Synthesis and Characterization of Comb and Centipede Multigraft Copolymers PnBA-g-PS with High Molecular Weight Using Miniemulsion Polymerization

Advanced Electron Microscopy of Nanophased Synthetic Polymers and Soft Complexes for Energy and Medicine Applications

After decades of developments, electron microscopy has become a powerful and irreplaceable tool in understanding the ionic, electrical, mechanical, chemical, and other functional performances of next-generation polymers and soft complexes. The recent progress in electron microscopy of nanostructured polymers and soft assemblies is important for applications in many different fields, including, but not limited to, mesoporous and nanoporous materials, absorbents, membranes, solid electrolytes, battery electrodes, ion- and electron-transporting materials, organic semiconductors, soft robotics, optoelectronic devices, biomass, soft magnetic materials, and pharmaceutical drug design. For synthetic polymers and soft complexes, there are four main characteristics that differentiate them from their inorganic or biomacromolecular counterparts in electron microscopy studies: (1) lower contrast, (2) abundance of light elements, (3) polydispersity or nanomorphological variations, and (4) large changes induced by electron beams. Since 2011, the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory has been working with numerous facility users on nanostructured polymer composites, block copolymers, polymer brushes, conjugated molecules, organic-inorganic hybrid nanomaterials, organic-inorganic interfaces, organic crystals, and other soft complexes. This review crystalizes some of the essential challenges, successes, failures, and techniques during the process in the past ten years. It also presents some outlooks and future expectations on the basis of these works at the intersection of electron microscopy, soft matter, and artificial intelligence. Machine learning is expected to automate and facilitate image processing and information extraction of polymer and soft hybrid nanostructures in aspects such as dose-controlled imaging and structure analysis.

Synthesis of polymeric topological isomers based on sequential Ugi-4CR and thiol–yne click reactions with sequence-controlled amino-functionalized polymers

Polymeric topological isomers have been designed and synthesized with sequence-controlled amino functionalized polymers.

Synergy, competition, and the "hanging" polymer layer: Interactions between a neutral amphiphilic 'tardigrade' comb co-polymer with an anionic surfactant at the air-water interface

Understanding the structure of polymer/surfactant mixtures at the air-water interface is of fundamental importance and also of relevance to a variety of practical applications. Here, the complexation between a neutral 'tardigrade' comb co-polymer (consisting of a hydrophilic polyethylene glycol backbone with hydrophobic polyvinyl acetate grafts, PEG-g-PVAc) with an anionic surfactant (sodium dodecyl sulfate, SDS) at the air-water interface has been studied. Contrast-matched neutron reflectivity (NR) complemented by surface tension measurements allowed elucidation of the interfacial composition and structure of these mixed systems, as well as providing physical insights into the polymer/surfactant interactions at the air-water interface. For both polymer concentrations studied, below and above its critical aggregation concentration, cac, (0.2 cac and 2 cac, corresponding to 0.0002 wt% or 0.013 mM and 0.002 wt% or 0.13 mM respectively), we observed a synergistic cooperative behaviour at low surfactant concentrations with a 1-2 nm mixed interfacial layer; a competitive adsorption behaviour at higher surfactant concentrations was observed where the polymer was depleted from the air-water interface, with an overall interfacial layer thickness ~1.6 nm independent of the polymer concentration. The weakly associated polymer layer "hanging" proximally to the interface, however, played a role in enhancing foam stability, thus was relevant to the detergency efficacy in such polymer/surfactant mixtures in industrial formulations.

Thermoset elastomers covalently crosslinked by hard nanodomains of triblock copolymers derived from carvomenthide and lactide: tunable strength and hydrolytic degradability

Sustainable, mechanically reinforced, and hydrolytically degradable thermoset elastomers were synthesized by one-pot, three-step synthesis & crosslinking.

Design, synthesis, and characterization of lightly sulfonated multigraft acrylate-based copolymer superelastomers

Multigraft copolymer superelastomers consisting of a poly(n-butyl acrylate) backbone and polystyrene side chains were synthesized and the viscoelastic properties of the non-sulfonated and sulfonated final materials were investigated using extensional rheology (SER3). The non-linear viscoelastic experiments revealed significantly increased true stresses (up to 10 times higher) after sulfonating only 2-3% of the copolymer while the materials maintained high elongation (<700%). The linear viscoelastic experiments showed that the storage and loss modulus are increased by sulfonation and that the copolymers can be readily tuned and further improved by increasing the number of branching points and the molecular weight of the backbone. In this way, we show that by tuning not only the molecular characteristics of the multigraft copolymers but also their architecture and chemical interaction, we can acquire thermoplastic superelastomer materials with desired viscoelastic properties.

Polypeptide self-assemblies: nanostructures and bioapplications

Polypeptide copolymers can self-assemble into diverse aggregates. The morphology and structure of aggregates can be varied by changing molecular architectures, self-assembling conditions, and introducing secondary components such as polymers and nanoparticles. Polypeptide self-assemblies have gained significant attention because of their potential applications as delivery vehicles for therapeutic payloads and as additives in the biomimetic mineralization of inorganics. This review article provides an overview of recent advances in nanostructures and bioapplications related to polypeptide self-assemblies. We highlight recent contributions to developing strategies for the construction of polypeptide assemblies with increasing complexity and novel functionality that are suitable for bioapplications. The relationship between the structure and properties of the polypeptide aggregates is emphasized. Finally, we briefly outline our perspectives and discuss the challenges in the field.

All-acrylic superelastomers: facile synthesis and exceptional mechanical behavior

All-acrylic multigraft copolymers made by a facile synthesis procedure exhibit elongation at break >1700% and strain recovery behavior far exceeding those of commercial acrylic and styrenic triblock copolymers.

Fabrication of polymer capsules by an original multifunctional, active, amphiphilic macromolecule, and its application in preparing PCM microcapsules

Based on our recent discovery that D-PGMA solution showed excellent amphiphilic and reinitiation properties, an eco-friendly, facile and scalable method to prepare polymeric capsules was proposed.

Facile fabrication of poly(glycidyl methacrylate)-b-polystyrene functional fibers under a shear field and immobilization of hemoglobin

PGMA-b-PS fibers were fabricated under a shear field for immobilization of bovine hemoglobin which has potential applications in blood substitutes.

Block Copolymers: Synthesis, Self-Assembly, and Applications

Research on block copolymers (BCPs) has played a critical role in the development of polymer chemistry, with numerous pivotal contributions that have advanced our ability to prepare, characterize, theoretically model, and technologically exploit this class of materials in a myriad of ways in the fields of chemistry, physics, material sciences, and biological and medical sciences. The breathtaking progress has been driven by the advancement in experimental techniques enabling the synthesis and characterization of a wide range of block copolymers with tailored composition, architectures, and properties. In this review, we briefly discussed the recent progress in BCP synthesis, followed by a discussion of the fundamentals of self-assembly of BCPs along with their applications.

Combination of magnetic and enhanced mechanical properties for copolymer-grafted magnetite composite thermoplastic elastomers

Composite thermoplastic elastomers (CTPEs) of magnetic copolymer-grafted nanoparticles (magnetite, Fe3O4) were synthesized and characterized to generate magnetic CTPEs, which combined the magnetic property of Fe3O4 nanoparticles and the thermoplastic elasticity of the grafted amorphous polymer matrix. Fe3O4 nanoparticles served as stiff, multiple physical cross-linking points homogeneously dispersed in the grafted poly(n-butyl acrylate-co-methyl methacrylate) rubbery matrix synthesized via the activators regenerated by electron transfer for atom transfer radical polymerization method (ARGET ATRP). The preparation technique for magnetic CTPEs opened a new route toward developing a wide spectrum of magnetic elastomeric materials with strongly enhanced macroscopic properties. Differential scanning calorimetry (DSC) was used to measure the glass transition temperatures, and thermogravimetric analysis (TGA) was used to examine thermal stabilities of these CTPEs. The magnetic property could be conveniently tuned by adjusting the content of Fe3O4 nanoparticles in CTPEs. Compared to their linear copolymers, these magnetic CTPEs showed significant increases in tensile strength and elastic recovery. In situ small-angle X-ray scattering measurement was conducted to reveal the microstructural evolution of CTPEs during tensile deformation.

Synthesis and characterization of brush-like multigraft copolymers PnBA-g-PMMA by a combination of emulsion AGET ATRP and emulsion polymerization

In this paper, poly(n-butyl acrylate)-g-poly(methyl methacrylate) multigraft copolymers were synthesized by macromonomer technique and miniemulsion copolymerization. The PMMA macromonomers were obtained by an activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) in emulsion system and subsequent allylation. Then the copolymerization of different macromonomers with nBA was carried out in miniemulsion system, obtaining multigraft copolymers with high molecular weight. The latex particles and distribution of emulsion AGET ATRP and miniemulsion copolymerization were characterized using laser light scattering. The molecular weight and polydispersity indices of macromonomers and multigraft copolymers were analyzed by gel permeation chromatography, and the number-average molecular weight range is 187,600-554,800 g/mol for PnBA-g-PMMA copolymers. In addition, the structural characteristics of macromonomer and brush-like copolymers were determined by infrared spectra and (1)H nuclear magnetic resonance spectroscopy. The thermal performance of brush-like copolymers were characterized by differential scanning calorimetry and thermogravimetric analysis. Atomic force microscopy results showed that the degree of microphase separation was varying with increasing PMMA content in PnBA-g-PMMA. The dynamic rheometer analysis revealed that multigraft copolymer with PMMA content of 31.4% exhibited good elastomeric properties to function as a TPE. These multigraft copolymers show a promising low cost and environmental friendly thermoplastic elastomer.

Synthesis and characterization of graft copolymers PnBA-g-PS by miniemulsion polymerization

PnBA-g-PS by emulsion AGET ATRP and miniemulsion polymerization.