Wax Crystallization from Solution in Hierarchical Morphology Templated by Random Poly(ethylene-co-butene) Self-assemblies

Mechanistic Study on the Influence of Wax on Hydrate Formation Process

To manage the interactions between wax and hydrate formation, a comprehensive understanding of the system's thermodynamics and flow characteristics is essential. Wax and hydrates coexist under low-temperature and high-pressure conditions, mutually influencing each other both thermodynamically and kinetically. This study focused on two main aspects: how wax affects the rate of hydrate formation in the oil-water system and how hydrate formation influences the thermodynamics of wax crystal precipitation. The presence of wax decreased the rate of hydrate formation, especially at higher wax contents. In systems with high wax content, over 70% of wax precipitated before hydrate formation, leading to less precipitation within the hydrate formation temperature range. With low water content, there were more nucleation sites for wax crystals in the oil phase, resulting in a greater difference in precipitation rates among different wax contents. For water content greater than 10%, the differences in precipitation rates were less significant, indicating a diminished effect of water content on wax crystal precipitation rates. Hydrates' hydrophilic nature had a limited impact on wax crystal nucleation and growth. Generally, wax crystals precipitate before hydrate formation, necessitating control measures for wax deposition during production processes.

Synthesis of crystallizable poly(behenyl methacrylate)-based block and statistical copolymers and their performance as wax crystal modifiers

Behenyl methacrylate-based diblock and statistical copolymers are evaluated as additives for the crystal habit modification of a model wax (n-octacosane) in n-dodecane. The statistical copolymers more strongly influence the wax crystal morphology.

How polymer additives reduce the pour point of hydrocarbon solvents containing wax crystals

We have investigated how four different pour point depressant (PPD) polymers affect the pour point transition in mixtures of a single pure wax in a solvent. We used either n-eicosane (C20), CH3(CH2)18CH3, n-tetracosane (C24), CH3(CH2)22CH3 or n-hexatriacontane (C36), CH3(CH2)34CH3 as the wax component with either n-heptane or toluene as the solvent component. For all wax-solvent combinations, the measured variation of wax solubility with temperature is well predicted by ideal solution theory. The variation of pour point temperature as a function of the overall wax concentration is quantitatively modelled using the idea that, for each overall wax concentration, the pour point occurs at a temperature at which a critical volume fraction ϕ* of wax crystals has precipitated. Close to the pour point temperature, extraction and examination of the wax crystals show they consist of polydisperse, irregularly-shaped platelets with axial ratios (h/d, where h is the plate thickness and d is the plate long dimension) in the range 0.005-0.05. It is found that the measured ϕ* values corresponding to the pour point transitions are weakly correlated with the wax crystal axial ratios (h/d) for all wax-solvent-PPD polymer combinations. These results indicate that the pour point transition occurs at a volume fraction larger than the value at which the volumes of rotation of the platelet crystals overlap, i.e., 2.5(h/d) < ϕ* < 11(h/d). PPD polymers work, in part, by increasing the wax crystal axial ratio (h/d), thereby increasing ϕ* and reducing the pour point temperature. Since the PPD's ability to modify the wax crystal shape relies on its adsorption to the crystal-solution surface, it is anticipated and observed experimentally that optimum PPD efficacy is correlated with the difference between the wax and the polymer solubility boundary temperatures. This finding and the mechanistic insight gained here provide the basis for a simple and rapid screening test to identify candidate species likely to be effective PPDs for particular wax systems.

Nucleolipid nanovectors as molecular carriers for potential applications in drug delivery

Novel thymidine- or uridine-based nucleolipids, containing one hydrophilic oligo(ethylene glycol) chain and one or two oleic acid residues (called ToThy, HoThy and DoHu), have been synthesized with the aim to develop bio-compatible nanocarriers for drug delivery and/or produce pro-drugs. Microstructural characterization of their aggregates has been determined in pure water and in pseudo-physiological conditions through DLS and SANS experiments. In all cases stable vesicles, with mean hydrodynamic radii ranging between 120 nm and 250 nm have been revealed. Biological validation of the nucleolipidic nanocarriers was ensured by evaluation of their toxicological profiles, performed by administration of the nanoaggregates to a panel of different cell lines. ToThy exhibited a weak cytotoxicity and, at high concentration, some ability to interfere with cell viability and/or proliferation. In contrast, DoHu and HoThy exhibited no toxicological relevance, behaving similarly to POPC-based liposomes, widely used for systemic drug delivery. Taken together, these results show nucleolipid-based nanocarriers as finely tunable, multi-functional self-assembling materials of interest for the in vivo transport of biomolecules or drugs.

Small-angle scattering model for multilamellar vesicles

A small-angle neutron-x-ray-light-scattering model for multilamellar vesicles is developed on the basis of a simple geometry. N spherical shells with radii of an arithmetic series are allowed for displacements DeltaR which are limited by DeltaR<R/N due to sterical reasons, with R being the radius of the vesicle. The model shows many properties over a large Q range which include a Guinier region, a first power law, a correlation peak, and a second power law connected to the surface properties of the bilayer. The first power law is related to the compactness of the vesicle and lies between Q(-2) for surfaces and Q(-4) for compact volumes (Porod law). The exact exponent is related to the number of shells N. The correlation peak has a maximum sharpness for rather small displacements DeltaR, but no second order peak is predicted. Only for rather large displacements the correlation peak widens up and shifts to smaller scattering angles. Then the important bilayer spacing is larger. The predictive power of the model lies in the connection of the compactness with N and in the maximum correlation peak sharpness. This model considers many length scales at a time while existing theories focus on length scales of the bilayer spacing and the bilayer itself.