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High-throughput biological assays were used to develop structure - antimicrobial relationships for polysiloxane coatings containing chemically bound (tethered) quaternary ammonium salt (QAS) moieties. The QAS-functional polysiloxanes were derived from solution blends of a silanol-terminated polydimethylsiloxane, a trimethoxysilane-functional QAS (QAS-TMS), and methylacetoxysilane. Since the QAS moieties provide antimicrobial activity through interaction with the microorganism cell wall, most of the compositional variables that were investigated were associated with the chemical structure of the QAS-TMS. Twenty different QAS-TMS were synthesized for the study and the antimicrobial activity of sixty unique polysiloxane coatings derived from these QAS-TMS determined toward Escherichia coli , Staphylococcus aureus , and Candida albicans . The results of the study showed that essentially all of the compositional variables significantly influenced antimicrobial activity. Surface characterization of these moisture-cured coatings using atomic force microscopy as well as water contact angle and water contact angle hysteresis measurements indicated that the compositional variables significantly affected coating surface morphology and surface chemistry. Overall, compositional variables that produced heterogeneous surface morphologies provided the highest antimicrobial activity suggesting that the antimicrobial activity was primarily derived from the relationship between coating chemical composition and self-assembly of QAS moieties at the coating/air interface. Using data modeling software, a narrow region of the compositional space was identified that provided broad-spectrum antimicrobial activity.

An automated, high-throughput adhesion workflow that enables pseudobarnacle adhesion and coating/substrate adhesion to be measured on coating patches arranged in an array format on 4x8 in.(2) panels was developed. The adhesion workflow consists of the following process steps: (1) application of an adhesive to the coating array; (2) insertion of panels into a clamping device; (3) insertion of aluminum studs into the clamping device and onto coating surfaces, aligned with the adhesive; (4) curing of the adhesive; and (5) automated removal of the aluminum studs. Validation experiments comparing data generated using the automated, high-throughput workflow to data obtained using conventional, manual methods showed that the automated system allows for accurate ranking of relative coating adhesion performance.

An array of quaternary ammonium functionalized-polyhedral oligomeric silsesquioxane (Q-POSS) compounds with different alkyl chain lengths and counter ions were synthesized using a two-step process. First, octasilane POSS was functionalized with dimethylamino groups by hydrosilylation with allyldimethylamine. Next, partial quaternization of the tertiaryamino-functional POSS was achieved using an alkyl halide to produce the Q-POSS. Alkyl chain length of the Q-POSS compounds varied from -C 12 H 25 to -C 18 H 37 and the counter ions varied between chlorine, bromine, and iodine. Moisture-cured polysiloxane coatings were prepared by dispersing Q-POSS molecules into a solution blend of silanol-terminated polydimethylsiloxane, methylacetoxysilane, and a catalyst. To evaluate the utility of the Q-POSS molecules as a broad-spectrum antimicrobial additive, the antimicrobial activity of the coatings toward the Gram-negative bacterium, Escherichia coli, the Gram-positive bacterium, Staphylococcus aureus, and the opportunistic fungal pathogen, Candida albicans, was determined using an agar plating method. The results obtained showed that both the composition of the Q-POSS and the composition of the polysiloxane matrix affected antimicrobial properties. Compositions were identified that inhibited the growth of all three microorganisms on the coating surface. Surface Raman spectroscopic analysis was performed on selected set of coatings to understand the relative concentration of Q-POSS molecules at the coating surface.

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Moisture-curable polysiloxanes were modified with ionic groups to enable specific interactions between the polysiloxane matrix and silica nanoparticle reinforcement. A trimethoxysilane-functional quaternary ammonium salt (QAS) was used to modify the polysiloxane matrix. A comparison of the mechanical properties of coatings containing QAS modification to analogous coatings without QAS modification showed that QAS modification resulted in a dramatic improvement in mechanical properties of silica nanoparticlereinforced coatings. QAS modification provided major enhancements in both tensile modulus and toughness. The coatings were characterized using positron annihilation spectroscopy, photo-acoustic FT-IR, differential scanning calorimetry, transmission electron microscope, and atomic force microscopy. The characterization results suggested that the QAS moieties present in the polysiloxane matrix undergo specific interactions with the surface of silica nanoparticles enabling an enhancement in interfacial adhesion between the polymer matrix and the nanoparticles. Most likely, the specific interaction that provided the enhanced mechanical properties was an ion-dipole interaction involving silanol groups present on the surface of the silica nanoparticles. The enhanced modulus and toughness of these polysiloxane materials may enable their application as a fouling-release coating for ship hulls, since current polysiloxane-based fouling release coatings suffer from poor mechanical properties and durability.

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A high-throughput workflow was developed for the study of porous polymers generated using the process of chemically induced phase separation. The workflow includes automated, parallel preparation of liquid blends containing reactive, polymer network-forming precursors and a poragen, as well as a high-throughput poragen extraction process using supercritical CO 2 . A structure-process-property relationship study was conducted using epoxy-amine cross-linked networks. The experimental design involved variations in polymer network cross-link density, poragen composition, poragen level, and cure temperature. A total of 216 unique compositions were prepared. Changes in opacity of the blends as they cured were monitored visually. Morphology was characterized using a scanning electron microscope on a subset of the 216 samples. The results obtained allowed for the identification of compositional variables and process variables that enabled the production of porous networks.