Modification of calcium carbonate particles with surfactant significantly improves the properties of the calcium carbonate coating on paper. In this study, unmodified and CTAB (hexadecyltetramethylammonium bromide)- and oleate-modified calcium carbonate nanoparticles were prepared using the wet carbonation technique for paper coating. CTAB (cationic surfactant) and sodium oleate (anionic surfactant) were used to modify the size, morphology, and surface properties of the precipitated nanoparticles. The obtained particles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, zeta potential measurements, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). Coating colors were formulated from the prepared unmodified and modified calcium carbonates and examined by creating a thin coating layer on reference paper. The effect of calcium carbonate particle size and surface modification on paper properties, such as coating thickness, coating weight, surface roughness, air permeability, brightness, whiteness, opacity, and hydrophobicity, were investigated and compared with commercial ground (GCC) calcium carbonate-coated papers. The results show that the obtained calcium carbonate nanoparticles are in the calcite phase. The morphology of the prepared calcium carbonate nanoparticles is rhombohedral, and the average particle diameter is less than 100 nm. Compared to commercial GCC, the use of unmodified and CTAB- and oleate-modified calcium carbonate nanoparticles in paper coating improves the properties of paper. The highest measured paper properties were observed for paper coated with oleate-modifed nanoparticles, where an increase in smoothness (decrease in paper roughness) (+23%), brightness (+1.3%), whiteness (+2.8%), and opacity (+2.3%) and a decrease in air permeability (-26%) was obtained with 25% less coat weight. The water contact angle at a drop age time of 10 min was about 112° for the paper coated with oleate-modified nanoparticles and 42° for paper coated with CTAB-modified nanoparticles compared to 104° for GCC-coated paper.

Lactic acid oligomers were prepared using sodium and potassium hydroxyacids as initiators for lactide polymerization leading to the formation of surface active molecules in a one-pot synthesis, requiring no additional catalysts or volatile organic solvents. The initiator systems that were investigated included sodium and potassium salts of lactate, mandelate, γ-hydroxybutyrate, α-hydroxybutanoate, α-hydroxyhexanoate, α-hydroxyoctanoate, α-hydroxyisovalerate, and 2,2-bis(hydroxymethyl)butyrate. Poly(lactic acid) oligomers were successfully isolated from polymerizations initiated by all species listed using the catalyst-free synthetic route employed. The molecular weights of the oligomeric species ranged from 800 to 2400 Da (measured against poly(styrene) standards), and polydispersities were all below 1.5. All isolated polymers showed surfactant activity with low CMC values and a high propensity for aggregation that increases as molecular weight increases. Additionally, producing an A−B−A type polymeric structure, where the B block is defined as a moiety containing a single functional group, was shown to give improved application performance compared with the equivalent A−B type structure.