Single-Chain Polymer Nanoparticles for Application in Nanomedicine - Harnessing Biomaterials in Nanomedicine: Preparation, Toxicity, and Applications - page 33

from Cheng and co-workers [54], coil-nanoparticle-coil systems
are synthesised from a triblock copolymer precursor composed of
polystyrene- b -poly(2-vinylpyridine)- b -poly(ethylene oxide). In this
work, the middle block is collapsed by quaternisation of the pyridine
rings using dibromobutane as the cross-linker.

2.3 Characterization and Physical Properties

of SCPNs

As mentioned before, the synthesis of polymer nanoparticles with
controlled characteristics has become an appealing research topic
lately. The importance of obtaining nanoparticles with controlled
size and a tailored arrangement of functional groups is increasing,
due to the requirements of the specific potential applications.
While the strategies used to prepare nanoparticles above 20 nm are
generally successful, there is a trade off with respect to accessibility
and desired size. Synthesis of nanoparticles less than 20 nm in
size is invariably more difficult but yields particles of a more well-
defined composition. Moreover, nanomedicinal applications seem
to need structurally controlled delivery systems of less than 30 nm
to avoid accumulation in the liver and spleen, as well as unwanted
immunogenic reactions [31].
We have previously described that is essential to control the
concentration of the linear-chain polymer in solution to favour
intramolecular over intermolecular cross-linking. Intramolecular
cross-linking dominates at very low concentrations, but as soon as
the concentration increases polymer networks are generated due to
intermolecular cross-linking. As described by Li et al . not only the
concentration but the sizes of the linear precursors determine the
reaction rates [55].
Most of the physical properties of polymers used to obtain SCPNs
change once they have been converted into nanoparticles. There
are several techniques that are utilized to study these properties.
The molecular weight of the macromolecule is determined by gel
permeation chromatography (GPC). Intramolecular cross-linking
does not aff ect the molecular weight distribution of the polymer, but
the properties related to polymer size, such as hydrodynamic volume
and intrinsic viscosity, are aff ected [42]. As the GPC measurement
is proportional to the hydrodynamic volume, when a random coil