Role of alkyl chain length and mole concentration of hydrophobic moiety in association behavior of amphiphilic polyelectrolytes in aqueous media

Preparation and Characterization of Hydrophobic-Associated Microspheres for Deep Profile Control in Offshore Oilfields

Microspheres have excellent sealing performances such as injectivity, bridging-off, deep migration, and deformation performances, but their plugging effects are limited by the fast swelling rate and poor viscoelasticity. In this study, we synthesized a novel modified microsphere with polymerizable surfactant monomers and cationic monomers. We investigated the influence factors on the swelling performance and rheological properties of the microspheres and explored the ways to improve the plugging performance of hydrophobic-associating microspheres. The association behaviors in aqueous media of poly(acrylamide-co-methacry loyloxyethyl trimethyl ammonium chloride-co-n-dodecyl poly(etheroxy acrylate) P(AM-DMC-DEA) are proven to be mediated by the DEA content. Moreover, the hydrophobic association interaction has a strong effect on the performance of microspheres such as swelling properties, the rheological performance, and plugging properties. The swelling properties of microsphere studies exhibited the slow swelling rate. The rheological performance measurements showed significant improvements; yield stress, and creep compliance increased rapidly from 404 to 2060 Pa and 3.89 × 10−4 to 1.41 × 10−2 1/Pa, respectively, with DEA content in microspheres rising from 0.0% to 0.22%. The plugging properties of microspheres were enhanced by the slow swelling performance and good viscoelasticity.

Polymer-hybridized liposomes anchored with alkyl grafted poly(asparagine)

Polymer-hybridized liposomes (PHLs) of saturated lecithin were formed by association of poly(asparagines) grafted with alkyl chains (PAsn-g-Cn). The thermal, physical, and surface properties of the polymer-hybridized liposomes were examined with varying polymer concentration, alkyl chain length (C(8), C(12), C(18), C(22)), and degree of substitution (DS) in the polymer. The inclusion of the polymer raised the membrane fluidity of liposomes. By the incorporation of small amount of polymer, the membrane rigidity of liposomes dropped sharply and then increased close to the original level as the polymer concentrations increased in the cases of PAsn-g-C(18) and PAsn-g-C(22). Also, the membrane rigidity and stability of PHLs increased with alkyl chain length at the same polymer concentration. The surface charge of PHL associated with PAsn-g-C(22) was changed by DS of alkyl chains. The polymer bearing long alkyl chains (C(12), C(18), C(22)) formed PHLs well at low polymer concentration and the number of disk-shaped polymer-lipid mixed micelles increased with polymer concentration. The anchored polymers induced shifts in gel-to-liquid crystal transition temperature (Tc) of the vesicles and Tc varied with polymer concentration, alkyl chain length, and DS of the polymer.

Effect of polymer characteristics on structure of polymer–liposome complexes

In the current study, we examined the effect of polymer characteristics on the structure of complexes formed between poly(methacrylic acid-co-n-alkyl methacrylate) and with phosphatidylcholine/cholesterol liposomes. We varied the polymer concentration in the vesicles, the preparation concentration of lipid and polymer components during preparation, the molecular weight of the polymer chain, the molecular weight of the polymer's hydrophobic side groups and their mole fraction. The vesicle behavior indicated polymer-free bilayers and bilayers complexed with polymer coexisted at low polymer concentrations. As the polymer concentration exceeds a critical level, however, the system became homogeneous, indicating bilayer uniformity of the bilayer. As the polymer content was raised, the vesicle size and fluidity increased, and the transition temperature decreased. We found that the vesicle size mostly affects the membrane fluidity. We also found that the thermal properties (transition temperature and the magnitude of heat capacity of the peak, DeltaCp) are governed by the effects of the polymer on the structure of bilayer. The length of the alkyl chain of the polymer is shown to significantly affect the structure of polymer-liposome complexes, as did the chain molecular weight and mole concentration of hydrophobic group in the polymer.