Bottlebrush polymer thin films may be attractive for the preparation of antifouling and/or stimuli-responsive surface coatings due to the high grafting density and conformational flexibility of polymeric side chains, but bottlebrush polymer thin films have not been previously reported and their surface properties are unknown. Herein, we report a study of the surface properties of mixed bottlebrush polymer (MBBPs) films. MBBPs with hydrophobic polystyrene (PS) and hydrophilic poly(ethylene glycol) (PEG) side chains are synthesized using a "graftingthrough" ring-opening metathesis polymerization (ROMP) approach. Stimuli-responsive MBBPs films are prepared by spin-casting a solution of MBBPs onto a solid surface, and the resulting film morphology and surface properties are characterized using atomic force microscopy (AFM), grazing-incidence small-angle X-ray scattering (GISAXS), water contact angle measurements, and X-ray photoelectron spectroscopy (XPS). The water contact angles of MBBPs films decrease or increase upon exposure of the MBBPs films to selective solvents methanol or cyclohexane, respectively. This contact angle change is dependent on the length of the PEG side chain; longer PEG side chains result in greater contact angle changes with solvent exposure. Consistent with watercontact angle measurements, XPS indicates enrichment of PEG or PS chains at the film surface after exposure of the MBBPs film to methanol or cyclohexane solvent vapors, respectively. Finally, it is demonstrated that bottlebrush polymer films can be stabilized by the addition of a radical cross-linker and irradiation with UV light. This work demonstrates that bottlebrush polymers enable the preparation of stimuli-responsive, "brush-like" polymeric coatings using simple solution processing methods.

Thermoresponsive shape memory polymers (SMPs) are stimuli-responsive materials that return to their permanent shape from a temporary shape in response to heating. The design of new SMPs which obtain a broader range of properties including mechanical behavior is critical to realize their potential in biomedical as well as industrial and aerospace applications. To tailor the properties of SMPs, “AB networks” comprised of two distinct polymer components have been investigated but are overwhelmingly limited to those in which both components are organic. In this present work, we prepared inorganic-organic SMPs comprised of inorganic polydimethyl-siloxane (PDMS) segments of varying lengths and organic poly(ε-caprolactone) (PCL) segments. PDMS has a particularly low Tg (−125 °C) which makes it a particularly effective soft segment to tailor the mechanical properties of PCL-based SMPs. The SMPs were prepared via the rapid photocure of solutions of diacrylated PCL40-block-PDMSm-block-PCL40 macromers (m = 20, 37, 66 and 130). The resulting inorganic-organic SMP networks exhibited excellent shape fixity and recovery. By changing the PDMS segment length, the thermal, mechanical, and surface properties were systematically altered.