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1. Initiator-dependent kinetics of lyotropic liquid crystal-templated thermal polymerization

   https://doi.org/10.1039/D1PY00127B  

   Saadat, Younes; Kim, Kyungtae; Foudazi, Reza (April 2021, Polymer Chemistry)

   null (Ed.)

   In this study, we examine the polymerization kinetics with different thermal initiators in lamellar and hexagonal lyotropic liquid crystal (LLC) structures directed by Pluronic L64. Ammonium persulfate is used to initiate the polymerization from the water phase, whereas azobisisobutyronitrile and benzoyl peroxide are employed to commence the reaction through the monomer phase. While the mesophase structure remains intact for all the initiation systems, the kinetics of polymerization and conversion vary significantly. The obtained differential scanning calorimetry (DSC) results reveal that, under the same conditions, the initiation from water (IFW) system results in enhanced reaction rates as well as higher monomer conversions compared to the initiation from oil (IFO) system. A higher termination rate in LLC nanoconfinements induces lower reaction rates in the IFO system. Moreover, our work on different LLC structures shows that the effect of nanoconfinement on the polymerization rate can be minimized through IFW. Chemorheology not only confirms the results obtained from DSC, but also shows that, in similar monomer conversions, the polymers obtained from the IFW system exhibit improved mechanical properties over the samples produced through the IFO process. 

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2. Recent Advances in Functional Materials through Cellulose Nanofiber Templating

   https://doi.org/10.1002/adma.202005538  

   Lamm, Meghan_E; Li, Kai; Qian, Ji; Wang, Lu; Lavoine, Nathalie; Newman, Reagan; Gardner, Douglas_J; Li, Teng; Hu, Liangbing; Ragauskas, Arthur_J; et al (February 2021, Advanced Materials)

   Abstract Advanced templating techniques have enabled delicate control of both nano‐ and microscale structures and have helped thrust functional materials into the forefront of society. Cellulose nanomaterials are derived from natural polymers and show promise as a templating source for advanced materials. Use of cellulose nanomaterials in templating combines nanoscale property control with sustainability, an attribute often lacking in other templating techniques. Use of cellulose nanofibers for templating has shown great promise in recent years, but previous reviews on cellulose nanomaterial templating techniques have not provided extensive analysis of cellulose nanofiber templating. Cellulose nanofibers display several unique properties, including mechanical strength, porosity, high water retention, high surface functionality, and an entangled fibrous network, all of which can dictate distinctive aspects in the final templated materials. Many applications exploit the unique aspects of templating with cellulose nanofibers that help control the final properties of the material, including, but not limited to, applications in catalysis, batteries, supercapacitors, electrodes, building materials, biomaterials, and membranes. A detailed analysis on the use of cellulose nanofibers templating is provided, addressing specifically how careful selection of templating mechanisms and methodologies, combined toward goal applications, can be used to directly benefit chosen applications in advanced functional materials. 

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3. Independently Tunable Thermal Conductance and Phononic Band Gaps of 3D Lattice Materials

   https://doi.org/10.1002/adem.201901004  

   Babatola, Oluseyi; Patil, Ganesh_U; Hsieh, Daniel; Matlack, Kathryn_H; Sinha, Sanjiv (December 2019, Advanced Engineering Materials)

   Lattice materials provide unusual thermal and vibrational properties but not within the same structure. Thermal and vibrational multifunctionality is, however, crucial for thermomechanical applications such as automotive, aerospace, building, transportation, and energy infrastructure. In applications involving mobility, both high heat transfer and low mass are desired. Although there have been various efforts to design multifunctional lattice materials, the focus has largely remained on quasi‐static mechanical and thermal properties or mechanical and vibrational properties. Herein, designs of realizable lattice materials are reported, which are inherently thermally resistive, with vastly improved thermal conductance and omnidirectional phononic band gaps. By redesigning the truss structures to serve as interconnected heat pipes, a three‐order‐of‐magnitude improvement in the specific thermal conductance is found. Nodal masses at truss junctions are further used to obtain full vibrational band gaps. It is shown that it is possible to independently tune vibrational and thermal properties within the same structure. This work provides background for the design and fabrication of multifunctional lattice materials that simultaneously prevent structural vibrations and enhance heat conduction. 

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4. Fish scale inspired structures - a review of materials, manufacturing and models

   https://doi.org/10.1088/1748-3190/ac7fd0  

   Hossain, Md Shahjahan; Ebrahimi, Hossein; Ghosh, Ranajay (October 2022, Bioinspiration & Biomimetics)

   Abstract Fish scales inspired materials platform can provide advanced mechanical properties and functionalities. These materials, inspired from fish scales take the form of either composite materials or multi-material discrete exoskeleton type structures. Over the last decade, they have been under intense scrutiny for generating tailorable and tunable stiffness, penetration and fracture resistance, buckling prevention, nonlinear damping, hydrodynamic and camouflaging functions. Such programmable behavior emerges from leveraging their unique morphology and structure-property relationships. Several advanced tools of characterization, manufacturing, modeling and computation have been employed to understand and discover their behavior. With the rapid proliferation of additive manufacturing (AM) techniques, and advancing envelope of modeling and computational methods, this field is seeing renewed efforts to realize even more ambitious designs. We present a review and recapitulation of the state-of-the art in fish scale inspired materials in this paper. 

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5. Additive manufacture of lightly crosslinked semicrystalline thiol–enes for enhanced mechanical performance

   https://doi.org/10.1039/c9py01452g  

   Childress, Kimberly K.; Alim, Marvin D.; Hernandez, Juan J.; Stansbury, Jeffrey W.; Bowman, Christopher N. (January 2020, Polymer Chemistry)

   Photopolymerizable semicrystalline thermoplastics resulting from thiol–ene polymerizations were formed via fast polymerizations and achieved excellent mechanical properties. These materials have been shown to produce materials desirable for additive manufacturing (3D printing), especially for recyclable printing and investment casting. However, while well-resolved prints were previously achieved with the thiol–ene thermoplastics, the remarkable elongation at break ( ε max ) and toughness ( T ) attained in bulk were not realized for 3D printed components ( ε max,bulk ∼ 790%, T bulk ∼ 102 MJ m −3 vs. ε max,print < 5%, T print < 0.5 MJ m −3 ). In this work, small concentrations (5–10 mol%) of a crosslinker were added to the original thiol–ene resin composition without sacrificing crystallization potential to achieve semicrystalline, covalently crosslinked networks with enhanced mechanical properties. Improvements in ductility and overall toughness were observed for printed crosslinked structures, and substantial mechanical augmentation was further demonstrated with post-manufacture thermal conditioning of printed materials above the melting temperature ( T m ). In some instances, this thermal conditioning to reset the crystalline component of the crosslinked prints yielded mechanical properties that were comparable or superior to its bulk counterpart ( ε max ∼ 790%, T ∼ 95 MJ m −3 ). These unique photopolymerizations and their corresponding monomer compositions exhibited concurrent polymerization and crystallization along with mechanical properties that were tunable by changes to the monomer composition, photopolymerization conditions, and post-polymerization conditioning. This is the first example of a 3D printed semicrystalline, crosslinked material with thermally tunable mechanical properties that are superior to many commercially-available resins. 

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