Surface Properties and Compatibility with Blood of New Quaternized Polysulfones

doi:10.4236/jbnb.2011.22015

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Journal of Biomaterials and Nanobiotechnology, 2011, 2, 114-124

doi:10.4236/jbnb.2011.22015 Published Online April 2011 (http://www.scirp.org/journal/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.

E-mail: ioan_silvia@yahoo.com

Received January 13th, 2011; revised January 16th, 2011; accepted January 21st, 2011.

ABSTRACT

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

1.Introduction

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))

Surface Properties and Compatibility with Blood of New Quaternized Polysulfones

116

PSF-DMEA

PSF-DMOA

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] .

1cos

lv lv

dlv







 (1)

vsvsv





 (2)

where



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)

WABLW AB

vsvsv





 (4)

where 2

vsvsv







 , 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

platelets.

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-Brom-naphtalin

(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



vsv











WAB



ABLW AB

sv sv



PSF-DMEA, DMF/MeOH

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

PSF-DMEA, DMF/water

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

PSF-DMOA, DMF/MeOH [27]

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/

Surface Properties and Compatibility with Blood of New Quaternized Polysulfones

118

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

interactions,



, 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

G (equations (6) and

(7)), and by the work of spreading of water,

W (equa-

tion (8)).



1cos

wlv water







(5)

where lv



and water



are given in Tables 1 and 2, re-

spectively.

ws sl





  (6)





pp dd

sllv svlv sv

 

 (7)



12 12 12

sac

LW d

v lvsvlvsvlvlv

WWW





 









  





(8)

According to literature [33,34] which specifies that

113





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-

ter,

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, ,

sio

(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

WSF DMEA > ,,

w PSF

WDMOA .

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.

Surface Properties and Compatibility with Blood of New Quaternized Polysulfones

119

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.





G

DMF/MeOH

Solvent mixtures

PSF-DMEA PSF-DMOA [27] PSF-DMEAPSF-DMOA [27] PSF-DMEA PSF-DMOA [27]

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 -

DMF/water

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



,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

120

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

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

Surface Properties and Compatibility with Blood of New Quaternized Polysulfones

122

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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