial free energy of PSF-DMEA and
PSF-DMOA, the work of spreading of water, ,
(Figure 2) takes negative values, caused by the hydro-
phobic surfaces, where the wo rk of water adhesion is low,
comparatively with the work of cohesion; at the same
time, it is observed that
3.3. Blood-Quaternized Polysulfone Interactions
Blood compatibility is dictated by the manner in which
their surfaces interact with blood constituents, like red
blood cells and platelets. To analyze the possibilities of
using the polysulfone with N-dimethylethylammonium
and N-dimethyloctylammonium chloride groups in bio-
medical applications, and for establishing its compatibil-
ity with blood, equation (8) was used, where ,
rbc and
p describe the work of spreading of red blood cells
and platelets [35]; when blood is exposed to a biomate-
rial surface, adhesion of cells occurs and the extent of
adhesion decides the life of the implanted biomaterials;
thus, cellular adhesion to biomaterial surfaces could ac-
tivate coagulation and the immunological cascades.
Therefore, cellular adhesion has a direct bearing on the
thrombogenicity and immunogenicity of a biomaterial,
and thus dictates its blood compatibility. In this paper,
we used the work of adhesion of the red blood cells as a
parameter for characterizing biomaterials versus cell ad-
hesion. The materials which exhibit a lower work of ad-
hesion would lead to a lower extent of cell adhesion than
hose with a higher w ork of adhesion.
opyright © 2011 SciRes. JBNB
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones
Copyright © 2011 SciRes. JBNB
Figure 2. Work of spreading of water, of red blood cells and of platelets over the surface of PSF-DMEA and PSF-DMOA
films prepared in different DMF/MeOH and DMF/water solvent mixture.
Table 4. Water interfacial tensions (
) and surface free energy (w
) for PSF-DMEA and PSF-DMOA films prepared in
different DMF/MeOH and DMF/water (% v/v), and interfacial free energy (GM
G) between two particles of quaternized
polysulfones in water phase.
Solvent mixtures
100/0 25.95 26.92 –67 –95.30 –1.90 –53.84
75/25 24.26 32.06 –68 –87.94 –48.52 –-64.12
50/50 18.47 37.15 –75 –111.38 –36.94 –74.30
45/55 - 29.91 - –89.18 - –59.82
25/75 19.15 - –74 - –38.30 -
75/25 16.50 21.66 –77 –102.41 –32.30 –43.32
60/40 - 20.08 - –103.57 - –40.16
50/50 17.60 25.30 –76 –97.70 –35.20 –50.60
40/60 15.57 - –79 - –31.14 -
Considering the surface energy parameters (lv
) given in Table 1 for red blood cells and platelets,
the work of spreading of blood cells and platelets was
estimated by equation (8), with surface free parameters
for films prepared from DMF/MeOH and DMF/water
solutions listed in Table 4.
Figure 2 shows positive values for the work of
spreading of red blood cells, ,
rbc , and negative values
for the work of spreading of platelets, ,
p, suggesting a
higher work of adhesion comparatively with that of co-
hesion for the red blood cells, but a smaller work of ad-
hesion comparatively with the one of cohesion for plate-
lets. These results suggest that the exposure of platelets
to PSF-DMEA and PSF-DMOA films determines an in-
crease of platelets cohesion, which is higher for PSF-
DMOA films, and that a good hydrophobicity can be
correlated with a good adhesion of the red blood cells on
the surface of the polysulfone films.
In summary, both red blood cells and platelets are ex-
tremely important in deciding the blood compatibility of
a material. Moreover, it is known that adhesion of the red
blood cells onto a surface, e.g. modified polysulfones, re-
quires knowledge of the interactions with the vascular
components. Thus, endothelial glycocalyx along with the
mucopolysaccharides adsorbed to the endothelial surface
of the vascular endothelium reject clotting factors and
platel ets—which have a sign ifican t rol e in th rombu s forma-
tion [3 6] . I n t h i s c o nt e xt , adhes i on o f the re d bl o od cells and
cohesion of platelets to surface films must be disc uss ed in
correlation with future specific biomedical applications.
These results seem to be applicable for evaluating bacte-
rial adhesion to the surfaces, and could be subsequently
employed for studying possible implanted induced infec-
ions, or for obtaining sem iperm eable mem b r a n es . t
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones
Figure 3. 2D and 3D AFM images with 20 x 20 μm2 scanned areas of the PSF-DMEA films obtained from DMF/MeOH solu-
tions: (a, a’) - 100/0; (b, b’) - 75/25 v/v; (c, c’) – 50/50 v/v; (d, d’) – 25/75.
Figure 4. 2D and 3D AFM images with 20 × 20 μm2 scanned areas of the PSF-DMEA films obtained from DMF/water solu-
tions: (a, a’) - 75/25 v/v; (b, b’) - 50/50 v/v; (c, c’) - 40/60.
Figure 5. Effect of surface roughness on the work of spreading of red blood cells over the surface of PSF-DMEA and
SF-DMOA films prepared from solutions in different DMF/MeOH and DMF/water solvent mixtures. P
opyright © 2011 SciRes. JBNB
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones 121
Table 5. Pore characteristics, including number of pores, area (μm2), depth (nm), diameter (μm), length (μm), and mean
width (μm), and surface roughness paramaters, including average roughness (Sa, nm), root mean square roughness (Sq, nm),
and average height from the height histogram (Ha, nm) of PSF-DMEA and PSF-DMOA films prepared from solutions in
DMF/MeOH and DMF/water (% v/v), with 20 20 μm2 scanned areas, corresponding to the 2D AFM images.
Pore characteristics Surface roughness
Solvent mixtures Number of pores Area Depth Diameter LengthMean width Sa Sq Ha
PSF-DMEA, DMF/MeOH (% v/v)
100/0 234 0.24 272.78 0.57 0.86 0.31 33.97 42.87231.14
75/25 268 0.27 259.59 0.62 0.94 0.32 31.89 41.47217.26
50/50 52 0.47 348.25 0.78 1.09 0.47 74.09 95.12402.61
25/75 37 1.10 242.07 1.18 1.73 0.62 48.36 59.80193.33
PSF-DMEA, DMF/water (% v/v)
75/25 147 0.51 245.19 0.86 1.25 0.48 37.41 47.76227.79
50/50 1080 0.06 89.57 0.23 0.47 0.15 6.87 9.27 77.43
40/60 42 2.19 230.10 1.64 2.43 0.86 44.98 57.61281.80
PSF-DMOA, DMF/MeOH (% v/v) [27]
100/0 9 10.43 25.64 3.33 6.24 1.45 14.11 16.8258
75/25 - - - - - - 14.43 19.9082
50/50 34 0.70 11.37 0.89 1.56 0.42 3.09 4.41 17
45/55 44 0.80 16.02 0.98 1.53 0.49 2.77 4.24 28
PSF-DMOA, DMF/water (% v/v) [27]
75/25 5 3.12 13.65 1.97 3.26 0.96 1.59 2.34 15
60/40 27 0.04 19.54 0.22 0.35 0.11 9.19 11.8370
50/50 18
2.09 5.55 1.46 2.63 0.64 1.52 2.17 8
3.4. Surface Morphology
It is generally agreed that the physicochem ical properties
of substratum surfaces are the main factors mediating the
compatibility with blood.
Figures 3 and 4 plot the bi- and three-dimensional
structure evidenced by AFM investigations of PSF-
DMEA films prepared with 100/0 v/v, 75/25 v/v, 50/50
v/v and 25/75 v/v, an d also with 75/25 v/v, 50 /50 v/v and
40/60 v/v of DMF/MeOH and DMF/water compositions
solvent mixtures, respectively. According to the images,
increasing the nonsolv ent content in the casting solutions
favored modification of surface morphology. Thus, Fig-
ure 3 and Table 5 show that average surface roughness
attains its maximum value at 50/50 v/v DMF/MeOH, and
favors the appearance of the smallest number of pores
with highest depth values. Also, the area, diameter, leng th
and mean width increase with increasing the nonsolvent
content. It shou ld be noted that the thermodynamic qua l-
ity of the solvent mixtures over the studied domain in-
creases with the addition of nonsolvent, at approximately
50/50 v/v DMF/MeOH becoming constant, while the
preferential adsorption of nonsolvent takes a maxim
value, according to Figure 1.
The presence of water as a nonsolvent in the solutions
used for casting films influenced the AFM images pre-
sented in Figure 4; a higher water content decreases the
thermodynamic quality of the DMF/water solvent mix-
tures (Figure 1) so that, at 50/50 v/v DMF/water, a
minimum value of surface roughness and a maximum
number of pores with minimum values of area, depth,
diameter, length and mean width, were observed. It may
be assumed that the specific interactions with the mixed
solvents employed in the study modify the PSF-DMEA
and PSF-DMOA solubility and determine modification
of the solution properties [23], according to Figure 1.
On the other hand, previous data [27] obtained for
PSF-DMOA in the same solvent mixtures evidenced that
the number of pores and their average size increases,
while the average surface roughness decreases with in-
creasing the content of nonsolvent, MeOH. For films
prepa red from DMF/water solu tions, the presence of w a-
ter as a nonsolvent in the casting solution decreases the
thermodynamic quality of the DMF/water solvent mix-
tures up to a 40 % water co mposition, so that, for the cor -
responding film, average surface roughness, the number
of pores and their depths take maximum values with a
minimum area.
Figure 5 plots the dependencies between root mean
square roughnesses and the work of spreading of the red
blood cells over the surface of PSF-DMEA and PSF-
DMOA films prepared from different DMF/MeOH and
opyright © 2011 SciRes. JBNB
Surface Properties and Compatibility with Blood of New Quaternized Polysulfones
DMF/water solvent mixtures. These results show that
surface morphology depends on the history of the formed
films, including the characteristics of quaternized poly-
sulfones and the thermodynamic quality of solvents.
Moreover, the results suggest that surface free energy
(surface hydrophobicity) and surface roughness are the
key parameters controlling the compatibility with the red
blood cells, known as a complicated process that depends
on many factors, including surface chemistry, hydropho-
bicity, and surface roughness. The contribution of each of
these factors i s difficult to establish , however, it is c lear ly
seen that PSF-DMOA is characterized by a lower com-
patibility with the red blood cells than PSF-DMEA. On
the other hand, the compatibility values are higher for PSF-
DMEA and lower for PSF-DMOA f ilms prepared in DMF/
water, compared with films prepared in DMF/ MeOH.
4. Conclusions
New quaternized polysulfones, prepared by quaternization
of chloromethylated polysulfone with N,N-dimethy-
lethylamine and N,N-dimethyloctylamine were investi-
gated to obtain information on their hydrophilic/hydrop-
hobic properties and blood compatibility. The history of
the formed films, prepared by a dry-cast process in DMF/
MeOH and DMF/water solvent/nonsolvent mixtures,
influenced the surface tension parameters, surface and
interfacial free energy and the work of spreading of water,
maintaining the surfaces hydrophobic characteristics of
both polysulfones. On the other hand, the results reflect
the capacity of N-dimethylethylammonium or N-dime-
thyloctylammonium chloride pendant groups to deter-
mine the acceptor or donor character of the polar terms,
caused by the inductive phenomena of alkyl radicals.
The AFM images showed that surface morphology is
characterized by roughness and nodules formations, de-
pending on the composition of solvent/nonsolvent mix-
tures, including the characteristics of quaternized poly-
sulfones and the thermodynamic quality of the solvents.
Moreover, the results suggest that:
surface hydrophobicity and surface roughness are
the parameters controlling the compatibility with
the red blood cells and platelets: a good hydropho-
bicity can be correlated with a good adhesion of the
red blood cells and with a good cohesions of the
platelets on the surface of the quaternized polysul-
fone films ;
high work of adhesion comparatively with work of
cohesion for the red blood cells, but a smaller work
of adhesion comparatively with the one of cohesion
for platelets was obtained;
the exposure of blood to both quaternized polysul-
fones involves higher platelets cohesion for PSF-
DMOA films, comparatively with PSF-DMEA films.
These results are useful in investigations on specific
biomedical applications, including evaluation of bac-
terial adhesion to the surfaces, and utilization of
modified polysulfones as sem ipermeable membranes.
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