Tailoring structure formation and mechanical properties of particle brush solids via homopolymer addition

2016 ◽  
Vol 186 ◽  
pp. 17-30 ◽  
Author(s):  
Michael Schmitt ◽  
Chin Ming Hui ◽  
Zachary Urbach ◽  
Jiajun Yan ◽  
Krzysztof Matyjaszewski ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Colloidal Crystal ◽  
Degree Of Polymerization ◽  
Structure Property ◽  
Precise Control ◽  
Property Relations ◽  
Linear Chains ◽  
Sensitive Dependence ◽  
Tethered Chains

Recent progress in the area of surface-initiated controlled radical polymerization (SI-CRP) has enabled the synthesis of polymer-grafted colloids with precise control over the architecture of grafted chains. The resulting ‘particle brush materials’ are of interest both from a fundamental as well as applied perspective because structural frustrations (associated with the tethering of chains to a curved surface) imply a sensitive dependence of the interactions between brush particles on the architecture of surface-tethered chains that offers new opportunities to design hybrid materials with novel functionalities. An important prerequisite for establishing structure–property relations in particle brush materials is to understand the role of homopolymer impurities that form, for example, by thermal self-initiation. This contribution presents a detailed discussion of the role of homopolymer additives on the structure and mechanical properties of particle brush materials. The results suggest that the dissolution of homopolymer fillers follows a two-step mechanism comprised of the initial segregation of homopolymer to the interstitial regions within the array and the subsequent swelling of the particle brush (depending on the respective degree of polymerization of brush and linear chains). Addition of even small amounts of homopolymer is found to significantly increase the fracture toughness of particle brush assembly structures. The increased resistance to failure could enable the synthesis of robust colloidal crystal type materials that can be processed into complex shapes using ‘classical’ polymer forming techniques such as molding or extrusion.

scholarly journals Mono- and Di-Quaternized 4,4′-Bipyridine Derivatives as Key Building Blocks for Medium- and Environment-Responsive Compounds and Materials

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 1 ◽  
Author(s):  
Raffaello Papadakis
Keyword(s):  
Heterocyclic Compounds ◽  
Building Blocks ◽  
Review Article ◽  
Redox Activity ◽  
Research Trend ◽  
Structure Property ◽  
Property Relations ◽  
Key Features ◽  
Novel Applications

Mono- and di-quaternized 4,4′-bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4′-bipyridine-based derivatives are exploited: their redox activity and their electrochromic aptitude. Contemporary materials and compounds encompassing these skeletons as building blocks are often characterized as multifunctional, as their presence often gives rise to interesting phenomena, e.g., various types of chromism. This research trend is acknowledged, and, in this review article, recent examples of multifunctional chromic materials/compounds of this class are presented. Emphasis is placed on solvent-/medium- and environment-responsive 4,4′-bipyridine derivatives. Two important classes of 4,4′-bipyridine-based products with solvatochromic and/or environment-responsive character are reviewed: viologens (i.e., N,N′-disubstituted derivatives) and monoquats (i.e., monosubstituted 4,4′-bipyridine derivatives). The multifunctional nature of these derivatives is analyzed and structure–property relations are discussed in connection to the role of these derivatives in various novel applications.

scholarly journals Printable homocomposite hydrogels with synergistically reinforced molecular-colloidal networks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Austin H. Williams ◽  
Sangchul Roh ◽  
Alan R. Jacob ◽  
Simeon D. Stoyanov ◽  
Lilian Hsiao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Yield Stress ◽  
Storage Modulus ◽  
Soft Robotics ◽  
Structure Property ◽  
Interpenetrating Networks ◽  
Precise Control ◽  
Remarkable Increase ◽  
Structure Property Relationships

AbstractThe design of hydrogels where multiple interpenetrating networks enable enhanced mechanical properties can broaden their field of application in biomedical materials, 3D printing, and soft robotics. We report a class of self-reinforced homocomposite hydrogels (HHGs) comprised of interpenetrating networks of multiscale hierarchy. A molecular alginate gel is reinforced by a colloidal network of hierarchically branched alginate soft dendritic colloids (SDCs). The reinforcement of the molecular gel with the nanofibrillar SDC network of the same biopolymer results in a remarkable increase of the HHG’s mechanical properties. The viscoelastic HHGs show >3× larger storage modulus and >4× larger Young’s modulus than either constitutive network at the same concentration. Such synergistically enforced colloidal-molecular HHGs open up numerous opportunities for formulation of biocompatible gels with robust structure-property relationships. Balance of the ratio of their precursors facilitates precise control of the yield stress and rate of self-reinforcement, enabling efficient extrusion 3D printing of HHGs.

scholarly journals Printable homocomposite hydrogels with synergistically reinforced molecular-colloidal networks

2020 ◽  
Author(s):  
Austin Williams ◽  
Sangchul Roh ◽  
Alan Jacob ◽  
Simeon Stoyanov ◽  
Lilian Hsiao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
3D Printing ◽  
Yield Stress ◽  
Storage Modulus ◽  
Soft Robotics ◽  
Structure Property ◽  
Interpenetrating Networks ◽  
Precise Control ◽  
Remarkable Increase ◽  
Structure Property Relationships

Abstract The design of hydrogels where multiple interpenetrating networks enable enhanced mechanical properties could benefit applications such as biomedical products, 3D printing, and soft robotics. We report a class of self-reinforced homocomposite hydrogels (HHGs) comprised of interpenetrating networks of multiscale hierarchy. A molecular alginate gel is reinforced by a colloidal network of hierarchically branched soft dendritic colloids (SDCs), which are also made of alginate. The reinforcement of the molecular gel with the nanofibrillar SDC network of the same biopolymer results in a remarkable increase of the HHG mechanical properties. The viscoelastic HHGs show >3× larger storage modulus and >4× larger Young's modulus than either constitutive network at the same concentration. Such synergistically enforced colloidal-molecular HHGs open numerous opportunities for formulation of biocompatible gels with robust structure-property relationships. Balance of the ratio of their precursors facilitates precise control of the yield stress and rate of self-reinforcement, enabling HHG 3D printing by extrusion.

Synthesis, microstructure, and mechanical properties of polycrystalline Cu nano-foam

MRS Advances ◽  
2018 ◽  
Vol 3 (8-9) ◽  
pp. 469-475 ◽  
Author(s):  
Chang-Eun Kim ◽  
Raheleh M. Rahimi ◽  
Nia Hightower ◽  
Ioannis Mastorakos ◽  
David F. Bahr
Keyword(s):  
Mechanical Properties ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Copper Acetate ◽  
Precursor Solution ◽  
Woven Fabric ◽  
Structure Property ◽  
Property Relations ◽  
Multi Scale ◽  
Cu Foam

AbstractA polycrystalline Cu foam with sub-micron ligament sizes was formed by creating a non-woven fabric via electrospinning with a homogeneous mixture of polyvinyl alcohol(PVA)-and copper acetate(Cu(Ac)2). Thermogravimetric measurement of the electrospun fabric of the precursor solution is reported. Oxidizing the precursor fabric at 773K formed an oxide nano-foam; subsequent heating at 573K with a reducing gas transformed the CuO nano-foam to Cu with a similar ligament and meso-scale pore size morphology. A cross-section prepared by focused ion beam lift-out shows the polycrystalline structure with multi-scale porosity. The mechanical property of the Cu nano-foam is measured by nano-indentation. The load-depth curves and deduced mechanical properties suggest that additional intra-ligament pores lead to unique structure-property relations in this non-conventional form of metal.

Assessing Structure-Property Relations of Diseased Tissues Using Nanoindentation and FTIR

2001 ◽  
Vol 711 ◽  
Author(s):  
Donna M. Ebenstein ◽  
Joan M. Chapman ◽  
Cheng Li ◽  
David Saloner ◽  
Joseph Rapp ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Calcium Content ◽  
Spectroscopic Techniques ◽  
Tissue Composition ◽  
Structure Property ◽  
Artery Wall ◽  
Tissue Samples ◽  
Tissue Microstructure ◽  
Property Relations ◽  
Fibrous Tissues

ABSTRACTDisease processes are often associated with changes in tissue composition. For example, in atherosclerosis lipid and calcification are often found in the artery wall, whereas in healthy arteries the tissue microstructure is dominated by highly organized collagen. Such variations in composition likely result in changes in the material properties of the tissue. However, this relationship has not been fully investigated in atherosclerotic vessels. Using a combination of nanoindentation and spectroscopic techniques, our goal was to assess how changes in tissue composition affect the tissue's mechanical properties. Fourier Transform Infrared Spectroscopy (FTIR) was used to assess the biochemical composition of the tissue samples, such as the lipid and calcium content of fibrous tissues in diseased arteries. Nanoindentation was used to measure the local mechanical properties of the same tissue samples. This information was then correlated by position in the sample to assess the contributions of different constituents to the overall structure-property relations of these tissues.

scholarly journals Multi-Scale Structure–Mechanical Property Relations of Graphene-Based Layer Materials

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4757
Author(s):  
Jingran Liu ◽  
Huasong Qin ◽  
Yilun Liu
Keyword(s):  
Mechanical Properties ◽  
Mechanical Property ◽  
Functional Materials ◽  
Scale Structure ◽  
Monolayer Graphene ◽  
Pristine Graphene ◽  
Multilayer Graphene ◽  
Structure Property ◽  
Property Relations ◽  
Multi Scale

Pristine graphene is one of the strongest materials known in the world, and may play important roles in structural and functional materials. In order to utilize the extraordinary mechanical properties in practical engineering structures, graphene should be assembled into macroscopic structures such as graphene-based papers, fibers, foams, etc. However, the mechanical properties of graphene-based materials such as Young’s modulus and strength are 1–2 orders lower than those of pristine monolayer graphene. Many efforts have been made to unveil the multi-scale structure–property relations of graphene-based materials with hierarchical structures spanning the nanoscale to macroscale, and significant achievements have been obtained to improve the mechanical performance of graphene-based materials through composition and structure optimization across multi-scale. This review aims at summarizing the currently theoretical, simulation, and experimental efforts devoted to the multi-scale structure–property relation of graphene-based layer materials including defective monolayer graphene, nacre-like and laminar nanostructures of multilayer graphene, graphene-based papers, fibers, aerogels, and graphene/polymer composites. The mechanisms of mechanical property degradation across the multi-scale are discussed, based on which some multi-scale optimization strategies are presented to further improve the mechanical properties of graphene-based layer materials. We expect that this review can provide useful insights into the continuous improvement of mechanical properties of graphene-based layer materials.

Exchange Spin Coupling from Gaussian Process Regression

2020 ◽  
Author(s):  
Marc Philipp Bahlke ◽  
Natnael Mogos ◽  
Jonny Proppe ◽  
Carmen Herrmann
Keyword(s):  
Machine Learning ◽  
Gaussian Process ◽  
Gaussian Process Regression ◽  
Molecular Magnets ◽  
Molecular Structures ◽  
Spin Coupling ◽  
Structure Property ◽  
Data Set ◽  
Uncertainty Estimates

Heisenberg exchange spin coupling between metal centers is essential for describing and understanding the electronic structure of many molecular catalysts, metalloenzymes, and molecular magnets for potential application in information technology. We explore the machine-learnability of exchange spin coupling, which has not been studied yet. We employ Gaussian process regression since it can potentially deal with small training sets (as likely associated with the rather complex molecular structures required for exploring spin coupling) and since it provides uncertainty estimates (“error bars”) along with predicted values. We compare a range of descriptors and kernels for 257 small dicopper complexes and find that a simple descriptor based on chemical intuition, consisting only of copper-bridge angles and copper-copper distances, clearly outperforms several more sophisticated descriptors when it comes to extrapolating towards larger experimentally relevant complexes. Exchange spin coupling is similarly easy to learn as the polarizability, while learning dipole moments is much harder. The strength of the sophisticated descriptors lies in their ability to linearize structure-property relationships, to the point that a simple linear ridge regression performs just as well as the kernel-based machine-learning model for our small dicopper data set. The superior extrapolation performance of the simple descriptor is unique to exchange spin coupling, reinforcing the crucial role of choosing a suitable descriptor, and highlighting the interesting question of the role of chemical intuition vs. systematic or automated selection of features for machine learning in chemistry and material science.

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