Intermolecular complexes of genomic polydisperse DNA with synthetic polycations have been studied. Two cationic polymers have been used, a homopolymer poly(methacryl oxyethyl trimethylammonium ...chloride) (PMOTAC) and its analogue grafted with poly(oxyethylene). The amount of poly(oxyethylene) grafts in the copolymer was 15 mol % and M w of the graft was 200 g/mol. Salmon DNA (sodium salt) was used. The average molecular weight (M w) of DNA was 10.4 × 106 g/mol. Conductivity, pH, and dynamic light scattering studies were used to characterize the complexes. The size and shape of the polyelectrolyte complex particles have been studied as a function of the cation-to-anion ratio in aqueous solutions of varying ionic strengths. The polyelectrolyte complexes have extremely narrow size distributions taking into account the polydispersity of the polyelectrolytes studied. The poly(oxyethylene) grafts on PMOTAC promote the formation of small colloidally stabile complex particles. Addition of salt shifts the macroscopic phase separation toward lower polycation content; that is, complexes partly phase separate with the mixing ratios far from 1:1. Further addition of salt to the turbid, partly phase separated solution results in the dissociation of complexes and the polycation and DNA dissolve as individual chains.
Interaction between anionic (and cationic) colloidal particles of silica having the particles diameters 12 and 22 nm with synthetic cationic (and anionic) polyelectrolytes of various nature and ...structure was studied by potentiometric, conductimetric spectroturbidimetric and viscometric methods in aqueous solution. It was shown that the complexation of silica nanoparticles with linear polyelectrolytes leads to formation of mostly stoichiometric interpolyelectrolyte complexes (IPEC) which precipitate from aqueous solution. Casting of water-soluble IPEC followed by thermal treatment gives thin composite films insoluble in water while ‘layer by layer’ (LbL) deposition of polyelectrolyte components onto silica sols leads to formation of multilayered nano- and microcomposites. The possible mechanism of formation of LbL multilayers consisting of silica sol (SiO2) ‘cores’ and polyethyeleneimine-polyacrylic acid (PEI-PAA) ‘shells’ was suggested. It was found that in diluted aqueous solution the radius of gyration, Rg and hydrodynamic radius, Rhmean of LbL particles are independent on LbL concentration and smaller than 100 nm. The zeta potential values of LbL particles are arranged between –10 and –30 mV. The average size of LbL particles estimated by scanning electron microscopy (SEM) is in the range of 200–500 nm. Thermal treatment of LbL multilayers followed by etching of (SiO2) ‘core’ by HF leads to formation of a series of spherical nanocavities and blob-like microcavities.
New hydrophilic polyampholytes have been synthesized by copolymerization of 1-vinylimidazole with sodium salts of acrylic and methacrylic acids. Copolymerization reactivity ratios of the monomers are ...equal to: 0.54
±
0.06 and 1.3
±
0.3 for 1-vinylimidazole–sodium acrylate, 0.23
±
0.01 and 2.6
±
0.2 for 1-vinylimidazole–sodium methacrylate systems, correspondingly. Isoelectric point of the copolymers changes continuously from 2.8 to 6.7 with increasing the 1-vinylimidazole content in contrast to polyampholytes with amino instead of imidazole side groups, whose isoelectric point changes discontinuously with changing composition. Static and dynamic light scattering data point to tendency of polyampholyte macromolecules to aggregation, even at pH values far from isoelectric point.
Various thermally responsive polymers and their derivatives form colloidally stable nanosized
particles upon heating of their aqueous solutions. A compilation of the types of polymers reported
to ...exhibit this behaviour is presented in this review, including poly(N-isopropylacrylamide),
poly(N-vinylcaprolactam), and poly(vinyl methyl ether) together
with their copolymers with either hydrophobic or hydrophilic monomers. In all cases experimental
evidence is presented, together with various theoretical models. Possible mechanisms responsible
for the stabilisation of these colloids are discussed.
The dilute solutions of poly(vinylcaprolactam) and its fullerene C
60
complex have been studied by high-velocity sedimentation, translational diffusion, viscometry, and static and dynamic light ...scattering. The experiments have been performed for the sample with
M
≈ 2.7 × 10
5
. In the absence of external action, supramolecular structures (clusters) whose size and molar mass are much higher than the corresponding characteristics of the polymer matrix appear in solutions of the poly(vinylcaprolactam)-C
60
complex. When subject to a strong centrifugal force or an intense shear flow, the supramolecular structures are destroyed and the molecular characteristics of the complex correspond to those of poly(vinylcaprolactam) macromolecules. The dynamics of destruction of the cluster organization in aqueous solutions of fullerene-polymer complexes has been investigated by high-velocity sedimentation. As the angular speed of ultracentrifuge rotor rotation is decreased from 55000 to 10000 rpm, the sedimentation constant
S
0
of the poly(vinylcaprolactam)-C
60
complex increases by a factor of ∼4. This behavior reflects changes in the size and molar mass of clusters with the centrifugal force acting upon complex macromolecules.
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