Diblock copolymer hydrodynamic radius

FIGURE 5.1.8 (a) Chemical structure of PEO-f)-P(NIPAAM-r-Ru(bpy)3). (b) Hydrodynamic radius (Rh) of the diblock copolymer in the reduced and the oxidized states of Ru(bpy) side chain as a fuixtion of temperature, (c) Oscillating profile of the of / h the diblock copolymer determined by time-resolved DLS measurements. 

The same type of diblock copolymer with slightly different block length was also characterized by Castro et al. with respect to its interaction with SDS [112]. The polymer is poly(styrene oxide)-PEO with 17 and 65 monomer units, respectively. In aqueous solution, this polymer forms micelles with a hydrodynamic radius of approximately 12.7 nm and an aggregation number of ca. 150 [113]. On the basis of measurements of the dissymmetry of the static light scattering intensity [114], the structure of the formed polymer micelles was found to be spherical [113]. The erne of this type of diblock copolymer was found to be very low. 

Quite a number of theories were developed over the years in order to predict, mainly for non-polyelectrolyte systems, the structural parameters of a micelle (CMC, association number Z, core radius shell thickness L, hydrodynamic radius as a function of the copolymer characteristics, for example its molecular weight and composition. For A-B diblock copolymers which were mainly examined and where the B sequence is forming the micellar core, these characteristics are defined by the corresponding polymerization degrees and Ng. In all these theories and by using various models and mathematical approaches, the total Gibbs free energy of the micelle is expressed as the sum of several contributions, mainly those related to the core the shell and the core/shell interface... 

As an example, the hydrodynamic miceUar radius Rh determined by DLS for a series of PS-PEO diblock copolymers is plotted in Figure 7.6 versus (Np o+ according to... 

The second experiment that was performed consisted of mixing the three components (diblock copolymer solution, homopolymer solution and protein solution) in three different ways, and following the light scattering intensity and hydrodynamic radius as a function of time [50]. For system A, it was found that, independently of the way of mixing, the same light scattering intensity and hydro-dynamic radius were found after 1 day. For system B, the intensity remained different for different preparation methods over a period of at least 10 days. The hydrodynamic radius remained the same from the start of the experiment. 

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