We report a simple route to engineer ultrathin polymer brush surfaces with wrinkled morphologies using post-polymerization modification (PPM), where the length scale of the buckled features can be tuned from hundreds of nanometers to one micrometer using PPM reaction time. We show that partial crosslinking of the outer layer of the polymer brush under poor solvent conditions is critical to obtain wrinkled morphologies upon swelling. Characterization of the PPM kinetics and swelling behavior via ellipsometry and the through-thickness composition profile via time-of-flight secondary ion mass spectroscopy (ToF-SIMS) provided keys insight into parameters influencing the buckling behavior.

Conjugated polyelectrolytes (CPEs), which combine a π-conjugated polymer backbone with pendant ionic functionalities, offer an opportunity for electrostatic control of materials properties. In this work, the mesoscale morphology and physical properties of a high-mobility conjugated polyelectrolyte are tuned by the addition of salt, variation of the charge-compensating counterion, and complexation with an oppositely charged polyelectrolyte containing the same π-conjugated backbone. In systems with a single polyelectrolyte species, added ions screen the electrostatic repulsions stabilizing the gel-phase, resulting in the dissolution of ionic cross-links and hydrophobic collapse. Exchanging the charge compensating counterion is found to enable finer structural control of the solution behavior and modulation of the self-doping behavior. Finally, novel CPE–CPE complexes resulting in dense solutions and gels of semiconductive material are produced by combination of oppositely charged polyelectrolytes. Such concentrated CPE formulations should be useful materials for mixed electronic–ionic conduction and pseudocapacitative energy storage.

Polymer brushes carrying pendent thiolactone functional groups were explored for the design of multifunctional homopolymer brush architectures using sequential and one-pot postpolymerization strategies.

Amine-anhydride reactions on polymer brushes provide a modular post-modification strategy to functional surfaces.

Poly(ethylene glycol) (PEG) hydrogels hold promise for in vivo applications but induce a foreign body response (FBR). While macrophages are key in the FBR, many questions remain. This study investigates temporal changes in the transcriptome of implant‐associated monocytes and macrophages. Proinflammatory pathways are upregulated in monocytes compared to control monocytes but subside by day 28. Macrophages are initially proinflammatory but shift to a profibrotic state by day 14, coinciding with fibrous capsule emergence. Next, this study assesses the origin of macrophages responsible for fibrous encapsulation using wildtype, C‐C Motif Chemokine Receptor 2 (CCR2)–/– mice that lack recruited macrophages, and Macrophage Fas‐Induced Apoptosis (MaFIA) mice that enable macrophage ablation. Subpopulations of recruited and tissue‐resident macrophages are identified. Fibrous encapsulation proceeds in CCR2–/– mice similar to wildtype mice. However, studies in MaFIA mice indicate that macrophages are necessary for fibrous capsule formation. These findings suggest that macrophage origin impacts the FBR progression and provides evidence that tissue‐resident macrophages and not the recruited macrophages may drive fibrosis in the FBR to PEG hydrogels. This study demonstrates that implant‐associated monocytes and macrophages have temporally distinct transcriptomes in the FBR and that profibrotic pathways associated with macrophages may be enriched in tissue‐resident macrophages.

A compressive strain applied to bilayer films (e.g. thin film adhered to a thick substrate) can lead to buckled or wrinkled morphologies, which has many important applications in stretchable electronics, anti-counterfeit technology, and high-precision micro and nano-metrology. A number of buckling-based metrology methods have been developed to quantify the residual stress and viscoelastic properties of polymer thin films. However, in some systems (e.g. solvent-induced swelling or thermal strain), the compressive strain is unknown or difficult to measure. We present a quantitative method of measuring the compressive strain of wrinkled polymer films and coatings with knowledge of the "skin" thickness, wrinkle wavelength, and wrinkle amplitude. The derived analytical expression is validated with a well-studied model system, e.g., stiff, thin film (PS) bonded to a thick, compliant substrate (PDMS). After validation, we use our expression to quantify the applied swelling strain of previously reported wrinkled poly(styrene-alt-maleic anhydride) brush surfaces. Finally, the applied strain is used to rationalize the observed persistence length of aligned wrinkles created during atomic force microscopy (AFM) lithography and subsequent solvent exposure.