Branched Wormlike Micelles Formed by Self-Assembled Comblike Amphiphilic Copolyelectrolytes

The structure of the self-assemblies formed by amphiphilic comblike copolyelectrolytes dispersed in water has been investigated by scattering techniques (light and neutron) and by transmission electronic microscopy. The comblike polymers consisted of a polystyrene backbone grafted with a fixed amount of pendant <i>N</i>,<i>N</i>-dimethyl quaternary ammonium alkyl groups of various lengths ranging from C12 up to C18. In aqueous solution, the polymers self-assembled into small spherical aggregates at low concentrations and into cylindrical aggregates above a critical concentration with a diameter that increased with the length of the alkyl side chains. The length of the cylindrical aggregates increased with increasing concentration, and branching occurred at higher concentration, which induced gelation above a critical percolation concentration. Growth and branching were favored by increasing the ionic strength of the solution. The dynamics slowed down with decreasing temperature and increasing alkyl length, and the assemblies of polymers with C16 and C18 pendant chains were kinetically frozen at 20 °C

Dynamic Mechanical Properties of Networks of Wormlike Micelles Formed by Self-Assembled Comblike Amphiphilic Copolyelectrolytes

The rheological properties of viscoelastic aqueous solutions of wormlike micelles formed by the self-assembly of comblike copolyelectrolytes have been investigated by flow and dynamic measurements. The comblike polymers consisted of a polystyrene backbone grafted with a fixed amount of pendant <i>N</i>,<i>N</i>-dimethyl quaternary ammonium alkyl groups of various lengths ranging from C12 up to C18. Upon increasing concentration, the increase in size of the wormlike micelles and their branching results in the formation of a system spanning network through a percolation process at a critical concentration that decreases when salt is added or when the temperature is decreased. In this manner transient gels are formed with a viscoelastic relaxation time that does not depend on the polymer concentration or on the ionic strength, but their elastic modulus increases with increasing polymer or salt concentration. When the size of the alkyl groups is increased from C12 to C16, the relaxation time increases very strongly, but the temperature dependence remains characterized by the same activation energy. For C18, the systems are frozen at least up to 80 °C

Structure and Dynamics of Dendronized Polymer Solutions: Gaussian Coil or Macromolecular Rod?

We investigate the conformation of well-defined dendronized polymers (denpols) based on poly­(norborene) (PNB) and poly­(<i>endo</i>-tricycle­[4.2.2.0]­deca-3,9-diene) (PTD) backbones employing static and dynamic light scattering. Their synthesis by ring-opening metathesis polymerization (ROMP) led to fully grafted and high molecular weight denpols with narrow polydispersity. In dilute solutions, the persistence lengths were estimated by static (radius of gyration) and dynamic (translational diffusion) chain conformational properties of the denpols and were compared to their homologue precursor PNB. The conformation of denpols with a third generation side dendron conforms to a semiflexible chain with a persistence length of about 6–8 nm, virtually independent of the contour length. In the semidilute regime, the thermodynamics and cooperative diffusion of denpols resemble the behavior of the precursor solutions as described by the scaling theory of flexible polymers above the crossover concentration. The assumption of extremely high chain rigidity for this class of polymers is clearly not supported, at least for the third generation dendron