Interaction between Nonionic Polymer Hydroxypropyl Methyl Cellulose (HPMC) and Cationic Gemini/Conventional Surfactants

Interactions between cellulose nanocrystals and conventional/gemini surfactants

Research on the interaction between surfactants and cellulose nanocrystals (CNC) has mainly focused on the interaction between CNC and conventional surfactants, and there are no reported studies on the interaction between CNC and gemini surfactants. The interactions between CNC and conventional surfactant (tetradecyltrimethylammonium bromide, termed as TTAB), asymmetric gemini surfactant ([C14H29(CH3)2N+(CH2)6N+(CH3)2C6H13]Br (14-6-6)) or symmetric gemini surfactant ([C14H29(CH3)2N+(CH2)6N+(CH3)2C14H29]Br2 (14-6-14)) were examined. With increasing surfactant concentration, interaction of TTAB/CNC was described by three regions, i.e. electrostatic interaction, CNC induced micellization and dilution of free micelles. However, in the case of gemini surfactant/CNC, four binding regimes were observed, i.e. cooperative adsorption, CNC induced micellization, formation and dilution of free micelles. The behavior of 14-6-6/CNC was similar to 14-6-14/CNC where CNC promoted the partition of gemini surfactant to the air-water interface at high surfactant concentration, while it was inhibited at low surfactant concentration. At low CNC concentration, micellization induced by CNC and aggregation of surfactant/CNC complexes were absent. pH had a minimal impact on the binding process at low CNC concentration, but it affected the binding at higher CNC concentration. Additionally, the presence of electrolytes influenced the micellization process induced by CNC by reducing the electrostatic interactions.

Coming to Order: Adsorption and Structure of Nonionic Polymer at the Oil/Water Interface as Influenced by Cationic and Anionic Surfactants

Polymer-surfactant mixtures are versatile chemical systems because of their ability to form a variety of complexes both in bulk solution and at surfaces. The adsorption and structure of polymer-surfactant complexes at the oil/water interface define their use surface chemistry applications. Previous studies have investigated the interactions between charged polyelectrolytes and surfactants; however, a similar level of insight into the interfacial behavior of nonionic polymers in mixed systems is lacking. The study herein uses vibrational sum frequency (VSF) spectroscopy to elucidate the molecular details of nonionic polyacrylamide (PAM) adsorption to the oil/water interface in the presence of surfactant. The polymer's adsorption and conformational structure at the interface is investigated as it interacts with cationic and anionic surfactants. Where the polymer will not adsorb to the interface on its own in solution, the presence of either cationic or anionic surfactant causes favorable adsorption of the polymer to the oil/water interface. VSF spectra indicate that the cationic surfactant interacts with PAM at the interface through charge-dipole interactions to induce conformational ordering of the polymer backbone. However, conformational ordering of polymer is not induced at the interface when anionic surfactant is present.

Enhancing the physical stability and supersaturation generation of amorphous drug-polyelectrolyte nanoparticle complex via incorporation of crystallization inhibitor at the nanoparticle formation step: A case of HPMC versus PVP

Amorphous drug-polyelectrolyte nanoparticle complex (or nanoplex in short) has emerged as a highly attractive solubility enhancement strategy of poorly-soluble drugs attributed to its simple and highly efficient preparation. The existing nanoplex formulation, however, exhibits poor amorphous form stability during long-term storage for drugs with high crystallization propensity. Using ciprofloxacin (CIP) and sodium dextran sulfate (DXT) as the model drug-polyelectrolyte nanoplex, we investigated the feasibility of incorporating crystallization inhibiting agents, i.e. hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), at the nanoplex formation step to improve the physical stability of the CIP nanoplex. The effects of the HPMC or PVP additions on the nanoplex's physical characteristics (i.e. size, zeta potential, CIP payload), CIP utilization rate, dissolution rate, and supersaturation generation were also examined. The results showed that the additions of HPMC or PVP increased the CIP nanoplex size (from 300 to 500 nm) and CIP utilization rate (from 65% to 90% w/w) with minimal impacts on the CIP payload (70-80% w/w). Their additions had opposite impacts on the nanoplex's colloidal stability due to surfactant nature of PVP. Significantly, unlike the CIP-DXT and CIP-DXT-PVP nanoplexes, the CIP-DXT-HPMC nanoplex remained amorphous after three-month accelerated storage, while also exhibited superior solubility enhancement (15-30% higher).

Preparation of Microcrystals of Piroxicam Monohydrate by Antisolvent Precipitation via Microfabricated Metallic Membranes with Ordered Pore Arrays

Microcrystals of piroxicam (PRX) monohydrate with a narrow size distribution were prepared from acetone/PRX solutions by antisolvent crystallization via metallic membranes with ordered pore arrays. Crystallization was achieved by controlled addition of the feed solution through the membrane pores into a well-stirred antisolvent. A complete transformation of an anhydrous form I into a monohydrate form of PRX was confirmed by Raman spectroscopy and differential scanning calorimetry. The size of the crystals was 7-34 μm and was controlled by the PRX concentration in the feed solution (15-25 g L-1), antisolvent/solvent volume ratio (5-30), and type of antisolvent (Milli-Q water or 0.1-0.5 wt % aqueous solutions of hydroxypropyl methyl cellulose (HPMC), poly(vinyl alcohol) or Pluronic P-123). The smallest crystals were obtained by injecting 25 g L-1 PRX solution through a stainless-steel membrane with a pore size of 10 μm into a 0.06 wt % HPMC solution stirred at 1500 rpm using an antisolvent/solvent ratio of 20. HPMC provided better steric stabilization of microcrystals against agglomeration than poly(vinyl alcohol) and Pluronic P-123, due to hydrogen bonding interactions with PRX and water. A continuous production of large PRX monohydrate microcrystals with a volume-weighted mean diameter above 75 μm was achieved in a continuous stirred membrane crystallizer. Rapid pouring of Milli-Q water into the feed solution resulted in a mixture of highly polydispersed prism-shaped and needle-shaped crystals.

Polymer-Amphiphile Interactions: An Overview

Interactions between the polymers and amphiphiles in aqueous solutions have generated considerable interest among researchers because of the widespread applications, relatively complex behavior and improved physicochemical properties of the mixtures. Numerous studies on the surfactant-polymer systems have been carried out in recent years and the number of scientific reports has considerably increased. Various applications of polymers in different areas and many works concerning the amphiphiles are being published every year. Usually, the mixed systems containing polymers and amphiphiles show solution properties different from those of individual solutions due to interaction between the components. The present review article mainly focuses on the behaviour of polymers in aqueous solutions, in the absence or presence of amphiphiles, such as surfactants, drugs, etc. It also summarizes effect of the nature of amphiphiles on aggregation properties of polymers in aqueous solution, and interaction of conventional as well as gemini surfactants with polymers.

Interactions between sodium polyacrylate and mixed surfactants of polyoxyethylene tert-octyl phenyl ether and dodecyltrimethylammonium bromide

Interactions between sodium polyacrylate and mixed surfactants of polyoxyethylene tert-octyl phenyl ether and dodecyltrimethylammonium bromide in 40 mM NaBr aqueous solutions were studied using isothermal titration calorimetry.

Aggregation of double-tailed ionic liquid 1,3-dioctylimidazolium bromide and the interaction with triblock copolymer F127

The aggregation of ionic liquid-based double-tailed surfactant, 1,3-dioctylimidazolium bromide ([Doim]Br) and its interaction with pluronic copolymer F127 were systematically investigated by nuclear magnetic resonance (NMR), surface tension, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC). It was found that the [Doim]Br aggregates are composed with the alkyl chains embedded in the micellar core and with the imidazolium rings parallel and staggered on the hydrophilic layer of micelles, which was generally different from the single-tailed IL [omim]Br. The hydrogen bonding between protons attached to the imidazolium rings and anion Br(-) was enhanced upon the aggregation of [Doim]Br. The aggregation of F127 was promoted by addition of [Doim]Br, which was more efficient than the single-tailed surfactant. At lower [Doim]Br content, [Doim]Br monomers embedded deeply into F127 micelle core. At higher [Doim]Br concentrations, the F127 micelles were disassociated, and then F127 chains penetrated into [Doim]Br micelle. In addition, the microstructure of F127/[Doim]Br complex can also be tuned by temperature.