Linear polypeptoid macromonomers with controlled chain length and composition were prepared by norbornene methylamine-initiated copolymerization of N-ethyl N-carboxyanhydride (Et-NCA) and Nbutyl N-carboxyanhydride (Bu-NCA). Polypeptoid bottlebrush copolymers with varying backbone length and side chain composition were subsequently synthesized using the grafting-through method via the ring-opening metathesis polymerization (ROMP) of norbornenyl-terminated poly(N-ethyl glycine)-ranpoly(N-butyl glycine) macromonomers. The bottlebrush copolypeptoids are thermally responsive with a cloud point transition in aqueous solution similar to the linear macromonomers. In contrast to the linear macromonomers, the cloud point transition of the bottlebrush copolypeptoids is strongly dependent on the thermal history of the solution. Freshly prepared aqueous solutions of the bottlebrush copolypeptoids do not exhibit any notable cloud point transition, whereas the solutions that have been thermally annealed at high temperature exhibit sharp and reversible cloud point transition. Intriguingly, upon inorganic salt addition, the aqueous solutions of the bottlebrush copolypeptoids exhibit normal cloud point transition which is independent of the solution thermal history. It was suggested that the thermal annealing and the presence of a salt facilitated the conformational reorganization of the bottlebrush copolypeptoids to favor hydrophobic collapse and intermolecular aggregation, resulting in a cloud point transition.

Hydrophobins are abundant amphipathic proteins produced by fungi. They have been interacting with oils in natural environments for millions of years; therefore, it is sensible to consider them as surfactants and dispersants for cleaning oil spills. To better understand the properties of these amphipathic proteins in seawater, a particular hydrophobin known as cerato-ulmin (CU; mass 7627 g/mol) was studied. CU is adept at forming strong membranes, as indicated by the capacity to stabilize gas-filled bubbles and oil-filled droplets with cylindrical and other nonspherical shapes. The limits of this unusual ability were tested using a wide variety of solvent conditions, including various salt solutions, alcohols, simple hydrocarbons (i.e., cyclohexane, dodecane), acids, and bases. CU concentrations ranged from 20 to 200 μg/mL. The bubbles and other structures made by CU in the presence of various gases span an enormous range of size, from nanometers to millimeters. After larger objects float to the surface, smaller structures remain, and these were found by light scattering to have a hydrodynamic diameter of ∼200 nm.

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A labeled green fluorescent polystyrene sulfonate (LNaPSS) has been synthesized using atom transfer radical polymerization of a styrene sulfonate monomer with a fluorescent co-monomer, fluorescein thiocyanate-vinyl aniline. As a result this 100 % sulfonated polymer contains no hydrophobic patches along the chain backbone besides the fluorescent marker itself. The concentration of the fluorescent monomer was kept low to maintain the characteristic properties of the anionic polyelectrolyte, LNaPSS. ATRP conditions facilitated the production of polymers spanning a range of molecular weights from 35,000 to 175,000 in gram-scale batches with polydispersity indices of 1.01-1.24. Molecular weight increased with the monomer to initiator ratio. Gel permeation chromatography results show a unimodal distribution, and the polymer structure was also confirmed by (1)H NMR and FT-IR spectroscopy. Fluorescence spectroscopy confirmed covalent bonding of fluorescein isothiocyanate to the polymer, indicating that the polymer is suitable as a probe in fluorescence microscopy. To demonstrate this ability, the polymer was used to locate structural features in salt crystals formed during drying, as in the evaporation of sea mist. A second application to probe diffusion studies is also demonstrated.