Development of combinatorial chemistry methods for coatings: high-throughput optimization of curing parameters of coatings libraries

Recycled Plastic Content Quantified through Aggregation-Induced Emission

The linearity of the plastics economy is wasteful and polluting. To encourage recycling and decrease diversion to landfill, new legislation within the EU and UK will tax single-use plastic products made with less than 30% recycled plastic. At present, quantitative determination of recycled content is elusive and existing methods are inconsistent. We present a fluorescence-based analytical technique to determine recycled content in plastic and (single use) packaging. Bathochromic shifts resulting from aggregation of the fluorescent brightener 4,4'-bis(2-benzoxazolyl) stilbene (BBS) in three commodity plastics [high-density polyethylene, polypropylene, and poly(ethylene terephthalate)] at loadings ≤0.5 wt % were used to systematically quantify simulated recycled contents as low as 10 wt %. Linear correlations were found between recycled content and three fluorescence-based properties: emission, lifetime, and resulting color. We demonstrate how this multi-branched verification system is completely independent of sample dimensions and processing conditions, has a negligible effect on polymer properties, and is inexpensive and highly compatible with existing recycling infrastructure.

Development of a High-Throughput Ion-Exchange Resin Characterization Workflow

A novel high-throughout (HTR) ion-exchange (IEX) resin workflow has been developed for characterizing ion exchange equilibrium of commercial and experimental IEX resins against a range of different applications where water environment differs from site to site. Because of its much higher throughput, design of experiment (DOE) methodology can be easily applied for studying the effects of multiple factors on resin performance. Two case studies will be presented to illustrate the efficacy of the combined HTR workflow and DOE method. In case study one, a series of anion exchange resins have been screened for selective removal of NO₃^- and NO₂^- in water environments consisting of multiple other anions, varied pH, and ionic strength. The response surface model (RSM) is developed to statistically correlate the resin performance with the water composition and predict the best resin candidate. In case study two, the same HTR workflow and DOE method have been applied for screening different cation exchange resins in terms of the selective removal of Mg²⁺, Ca²⁺, and Ba²⁺ from high total dissolved salt (TDS) water. A master DOE model including all of the cation exchange resins is created to predict divalent cation removal by different IEX resins under specific conditions, from which the best resin candidates can be identified. The successful adoption of HTR workflow and DOE method for studying the ion exchange of IEX resins can significantly reduce the resources and time to address industry and application needs.

High-Throughput Industrial Coatings Research at The Dow Chemical Company

At The Dow Chemical Company, high-throughput research is an active area for developing new industrial coatings products. Using the principles of automation (i.e., using robotic instruments), parallel processing (i.e., prepare, process, and evaluate samples in parallel), and miniaturization (i.e., reduce sample size), high-throughput tools for synthesizing, formulating, and applying coating compositions have been developed at Dow. In addition, high-throughput workflows for measuring various coating properties, such as cure speed, hardness development, scratch resistance, impact toughness, resin compatibility, pot-life, surface defects, among others have also been developed in-house. These workflows correlate well with the traditional coatings tests, but they do not necessarily mimic those tests. The use of such high-throughput workflows in combination with smart experimental designs allows accelerated discovery and commercialization.

A Novel High-Throughput Viscometer

A novel, rapid, parallel, and high-throughput system for measuring viscosity of materials under different conditions of shear rate, temperature, time, etc., has been developed. This unique system utilizes the transient flow of a complex fluid through pipettes. This approach offers significant practical advantages over microfluidic-based devices for viscosity screening: no cleanup is required, the method is high throughput (<1 h for 100 samples), and only small sample volumes (<1 mL) are used. This paper details for the first time the experimental and modeling efforts to implement this mass- and pressure-based viscosity measurement concept as a robust viscosity estimation tool. This approach is very well-suited for viscosity measurements in high-throughput formulation workflows, as it is rapid and parallel and operates directly on samples in various microtiter plate formats. We present systematic experimental observations together with numerical and analytical modeling approaches to characterize instrument capabilities and limitations. The complex transient flow of fluids through these pipettes leads to data-rich pressure profiles. Numerical and analytical modeling is then used to extract viscosity and other rheological parameters from these pressure profiles. We have successfully utilized this viscosity screening tool for a multitude of complex fluids including oils, paints, solvents, and detergents.

Multisize CdSe nanocrystal/polymer nanocomposites for selective vapor detection identified from high-throughput screening experimentation

We have implemented high-throughput spectroscopic screening tools for the investigation of vapor-selectivity of CdSe semiconductor nanocrystals of different size (2.8- and 5.6-nm diameter) upon their incorporation in a library of rationally selected polymeric matrices. This library of resulting sensing materials was exposed to polar and nonpolar vapors in air. Each of the sensing materials demonstrated its own photoluminescence vapor-response patterns. Two criteria for the evaluation of vapor responses of the library of sensing materials included the diversity and the magnitude of sensing responses. We have found several polymer matrices that simultaneously meet these criteria. Our new sensing materials based on polymer-embedded semiconductor nanocrystal reagents of different size promise to overcome photobleaching and short shelf life limitations of traditional fluorescent organic reagent-based sensing materials.

Combinatorial and high-throughput screening of materials libraries: review of state of the art

Rational materials design based on prior knowledge is attractive because it promises to avoid time-consuming synthesis and testing of numerous materials candidates. However with the increase of complexity of materials, the scientific ability for the rational materials design becomes progressively limited. As a result of this complexity, combinatorial and high-throughput (CHT) experimentation in materials science has been recognized as a new scientific approach to generate new knowledge. This review demonstrates the broad applicability of CHT experimentation technologies in discovery and optimization of new materials. We discuss general principles of CHT materials screening, followed by the detailed discussion of high-throughput materials characterization approaches, advances in data analysis/mining, and new materials developments facilitated by CHT experimentation. We critically analyze results of materials development in the areas most impacted by the CHT approaches, such as catalysis, electronic and functional materials, polymer-based industrial coatings, sensing materials, and biomaterials.

High-Throughput Adhesion Evaluation and Scale-up of Combinatorial Leads of Organic Protective Coatings

Coupling of combinatorial chemistry methods with high-throughput (HT) performance testing and measurements of resulting properties has provided a powerful set of tools for the 10-fold accelerated discovery of new high-performance coating materials for automotive applications. This approach replaces labor-intensive steps with automated systems for evaluation of adhesion of 8 × 6 arrays of coating elements that are discretely deposited on a single 9 × 12 cm plastic substrate. Performance of coatings is evaluated with respect to their resistance to adhesion loss. This parameter is one primary consideration in end-use automotive applications. Coating leads identified from the HT screening have been validated on the traditional scale. Details of these validation studies are discussed.

Combinatorial and High-Throughput Materials Science

There is increasing acceptance of high-throughput technologies for the discovery, development, and optimization of materials and catalysts in industry. Over the years, the relative synchronous development of technologies for parallel synthesis and characterization has been accompanied by developments in associated software and information technologies. This Review aims to provide a comprehensive overview on the state of the art of the field by selected examples. Technologies developed to aid research on complex materials are covered as well as databases, design of experiment, data-mining technologies, modeling approaches, and evolutionary strategies for development. Different methods for parallel synthesis provide single sample libraries, gradient libraries for electronic or optical materials, similar to polymers and catalysts, and products produced through formulation strategies. Many examples illustrate the variety of isolated solutions and document the barely recognized variety of new methods for the synthesis and analysis of almost any material. The Review ends with a summary of success stories and statements on still-present problems and future tasks.

Versatile platform for creating gradient combinatorial libraries via modulated light exposure

This article details the design, construction, and operation of flexible system that modulates light exposure for the purpose of fabricating continuous and discrete gradient combinatorial libraries. Designed for versatility, the device combines "off the shelf" components, modular accessories, and flexible computer control, so that it can be used for a variety of combinatorial research applications. Salient aspects and capabilities of the instrument are illustrated through two practical examples. The first case demonstrates how user defined exposure functions can be used to create continuous surface energy gradient libraries with a linear profile. The second example illustrates the creation of continuous and discrete libraries for mapping exposure-property functions in a photocurable polymer system.

Polymeric Sensor Materials: Toward an Alliance of Combinatorial and Rational Design Tools?

Increased selectivity, response speed, and sensitivity in the chemical and biological determinations of gases and liquids are of great interest. Particular attention is paid to polymeric sensor materials, which are applicable to sensors exploiting various energy transduction principles, such as radiant, electrical, mechanical, and thermal energy. Ideally, numerous functional parameters of sensor materials can be tailored to meet specific needs using rational design approaches. However, increasing the structural and functional complexity of polymeric sensor materials makes it more difficult to predict the desired properties. Combinatorial and high-throughput methods have had an impact on all areas of research on polymer-based sensor materials including homo- and copolymers, formulated materials, polymeric structures with engineered morphology, and molecular shape-recognition materials. Herein we report on the state-of-the-art, the development trends, and the remaining knowledge gaps in the area of combinatorial polymeric sensor materials design.