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PBMA-PCEMA block copolymer micelles, consisting of poly(2-cinnamoyloxyethyl methacrylate) (PCEMA) cross-linked core and poly(butyl methacrylate) (PBMA) hairs (shell), are used as model responsive soft colloids, where the core swelling can be tuned by changing solvent quality. Our extensive dynamic light scattering study, complemented by viscosity and small angle neutron scattering (SANS) measurements, demonstrates the richness of dynamics of such dense micellar suspensions and in particular the strong influence of solvent-mediated core swelling on the concentration dependence of the self-diffusion. Brownian dynamics (BD) simulations using appropriate effective core-core interactions support these findings. Such novel micelles offer new possibilities for controlling the interactions and macroscopic properties of colloidal suspensions.

The use of well-defined macromolecular assemblies with tunable interactions represents the key for exploring the regime of soft-material behavior between hard spheres and polymer coils. Colloidal stars are ideal choices for such a formidable task and especially for shedding light on the formation and properties of dynamically arrested states. In this brief review, we demonstrate the rich variety of kinetic frustration phenomena that can be encountered with such ultrasoft particles. We address two specific examples in particular: the reversible vitrification upon heating and the melting of star gels upon the addition of linear polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2931–2941, 2004

A rheological study of the phase behaviour and the dynamics in the immiscible region of a model partially miscible Upper Critical Solution Temperature (UCST) blend was carried out by using a series of nearly monodisperse polydimethylsiloxane (PDMS) of varying molecular weights blended with polyethylmethylsiloxane (PEMS). The complete phase diagram was established through steady shear rheology, optical microscopy and light scattering. The UCST, interfacial tension and morphology of these blends are very sensitive to the molecular weight of the constituents. Partial miscibility was observed only when the Mw of PDMS was sufficiently low. The viscoelastic behaviour in the phase separated region can be modeled successfully using the Palierne model. Une etude rheologique du comportement et de la dynamique de phases dans la region immiscible d'un melange modele a temperature de solution critique superieure (UCST) partiellement miscible, a ete realisee au moyen d'une serie de polydimethylsiloxane (PMDS) quasi monodisperse de differents poids moleculaires melange a du polyethylmethylsiloxane (PEMS). Le diagramme de phases complet a ete etabli par rheologie en cisaillement permanent, microscopie optique et diffusion de la lumiere. La UCST, la tension interfaciale et la morphologie de ces melanges sont tres sensibles au poids moleculaire de ces constituants. Une miscibilite partielle est observee uniquement lorsque le Mw du PMDS est suffisamment bas. Le comportement viscoelastique dans la region ou les phases sont separees peut etre modelise avec succes a l'aide du modele de Palierne.

The formation of macromolecular assemblies in solutions of side chain liquid crystal polymers, forming nematic mesophases in the melt, is investigated by dynamic isotropic and anisotropic light scattering for two molecular weights (65 and 286 kg/mol). The coexistence of single chains with supramolecular species is verified by examining dilute solutions in two different solvents. The shape and the overall dimensions of the macromolecular assemblies depend on molar weight and solvent. The high molar weight sample favors spherical aggregates versus the strongly non-spherical structures of the low molar weight.

SUMMARY: Depolarized light scattering of binary polymer blends in disordered state near the demixing critical point is considered both theoretically and experimentally. It is shown that the depolarized scattering in such systems is predominantly due to double scattering processes induced by composition fluctuations. For long enough polymer chains, this scattering is stronger than the contribution from intrinsic anisotropy fluctuations. The general equation for the static and dynamic double scattering function is obtained in terms of the system structure factor. The scattering functions are calculated both analytically and numerically (dynamic part) for polymer blends. We found that the depolarized intensity depends on the polymerization degree N and the relative distance from the critical point s =1‐ v*/v (where v is the Flory-Huggins interaction parameter and v* its critical value) as Ivh l N 2 /s 2 , which is in good agreement with the experimental data. It is also shown that the dynamic scattering function is decaying non-exponentially. We calculate the relaxation rate and the non-exponentiality parameter as functions of the scattering angle and s. These theoretical predictions are compared with experimental data for three chemically different blends.