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Poloxamer 407 (P407) is an ABA triblock polymer widely used in therapeutic delivery due to its temperature- dependent micellization and ordering behavior. However, using P407 to deliver therapeutics across biological barriers remains difficult, as additives that enhance drug flux often hinder formulation stability and mechanical properties. Methyl laurate (ML)a methyl ester oilwas recently identified as a promising additive for delivery across the eardrum; however, P407/ML easily phase-separates due to poor emulsion stability. Accordingly, we explore adding reverse poloxamers (RPs)BAB triblock polymers with the same blocks as P407 but in reverse orderto aqueous P407 as a strategy for controlling self-assembly, ordering, and formulation stability. Differential scanning calorimetry (DSC), rheology, and small-angle X-ray scattering (SAXS) reveal that ML induces ordering at low P407 concentrations due to ML encapsulation within micelles. While adding ML challenges formulation stability at both low and high temperatures, adding RPs (17R2 or 17R4) enhances emulsion stability and raises the maximum modulus. However, only the more hydrophilic 17R4 significantly alters self-assembly and rheological transitions in P407/ML. As P407 micellization is well separated from dehydration of 17R4 with increasing temperature, 17R4 chains remain soluble for a wide temperature range, effectively delaying ordering in P407/ ML by obstructing contact between micelle coronas. Following dehydration, 17R4 localizes in the micelle corona, altering the P407 aggregation number. In contrast, the low aqueous solubility of 17R2 leads to localization near the micelle core−corona interface; such localization drives cubic ordering in the absence of ML but has little impact on self-assembly when ML is present. These differences in RP solubility and incorporation mechanismand their impact on P407 rheology, self-assembly, and ordering provide a framework for selecting the optimal RP type and quantity to produce P407 drug delivery vehicles with well-controlled properties for target applications. 

Magnetic field processing is promising for directing and enhancing self-assembly of diamagnetic block copolymers (BCPs) via domain alignment, but is typically limited to high field strengths and few polymer chemistries. Herein, a novel magnetic field-induced ordering mechanism distinct from domain alignment is demonstrated in aqueous, spherical BCP micelles. Here, low-intensity magnetic fields (B< 0.5 T) induce an anomalous disorder-to-order transition, accompanied by a several order-of-magnitude increase in shear modulus-- effectively transforming a low viscosity liquid into an ordered soft solid. The induced moduli are orders of magnitude larger than those resulting from thermally-induced ordering. Further magnetization induces cubic-to-cylinder order-to-order transitions. Comprehensive characterization via magnetorheology, small- and wide-angle X-ray scattering, differential scanning calorimetry, and vibrational spectroscopy reveals a significant reduction in micelle size and aggregation number relative to zero-field temperature- or concentration-induced ordering, suggesting that B-fields strongly alter polymer-solvent interactions. This extraordinary BCP ordering strategy enables discovery of structures and d-spacings inaccessible via traditional processing routes, thus providing a new platform for developing advanced materials with precisely-controlled features. 

Polymer solution processability in extensional-flow dominated operations is strongly influenced by polymer conformation and solution phase behavior. Cosolvent addition can be used to tailor polymer conformation and solution phase behavior to yield formulations that are amenable to processes such as spraying and atomization, coating, and fiber spinning. The addition of N,N-dimethylformamide (DMF) to aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions induces unique phase behavior and microstructure formation, yet the effects on solution processability have remained unexplored. In this work, the effect of DMF cosolvent content on the rheology (both shear and extensional) and microstructure of PNIPAM solutions is investigated. While all examined PNIPAM solutions exhibit nearly Newtonian steady shear behavior regardless of DMF content, the same solutions exhibit varying degrees of extensibility. Surprisingly, the extensional relaxation time increases by more than twenty-fold with increasing DMF content in the water-rich regime. In the DMF-rich regime, however, solution extensibility dramatically decreases. Interestingly, this unique variation in extensional flow behavior does not scale as expected based on changes in the measured intrinsic viscosity and radius of gyration. Instead, a mechanism is proposed that relates the extensional flow behavior to the solution microstructure, which is found to vary with DMF content in light scattering measurements. In the water-rich regime, DMF molecules are proposed to bridge PNIPAM chains via hydrogen bonding and hydrophobic interactions, resulting in physically crosslinked aggregates. In extensional flows, these aggregates behave like a polymer with higher apparent molecular weight, increasing the extensional relaxation time. In the DMF-rich regime, non-bridging DMF molecules increasingly solvate individual PNIPAM chains; consequently, more individual chains are stretched in extensional flows, leading to a reduction in the extensional relaxation time. These findings demonstrate that interactions between components in these ternary systems have unexpected but significant implications in solution extensional flow behavior. Additionally, in the case of PNIPAM/DMF/water, the processability of polymer-containing formulations can be modulated for spraying or for fiber spinning applications just by varying cosolvent (DMF) content. 

The nanoscale structure formation and optical response of aqueous thermoresponsive polymers with reactive silane groups can be widely tunedviapolymer architecture and organic cosolvent incorporation. 

Abstract Chemical permeation enhancers (CPEs) represent a prevalent and safe strategy to enable noninvasive drug delivery across skin‐like biological barriers such as the tympanic membrane (TM). While most existing CPEs interact strongly with the lipid bilayers in the stratum corneum to create defects as diffusion paths, their interactions with the delivery system, such as polymers forming a hydrogel, can compromise gelation, formulation stability, and drug diffusion. To overcome this challenge, differing interactions between CPEs and the hydrogel system are explored, especially those with sodium dodecyl sulfate (SDS), an ionic surfactant and a common CPE, and those with methyl laurate (ML), a nonionic counterpart with a similar length alkyl chain. Notably, the use of ML effectively decouples permeation enhancement from gelation, enabling sustained delivery across TMs to treat acute otitis media (AOM), which is not possible with the use of SDS. Ciprofloxacin and ML are shown to form a pseudo‐surfactant that significantly boosts transtympanic permeation. The middle ear ciprofloxacin concentration is increased by 70‐fold in vivo in a chinchilla AOM model, yielding superior efficacy and biocompatibility than the previous highest‐performing formulation. Beyond improved efficacy and biocompatibility, this single‐CPE formulation significantly accelerates its progression toward clinical deployment. 

Abstract Extensional flow properties of polymer solutions in volatile solvents govern many industrially-relevant coating processes, but existing instrumentation lacks the environment necessary to control evaporation. To mitigate evaporation during dripping-onto-substrate (DoS) extensional rheology measurements, we developed a chamber to enclose the sample in an environment saturated with solvent vapor. We validated the evaporation-controlled DoS device by measuring a model high molecular weight polyethylene oxide (PEO) in various organic solvents both inside and outside of the chamber. Evaporation substantially increased the extensional relaxation time $$\lambda _{E}$$ λ E for PEO in volatile solvents like dichloromethane and chloroform. PEO/chloroform solutions displayed an over 20-fold increase in $$\lambda _{E}$$ λ E due to the formation of an evaporation-induced surface film; evaporation studies confirmed surface features and skin formation reminiscent of buckling instabilities commonly observed in drying polymer solutions. Finally, the relaxation times of semi-dilute PEO/chloroform solutions were measured with environmental control, where $$\lambda _{E}$$ λ E scaled with concentration by the exponent $$m=0.62$$ m = 0.62 . These measurements validate the evaporation-controlled DoS environment, and confirm that chloroform is a good solvent for PEO, with a Flory exponent of $$\nu =0.54$$ ν = 0.54 . Our results are the first to control evaporation during DoS extensional rheology, and provide guidelines establishing when environmental control is necessary to obtain accurate rheological parameters. 

The formation and evolution of a heterogeneous flow and flow reversal are examined in highly elastic, gel-like wormlike micelles (WLMs) formed from an amphiphilic triblock poloxamer P234 in 2M NaCl. A combination of linear viscoelastic, steady shear, and creep rheology demonstrate that these WLMs have a yield stress and exhibit viscoelastic aging, similar to some soft glassy materials. Nonlinear shear rheology and rheoparticle tracking velocimetry reveal that these poloxamer WLMs undergo a period of strong elastic recoil and flow reversal after the onset of shear startup. As flow reversal subsides, a fluidized high shear rate region and a nearly immobile low shear rate region of fluid form, accompanied by wall slip and elastic instabilities. The features of this flow heterogeneity are reminiscent of those for aging yield stress fluids, where the heterogeneous flow forms during the initial stress overshoot and is sensitive to the inherent stress gradient of the flow geometry. Additionally, macroscopic bands that form transiently above a critical shear rate become “trapped” due to viscoelastic aging in the nearly immobile region. This early onset of the heterogeneous flow during the rapidly decreasing portion of the stress overshoot differs from that typically observed in shear banding WLMs and is proposed to be necessary for observing significant flow reversal. Exploring the early-time, transient behavior of this WLM gel with rheology similar to both WLM solutions and soft glassy materials provides new insights into spatially heterogeneous flows in both of these complex fluids.