Carboxylic acid cellulose nanocrystals (CNC-COOHs) that have been covalently functionalized (via peptide coupling chemistry) with a range of different hydrophobic groups have been investigated as nanoparticle surfactants to stabilize styrene-in-water nanoemulsions. It is shown that the size and stability of these nanoemulsions depend on both the amount of surface carboxylic acid groups as well as the amount and type of hydrophobic alkyl groups on the CNC surface. Two different biosources for the CNCs, microcrystalline cellulose (MCC) and Miscanthus x. Giganteus (MxG), were investigated to see the effect that the CNC aspect ratio has on these nanoemulsions. Stable oil-in-water (o/w) Pickering emulsions with particle diameters of only a few hundred nanometers can be accessed using these hydrophobic functionalized CNCs, and the resulting emulsions can be polymerized to access nanometer sized latexes. The hydrophobic/hydrophilic balance of the functionalized CNCs was found to be critical to lower the interfacial tension between oil and water, which allowed access to stable emulsions with droplet diameters <1 μm. The ability to stabilized nanosized emulsions and latexes extends the potential of CNCs as green surfactants for numerous technological applications, such as food, cosmetics, drug delivery systems, and coatings.

A new approach for reprocessing of existing thermoset waste is presented. This work demonstrates that unrecyclable thermoset materials can be reprocessed using the concept of associative dynamic bonding, vitrimers. The developed recycling methodology relies on swelling the thermoset network into a solution of a catalyst, which enables transesterification reactions allowing dynamic bond exchange between ester and hydroxyl groups within the thermoset network. Thermal and mechanical properties for recycled polyurethane and epoxy networks are studied and a strategy to maintain the properties of recycled materials is discussed. The developed methodology promises recycling and even upcycling and reprocessing of previously thought intractable materials. Moreover, processability of vitrimerized thermosets with common thermoplastic manufacturing methods opens up the possibility of tuning recycled networks by adding nanoparticles. This flexibility keeps the application window of recycled thermosets very broad.

Different rheological quantities, such as the zero shear-rate viscosity η0 and the linear steady-state elastic compliance J e 0 of long-chain branched metallocene-catalyzed ethene homopolymers and ethene-/α-olefin copolymers with a polydispersity M w /M n ≈ 2, were correlated with the molar mass M w and degree of long-chain branching λ. A linear reference for the δ(|G * |) plot was used to show the effect of long-chain branches on this rheological property. The linear steady-state elastic compliance J e 0 correlated with the zero shear-rate viscosity increase factor η0/η0 lin and the characteristic phase angle δ c . However, the latter only works when compensating for the influence of the molar mass on J e 0 by the relationship between J e 0 and M w established elsewhere (Stadler and Münstedt, JoR, 2008). The characteristic phase angle δ c and zero shear-rate viscosity enhancement factor η0/η0 lin are linked to each other by the linear dependencies for the type I and type II viscosity functions.

Vitrimers are a class of covalent adaptive networks which, unlike other covalent networks, can be thermally reprocessed, recycled, and are self‐healing. In this research, a polyurethane vitrimer network is prepared using 1,4‐phenylene diisocyanate and excess amount of polycaprolactone polyol. The dynamic nature of this network is provided by a dual effect of dynamic transesterification reactions as well as dynamic transcarbamoylation reactions. This vitrimer can be reshaped, be recycled, and heal potential defects at high enough temperatures. A fast healing strategy is developed by the addition of small amounts (0.05 wt%) of carbon nanotubes (CNTs) which enables the use of microwave radiation for an efficient fast healing process. Using this strategy the healing time decreases more than 30 times compared to using a conventional oven. CNTs also enhance the vitrimer mechanical properties and compensate for the mechanical property loss of the dynamic PU network in comparison to the permanent PU network.

Microfluidic platform for the synthesis of complex nanocapsules is presented via a controlled self-assembly. The monodisperse nanocapsules in the range of 50-200 nm consist of a dendritic polyethylene core and a Pluronic copolymer shell. The resultant nanocarriers encapsulate large amount of hydrophobic anticancer drug like paclitaxel while providing a low complement activation as well as sustained release profile with high tunability.

One of the notorious problems in dielectric elastomer actuators (DEAs) is electromechanical instability resulting in uncontrolled breakdown, which precludes large reversible strokes. We resolved this issue by using thermoplastic elastomers (plastomers) self-assembled from linear-bottlebrush-linear triblock copolymers composed of poly­(methyl methacrylate) linear blocks and polydimethylsiloxane brush blocks. These materials demonstrate a unique combination of initial softness and intense strain-stiffening at larger deformations, which is analogous to the signature behavior of biological tissues. Plastomer-based free-standing DEAs operate at low electric fields (∼1 V/μm–1) and enable large (5-fold) reversible strokes. Given the excellent thermal stability and hydrophobicity of silicone, these solvent-free materials are good candidates for the design of artificial muscles and are capable of operating in a broad range of environments, including the human body and ocean, without losing actuation performance.

Linear−bottlebrush−linear (LBL) triblock copolymers were synthesized via a two-step atom transfer radical polymerization (ATRP): (i) grafting-through polymerization of monomethacryloxypropyl-terminated poly(dimethylsiloxane) (PDMS 11 MA) macromonomers, which yielded difunctional P-(PDMS 11 MA) bottlebrush macroinitiators, followed by (ii) the growth of linear poly(methyl methacrylate) chains at both ends of the bottlebrush backbone. Upon microphase separation, LBL triblock copolymers self-assembled into thermoplastic elastomers (plastomers) that exhibited tissue-like mechanical properties controlled by triblock composition and architecture. The mechanical properties of plastomers obtained from different synthetic batches initially demonstrated variability due to the deleterious termination of chain ends, resulting in undesired side products, consisting of linear−brush diblocks and bottlebrush monoblocks in the final product. Therefore, the kinetics of grafting-through polymerization of PDMS 11 MA macromonomers was studied to establish correlations between reversible first-order kinetic trends and network mechanical properties. By varying the reaction conditions, including the initial monomer concentration, targeted degree of polymerization, and solvent, the syntheses of macroinitiators and chain extensions were optimized with improved chain-end fidelity while maintaining a high yield and provided elastomers with consistent desired mechanical properties.

We investigated the effects of soft dendritic polyethylene (dPE) nanoparticles on the rheological properties of a linear polystyrene (PS) matrix. The viscosity of PS−dPE nanocomposites is found to exhibit nonmonotonic dependence on the dPE concentration. In particular, with the addition of 1% dPE nanoparticles, we already observe more than 1 order of magnitude reduction in viscosity. The minimum viscosity was observed at 5% nanoparticles. At dPE concentrations higher than 5%, nanocomposite viscosity increases by addition of nanoparticles, yet it remains below the viscosity of PS. Addition of nanoparticles not only influences the terminal relaxation times of the nanocomposites but also affects their whole relaxation spectra. The viscosity of PS−dPE nanocomposites at high temperature is found to reversibly evolve with time, which proves the existence of supramolecular interactions between the PS matrix and the nanoparticles. Atomic force microscopy confirms that dPE nanoparticles are well distributed in the PS matrix, though each component of the nanocomposite exhibits its own glass transition. While the origin of viscosity reduction remains unknown, it cannot be attributed to confinement, free volume effect, change of entanglement density, surface slippage, shear banding, or particle induced shear thinning.