•Unusual micellisation process occurs in the system C16TAB/FSN-100 mixture solutions.•FSN-100 forms disc-like micelles with aggregation number of 65.•C16TAB forms globular, charged micelles with a larger aggregation number than FSN-100.Many technological formulations contain mixtures of surfactants, each contributing some distinct property. Characteristics of each surfactant are often modulated in the mixture, based on the interactions between the various components present. Here, the mixing of the hydrocarbon surfactant cetyltrimethyl ammonium bromide (C16TAB) and the fluorocarbon surfactant, Zonyl-FSN-100 with average chemical structure of C8F17C2H4 (OC2H4)9OH, is quantified, in particular, the size and shape of the micelles and their critical micelle concentration (CMC). The CMC data suggest there are specific interactions between the two components which are strongly antagonistic. Small-angle neutron scattering (SANS) has been used to quantify the size and shape of the micelle, and these data indicate that the single component FSN-100 forms disc-like micelles with a small aggregation number (∼65) and the C16TAB forms globular, charged micelles with a larger aggregation number (135). The aggregation number of the mixed micelle is substantially greater than either of the pure species. Overall, a detailed study of CTAB, FSN-100 and their mixture systems will be presented in this paper.

Structural properties such as size, shape and density distribution of a range of N-(2-hydroxypropyl)methacrylamide (HPMA) polymers in various solvent models have been investigated. Common atomistic force fields were compared against rotational barriers and relative conformational energies obtained from ab initio and density functional theory (DFT) data for a monomer and dimer of HPMA. This identified the AMBER99 parameter set as the most appropriate for representing the structures and so AMBER99 was employed for all molecular dynamics simulations. MD trajectories were calculated for a range of polymer sizes from 4 to 265 repeat units (2 to 35 kDa). The time averaged radius of gyration was extracted from trajectories and interpreted in the context of Flory's mean field approach. Comparison with data obtained from small angle neutron scattering (SANS) experiments was then used to differentiate between alternative solvent models. The shape adopted by such polymers was evaluated by fitting structures to ellipsoids, to allow separate analysis of radius and density profile along each axis. The density distribution of atoms was defined using these ellipsoids according to centre of mass or centre of neutron scattering lengths, the latter allowing direct comparison with experimental SANS data. We show that computational simulation of such polymers has practical application in obtaining detailed morphological information of polymer solution structure, and as a benchmark for coarse-grained methods.

Metallosurfactants comprising copper(II) (Cu(NO3)2) and zinc(II) (Zn(NO3)2) nitrate complexes of 2,5-dimethyl-7-hydroxy-2,5-diazaheptadecane were found to form stable oil-in-water microemulsions—metallomicroemulsions—that could solubilise toluene in the presence of butanol. A detailed contrast-variation scattering analysis, employing both neutrons and X-rays, in conjunction with pulsed-gradient spin-echo NMR and simple phase diagram construction, demonstrated that the system formed is that of a conventional microemulsion—a core comprising toluene, separated from the aqueous phase by the surfactant and co-surfactant/co-solvent. This study further demonstrates the versatility of metallosurfactants and the similarity of their physical chemistry behaviour to that of conventional surfactants.

Copolymers based on poly(N-(2-hydroxypropylmethacrylamide)) with conjugated Doxrubicin are established as candidate anticancer therapeutics. Two HPMA-co-polymers (ca. 35000 g mol−1) with 2.5 and 8 mol % gly-phe-leu-gly peptidyl side-chain content have been modified using linear hydrocarbon and small aromatic molecules as simple drug mimics. This first contrast-variation SANS study on these systems demonstrates, combined with detailed modeling, a controlled switch from random coil to a more defined morphology induced by inclusion of a series of model drug mimics. Relatively small changes in drug-mimic type and loading can significantly alter the solution conformation, and we tentatively propose a helical type structure that is more or less tightly wound, depending on both hydrophobe loading and type. The results presented have important implications for understanding the influence of conjugate structure on solution properties, which is an important factor influencing biological and clinical activity.

Mixtures of common polymeric excipients and hydrofluoroalkane (HFA) liquids show rich and complex phase behaviour. Phase diagrams and phase compositions are reported for poly(ethylene glycol)s with varying levels of end-group methylation in mixed solvent systems consisting of the model propellant 2H,3H-perfluoropentane (HPFP) and the fully fluorinated analogue perfluoropentane (PFP). Studies have been performed as a function of molecular weight as well as end group chemistry (monomethyl, MM; dimethyl, DM; and dihydroxyl, DH), and for binary polymer mixtures in HPFP/PFP solvent systems. The solvent composition required to induce phase separation by addition of the non-hydrogen bonding PFP is strongly dependent on end-group concentrations. It shows a linear increase with increasing methylation, whilst remaining insensitive to OH group concentration in dihydroxylated PEG systems. For single polymer systems it is observed that strong partitioning of the polymer is observed, and changes in polymer concentration occurring across the phase diagram are a result of changing solvent partitioning between upper and lower phases. These solvent effects are dependent on the composition (wt% PFP) in the solvent mixture. The linear dependence of solvent composition required to induce phase separation at fixed polymer concentration on end group concentrations can be used to predict the phase behaviour for mixtures of monomethylated PEG with either dimethyl or dihydroxyl PEGs, whereas mixtures of dihydroxyl with dimethyl end-capped PEGs show a deviation from linear behaviour with dominance of the dihydroxyl end groups, which is reflected in the obtained phase diagrams. This study hence progresses understanding of factors that influence solubility of PEG-type polymers in HFAs and will facilitate the identification of predictive methodologies for formulation.