Reihs and coworkers [17] reported nanoparticular complexes between
PDADMAC or PLL and copolymers of maleic acid at n
À /n
+
¼ 0.6, which
increased in size from around 60 to 120 nm by increasing c PEL . This was explained
by subsequent exceeding of the overlap concentration of either of the PEL
components, which increased the complexation and aggregation probability.
Recently, the dependence of PEC particle size on PEL concentration (c PEL ) was
reported by our group [48]. PEC-0.6 particles of PEI/PAC were prepared in
dependence of c PEL , whereby PEI with M w ¼ 750,000 g/mol and PAC with
M w ¼ 50,000 g/mol were used in these series. The plot of particle size and count
rate versus c PEL is given in Fig. 16. Generally, by varying c PEL it is possible to
generate PEC-0.6 particles of PEI/PAC with defined diameters D H of 200–1,000 nm.
Generally, the PEC particle size increased with c PEL . However, for c PEL > 0.01 M,
the PEC dispersions tend to instability, as can be seen from the drop in count rate. As
an explanation for the increasing PEC particle size with increasing c PEL we assume an
influence of the Debye length, which is a measure of electrostatic reach. As pointed
out by Wandrey [70], not only increasing salt but also PEL concentration decreases
the Debye length of a PEL system. Hence, based on the model of aggregation of
primary PEC to secondary PEC particles due to short range dispersive interactions,
we suggest that increasing c PEL results in reduced electrostatic repulsion between
like-charged primary PEC particles and thus in their elevated dispersive attraction.
Furthermore, an increase in c PEL might also result in a larger number of primary PEC
particles per volume. Both could lead to larger secondary PEC particle sizes, but
exceeding certain c PEL values can also lead to precipitation.
8
9
10
9
8
6
-5
-4
-3
3
2
1
log c c
7
10 log M w
log M w
log a m
log a m
M w ~c c
1.7
a m ~c 0.58
2
3
Fig. 15 Dependence of PEL concentration on the M W of PDADMAC/PSS PEC particles. (From
[27] with kind permission of ACS)
218
M. M€ uller
PDADMAC or PLL and copolymers of maleic acid at n
À /n
+
¼ 0.6, which
increased in size from around 60 to 120 nm by increasing c PEL . This was explained
by subsequent exceeding of the overlap concentration of either of the PEL
components, which increased the complexation and aggregation probability.
Recently, the dependence of PEC particle size on PEL concentration (c PEL ) was
reported by our group [48]. PEC-0.6 particles of PEI/PAC were prepared in
dependence of c PEL , whereby PEI with M w ¼ 750,000 g/mol and PAC with
M w ¼ 50,000 g/mol were used in these series. The plot of particle size and count
rate versus c PEL is given in Fig. 16. Generally, by varying c PEL it is possible to
generate PEC-0.6 particles of PEI/PAC with defined diameters D H of 200–1,000 nm.
Generally, the PEC particle size increased with c PEL . However, for c PEL > 0.01 M,
the PEC dispersions tend to instability, as can be seen from the drop in count rate. As
an explanation for the increasing PEC particle size with increasing c PEL we assume an
influence of the Debye length, which is a measure of electrostatic reach. As pointed
out by Wandrey [70], not only increasing salt but also PEL concentration decreases
the Debye length of a PEL system. Hence, based on the model of aggregation of
primary PEC to secondary PEC particles due to short range dispersive interactions,
we suggest that increasing c PEL results in reduced electrostatic repulsion between
like-charged primary PEC particles and thus in their elevated dispersive attraction.
Furthermore, an increase in c PEL might also result in a larger number of primary PEC
particles per volume. Both could lead to larger secondary PEC particle sizes, but
exceeding certain c PEL values can also lead to precipitation.
8
9
10
9
8
6
-5
-4
-3
3
2
1
log c c
7
10 log M w
log M w
log a m
log a m
M w ~c c
1.7
a m ~c 0.58
2
3
Fig. 15 Dependence of PEL concentration on the M W of PDADMAC/PSS PEC particles. (From
[27] with kind permission of ACS)
218
M. M€ uller