4 research outputs found
Monitoring Biopolymer Degradation by Taylor Dispersion Analysis
This
work aims at demonstrating the interest of modern Taylor dispersion
analysis (TDA), performed in narrow internal diameter capillary, for
monitoring biopolymer degradations. Hydrolytic and enzymatic degradations
of dendrigraft poly-l-lysine taken as model compounds have
been performed and monitored by TDA at different degradation times.
Different approaches for the data processing of the taylorgrams are
compared, including simple integration of the taylorgram, curve fitting
with a finite number of Gaussian peaks, cumulant-like method and Constrained
Regularized Linear Inversion approach. Valuable information on the
kinetics of the enzymatic/hydrolytic degradation reactions and on
the degradation process can be obtained by TDA
Measuring Arbitrary Diffusion Coefficient Distributions of Nano-Objects by Taylor Dispersion Analysis
Taylor dispersion analysis is an
absolute and straightforward characterization
method that allows determining the diffusion coefficient, or equivalently
the hydrodynamic radius, from angstroms to submicron size range. In
this work, we investigated the use of the Constrained Regularized
Linear Inversion approach as a new data processing method to extract
the probability density functions of the diffusion coefficient (or
hydrodynamic radius) from experimental taylorgrams. This new approach
can be applied to arbitrary polydisperse samples and gives access
to the whole diffusion coefficient distributions, thereby significantly
enhancing the potentiality of Taylor dispersion analysis. The method
was successfully applied to both simulated and real experimental data
for solutions of moderately polydisperse polymers and their binary
and ternary mixtures. Distributions of diffusion coefficients obtained
by this method were favorably compared with those derived from size
exclusion chromatography. The influence of the noise of the simulated
taylorgrams on the data processing is discussed. Finally, we discuss
the ability of the method to correctly resolve bimodal distributions
as a function of the relative separation between the two constituent
species
Polydispersity Analysis of Taylor Dispersion Data: The Cumulant Method
Taylor
dispersion analysis is an increasingly popular characterization
method that measures the diffusion coefficient, and hence the hydrodynamic
radius, of (bio)polymers, nanoparticles, or even small molecules.
In this work, we describe an extension to current data analysis schemes
that allows size polydispersity to be quantified for an arbitrary
sample, thereby significantly enhancing the potentiality of Taylor
dispersion analysis. The method is based on a cumulant development
similar to that used for the analysis of dynamic light scattering
data. Specific challenges posed by the cumulant analysis of Taylor
dispersion data are discussed, and practical ways to address them
are proposed. We successfully test this new method by analyzing both
simulated and experimental data for solutions of moderately polydisperse
polymers and polymer mixtures
Structure of Nanoparticles Embedded in Micellar Polycrystals
We investigate by scattering techniques the structure
of water-based
soft composite materials comprising a crystal made of Pluronic block-copolymer
micelles arranged in a face-centered cubic lattice and a small amount
(at most 2% by volume) of silica nanoparticles, of size comparable
to that of the micelles. The copolymer is thermosensitive: it is hydrophilic
and fully dissolved in water at low temperature (<i>T</i> ∼ 0 °C), and self-assembles into micelles at room temperature,
where the block-copolymer is amphiphilic. We use contrast matching
small-angle neuron scattering experiments to independently probe the
structure of the nanoparticles and that of the polymer. We find that
the nanoparticles do not perturb the crystalline order. In addition,
a structure peak is measured for the silica nanoparticles dispersed
in the polycrystalline samples. This implies that the samples are
spatially heterogeneous and comprise, without macroscopic phase separation,
silica-poor and silica-rich regions. We show that the nanoparticle
concentration in the silica-rich regions is about 10-fold the average
concentration. These regions are grain boundaries between crystallites,
where nanoparticles concentrate, as shown by static light scattering
and by light microscopy imaging of the samples. We show that the temperature
rate at which the sample is prepared strongly influence the segregation
of the nanoparticles in the grain-boundaries