Effect of processing conditions on the mechanical properties of bio-inspired mechanical gradient nanocomposites

Zhang, Yefei; Edelbrock, Alexandra N.; Rowan, Stuart

doi:10.1016/j.eurpolymj.2019.03.022

Cited by 17 publications

(32 citation statements)

References 62 publications

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“…As such, it was possible to obtain wateractivated mechanical gradients with a wet modulus contrast, E′ stiff /E′ soft , of about 7 between cross-linked and un-crosslinked materials. 41 While this initial study showed that it was possible to access water-activated mechanical gradients in CNC composites, the wet mechanical contrast achieved in these first-generation bioinspired nanocomposites is still far away from the gradient observed in squid beak materials (E′ stiff /E′ soft ca. 7 vs 100).…”

Section: ■ Introductionmentioning

confidence: 95%

“…It is worthy of note that, in the first-generation of these bioinspired nanocomposites, in which cross-linking only occurs between the CNCs, there is no change in the T g of the PVAc matrix after UV irradiation. 40,41 The formation of covalent networks within the P(VAc-co-VP)/t-CNC-COOH nanocomposites can be further demonstrated by the increase in plateau storage modulus (E′) after 2−40 min of UV irradiation. The plateau E′ at 80 °C (ca.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Squid Beak Inspired Cross-Linked Cellulose Nanocrystal Composites

et al. 2020

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Bioinspired cross-linked polymer nanocomposites that mimic the water-enhanced mechanical gradient properties of the squid beak have been prepared by embedding either carboxylic acid-or allylfunctionalized cellulose nanocrystals (CNC) into an alkene-containing polymer matrix (poly(vinyl acetate-co-vinyl pentenoate), P(VAc-co-VP)). Cross-linking is achieved by imbibing the composite with a tetrathiol cross-linker and carrying out a photoinduced thiol−ene reaction. Central to this study was an investigation on how the placement of cross-links (i.e., within matrix only or between the matrix and filler) impacts the wet mechanical properties of these materials. Through cross-linking both the CNCs and matrix, it is possible to access larger wet mechanical contrasts (E′ stiff /E′ soft = ca. 20) than can be obtained by just cross-linking the matrix alone (where contrast E′ stiff /E′ soft of up 11 are observed). For example, in nanocomposites fabricated with 15 wt % of allyl-functionalized tunicate CNCs and P(VAc-co-VP) with about 30 mol % of the alkene-containing VP units, an increase in the modulus of the wet composite from about 14 MPa to about 289 MPa at physiological temperature (37 °C) can be observed after UV irradiation. The water swelling of the nanocomposites is greatly reduced in the cross-linked materials as a result of the thiol−ene cross-linking network, which also contributes to the wet modulus increase. Given the mechanical turnability and the relatively simple approach that also allows photopatterning the material properties, these water-activated bioinspired nanocomposites have potential uses in a broad range of biomedical applications, such as mechanically compliant intracortical microelectrodes.

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Section: ■ Introductionmentioning

confidence: 95%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Squid Beak Inspired Cross-Linked Cellulose Nanocrystal Composites

et al. 2020

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“…The thickness of the produced film can be controlled by UV treatment, and the results show that the film exhibit enhanced mechanical properties when it is heated above its glass transition temperature during the UV irradiation. The film thickness is also an important factor influencing the degree of crosslinking ( Zhang et al., 2019 ). These bioinspired structural design strategies lay the foundation for the design and preparation of other complex structural materials in renewable architecture and related fields.…”

Section: Bioinspired Applications From Gradient Organismsmentioning

confidence: 99%

Progress in Bioinspired Dry and Wet Gradient Materials from Design Principles to Engineering Applications

Dong

Hong

et al. 2020

iScience

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Summary Nature does nothing in vain. Through millions of years of revolution, living organisms have evolved hierarchical and anisotropic structures to maximize their survival in complex and dynamic environments. Many of these structures are intrinsically heterogeneous and often with functional gradient distributions. Understanding the convergent and divergent gradient designs in the natural material systems may lead to a new paradigm shift in the development of next-generation high-performance bio-/nano-materials and devices that are critically needed in energy, environmental remediation, and biomedical fields. Herein, we review the basic design principles and highlight some of the prominent examples of gradient biological materials/structures discovered over the past few decades. Interestingly, despite the anisotropic features in one direction (i.e., in terms of gradient compositions and properties), these natural structures retain certain levels of symmetry, including point symmetry, axial symmetry, mirror symmetry, and 3D symmetry. We further demonstrate the state-of-the-art fabrication techniques and procedures in making the biomimetic counterparts. Some prototypes showcase optimized properties surpassing those seen in the biological model systems. Finally, we summarize the latest applications of these synthetic functional gradient materials and structures in robotics, biomedical, energy, and environmental fields, along with their future perspectives. This review may stimulate scientists, engineers, and inventors to explore this emerging and disruptive research methodology and endeavors.

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“…The modulus variation depending on the temperatures of the SMPs was critical to achieve the shape memory effects (Zhang et al, 2019). The time-dependent storage modulus (E') of the composites is shown in Figure 3.…”

Section: Mechanical Variation Of the Composites Without Interfacial Estimationmentioning

confidence: 99%

Theoretical and experimental studies on interfacial effects in cellulose nano crystal-shape memory polymer composites

Luo

Yao

Zhou

et al. 2020

PRT

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Purpose The purpose of this paper is to study the interfacial effect on mechanical properties of the cellulose nano crystal (CNC)–shape memory polymer (SMP) composites by using combination of the theoretical and experimental approaches. Design/methodology/approach SMP composites were fabricated by introducing CNCs into crystalline shape memory polyurethane. The morphological, thermal and mechanical properties were comprehensively investigated. Theoretical approach based upon the percolation model was used to simulate the storage modulus E’ variation of the composites in crystalline and amorphous states, respectively. The classic two-phase percolation model was used for the amorphous-state composites. Furthermore, a three-phase model consisting of interfacial regions was created for the crystalline-state composites. Findings The deviation of nano fillers mechanical reinforcements was disclosed as the composites triggered thermal transitions. Modified percolation theory involving the interfacial effects greatly enhanced the simulation accuracy. Research limitations/implications The study made the traditional percolating theory suitable for dynamic modulus and polymorphs polymers in terms of mechanics, which may extend the potential application. Originality/value The findings may greatly benefit the development of novel interfacial reinforcing theory and intelligent polymeric nanocomposites featuring polymorphs and dynamic properties.

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Effect of processing conditions on the mechanical properties of bio-inspired mechanical gradient nanocomposites

Cited by 17 publications

References 62 publications

Squid Beak Inspired Cross-Linked Cellulose Nanocrystal Composites

Squid Beak Inspired Cross-Linked Cellulose Nanocrystal Composites

Progress in Bioinspired Dry and Wet Gradient Materials from Design Principles to Engineering Applications

Theoretical and experimental studies on interfacial effects in cellulose nano crystal-shape memory polymer composites

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