Handbook of Size Exclusion Chromatography and Related ...

Also of note in Fig. 13b is how highly the scattering is suppressed when SDS is
present with the PVP in asalt-free solution. This is again amanifestation of the
electrostatically enhanced A2 due to the electrical charging of PVP by SDS.
In contrast, when such a solution is exposed to salt (e.g., 0.1M NaCl in
Fig. 13b) the scattering is actually higher than when no SDS is present,
reflecting the fact that A2 has been greatly lowered by the NaCl, and that the
mass of the complex formed by SDS and PVP is significantly greater than the
mass of the PVP alone.
Figure 14 shows how these two latter factors are affected by salt. A
procedure for determining the mass ratio of SDS to PVP in the aggregates r, was
presented in Ref. 7. Figure 14 shows that r increases from 0.6 to 1.6 as [NaCl]
increases, for PVP under saturating SDS conditions, due to the decrease in
repulsion among the charged SDS groups. A significant decrease in A2 from
0.0022 to 0.0003 is also seen as [NaCl] increases.
4 SUMMARY
Use of automatic continuous mixing, together with multiple detectors provides
state-of-the-art characterization for polymers in a variety of equilibrium and
nonequilibrium contexts. ACOMP is one of the ACM family of techniques that
promises the greatest long-term economic impact, both in terms of fundamental
research and on-line reactor control. ACOMP is rapidly being adapted to a wide
variety of polymerization reaction contexts, including batch and continuous
reactors, homogeneous and inhomogeneous media, and those that produce
slurries, pellets, and phase-separated products. Significant improvement in
the front end, involving the ACM portion, is expected to augment greatly the
versatility of ACOMP.
ACM should steadily find new monitoring applications for degradation,
aggregation, microcrystallization, and other phase-separation processes. ACM in
the equilibrium characterization milieu should prove to be immensely labor
saving, especially for the study of complex systems, such as those involving
polyelectrolytes, salts, and surfactant agents.
Also on the horizon is a new application for light scattering; simultaneous
multiple sample light scattering, or SMSLS (74). This takes advantage of the
greatly lowered expense of light-scattering sample cells (75), laser light, and
sensitive photodetection to gang many independent cells together to form an
instrument unified under the control of a single computer. Applications are
expected in combinatorial and high-throughput methods applied to new polymer
synthesis (76–78), shelf-life and stability measurements, aggregation, dissolution,
and multiple reactor sampling.
© 2004 by Marcel Dekker, Inc.