The modification of an emulsion polymerization with a water-miscible alcohol and a hydrocarbon nonsolvent for the polymer can influence the morphology of the particles. The formation of monodispersed particles with a hollow structure or diffuse microvoids is possible. Both kinetic and thermodynamic aspects of the polymerization dictate which particle morphology is obtained. Complete encapsulation of the hydrocarbon occurs provided low molecular weight polymer is formed initially in the process. Subsequent addition of a cross-linking monomer stabilizes the morphology. The final particle size can be defined by small nucleating latex seed particles. Monodispersed hollow particles with diameters from 0.2 to 1 μm are possible. Void fractions as high as 50% are feasible. The phase separation of polystyrene within the styrene−isooctane dispersion has been modeled with the Flory−Huggins theory. The encapsulation has been discussed in terms of interaction parameters, transport processes, polymer molecular weight, and interfacial tension effects.

Polyamides derived from l-methyl-4,5-imidazoledicarboxylic acid and aliphatic diamines such as hexamethylenediamine, neopentylenediamine, and ethylenediamine are synthesized and characterized.The polymers have inherent viscosities up to 0.56 dL/g, are amorphous, have good thermal stability, and are soluble in a wide range of solvents. The amide proton of the carboxamide at the 5-position of the imidazole intramolecularly hydrogen bonds to the carbonyl oxygen at the 4-position. There is little or no evidence of intermolecular hydrogen bonding occurring in the polyamides. The nonsymmetric diacid creates constitutional isomerism in the polymers. This isomerism can be detected at various levels, by NMR spectroscopy, in the polyamides depending on the diamine portion and the solvent used.

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Size-exclusion chromatography (SEC), coupled with differential viscometry detection (SEC/DV), is applied to the dilute suspension characterization of solvent-swollen cross-linked polymeric nanoparticles (PNPs). Cross-linked, unimolecular polymeric nanoparticles in the 5−50 nm weight-average diameter (d w ) range were prepared by batch and semibatch microemulsion polymerization techniques and isolated. SEC and SEC/DV characterization techniques yield, based on the principle of universal calibration, a wealth of information regarding the structural attributes of PNPs, including apparent and absolute molecular weight distributions, apparent and absolute molecular weight averages, peak and weightaverage particle diameters, particle size distributions in both the solvent-swollen and solvent-free states, particle conformation (shape), and an estimate of the volumetric swell factor. These structural parameters are critical to understanding PNP performance, and all are obtained in a single rapid chromatographic experiment, when conducted under conditions where universal calibration applies. Particle sizes determined under such conditions are in excellent agreement with those obtained by dynamic light scattering, transmission electron microscopy, hydrodynamic chromatography, and SEC/static light scattering (SEC/SLS). In addition, Mark−Houwink exponents of approximately zero were found across the molecular weight and size distribution of many of these tightly cross-linked PNPs, which is consistent with a spherical particle conformation in these dilute suspensions. The SEC/DV methods are especially valuable to characterize the diameter, volume swell factor, and suspension conformation of small (4−5 nm d w ) PNPs.

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