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Abstract

Application of the SSA thermal fractionation technique to thermoplastic polyurethanes and recycled polyolefin blends

Successive Self-Nucleation and Annealing (SSA) is a powerful thermal fractionation technique designed and implemented by Müller et al.1,2 that can efficiently characterize the distributions of defects (branches, comonomers, tacticity, among others) along crystallizable chains. SSA applies a series of successive cooling and heating runs to a self-nucleated sample that promotes the creation of a series of thermal fractions with a specific lamellar thicknesses and melting point distribution thanks to the presence of defects along the chains. Recently, we applied SSA to characterize thermoplastic polyurethanes (TPUs)3 and polyethylene/polypropylene blends4. The changes in structure and morphology of TPUs before and after SSA fractionation were monitored by Differential Scanning Calorimetry (DSC), in situ real-time Small and Wide-angle X-ray scattering synchrotron experiments (SAXS/WAXS) and Atomic Force Microscopy (AFM). The SSA fractionated samples experienced a general increase in lamellar thickness that has been revealed by both AFM and SAXS and a distribution of lamellar thickness estimated by DSC and AFM. The refined crystalline structure obtained after SSA produced a number of clear WAXS reflections, as compared to the unfractionated materials, facilitating the determination of the TPUs crystallinity degree by WAXS.

On the other hand, a new tailor-made SSA protocol, able to fractionate both PE and PP in the same temperature protocol, was designed and implemented. The fractionation of model blends with known composition allowed the assessment of the temperature ranges where co-crystallization among the blend components did not occur, enabling the development of a method for the quantitative evaluation of the amount of the high melting PE component and of the PP phase in a blend. Finally, the composition of two recycled blends was successfully assessed by means of the novel quantitative method and the results were compared with those achieved by a solution-based fractionation technique on the same materials.

1. Müller, A. J.; Hernández, Z. H.; Arnal, M. L.; Sánchez, J. J. Polym. Bull., 1997, 39, 465-472
2. Müller, A. J.; Michell, R. M.; Pérez, R. A.; Lorenzo, A. T. Europ. Polym. J., 2015, 65, 132-154
3. Fernández-d'Arlas, B.; Maiz, J.; Pérez-Camargo, R. A.; Baumann, R-P.; Pöselt, E.; Dabbous, R.; Stribeck, A.; Müller, A. J. Polym. Cryst., 2021, 4, e10148, 1-12
4. Carmeli, E.; Tranchida, D.; Albrecht, A.; Müller, A. J.; Cavallo, D. Polymer, 2020, 203, 122791, 1-14

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Bio - Dr. Jaime Grunlan is the Leland T. Jordan ’29 Chair of Mechanical Engineering at Texas A&M University, where he has worked for 17 years. He holds joint appointments in the Department of Materials Science and Engineering and the Department of Chemistry. He is a world leader in polymeric thermoelectric materials, gas barrier layers and environmentally-benign, flame retardant nanocoatings. He holds 14 issued U.S. patents and several EU patents that have been licensed to more than 10 companies. He has published more than 170 journal papers, with more than 19,000 citations. Dr. Grunlan has graduated 25 PhD students and has mentored more than 50 undergraduate students in his research laboratory. His work has been highlighted in the New York Times. He is an Editor of the Journal of Materials Science and serves on the International Advisory Board for Macromolecular Rapid Communications and Macromolecular Materials and Engineering. In 2018, Prof. Grunlan became a Fellow of the American Society of Mechanical Engineers (ASME) and was awarded a doctorate honoris causa (i.e. honorary doctorate) from the University of South Brittany (Lorient, France). In 2019, he became a Senior Member of the National Academy of Inventors (NAI).

Abstract

Water-Based Multifunctional Nanocoatings from Polyelectrolyte Complexation: Opportunities & Challenges

Layer-by-layer (LbL) assembly is a conformal coating “platform” technology capable of imparting a multiplicity of functionalities on nearly any type of surface in a relatively environmentally friendly way. At its core, LbL is a solution deposition technique in which layers of cationic and anionic materials (e.g. nanoparticles, polymers and even biological molecules) are built up via electrostatic attractions in an alternating fashion, while controlling process variables such as pH, coating time, and concentration. Here we are producing nanocomposite multilayers (50 – 1000 nm thick), having 10 – 96 wt% clay, that can be completely transparent, stop gas permeation, and impart extreme heat shielding to polymeric substrates. In an effort to impart flame retardant behavior to fabric using fewer processing steps, a water-soluble polyelectrolyte complex (PEC) was developed. This nanocoating is comprised of polyethylenimine and poly(sodium phosphate) and imparts self-extinguishing behavior to cotton fabric in just a single coating step. Adding a melamine solution to the coating procedure as a second step renders nylon-cotton blends self-extinguishing. More recently, a PEC coating was developed for polyester-cotton. It passes vertical flame testing after five standard washes or 8 hours in boiling water. Either of these two coating techniques can be deposited using flexographic printing or spray-coating tools. Similar PEC coatings exhibit very low oxygen transmission rate that is useful as a foil replacement layer for food packaging. Opportunities and challenges will be discussed. Our work in these areas has been highlighted in C&EN, ScienceNews, Nature, Smithsonian Magazine, Chemistry World and various scientific news outlets worldwide. For more information, please visit my website: http://nanocomposites.tamu.edu

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Abstract

Design of Polymer-Derived Nanoparticles, Nanorods And Porous Microparticle

A number of applications benefit from nanoparticles, nanorods, and porous microparticles, such as those encountered in catalysis, drug delivery, anticorrosion coatings, or cleaning of noxious chemicals. This talk will focus on synthesis strategies for obtaining large quantities of such functional materials from polymer sources.  In the first example, a set of new nanoparticles are synthesized at room temperature by combining two oppositely charged non-toxic biopolymer polyelectrolytes in the form of chitosan and lignosulfonate. The influence of factors, such as the intensity of mixing, total solid content, and the reactant ratio on the nanoparticle size, composition, and porosity is investigated using a turbidimeter, dynamic light scattering method, and zeta potential values. A dense hydrophobic core surrounded by a positively charged hydrophilic shell is proposed as a possible structure of the nanoparticles. The interactions between chitosan and lignosulfonate are predominantly governed by the electrostatic forces with a minor role played by hydrogen bonding. The particle size and porosity are seen to increase with an increase of the total solid content while the number of particles is determined from the ratio of the two reactants.

The second example discusses fabrication of highly porous polyimide aerogel microparticles and microrods of diameter 200-1000 µm from a surfactant-free, two-phase, silicone oil/dimethylformamide (DMF) oil-in-oil (O/O) system using a simple microfluidic device. The polyimide sol prepared in DMF is turned into droplets suspended in silicone oil in the microfluidic device. The droplets are guided to a heated silicone oil bath to accelerate sol-gel transition and imidization reactions, thereby yielding spherical, discrete gel microparticles that do not undergo coalescence. The discrete gel microparticles are isolated and supercritically dried to obtain aerogel microparticles. The microparticle size distribution shows dependence on dispersed and continuous phase flowrates in the microfluidic channels. The microparticle surface morphology shows dependence on silicone oil bath temperature. The results are discussed in light of existing literature work on fabrication of solid microparticles, mesoporous microparticles, leading finally to a novel microfluidic process for continuous manufacturing of core-shell microparticles with mesoporous shell materials. Such particles find applications in absorption of noxious liquids and as hosts for catalysts.

The principles from the above examples will be summarized in the form of guideline

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In-process characterization of polymer nanocomposites during extrusion

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Abstract

Advanced Polymer-based Electromagnetic Shields

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Complex Polymeric Materials Through Self-Assembly Initiated by Small Molecules: Reversible Gels, Ionomers, and Rubbery Polymers

Approaches to the modification of the properties of soft polymeric materials that are produced by assembly or disassembly upon the addition or removal of seemingly benign stimuli will be presented. The principal polymers investigated are commercially available poly(dimethylsiloxanes) that have been substituted with amine, amidine, or imidazoline groups. The stimuli to change the polymer properties are small molecules such as mono- and di-carboxylic acids or triatomic molecules (such as CO2 and CS2). Two applications of these materials for conservation science and for the destruction of halogenated pollutants will be shown.

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Polymer Self-Assembly based Functional Materials

In this presentation the formation of polymer self-assembly derived advanced functional materials and devices is discussed from a combination of block copolymer self-assembly directed organic as well as inorganic nanoparticles. The emphasis will be on the development of wet chemical methodologies towards controlled nanostructures resulting in specific function. Experiments will be compared to theoretical predictions to provide physical insights into formation principles and specific properties. The aim of the described work is to understand the underlying fundamental chemical, thermodynamic and kinetic formation principles as well as nanostructure-property correlations enabling generalization of results over a wide class of materials systems. Work will cover structure formation at or close to the thermodynamic equilibrium as well as approaches where systems are systematically driven away from equilibrium. Examples will include block copolymer self-assembly directed gyroidal mesoporous carbons for the realization of three-dimensional (3D) battery architectures, shape control of hierarchical porous all-organic thin films via transient laser heating and their conversion into 3D periodic mesoporous semiconductors, as well as block copolymer self-assembly directed quantum materials in the form of gyroidal mesoporous superconductors.

References

1. R. P. Thedford, P. A. Beaucage, E. M. Susca, C. A. Chao, K. C. Nowack, R. B. Van Dover, S. M. Gruner, U. Wiesner, Superconducting Quantum Metamaterials from High Pressure Melt Infiltration of Metals into Block Copolymer Double Gyroid Derived Ceramic Templates, Adv. Funct. Mater. (2021), 2100469(1-9).
2. J. G. Werner, G. G. Rodríguez-Calero, H. D. Abruña, U. Wiesner, Block Copolymer Derived 3-D Interpenetrating Multifunctional GyroidalNanohybrid for Electrical Energy Storage,Energy Environ. Sci. 11, 1261-1270 (2018).
3. S. W. Robbins, P. A. Beaucage, H. Sai, K. W. Tan, J. P. Sethna, F. J. DiSalvo, S. M. Gruner, R. B. van Dover, U. Wiesner, Block copolymer self-assembly directed synthesis of mesoporous gyroidal superconductors, Science Advances 2, e1501119 (2016).
4. K. W. Tan, B. Jung, J. G. Werner, E. R. Rhoades, M. O. Thompson, U. Wiesner, Transient Laser Heating Induced Hierarchical Porous Structures from Block Copolymer Directed Self-Assembly, Science 349, 54-58 (2015).
5. Z. Li, K. Hur, H. Sai, T. Higuchi, A. Takahara, H. Jinnai, S. M. Gruner, U. Wiesner, Linking experiment and theory for three-dimensional networked binary metal nanoparticle-triblock terpolymer superstructures, Nat. Commun. 5, 3247 (2014).
6. H. Sai, K. W. Tan, K. Hur, E. Asenath-Smith, R. Hovden, Y. Jiang, M. Riccio, D. A. Muller, V. Elser, L. A. Estroff, S. M. Gruner, U. Wiesner, Hierarchical porous polymer scaffolds from block copolymers, Science 341, 530-534 (2013).

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Abstract

Engineering at the Nanoscale: A Strategy for Developing High Performance Functional Materials

Bio - Dr. Luyi Sun is a professor in the Department of Chemical and Biomolecular Engineering and the Polymer Program, Institute of Materials Science at the University of Connecticut. He received his PhD from the University of Alabama in 2004. After his postdoctoral training in Texas A&M University, he worked as a Senior Research Engineer at TOTAL Petrochemicals USA, Inc. from 2006 to 2009. Dr. Sun started his academic career as an Assistant Professor at Texas State University from 2009, and moved to University of Connecticut in 2013. Dr. Sun’s current research focuses on the design and synthesis of nano-structured multifunctional hybrids for various applications. The scientific results by Dr. Sun’s group have been reported by major media including Chemical & Engineering News of the American Chemical Society, Plastics Engineering magazine of the Society of Plastics Engineers (SPE), New Scientist, Smithsonian Magazine, Yahoo, MSN, etc. Dr. Sun is a Fellow of the Society of Plastics Engineers (SPE), a Fellow of the Royal Society of Chemistry (RSC), and a Member of the Connecticut Academy of Science and Engineering (CASE).

Abstract

Bioinspired Surface Engineering for Mechanochromism and Thermal Management

In nature, some marine organisms, such as Vogtia and Cephalopods, have evolved to possess camouflage traits by dynamically and reversibly altering their transparency, fluorescence, and coloration via muscle controlled surface structures and morphologies. To mimic this display tactics, we designed similar deformation controlled surface engineering via strain-dependent cracks and folds to realize four types of mechanochromic devices: (1) transparency change mechanochromism (TCM), (2) luminescent mechanochromism (LM), (3) color alteration mechanochromism (CAM), and (4) encryption mechanochromism (EM), based on a simple bilayer system containing a rigid thin film atop a soft substrate. These devices exhibit a wide scope of mechanochromic responses with excellent sensitivity and reversibility. Based on a similar bilayer system with strain-dependent cracks together with a stretchable heater, we developed a thermal system whose effective surface thermal emissivity originating from the combination of the film and the exposed substrate can be instantaneously and reversibly modulated simply via mechanical means. Additionally, the system demonstrates intriguing thermographic-based applications in finger motion sensing, information encryption, multiplexing display, and thermal camouflage. Both the mechanochromism and thermal management systems are expected to find widespread application.