Polyureas (PURs) are a competitive polymer to their analogs, polyurethanes (PUs). Whereas PUs’ main functional group is carbamate (urethane), PURs contain urea. In this revision, a comprehensive overview of PUR properties, from synthesis to technical applications, is displayed. Preparative routes that can be used to obtain PURs using diisocianates or harmless reagents such as CO₂ and NH₃ are explained, and aterials, urea monomers and PURs are discussed; PUR copolymers are included in this discussion as well. Bulk to soft components of PUR, as well as porous materials and meso, micro or nanomaterials are evaluated. Topics of this paper include the general properties of aliphatic and aromatic PUR, followed by practical synthetic pathways, catalyst uses, aggregation, sol–gel formation and mechanical aspects.

ZnO nanoparticles having spherical and rod shapes with high crystallinity and uniform average crystallite sizes were prepared by a new route named the glycerol–urea (GU) route. The syntheses were carried out using Zn(NO₃)₂·6H₂O and NaOH in a 3 : 1 mol ratio of G : U solution under stirring at 70 °C. These reactions took less than 1 hour to completion with a high mass yield. NaCl and LiCl salts were added to attempt to modulate crystallites morphology and size. The effect of LiCl led to smaller spherical particles with an average size of 11(2) nm, whereas NaCl resulted in rod-shaped ZnO nanoparticles having an average length of 44(7) nm and an average diameter of 12(2) nm; whereas GU synthesis (no salt) led to 19(3) nm nanoparticles. Detailed X-ray powder diffraction, FT-IR and UV-Vis analyses confirmed the typical wurtzite structure of the particles. Electron microscopy images (SEM and TEM) showed the morphology and size of the ZnO nanoparticles. Photoluminescence revealed different behaviors related to defects and exciton emission.

Microsphere size is a primary determinant of solute release velocity. We present here a rational way for producing PLGA microspheres with different and controlled sizes. The following process variables were studied: Stirring velocity during the second emulsion step, dispersed and continuous phases volume ratio, and poly(vinyl alcohol) concentration in the continuous phase. A full factorial experimental design 2³ with triplicate at the central point was used to determine the influence of variables on PLGA microsphere mean size. The stirring velocity and poly(vinyl alcohol) concentration were the main variables at 0.95 significance level. An influence of PVA and stirring velocity on microspheres size is observed, there is no correlation for DP/CP volume ratio on size of microspheres. By combining the two variables—the stirring velocity and poly(vinyl alcohol) concentration, the surface response was analyzed. The increase of poly(vinyl alcohol) concentration with concomitant increase on stirring velocity produced microspheres with the lower sized. In contrast the lower poly(vinyl alcohol) concentration and the lower stirring velocity used produced the higher microspheres sized. Uniformly spherical and smooth microspheres (4–15 μm of diameter) were obtained. No significant difference was observed on Ponca Sloading within the experimental region. Our results open the possibility of formulating PLGA microspheres with custom sizes performing a minimum of experiments as required for specific applications.