Poly(methyl methacrylate) (PMMA) was melt mixed 30:70 into polystyrene (PS) with and without symmetric P(S-b-MMA) diblock copolymers. The molecular weight of the components was varied. After 5 min of shear mixing, the PMMA was dispersed into roughly spherical, submicron particles. Particle size was measured by light scattering and transmission electron microscopy. As little as 1% copolymer led to a significant reduction in PMMA particle size, although larger amounts were needed to make the particles stable to annealing (180 °C for 15 min). The principle role of block copolymers in controlling morphology appears to be in preventing coalescence. Preventing dynamic coalescence leads to size reduction, while preventing static coalescence results in stability or compatibilization. We estimate that less than 5% of the interface needs to be covered to prevent dynamic coalescence while ∼20% is necessary to impart static stability. Mobility, critical micelle concentration, and molecular weight of the block copolymer also appear to be important. Lowering the molecular weight of the PMMA phase from 43 000 to 11 000 resulted in dramatically lower particle size (700 vs 60 nm). These variables are discussed in terms of a qualitative balance between rate of diffusion and rate of area generation during blending.

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We describe the quantitative synthesis of new pyrene labeled cyclodextrin-based polyrotaxane starting from pseudopolyrotaxane of alpha,omega-dimethacrylate poly(ethylene oxide) (PEO) and alpha-cyclodextrins (alpha-CDs). Using a solvent mixture (H2O/dimethyl sulfoxide (DMSO)), an almost quantitative conversion in polyrotaxane can be achieved using the coupling reaction between methacrylic functions and 1-pyrene butyric acid N-hydroxysuccinimide ester. This result is due to the fast blocking reaction of the pseudopolyrotaxane telechelic functions. The polyrotaxanes are characterized by NMR, size exclusion chromatography (SEC), and small-angle neutron scattering (SANS). A rodlike structure of the polyrotaxane is evidenced by SANS, and a persistence length of 70 A is determined. This result corresponds to an almost completely stretched PEO chain of 1000 g.mol(-1) molecular weight. We furthermore studied the opposite case of low packing density polyrotaxanes that were also silylated to suppress interactions between cyclodextrins. We observed a random coil structure only for silylated low packed polyrotaxane. This result demonstrates that both hydrogen bonding and packing density can explain the rodlike structure of cyclodextrin-based polyrotaxane.